SYNTHESIS, REACTIVITY, AND STRUCTURAL CHARACTERIZATION OF THE DINUCLEAR ZIRCONOCENOPHANE COMPLEXES [SIME2(C5H4)2][(C5H5)ZR(MU-X)]2 (X = S, CL)

The treatment of [SiMe2(C5H4)2][CpZrH(mu-H)]2 with elemental sulfur affords the disulfido-bridged dinuclear Zr(IV) complex [SiMe2(C5H4)2][CpZr(mu-S)]2 (1). Ambient photolysis of [SiMe2(C5H4)2]-[CpZrCl(mu-H)]2 proceeds with the reductive elimination of H2 and the formation of the corresponding dichloro-bridged dinuclear Zr(III) complex [SiMe2(C5H4)2][CpZr(mu-Cl)]2 (2). These diamagnetic zirconocenophane compounds have been characterized by H-1 and C-13 NMR measurements, electronic spectroscopy, elemental analysis, and X-ray crystallographic methods. Reactivity studies of 1 and 2 with various Lewis bases were used to evaluate the susceptibility of the Zr-(mu-X)-Zr (X = S, Cl) bridges to cleavage. No detectable reaction of 1 with PMe3, CNMe, or pyridine is observed within the temperature range of 20-130-degrees-C, whereas the addition of PMe3 or THF to 2 is accompanied by the formation of dinuclear paramagnetic Zr(III) adducts, which have been identified in solution by EPR. The reactions of 2 with Ph3P = O and CO2 occur with O atom abstraction giving the oxo-bridged species [SiMe2(C5H4)2]-[CpZrCl]2(mu-O). Compounds 1 and 2 both crystallize in a monoclinic lattice of P2(1)/c symmetry (Z = 4) with unit cell parameters of a = 17.148 (5) angstrom, b = 8.178 (2) angstrom, c = 15.611 (4) angstrom, beta = 91.95 (2)-degrees and a = 17.126 (2) angstrom, b = 8.098 (1) angstrom, c = 15.624 (4) angstrom, beta = 91.16 (2)-degrees, respectively. In each case, the central Zr2(mu-X)2 core is nearly planar with the Zr...Zr interatomic separation being 3.5210 (6) and 3.3853 (4) angstrom in 1 and 2, respectively.