REACTIVITY OF TA(7)-CYCLOHEPTATRIENYL)(ETA(5)-CYCLOPENTADIENYL)M (M=TI, NB) TOWARD DITHIOACETIC ACID - PREPARATION AND CHARACTERIZATION OF (ETA(5)-C5H5)TI(S2CCH3)3 AND (ETA(5)-C5H5)NB(ETA(2)-S2)(S2CCH3)2

A method for the high-yield syntheses (up to 85%) of the two new compo unds (eta5-C5H5)Ti(S2CCH3)3 (1) and (eta5-C5H5)Nb(eta2-S2)(S2CCH3)2 (2 ) from (eta7-C7H7)M(eta5-C5H5) (M = Ti, Nb) and dithioacetic acid, CH3 CS2H, is described. Both compounds are characterized by elemental anal ysis, H-1 and C-13 NMR spectroscopy, infrared spectroscopy, mass spect rometry, and X-ray crystallography. Compound 1 crystallizes in orthorh ombic space group Pbca with a = 16.964(5) angstrom, b = 24.545(10) ang strom, c = 7.832(2) angstrom, V = 3261(9) angstrom3, Z = 8, R = 0.0558 , and R(W) = 0.0655. Compound 1 exists in the crystalline state as dis crete seven-coordinate molecules; the coordination environment of the central Ti(IV) atom is a slightly distorted pentagonal bipyramid. A et a5-C5H5 ring occupies one axial site, two bidentate dithioacetate grou ps occupy four equatorial sites, and a third bidentate dithioacetate g roup spans the remaining axial and equatorial sites. The average equat orial Ti-S distance of 2.619 angstrom is appreciably longer than the a xial Ti-S distance, 2.545(3) angstrom. Compound 2 crystallizes in spac e group P2(1)/c with a = 13.365(2) angstrom, b = 7.906(4) angstrom, c = 13.710(2) angstrom, beta = 96.44(3)-degrees, V = 1440(l) angstrom3, Z = 4, R = 0.038 49, and R(W) = 0.054 75. Crystals of 2 consist of dis crete seven-coordinate molecules; the coordination environment of the central Nb(V) atom is a severely distorted pentagonal bipyramid. A eta 5-C5H5 ring occupies one axial site, and a ''side-on' bonded disulfide , eta2-S2, occupies two equatorial sites. The remaining positions are occupied by two nonequivalent bidentate dithioacetate ligands. A varia ble-temperature H-1 NMR study on 2 shows rapid interconversion between the two dithioacetate environments at 47-degrees-C (DELTAG = 17.1 +/ - 0.1 kcal mol-1).