Educational Background:

PhD, California Institute of Technology, 1981 BS, Massachusetts Institute of Technology, 1976

Awards:

• Fellow, American Academy of Arts and Sciences • Casimir Funk Natural Science Award, Polish Institute of Arts & Sciences of America (1998) • Dow Chemical Co., Synthesis Technical Advisory Board • Visiting Miller Research Professorship, Univ. California, Berkeley (1995) • Fellow, Alfred P. Sloan Foundation • Union Carbide Innovation Recognition Program 1988 • Chair, Organometallic Subdivision, ACS Division of Inorganic Chemistry, 1994-95 • Executive Committee, ACS Division of Inorganic Chemistry, 1991-93 • Consultant, Teltech Resource Network

Research Description:

The interests of our group encompass the synthesis, reactivity and applications of transition metal complexes, primarily those of the early metals (groups 4-7).

Using sterically bulky ligands (e.g, silox(^tBu₃SiO), ^tBu₃SiNH, ^tBu₃SiN and tritox (^tBu₃CO)), we have explored the reactivity of low coordinate metal centers that cleave CX (X = H, C, heteroatom) bonds. Transient imido derivatives such as (silox)₂Ti=NSi^tBu₃ reversibly add R-H bonds to form (silox)₂(^tBu₃SiNH)TiR; isotope effects of these 1,2-RH-addition and 1,2-RH-elimination events are currently under study. Indirect evidence of d⁰ alkane complexes, such as the methane complex (^tBu₃SiN)₃W(CH₄), has recently been obtained.

(silox)₃Nb(h²-C,N-py), an unusual h²-pyridine complex, afforded (silox)₃Nb=CH-HC=CH-HC=CH-N=Nb(silox)₃ and free py upon thermolysis, while related C-N bond cleavage reactions were observed for similar picoline complexes. More recently, thermolysis of [(silox)₃Nb]₂(µ:h²,h²-C₈H₈) has yielded a dehydrogenation product, [(silox)₃Nb]₂(µ:h²,h²-C₈H₆), a cyclooctatrieneyne species.

Metal-metal bonds that possess intriguing structural characteristics or exhibit unusual reactivity are also under study. Bonds of cylindrical symmetry appear to maximize metal-metal :-bonding in heterobimetallic species, as evidenced by the 2.21 Å bond distance in Ti(µ-OCMe₂CH₂Ph₂P)₃Rh. The Re+Re bond in [(silox)₂Re(O)]₂ is strong enough to discourage µ-oxo formation in favor of terminal oxo ligands.

Our solid state effort is focused on a new class of materials termed Covalent, Metal-Organic Networks (CMON). Dihydroxyfunctionalized organic spacers are combined with various early metal alkoxides to yield 1- (e.g., ladder compound, [cis-Ti(µ_1,7-OC₁₀H₆O)₂(py)₂]:), 2- (e.g., planar [trans-Ti(µ_1,4-OC₆H₄O)₂(py)₂.py]:) and 3-dimensional (e.g., [Ti₂(µ_1,4-OC₆H₄O)₂(µ_1,4:h₂,h₁-OC₆H₄O)₂(OH₂)₂.(H₂O)₂.(HOC₆H₄OH).2(MeCN)]:) crystalline solids. Approaches to conventional polymers are centered on imido bridging ligands, while dendridic species contain quinone linkages that foment intermetallic communication. Our network solids are related via a similar theme. We have used quinones to prepare extended networks such as [{(OC₆H₄O)(HOC₆H₄O)}₂Ti(µ-OC₆H₄OH)₂]: and various solvated derivatives.

Analytical methods employed include NMR (solution and solid state), IR, EPR and UV-VIS spectroscopies, and X-ray diffraction experiments, including utilization of the facilities at the Center of High Energy Synchrotron Studies (CHESS). Molecular orbital calculations (Extended Hückel, GAMESS, DFT) are routinely used to augment experimental studies. Mechanistic investigations involve kinetics, isotopic labeling, and the trapping of reactive intermediates, while synthetic techniques range from conventional solid-state, Schlenk and dry-box manipulations to utilization of high vacuum systems.

Selected Publications:

Sydora, O. L.; Wolczanski, P. T.; Lobkovsky, E. B. Ferrous Wheels, Ellipse [(^tBu₃SiS)FeX]_n and Cube [(^tBu₃SiS)Fe(CCSi^tBu₃)]₄. Angew. Chem. Int. Ed. 2003, 4, 22685-2687.

Veige, A. S.; Slaughter, L. M.; Lobkovsky, E. B.; Wolczanski, P. T.; Matsunaga, N.; Decker, S. A.; Cundari, T. R. Symmetry and Geometry Considerations of Atom Transfer: Deoxygenation of (silox)₃WNO and R₃PO (R = Me, Ph,^tBu) by (silox)₃M (M = V, NbL (L = PMe₃, 4-picoline), Ta; silox = ^tBu₃SiO). Inorg. Chem. 2003, 42, 6204-6224.

Sydora, O. L.; Wolczanski, P. T.; Lobkovsky, E. B.; Rumberger, E.; Hendrickson, D. N. First row wheels {(^tBu₃SiS)MX}₁₂ (M = Co, X = Cl; M = Ni, X = Br) are common amidst simpler (e.g., [(^tBu₃SiS)Ni]₂(m-SSi^tBu₃)₂) and more complex (e.g., [(m-SSi^tBu₃)Ni]₅(m₅-S)) aggregates. Chem. Commun. 2004, 650-651

Chadeayne, A. R.; Wolczanski, P. T.; Lobkovsky, E. B. The Course of (R₂R'SiO)₃TaCl₂ (R = ^tBu, R'= H, Me, Ph, ^tBu (silox); R =ⁱPr, R' = ^tBu, ⁱPr) Reduction is Dependent on Siloxide Size. Inorg. Chem. 2004, 43, 3421-3432.