Scientific Program
Saturday,
November 2, 1996
Otto Maass Room 112
9:OOAM Introductory Remarks
9:15-10:15 Plenary Lecture
by Professor Robert J. Bergman,
Dept. of
Chemistry, University of California, Berkeley, California USA.
10:15-10:45 Coffee Break
Session
I
Otto Maass Room 112
Session
Chair: Ms. Heather Gass
10:45-11:05 Characterization
and Polymerization Abilities of the Novel Complex
Cp*TiMe(C6F5)(m -Me)B(C6F5)3
S. Ewart, M. Sarsfield and M.C. Baird*, Department of Chemistry, Queen's University,
Kingston (Ontario), Canada K7L 3N6.
The
novel monopentamethylcyclopentadienyltitanium complex Cp*TiMe(C6F5)
(1) has been synthesized
via
the reaction of Cp*TiMe2Cl with Li(C6F5) at 195 K. B(C6F5)3
reacts with 1 to abstract a methyl group,
forming
the methyl-bridged species Cp*TiMe(C6F5)(m -Me)B(C6F5)3 (2). Complex 2 is unstable above
283
K; it has not been isolated, but has been observed in the NMR. 2 has also been
shown to be an active
catalyst
towards the polymerization of a variety of a-olefins. Both complexes 1 and 2 exhibit interesting
NMR
spectra due to fluorine coupling to the terminal methyl group. The spectra, reactivity and
polymerization
abilities of these complexes will be compared to the analogous complexes
Cp*TiMe3 and
Cp*TiMe2(C6F5)(m -Me)B(C6F5)3.
11:05-11:25 Rhodium(l) Mixed Phosphine/Amine
Complexes:
Synthesis, Structure and
Reactivity
Maria G.L.
Petrucci. Anne-Marie Lebuis, Ashok K. Kakkar*,
Department of Chemistry, McGill University, Montreal (Quebec), Canada H3A 2K6
Rh(l)
complexes are amongst the widely known and extensively studied homogeneous
catalysts. Ligand dissociation is an
important first step in such reactions.
We have embarked on the synthesis and detailed study of the chemistry of
Rh(l) complexes containing Cl, CO, PR3 and primary/secondary/or
tertiary amine ligands. These d8-Rh(I)
complexes are easily accessible via bridge-splitting reactions, and are
extremely stable. The amine ligand is
sufficiently labile in these complexes, and its substitution chemistry under
the influence of donor ligands will be discussed. The structurally characterized RhCI(CO)(PPh3)(NEt2H)
complex reacts with perhaloalkanes such as CX4 (X= Cl, Br, 1) to
yield the anionic complex [(PR3)(CO)RhX4]-[NR2H2]+. A detailed look at this reaction including
its crystal structure will also be presented.
11:25-11:45 Methyl(hydrido)platinum(IV) Complexes
that are Resistant to Reductive
Elimination, Including the First (m-Hydrido)diplatinum(IV) Complex
Geoffrey S.
Hill, Jagadese J. Vittal and
Richard J. Puddephatt, Department of Chemistry, University of Western Ontario,
London (Ontario), Canada N6A 5B7
The complex fac-[PtMe3(O3SCF3)(bu2bpy)]
(bu2bpy = 4,4’-di-tert-butyl-2,2’bipyridine)
reacts with NaBH4 to afford the cationic [Pt2(m-H)Me6(bu2bpy)2]O3SCF3
(1). This is the first
example of a (m-hydrido)diplatinum(IV) complex. Complex 1 is indefinitely stable at
room temperature, both as a solid and in solution, which allowed full
characterization by 'H and 295Pt NMR spectroscopy and X-ray
crystallography. The presence of a
large excess of NABH4 results in formation of an equilibrium mixture
of 1 and two equivalents of [PtHMe3(bu2bpy)] (2).
These new
methyl(hydrido)platinum(IV) complexes 2 and 1, which have no ligand
which can easily dissociate, are thermally stable to reductive elimination of
methane and to isotopic exchange within PtD(CH3) groups, thus giving
strong support to the theory that both reactions occur within a 5-coordinate
intermediate [PtHMe2(bu2bpy)]+.
11:45-12:05 Preparation,
Characterization, and Reactivities of Cationic, Indenyl Complexes of Ni
Rainer
Vollmerhaus,
Isabelle Dubuc, and D. Zargarian, Departement de Chimie, Universite de
Montreal, Montreal (Quebec), Canada H3C 3J7.
This
presentation will discuss our recent results in the preparation, characterization, and reactivity studies of the
cationic complexes [(Ind)Ni(PR3)L]+ (L= PR'3,
RCN, amine, olefin, etc.).
12:05-1:30 LUNCH
Session
Chair: Ms. Maria Petrucci
1:30-1:50 Homogeneous
Transition-Metal Catalysis of Claus Chemistry
Alan Shaver, Helene L.
Boily, Mohammad El-khateeb, Anne-Marie Lebuis, Department of Chemistry,
McGill University, Montreal (Quebec), Canada H3A 2K6
The Claus Process converts H2S and SO2 to H2O
and S8
(2H2S +
SO2 à 3/8S8 + 2H20). It is the second step in the
process whereby sulfur is removed from crude oil, the first being
hydrodesulfurization (HDS). The H2S
produced by HDS is partially oxidized and combined with SO2 over
alumina in a highly efficient process whose mechanism, nevertheless, is
unknown. We have developed three
conceptual models of the Claus process (shown below) and will report on studies
directed towards homogeneous transition metal mediated Claus chemistry. For example, treatment of (PPh3)3PtS3O2
with a source of RS+ gave complexes containing the Pt-S(O)2-SR moiety. In addition, combination of cis-(PPh3)2pt(SH)2 with SO2 gave (PPh3)2ptS3O and H2O; a
reaction which mimics Claus chemistry. Both
the latter complex and its precursor catalyse Claus chemistry.
