2 is an orange-red crystalline solid whose 31P-NMR spectrum exhibits a singlet (6 = 42.0). Crystallization of 2 from pyridineln-hexane (2/1) yields single crystals suitable for determining the structure by X-ray diffraction[91 (Fig. 1). The titanium atom has a distorted octahedral coordination, the corners of the octahedron being formed by three pyridine molecules (N31, N41, N51), two chlorine atoms (CI 1, (212) and the nitrogen atoms of the imido ligand. The Ti-N bond length (172.0(2) pm) is similar to that in the Ti-N unit of the eight-membered P-0-N-Ti heterocycle [Ph,PONTiCI, . 2MeCN], (173.9 pm).181 The coordination of the imido ligand to the titanium atom is almost linear (Ti-N-P 172.5(2)"), showing that the ligand acts as a four-electron donor. The pyridine molecule trans to the imido ligand is much more loosely bound (Ti-N41 243.9(2)pm) than the other two pyridine molecules (average Ti-N 222.7 pm).
Evidently, therefore, the imidotitdnium compounds that have so long been sought can be stabilized by coordination with electron pair donors on the titanium atom. The first results on the chemistry of these compounds are reported by Rothwell et al. in another communication.[41 Experimental 1. 10 g (29.0 mmol) of N.N-bis(trimethylsily1)aminodiphenylphosphane was dissolved in 150 mL of benzene, mixed with 0.93 g of sulfur (3.625 mmol. referred to &), and heated for 3 h at 50-60-C. After evaporating off the solvent under vacuum the colorless residue was recrystallized from MeCN. Yield 9 7 g (89%); m.p. 116'C. "P NMR (101.26MHz. 85% H,PO,. C,H,. CDCI,): 8 = 61.0 (s); "Si NMR (49.69 MHz, TMS, C,H6, CDCI,): d = 10.7 (d. 2J(29Si.3'P) = 1.2 Hz); MS (EI): mlz 377 ( M e , 16%). 362 (MO-Me, 100%).
- lnto a solution of 1.5 g (4.0 mmol) of 1 in 50 mL CH,CI, at -15 'C was slowly added a solution of0.76 g (4.0 mmol) of TiCI, in 25 mL of CH,CI,. The mixture was then allowed to slowly warm up to room temperature and was stirred for a further 20 h. After evaporating off the solvent under vacuum the yellow residue was recrystallized from pyridineln-hexane (211). This yielded a mixture of a yellow powdery solid and orange-red crystals of 2. The solvent and the powdery solid were decanted off from the crystals, which were then sorted to find a crystal suitable for the X-ray structure determination. Yield of 2 0 63 g (27%). M.p. 125 C (decomp.) IR (Nujol/KBr): Y = 16051~1). 1377(st). lllO(st), 1070(st), 1012(st), 698(st), 520(st) cm-'.