Reactivity of (.eta.7-cycloheptatrienyl)(.eta.5-cyclopentadienyl)M (M = titanium, niobium) 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 compounds ([eta][sup 5]-C[sub 5]H[sub 5])Ti(S[sub 2]CCH[sub 3])[sub 3] (1) and ([eta][sup 5]-C[sub 5]H[sub 5])Nb([eta][sup 2]-S[sub 2])(S[sub 2]CCH[sub 3])[sub 2] (2) from ([eta][sup 7]-C[sub 7]H[sub 7])M([eta][sup 5]-C[sub 5]H[sub 5]) (M = Ti, Nb) and dithioacetic acid, CH[sub 3]CS[sub 2]H, is described. Both compounds are characterized by elemental analysis, [sup 1]H and [sup 13]C NMR spectroscopy, infrared spectroscopy, mass spectrometry, and X-ray crystallography. Compound 1 crystallizes in orthorhombic space group Pbca. Compound 1 exists in the crystalline state as discrete seven-coordinate molecules; the coordination environment of the central Ti(IV) atom is a slightly distorted pentagonal bipyramid. A [eta][sup 5]-C[sub 5]H[sub 5] ring occupies one axial site, two bidentate dithioacetate groups occupy four equatorial sites, and a third bidentate dithioacetate group spans the remaining axial and equatorial sites. The average equatorial Ti-S distance of 2.619 [angstrom] is appreciably longer than the axial Ti-S distance, 2.545(3) [angstrom]. Compound 2 crystallizes in space group P2[sub 1]/c. Crystals of 2 consist of discrete seven-coordinate molecules; the coordination environment of the central Nb(V) atom is a severely distorted pentagonal bipyramid. A [eta][sup 5]-C[sub 5]H[sub 5] ring occupies one axial site, and a [open quotes]side-on[close more » quotes] bonded disulfide, [eta][sup 2]-S[sub 2], occupies two equatorial sites. The remaining positions are occupied by two nonequivalent bidentate dithioacetate ligands. A variable-temperature [sup 1]H NMR study on 2 shows rapid interconversion between the two dithioacetate environments at 47[degrees]C ([Delta]G[double dagger] = 1.7 [+-] 0.1 kcal mol[sup [minus]1]). 46 refs., 1 fig., 7 tabs. « less