1:50-2:10 CO/Imine
Insertion into Palladium Methyl Bonds:
Rania Dghaym and Bruce Arndtsen, Department of Chemistry, McGill
University, Montreal (Quebec), Canada H3A 2K6
The Pd catalyzed alternating co-polymerization of imines and CO is being
investigated as a potential general and flexible route to peptides and their
derivatives. The alternating insertion
of imine and CO into the palladium carbon bond of L2PdR+X-
(where L2 is a bidentate N or P ligand and X- is a non
coordinating counterion) is expected to yield a poly-amide backbone, in analogy
to olefin/CO co-polymerization systems.
Initial studies have shown that the addition of imine to L2Pd(CH3)+X-
results in imine coordination through nitrogen, generating L2Pd(CH3)(RN=C(H)Tol)+Otf-
. While these complexes am inert towards insertion, addition of CO yields
the palladium acyl complex, which under mild heating results in the clean
formation of the palladium bound amide L2Pd[C(H)ToIN(R)COCH3]+Otf-. These complexes have been structurally
characterized to be chelated to the palladium center through the amide oxygen,
formed by an unusually thermodynamically and kinetically favorable insertion of
imine into the palladium-acyl bond. The
effects of different bidentate ligands, solvents, and Lewis acid co-catalysts
upon the elaboration of this reaction into co-polymerization process are
currently being examined.
2:10-2:30 Preparation
and Properties of
(Cyclopentadienyl)Vanadium Cluster Compounds
Colin D. Abernethy, Frank Bottomley and Andreas Decken, Department of Chemistry,
University of New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada.
Inorganometallic clusters are of interest since they contain electrons
which occupy delocalized non-bonding orbitals.
These cluster electrons give rise to many unusual magnetic properties. The antiferromagnetic cluster [Cp*VCl2]3
was synthesized from VCl3(thf)3 and Bu3SnCp*. It was oxidized by NaN3 to [Cp*V2(N)Cl]2
, and by O2 to Cp*VCl2(O). Reduction of [Cp*V(N)Cl]2 by
Na/Hg, Mg or Li3N
gave the
diamagnetic cubane[Cp*VN]4.
Reduction of Cp*VCl2(O) gave the paramagnetic cubane [Cp*VO]4
as well as [CP*V]4(O)6. The magnetic and electrochemical
properties of these clusters will be discussed.
2:30-2:50 Reactivities
of B2cat2 and B2cat3 Toward Low
Valent Rh(I) Complexes
C. Dai
and T.B. Marder, Department of Chemistry, University of Waterloo, Waterloo
(Ontario), Canada N2L 3GI; A.J. Scott, W. Clegg, Department of Chemistry,
University of Newcastle upon Tyne, England, NEI 7RU; N.C. Norman, School of
Chemistry, University of Bristol, Bristol, England BS8 ITS.
The complex [(Pme3)4RhMe] (3) reacts with B2cat2
(1) (cat=1,2-O2C6H4) yielding the
electron-rich Rh(l) boryl complex [(Pme3)4Rh(Bcat)] (4)
and MeBcat (5). However, the reaction of (3) with B2cat3
(2) also gives rise to MeBcat (5) and [(PMe3)4Rh][Bcat2]
(6). Furthermore, a series of novel
Rh(l) Zwitterion complexes of (h6-catBcat)RhL2 can
be readily synthesized by the reaction of (acac)RhL2 with B2cat3.
The reactivities of B2cat2 and B2cat3
will be discussed.
2:50-3:10 Kinetics
and Mechanism of Oxidative Addition of HER3 (E = Si, Ge, Sn,
R = phenyl or alkyl) to H2Os3(CO)10
Robert J. Hall, Jerome B. Keister, Dept. of Chemistry, SUNY at Buffalo, USA.
The study of oxidative addition of hydrogen containing compounds has
been quite extensive for catalysts containing one metal center. Previous workers have described the addition
of HER3 compounds to H2Os3(CO)10 to form complexes H3Os3(CO)10-nER3n.
The kinetics and
mechanism of these additions to H2Os3(CO)IO, an unsaturated cluster have
been investigated. The results show
that the reaction is first order in cluster and first order in HER3. This study is the first of its kind for a
cluster. The results of this study will
be compared with the oxidative additions of similar HER3 compounds
to a square planar system from the literature.
3:10-3:40 COFFEE BREAK
Session Chair: Ms. Virginie Guillemette
3:40-4:00 Metal
Catalyzed Transformations of Phosphacumulenes
David
S. Glueck,
Marie-Anne David, John B. Alexander, Denyce K. Wicht, Michael A. Walters, Department
of Chemistry, Dartmouth College, Hanover, NH 03755, USA
The phosphacumulenes Mes*PCX [Mes* = 2,4,6-(t-Bu)3C6H2;
X = CPh2 (1); X = NPh (2); X = 0 (3)]
undergo a variety of novel reactions catalyzed by low-valent Rh, Pd, and
Pt complexes. Catalytic isomerization
of 1, dimerization of 2, and decarbonylation of 3 will be
described, along with mechanistic information obtained from related
stoichiometric reactions.
4:00-4:20 Synthesis
and Characterization of Elastomeric Poly(propylene) using Novel Zirconium
Catalysts
Anna Bravakis, William J. Gauthier and Scott Collins, Department of Chemistry,
University of Waterloo, Waterloo (Ontario), Canada N2L 3GI.
We and others have reported that elastomeric poly(propylene) (eIPP) can
be prepared using unsymmetrical, ansa-titanocene and hafnocene catalysts (e.g.
Me2Si(Ind)(Cp)MCI2) in combination with MAO under a
variety of conditions. An alternative
approach, which lead to the synthesis of eIPP with quite different physical
properties, involves the use of "oscillating" metallocene catalysts
(e.g. (2-Ph-Ind)2ZrCI2)-
In this
presentation, we will describe the synthesis and characterization of a
representative member of a family of unsymmetrical zirconocene complexes, which
combine both high activity and the production of higher MW, stereoregular,
poly(propylene) such that elastomeric material is produced. The response of these systems to changes in
polymerization conditions, in terms of mechanisms for propagation, and the
physical properties of eIPP will be discussed.
