STEREOCHEMICAL NONRIGIDITY IN HETEROBIMETALLIC COMPLEXES CONTAINING THE BENT METALLOCENE THIOLATE FRAGMENT

The physical properties and reactions of Cp2Ti(S-p-C6H4X)2 (1) and Cp2Ti(mu-S-p-C6H4X)2Mo(CO)4 (2) (X = Cl, H, CH3, OCH3) complexes as well as the mechanism of the Cp site equilibrium process in bimetallic complexes were investigated. Cyclic voltammographs recorded in CH2Cl2 showed two reversible waves for Ti(IV) reversible Ti(III) and Mo(0) reversible Mo(I) processes in 2 and one reversible wave for Ti(iV) reversible Ti(III) in 1. Positions of these waves varied uniformly with the Hammett-sigma-parameter of the X substituent. Variable-temperature H-1 NMR studies provided values for DELTA-G double-ended dagger of the Cp equilibration process which are ca. 30 kJ/mol smaller than DELTA-G double-ended dagger for Cp2Ti(S-p-C6H4X)2 displacement from 2 by CO. This indicates that the fluxional process in 2 does not occur through a ligand dissociation process and argues for a mechanism of pyramidal inversion on sulfur. The X-ray structure for Cp2Ti(mu-S-p-C6H4Cl)2Mo(CO)4 (2a) is reported. Complex 2a crystallizes in the monoclinic space group P2(1)n, with a = 12.396 (7) angstrom, b = 16.78 (2) angstrom, c = 12.838 (9) angstrom, beta = 94.29 (5)-degrees, Z = 4, and V = 2662 (3) angstrom 3. The Ti atom is in pseudotetrahedral coordination environment whereas the Mo is octahedrally coordinated. The S1-Ti-S2 and S1-Mo-S2 angles are obtuse (100.8 (1) and 97.6 (1)-degrees, respectively and Ti-S-Mo angles are acute (80.8 (1)-degrees) in the planar Ti-S2-Mo ring, supportive of metal-metal interactions implied by spectroscopic and electrochemical data. The phenyl groups are in an anti arrangement with respect to the Ti-S2-Mo plane.