ALAN SHAVER, JAMES M. MCCALL, VICTOR W. DAY, and SARAH VOLLMER. Can. J . Chem. 65, 1676Chem. 65, (1987.The crystal and molecular structures of ( T~~-C~H~)~Z~S~, 2, and ( q 5 -C 5~5 )~f S 5 , 3, have been determined by single crystal diffractometry methods. Both compounds crystallized with four molecules in a monoclinic unit cell of dimensions: a = 8.984(3)A, b = 13.336(4)A,c = 11.421(2)A, P = 93.10(2)"for2, and a = 9.012(2)A, b = 13.291(2)A, c = 11.381(2) A, p = 93.25(1)" for 3; the space group is P21 /n for both. These crystals of 2 and3 are thus isomorphous with those of (CSH5)2TiS5, 1, studied by Epstein et al. (3a). The structures of all three complexes are very similar consisting of a cyclohexane-like six-membered MS5 ring with two C5H5 rings attached to the metals in an axial and equatorial position. The coordination spheres of 2 and 3 are less crowded than that of 1. The consequences of this are discussed with respect to the barriers to ring inversion in these complexes. Introduction Recently a general method for the preparation of metallacyclosulfanes (i.e. species of the type MS,) was reported (1). Treatment of the appropriate dichloro precursors with nonaqueous solutions of Li2S,, prepared in situ, gave the series Cp2MS5 and C P *~M S~, where M = Ti, Zr, and Hf, Cp = C5H5, and Cp* = C5Me5. The complex Cp2TiS5, 1, had been reported previously (2) and had been shown (3) to have a cyclohexanelike six-membered ring with axial and equatorial Cp rings. At room temperature ring inversion is slow on the nrnr time scale for the titanium complex (4); however, only upon cooling the