4:20-4:40 Mechanism
of Inhibition of Protein Tyrosine Phosphatases by Vanadate and
Pervanadate
Gregory Huyer, John Kelly, Michael J. Gresser, and Chidambaram Ramachandran, Department of
Biochemistry,
Merck Frosst Centre for Therapeutic Research, Pointe-Claire - Dorval (Quebec),
Canada
H9R 4P8
Vanadate and pervanadate (the complexes of vanadate with hydrogen
peroxide) are two commonly used general protein tyrosine phosphatase (PTP)
inhibitors. These compounds also have
insulin mimetic properties, an observation that has generated a great deal of
interest and study. As a careful
kinetic study of the two inhibitors has been lacking, we sought to analyze
their mechanisms of inhibition. Our
results show that vanadate is a competitive inhibitor for the phosphatase
PTP1B, with a Ki of 0.38 `O
0.02 EM. EDTA, which is known to
chelate vanadate, causes an immediate and complete reversal of the inhibition
due to vanadate when added to an enzyme assay.
Pervanadate, by contrast, inhibits by irreversibly oxidizing the
catalytic cysteine of PTP1B, as determined by mass spectrometry. Reducing agents such as DTT that are used in
PTP assays to keep the catalytic cysteine reduced and active were found to convert
pervanadate rapidly to vanadate. Implications
for the use of these compounds as inhibitors and rationalization for some of
their in vivo effects are considered.
4:40-5:00 Metal-Ligand
Orbital Mixing Ruthenium(II) Complexes
Elaine S, Dodsworth, Mehrdad Ebadi, Sergei I. Gorelsky and A.B.P.
Lever, Dept. of Chemistry, York
University, North York (Ontario), Canada M3J IP3
Several techniques, especially electronic spectroscopy, electrochemistry
and ZINDO calculations, are used to explore metal-ligand bonding in some series
of mixed-ligand ruthenium(II) complexes containing N-donor ligands. The ligands studied, 2,2'-bipyridine,
2,2'-bipyrazine, azopyridine and benzoquinonediimine, have quite widely varying
donor and acceptor abilities and consequently show very different degrees of
metal-ligand orbital mixing in their complexes. Our understanding of these systems should be helpful in the
design of conducting polymeric systems containing transition metals.
5:00-5:20 C-S
and C-H Bond Cleavage Reactions of Cyclopentadienyl-Titanium Thiolate
Complexes
Andrea Firth and Douglas
Stephan, Department of Chemistry and Biochemistry, University of Windsor,
Windsor (Ontario), Canada N9B 3P4
The reactivity of cyclopentadienyl-titanium thiolates were studied by
moderating the accessibility of the coordination sphere about titanium as well
as adjusting the electrophilicity at the metal centre. Thermally induced C-S bond cleavage
reactions of complexes of the form CpTi(SR)xL3-x
afforded both dimeric and cluster compounds depending on the thiolate
substituents. In contrast, the thermal
reaction of CpTiMe(SEt)(OR) lead to C-H bond activation and the
metallacyclopropane species [CpTi(SCHMe)(OR)]2. These disparate reaction pathways will be discussed.
Session Chair:
Dr.
Ross D. Markwell
10:45-11:05 Architectural
and Molecular Weight Control in the Transition Metal Catalyzed
Ring-Opening Polymerization (ROP) of Silicon-Bridged
[l]Ferrocenophanes
Paloma Gomez-Elipe, Peter M. Macdonald and Ian Manners, Department of Chemistry,
University of Toronto, Toronto (Ontario), Canada M5S 3H6
Our recent studies which have shown that transition metal-catalyzed ROP
of silicon-bridged [1]ferrocenophane permits convenient control of both the
architecture and molecular weight of the resulting
poly(ferrocenylsilanes). Thus
Pt-catalyzed ROP of the unsymmetrical species Fe(h-C5Me4)(h-C5H4)SiMe2
yielded the regioregular polymer [Fe(h-C5Me4)(h-C5H4)SiMe2]n.
Treatment of the symmetrical [1]ferrocenophane [Fe(h-C5H4)SiMe2]
with Pt catalyst in the presence Of Et3SiH allowed the molecular
weight of the resulting poly(ferrocenylsilane) to be controlled from MW
= 2,000 - 100,000. The presence of Et3Si and SiH end groups was
confirmed spectroscopically. Use of
poly(methylhydrosiloxane) materials as the Si-H source allowed the synthesis of
novel poly(siloxane)-graft-poly(ferrocenylsilane) copolymers.
11:05-11:25 Substitution
Chemistry of Ti(Ill) Amido Complexes with Pyridine Derivatives and
Pyrazine
Istvan Kovacs, Ludmila
Scoles, Michel Dionne and Sandro Gambarotta, Department of Chemistry,
University of Ottawa, Ottawa (Ontario), Canada K1N
6N5
The "ate" complexes (R2N)2Ti(m-Cl)2Li(TMEDA) (R
= i-Pr, Cy) (1) containing a stabilized "(R2N)2TiCl"
unit, an analogue of "Cp2TiCl", readily undergo
LiCI(TMEDA) displacement by pyridine (py), t-butyl pyridine (tBupy),
2,2'- and 4,4'-dipyridyl (bipy) as well as pyrazine (pyr). Complexes (R2N)2Ti(py)Cl
were found to maintain an equilibrium with the dimer [(R2N)2TiCl]2(C5H5N)2
(2) through the novel dearomatization and tail-to-tail radical coupling
of two pyridine ligands. Steric
hindrance in (R2N)2Ti(tBupy)Cl (3), however,
prevented dimerization. Dinuclear
complexes of the type [(R2N)2TiCl]2(N N) were isolated from the
reaction of 1 with 4,4'-dipy and pyr and exhibited extensive spin
pairing through the ligand p-system. Reactions with
2,2'-dipy resulted in the formation of pentacoordinated (R2N)2Ti(dipy)Cl
(4). Crystal structures and
other characteristics of 1-4, as well as some chemistry of 4 will
be presented.
11:25-11:45 Lego:
Building Blocks for Inorganometallic Polymers
Ralph Ruffolo, M. Stradiotto,
T. Kuhnen, M.J. McGlinchey and M.A. Brook, Department of Chemistry,
McMaster University, Hamilton (Ontario), Canada L8S
4MI
The interesting optical and conducting properties of inorganometallic
polymers have led many research groups to prepare and study linear compounds
which contain main group elements in the backbone. Our research group has found that hydrosilylation of silanes with
allylsilanes provides a facile route to linear compounds of this type. In all model studies, the allylsilane used
was trimethylsilylethynyldimethylallylsilane and the crosslinking agents
included diphenylsilane and 1,2-tetramethyldisilane. Another goal was to incorporate sites that allow transition
metals to be added after synthesis of the organometallic backbone. Dimeric species, incorporating
(arene)chromiumtricarbonyl and/or cobalt clusters have been synthesized and
characterized by X-ray crystallography.
11:45-12:05 Electrochemical
Lithium Insertion in a New Class of Polymer (and Monomer)-Intercalated
Molybdenum Oxides
T.A. Kerr, H. Wu, L.F. Nazar, Department of Chemistry,
University of Waterloo, Waterloo (Ontario), Canada N2L 3G I
The MoO3 host lattice is eminently
suitable for Li insertion reactions owing to its layered structure, and
therefore has been proposed as a cathodic material in secondary lithium
batteries and electrochromic devices.
Its reported disadvantages are relatively slow kinetics for Li transport,
an electronically insulating state when fully oxidized, and poor cycling
behaviour. To attempt to enhance these
properties, conductive polymers such as poly(aniline) and poly(pyrrole), or
simply a monomer, aniline, have been incorporated to form novel nanocomposite
materials. The redox capacity of the
intercalated guest can, in principle, both augment that of the oxide and affect
lithium ion transport between the layers by virtue of propping the oxide layers
further apart that in their native state.
The properties of these nanocomposites with respect to electrochemical
Li insertion were compared to those of the alkali molybdenum oxide using the
materials as cathodes in conventional lithium cells. The electrochemical behavioural differences will be presented
herein.
12:05-1:30
LUNCH
Session Chair:
Ms.
Heather Gass
1:30-1:50 Novel
Titanium-Glycolate-Surfactant Mesostructures
Deepa Khushalani and G. A. Ozin, Materials Chemistry, Research
Group, Lash Miller Chemical Labs,
University of Toronto, Toronto (Ontario), Canada M5S
3H6
The synthesis and characterization of novel
titanium-glycolate-surfactant mesostructures will be presented. New sol-gel type precursors were
synthesized, involving six-coordinated titanium glycolate complexes and surfactants,
which on hydrolysis yield interesting new mesophase materials. These structures can be indexed on a
hexagonal unit cell with d100 being ca. 45 oA.
Characterization using powder X-ray diffraction, FT-Raman, FT-IR and UV-Vis
spectroscopy, and thermal analysis will be presented. An analogy is made to five-coordinate silicon glycolate sol-gel
type precursors that have been previously synthesized in our laboratory. These materials have been used for the
formation of mesolamellar structures with a d100 spacing of ca. 30
oA.. They can be subsequently converted into a
siliceous mesoporous hexagonal phase, akin to MCM-41 (d100 spacing
being ca. 34 oA.).1 1. Kresge, C.T.; Leonowicz,
M.E.; Roth, W.J.; Vartuli, J.C.; Beck, J.S. Nature 1992, 359, 710.
1:50-2:10 Phase
Transitions Induced By Ball Milling in Superionic PbSnF4
M. Cecilia Madamba and Georges Denes, Laboratory of Solid State Chemistry and Mossabauer
Spectroscopy, Laboratories for Inorganic Materials, Concordia University,
Montreal (Quebec), Canada.
PbSnF4 is the highest performance fluoride ion conductor know
to date. It undergoes several phase
transitions versus temperature and versus preparation conditions. The following phases are known: orthorhombic
o-PbSnF4 and tetragonal a-PbSnF4 stable at ambient
temperature, tetragonal b-PbSnF4 metastable at ambient temperature, and cubic g-PbSnF4 stable
only at high temperature. The structure
of all phases is closely related to that of b-PbF2 (fluorite-type). Upon ball
milling, all undergo a phase transition to microcrystalline g-PbSnF4, and in
every case, annealing of the ball milled material gives a-PbSnF4.
2:10-2:30 New
Developments in Technetium(VII) and Rhenium(VII) Oxofluoride
Chemistry
Nicolas LeBlond, William
J. Casteel Jr., Helene P.A. Mercier and Gary J. Schrobilgen, Department of
Chemistry, McMaster University, Hamilton (Ontario)
Canada L8S 4M 1.
Fluorination of Tc2O7 by XeF6 in
anhydrous HF has provided the second example of a Tc(VII) oxofluoride, TcO2F3. The volatile adduct, TcO2F3●XeO2F2,
is formed as a by-product of the synthesis of TcO2F3 and
is the first adduct of XeO2F2 to be structurally
characterized by X-ray diffraction. The
fluoride ion affinity of TcO2F3 was investigated and led
to the synthesis and X-ray structure determination of the novel cis-TcO2F4-
anion. Both TcO2F3
and ReO2F3 exhibit fluoride ion donor properties in the
presence of strong fluoride ion acceptors, leading to the isolation of the
adducts, TcO2F3●M'F5 and ReO2F3-M'F5
(M' = As, Sb), and the X-ray structural determination of ReO2F3●SbF5 and TcO2F3●SbF5. The last in
the series of Tc(VII) oxofluoride, TcOF5, was prepared from the
reaction of KrF2 with TcO2F3 and characterized
by vibrational spectroscopy and 99Tc and 19F NMR spectroscopy.
2:30-2:50 ZSM-5
Zeolite with New Microporosity Formed by Desilication and Subsequent
Thermal Treatment
R. Le Van Mao, G. Denes,
S.T. Le and D. Ohayon, Department of Chemistry and Biochemistry,
Concordia University, Montreal (Quebec), Canada H3G
IM8
Controlled desilication of ZSM-5 zeolite using an aqueous solution of
sodium carbonate results in a significant decrease of the Si/Al atom
ratio. There is apparently no
significant change in the structure and the degree of crystallinity of the
zeolite material, although the variation of the Si/Al ratio is as important as
30-40%. Micropores of 0.49nm, i.e.
smaller than those of the parent zeolite, are formed during the desilication. The resulting zeolite shows ion-exchange
(with Ca+2) and catalytic (synthesis of methyl tert-butyl
ether, MTBE) activities much higher than those of the parent zeolite owing to
the increase of the density of Al tetrahedra sites (by unit weight or unit
surface area). Activation of the
desilicated zeolite at a temperature higher than 300ºC, provokes a shift of
these newly formed micropores to 0.56nm in size, resulting in a solid material
with single-sized micropores. This is
probably the origin of further improvements in the ion-exchange and catalytic
performances of the material.
2:50-3:10 Co-ordination
of Thia-Crown Ethers with Nickel, Cobalt, Copper & Iron: The
SIC-LSD-VWN-R Method
M.A. Whitehead, Department of
Chemistry, McGill University, Montreal (Quebec), Canada H3A 2K6
The Self Interaction Corrected Local Spin Density Method with the Vosko,
Wilks and Nazair Correlation terms and the Relativistic Corrections within the
Self Consistent Field Iteration is applied to the co-ordination between the
crown-ether 18S6 and Nickel, Cobalt, Copper and Iron. The dibenzo 18S6 co-ordination compounds are
also studied. Energy Levels and Orbital
Density Diagrams are presented.
3:10-3:40 COFFEE BREAK
Session Chair:
Mr.
Russell Tuling
3:40-4:00 Metal-Ligand
Coupling Elements and Antiferromagnetic Superexchange in Ruthenium Dimers
Robert J. Crutchley, Mark L. Naklicki, Christopher A. White, and Lisa L. Plante, Department
of Chemistry, Carleton University, Ottawa (Ontario), Canada, KIS 5B6
The antiferromagnetic exchange constant can be calculated using
equations developed by Anderson and more recently by Solomon, from the energy,
intensity, and bandwidth of the appropriate ligand-to-metal charge transfer
transition. Creutz, Newton and Sutin
have shown that the equations for the electronic coupling element derived for
charge transfer and mixed-valence complexes by Mulliken and Hush, respectively,
are exact within a two-state model and can be used to obtain metal-ligand
coupling elements. By using these
equations and the solvent dependent LMCT spectral data of a series of [{(NH3)5Ru}2(m-L)]4+
complexes, where L is a substituted 1,4-dicyanamidobenzene dianion derivative,
we have calculated antiferromagnetic exchange constants and compared these values
to those estimated from room temperature magnetic susceptibility. The correlation between these values is
quite good.
4:00-4:20 Influence
of Metal Oxide Modification of Alumina on the Dispersion and Activity of
Vanada Catalysts
L. Jhansi Lakshmi, Elmer C. Alyea, Department of Chemistry and Biochemistry, University
of Guelph, Guelph (Ontario), Canada NIG 2WI
Alumina was modified with 10% MOx (MOx = TiO2,
ZrO2, La2O3 or MgO) prior to its impregnation
with 12wt% vanadia. The catalysts were
characterized by X-ray diffraction (XRD), laser Raman spectroscopy (LRS),
electron spin resonance (ESR) and oxygen chemisorption. The activities of the catalysts were
determined by methanol partial oxidation and their acid-base properties were
evaluated for the decomposition of isopropanol. Metal oxide modification is found to influence significantly the
surface coverage and the methanol partial oxidation activity of vanadia
supported on alumina. With proper MOx
modification enhanced reducibility of vanadia could be attained, which in turn
makes the partial oxidation more facile.
4:20-4:40 Calorimetric
Properties of the Organometallic {[M(dmb)2]Y}n
Polymers
Martin Turcotte, Daniel
Fortin and Pierre D. Harvey, Département de Chimie, Université de
Sherbrooke, Sherbrooke, (Quebec), Canada J1K 2R1
The synthesis of new organometallic {[M(dmb)2]Y]n
polymers have been performed where M = Cu, Ag; dmb = 1,8-diisocyano-p-menthane;
Y = PF6, CH3COO, BF4, NO3, CIO4. DSC (differential scanning calorimetry)
measurements show that these rigid polymers undergo a second-order phase
transition. By means of various
physical techniques, this phase transition is interpreted by a gain of ionic
mobility in the high-temperature phase.
4:40-5:00 Characterization
and Reactivity of Silica Supported Chromium (IV) Fragments
Jamila Nait Ajjou and Susannah L. Scott, Department of
Chemistry, University of Ottawa, Ottawa (Ontario), Canada K1N 6N5.
Cr/SiO2 is a catalyst for ethylene
polymerization, but the nature of the active site and the mechanism of
polymerization is still unknown. We
have prepared well-defined silica-supported alkyl Cr species to test their
activity in polymerization. The
reaction of CrR4 (R= neopentyl, trimethylsilylmethyl) with the
surfaces of partially dehydroxylated silicas leads to the formation of SiOCrR3
(1) and (SiO)2CrR2 (2). A chemisorption mechanism involving
competing protonation by surface hydroxyl groups and a-H elimination is
proposed. The chemisorbed species were
characterized by IR, EPR, UV-Vis and magnetic susceptibility measurements. 1
and 2 are unreactive towards water, CO and olefins at room
temperature. At 60ºC, 2 undergoes
a clean elimination of one alkyl ligand to form (SiO)2Cr=CH(CMe3),
which polymerizes ethylene and propylene.
Possible mechanisms for catalysis will be discussed.
5:00-5:20 Dithiazolyl
Radicals: Enroute to New Molecular Materials
R.W. Reed, A.W. Cordes, J.D. Goddard, R.C. Mahwinney, R.T.
Oakley, N.A. George, H. Zhang, Dept. of Chemistry and Biochemistry, University
of Guelph, Guelph (Ontario), Canada N1G 2W1, and Dept. of Chemistry and
Biochemistry, University of Arkansas, Fayetteville, Arkansas, 72701, USA.
The search for new molecular materials with
conductive and/or magnetic properties has led several research groups to
explore the chemistry and transport properties of heterocyclic thiazyl radicals
and their derivatives. Within this
context the 1,3,2-dithiazolyl system represents a useful building block that
has yet to be closely examined in the solid state. Preparation and characterization of a series of monofunctional
and difunctional 1,3,2-dithiazolyl radicals; along with results from
theoretical, structural and spectroscopic investigations will be discussed.
Sunday, November
3, 1996
Session
I
Otto Maass Room 112
Session Chair: Ms. Rania Dghaym
9:10-9:30 Solid-State
Nuclear Magnetic Resonance Studies of Triphenylsilyl-, Diphenyltin- and
Triphenyltin(pentacarbonyl)manganese(l) Complexes
Dharamdat
Christendat,
Jordan H. Wosnick, Ivor Wharf, Ian S. Butler and Denis F.R. Gilson, Department
of Chemistry, McGill University, Montreal (Quebec), Canada H3A 2K6
Crystal structures and solid-state CP-MAS NMR spectra
of triphenylsilyl, diphenyltin and
triphenyltin(pentacarbonyl)manganese(l) complexes have been
obtained. Second-order quadrupolar
effects were observed and the spectra were analysed to give the one-bond
coupling constants, 1J(Mn-Si) and 1J(Mn-Sn), the 55Mn
nuclear quadrupole coupling constants, the chemical shift anisotropies and the
anisotropy in J, where the analysis permits.
9:30-9:50 The
CNS Model: A New Approach to Metal-Metal Coupling in Mixed-Valence
Complexes
Chris Evans, M.L. Naklicki, A.R. Rezvani, V.K. Kondratiev and
R.J. Crutchley, Department of
Chemistry, Carleton University, Ottawa (Ontario),
Canada K1S 5B6
Metal-metal coupling in dinuclear complexes has traditionally been
expressed either by the simple Hush model, applicable only to weakly coupled
systems, or by more rigorous (and consequently more cumbersome)
treatments. A recent model proposed by
Creutz, Newton, and Sutin (CNS) retains the simplicity of the Hush model yet
exhibits applicability to more strongly coupled systems. Experimental data for a series of strongly
coupled mixed-valence ruthenium complexes are compared to CNS and Hush model
predictions.
9:50-10:10 Photoelectron
Spectra of Trimethylphosphine Substituted Tungsten Carbonyls: Spin-Orbit
Splittings, Ligand Field Effects, Ligand Additivity Effects and Core
Valence Ionization Correlations
Jingcun Wu, G. M. Bancroft, R. J. Puddephatt, Y.-F. Hu and K. H. Tan, Dept. of
Chemistry, University of Western Ontario, London (Ontario), Canada N6A 5B7,
Canadian Synchrotron Light Radiation Facility, University of Wisconsin,
Stoughton, Wisconsin 53589 USA
Gas-phase high resolution broad-scan photoelectron spectra (including
valence, inner valence, and core levels) are reported for a series of PMe3
substituted tungsten carbonyls: W(CO)6, W(CO)5Pme3,
cis-W(CO)4(Pme3)2,and trans-W(CO)4(PMe3)2. The inner valence spectra are interpreted by
comparison with the published results.
He I spectra of the valence levels and W 5d regions of these complexes
are also reported. Spin-orbital
splittings, ligand field effects and vibrational structures are observed
in the spectra of both W 5d and W 4f regions.
The binding energies (or ionization energies) in the spectra of both W
5d valence level and W 4f core level regions are shifted, respectively and
almost linearly, to lower energies with each successive step of ligand
substitution which confirms the ligand additivity model predictions for these
complexes. The Jolly's corevalence
ionization correlation model can also be illustrated in these complexes by
comparison of the core (W 4f) and valence (W 5d) shift data. Spectra of W(CO)4NBD ( the
intermediate product for synthesizing cis-W(CO)4(PMe3)2, NBD=bicycloheptadiene,
norbornadiene) are also reported.
10:10-10:30 Activation
and Catalytic Oligomerization of Primary Phosphines by Group IV and
V Transition Metal Hydrides
Nola Etkin, M. T. Benson, D. W. Stephan and M. J. McGlinchey, Dept. of Chemistry
and Biochemistry, University of Windsor, Windsor (Ontario), N9B 3P4; Dept. of
Chemistry, McMaster University, Hamilton (Ontario), Canada L8S 4M1
The anionic trihydride complex [Cp*2ZrH3]-
catalytically converts primary phosphines to the cyclic oligomers (PR)5. When the reaction is applied
to the difunctional 1,2-bisphosphinobenzene, a highly unusual P16
macrocycle is isolated. In an attempt
to extend this methodology to other, more easily accessible catalyst systems,
the reactions of the neutral Group V trihydrides Cp†2MH3 (M = Nb, Ta;
Cp† = Cp, Me3SiCp)
with primary phosphines were examined.
Although no catalytic activity was observed, the phosphanato complexes
Cp†2MH(PR)2 were
formed cleanly. The parent complex, Cp2TaH(PH)2
was prepared by the reaction of Cp2TaH3 with white
phosphorus. This complex, although
similar in structure to the substituted derivatives, displays fluxional
behavior, suggesting a rapid equilibration between two or more conformations of
the metallacycle.
10:30-11:00 COFFEE
BREAK
11:00-11:20 Hydrosilation/Hydrogenation
of Pyridines with PhMeSiH2 Catalyzed by Dimethyltitanocene
Ronghua Shu, Leijun Hao and John F. Harrod, Department of
Chemistry, McGill University, Montreal (Quebec), Canada H3A 2K6
Dimethyltitanocene catalyzed hydrosilation/hydrogenation of series of
pyridine compounds including pyridine, 3-picoline, 4-picoline, 3,5-lutidine was
studied. This is the first time that
the hydrosilation of pyridines was achieved under homogeneous catalytic conditions. The proposed mechanism which involves the
formation of a pyridyl silyl titanium compound has been discussed.
11:20-11:40 Indenyl
Phthalimido and Succinimido Complexes of Ni: Preparation,
Characterization,
Bonding and Reactivities
Isabelle Dubuc and D. Zargarian, Département de Chimie,
Université de Montréal, Montreal (Quebec), Canada H3C 3J7
This presentation will show that complexes of the type (Ind)Ni(PR3)NRR'
are stable only when R and R' are strongly electron withdrawing groups;
otherwise, strong p(p)N-d(p)Ni interactions lead to decomposition. The main spectroscopic and structural
features of these complexes, as well as their reactivities, will be discussed.
11:40-12:00 Organometallic
Chemistry of Group 5 and 6 Metals involving Amido Ligands
Kamalesh Babu P. Ruppa and Sandro Gambarotta,
Department of Chemistry,
University of Ottawa, Ottawa (Ontario), Canada KIN 6N5
Early transition metal chemistry with amide
ligands have attracted considerable interest because of some important
transformations performed by the species which includes N2 activation, NO cleavage, C-H
bond metathesis, H-transfer etc.
Currently, we are investigating the reactivity of Group 5 and 6 metals
with new bulky amide ligand, L(L = N(Ad)(C6H3Me2-3,5)).
In particular the reactivity studies of the corresponding Chromium and Niobium
amido complexes will be presented.
Reaction of [CrL2(THF)2] or [CrL3] with
O2 yielded [CrL2O2]
which has been structurally characterized.
Conproportionation reaction occurs between [CrL2O2]
and [CrL2(THF)2] to give Cr(IV) dioxygen bridged dimer.
The abstraction of oxygen from these Cr-O complexes by various alkenes
is under investigation. The reaction of
[NbCl4(THF)2] with LiL in a ratio of 1:3 gave [NbL3Cl]. Niobium trisamido methyl and ynolate
derivatives were also been synthesized starting from [NbL3Cl]. The structural and spectroscopic aspects of
these complexes will be discussed.
12:00-12:20 Synthesis
and Characterization of a Novel Transition Metal Fulleride
D.M. Thompson, L. French,
E. Jandciu, D.K. Patel and M.C. Baird, Dept. of Chemistry, Queen's University,
Kingston (Ontario), Canada K7L 3N6
While considerable attention has been paid to
the superconducting alkali metal intercalates of C60, relatively
little has been given to the corresponding transition metal intercalates. Reactions of C60 with Na[Co(CO)4]
in THF have been studied. A complete
loss of intensity of the carbonyl absorptions in the IR is observed during the
reaction. We have determined that a) the
stoichiometry of the product is Na(Co C60)2.xTHF,
b) there is a one electron reduction of the fullerene, c) cobalt is coordinated
to the fulleride, d) the compound has two unpaired electrons, and e) the
product is a weak antiferromagnet. We
are currently synthesizing crystals so that we may solve the product's
structure using x-ray diffraction.
Similar results are obtained when Na2[Fe(CO)4] is
reacted with C60, while the reaction of Na[CpFe(CO)2]
with C60 results in the generation of [CpFe(CO)2]2
and NaC60.
Sunday, November 3, 1996
Session 11
Otto Maass Room 10
Session Chair: Ms. Clare Edwards
9:10-9:30 Skeletal
Substitution of Boron in a Cyclic Boratophosphazene: A Novel Route to
New Group 15
Heterocyclophosphazenes
Derek P. Gates, Louise M. Liable-Sands,
Glenn P.A. Yap, Arnold L. Rheingold and Ian Manners, Department of Chemistry,
University of Toronto, Toronto (Ontario), Canada M5S 3H6; Department of
Chemistry and Biochemistry, University of Delaware, Newark, Delaware, 19716 USA
An unusual example of a skeletal ring atom
substitution reaction has been discovered in which the BX2 group in a boratophosphazene
ring is replaced by, for example, AsX4 or SbX4 fragment to provide a
convenient route to inaccessible heterocyclophosphazenes. Details of this reaction and full
characterization of the newly synthesized heterocycles will be presented.
9:30-9:50 Oligothiophenes
End-Capped by Nitriles - Preparation and Structures of a,w-dicyanooligothiophenes NC-(C4H2S)n-CN
(n = 3-6)
C.D. MacKinnon, R.T. Oakley
and R.W. Reed, Department of Chemistry and Biochemistry, University of Guelph,
Guelph (Ontario), Canada, N1G 2W1; T.M. Barclay and A.W. Cordes, Department of
Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas, 72701
USA
Oligothiophenes have shown great promise in being
useful materials in electronic devices.
In spite of this, and due to the nature of the compounds, very little
crystallographic data has been reported.
In this paper, the synthesis of a series of (a,w-dicyano substituted
oligothiophenes NC-(C4H2S)n-CN is
described. Crystals suitable for X-ray
crystallographic analysis were grown by sublimation, and the structures are
reported. The electronic nature of
these compounds will be discussed, based on the results of UV-visible
spectroscopy and MNDO calculations.
9:50-10:10
Registered Growth of Mesoporous Films
Hong Yang and Geoffrey Ozin, Materials Chemistry Research
Group, Lash Miller Chemical Laboratories, University of Toronto, Toronto (Ontario),
Canada M5S 3H6
Templated deposition of inorganic films at structured
interfaces is an important endeavor in terms of both the basic materials
and the technological ramification of using them in diverse applications in
catalysis, separation and nanostructured materials. It has been demonstrated that the structured interfaces of
surfactant micellar assemblies and liquid crystals can function as templates
for the deposition of silicatcs to form mesoporous silica Powders, Recently
mesoporous silica films grown on structured interfaces, such as
solid-water, airwater and oil-water interfaces in an oriented fashion have
been reported (See Nature, 379, 703 (1996); ibid, 381, 589
(1996); Science, 273, 768 (1996); ibid, 273, 892
(1996)). Here we present our recent
research on the micellar based assembly of surfactant-silica mesoporous films
with a focus on registered growth on atomically flat surfaces, such as, freshly
cleaved mica and high quality pyrolytic graphite.
10:10-10:30 Electroluminescent
Materials Containing Transition Metal Luminophores
Jonathan Veinot, W.J. Pietro, Department of Chemistry, York
University, North York, Toronto (Ontario),
Canada M3J I P3
Recently, a new approach to electronic excitation, including luminescence, has received much attention. It has been shown that the application of an electric field on to a luminescent material may result in the emission of light. Existing studies have primarily been confined to conventional semiconductors and highly conjugated organic compounds. We have shown that transition metal complexes, incorporated into polymer matrices, can exhibit electroluminescent behaviour. Through careful design, these species may in fact be easily wavelength tuneable for varied applications through the modification of the ligand environment of the transition metal center.
10:30-11:00 COFFEE
BREAK
11:00-11:20 Synthesis,
Reactivity and Structure of Alkylamidinate Germanium(IV)
Chalcogenido Complexes
S. Foley, D. Richeson, Department of Chemistry, University of Ottawa, Ottawa
(Ontario),
Canada K1N 6N5
As part of our general interest in the synthesis and coordination
chemistry of bulky alkylamidinates, [RNC(R')NR]- (R = cyclohexyl;
R'= CMe3, Me), we are exploring their use as ligands in
organometallic and coordination compounds of the post-transition metals. We will report on the synthesis of a new
family of Ge(II) complexes which have been characterized by spectroscopic and
X-ray crystallographic analysis. Reactions
of Ge(Il)[CyNCR'NCy]2 with styrene sulfide and elemental selenium
produce unique monomeric terminal chalcogenido-germanium complexes. Investigations into atom transfer reactions
of chalcogenido M(IV) alkylamidinate complexes with M(II) alkylamidinates will
also be presented and the features which differentiate these reactions will be
discussed.
11:20-11:40 Electrochemical
Li Insertion in Layered and Tunnel-Structure Manganese Oxides
M.J. Duncan, F. Leroux, L.F. Nazar, Department of Chemistry,
University of Waterloo, Waterloo
(Ontario), Canada N2L 3G1
New oxide materials are being sought for the advancement of Li rechargeable battery technology. Various manganese oxides have been examined as active cathode materials. We report here a comparison of the electrochemical properties of a tunnel-structured manganese oxide, todorokite, its layered precursors birnessite and buserite, and organic-cation modified material. Mg+2 cations residing in the interlayer gallery of the [MnO6l octahedral sheets of buserite are believed to act as 'templating' agents during the hydrothermal synthesis of todorokite. Lithium intercalation has been studied in these different manganese oxide systems which revealed differences in terms of capacity and cyclability with the nature and morphology of the manganese oxide (2D vs. 3D). We report here, the first studies of Li intercalation into todorokite.
11:40-12:00 Site-Specific
Oxygen-18 Labeling of Silica-supported Vanadium(V) Complexes Derived
from Molecular Precursors for the Determination of Catalytic
Oxidation
Gordon
Rice and
Susannah Scott, Department of Chemistry, University of Ottawa, Ottawa
(Ontario), Canada K1N 6N5
The
gas phase reactions of O=VCl3 and O=V(OiPr)3
with the hydroxyl groups of amorphous silica yield the well-defined surface
complexes ≡SiOV(O)X2.
These complexes have been characterized by 51V MAS and 13C
CP-MAS NMR and infrared spectroscopies.
The incorporation of isotope labels into specific positions of the
supported transition metal complexes has also been accomplished. For example, we can prepare ≡SiOV(18O)X2
and ≡Si18OV(O)X2. The surface complexes undergo
clean ligand substitutions, for example, with alcohols to form
≡SiOV(O)Cl(OR) and ≡SiOV(O)(OR)2. These reactions do not displace or dilute
the isotope labels. By isotope analysis
of the products, we have demonstrated that thermal and photochemical oxygen
transfer reactions of ≡SiOV(O)Cl2 with the substrates ArNCO
and CO involve only the terminal oxo ligand.
12:00-12:20 Metal Stabilized Cyclopentadienyl
Cations
James A. Dunn, Ralph Ruffolo, Suzie Rigby, Dr. M.J. McGlinchey* and Dr. M.A. Brook*,
Department of Chemistry, McMaster University, Hamilton (Ontario), Canada L8S
4M1.
It has recently been established that a wide variety of organometallic
moieties have the ability to provide anchimeric assistance to
electron-deficient centers. We are
interested in the stabilization of cyclopentadienyl cations. Although cyclopentadienyl anions are stable,
the cations are anti-aromatic. Our
efforts have been focussed towards the synthesis of cobalt-stabilized alkynylcyclopentadienyl
cations. These species exhibit
fluxional processes which can be elucidated by variable temperature NMR. In addition, we have been able to obtain
X-ray crystallographic data of the mixed metal cluster
(TMS-C≡C-fluoreny])FeCo(CO)6, effectively a fluorenyl
cation.
End of Meeting