The Tungsten-to-Tungsten Triple Bond. 7. Replacement of Dimethylamido by Chloro Groups in Hexakis (dimethylamido)ditungsten and -dimolybdenum Compounds; the Preparation, Properties and Structure of Dichlorotetrakis-(dimethylamido)ditungsten and -dimolybdenum.

M2(NMe2)6 compounds (M = Mo,W) react with Me3SiCl (2 equiv) in hydrocarbon solvents to give M2Cl2(NMe2)4 and Me3SiNMe2. An amine catalyzed reaction sequence is proposed: (1) HNMe2 + Me3SiCl yields Me3SiNMe2 + HCl (ii) M-NMe2 + HCl yields M-Cl + HNMe2. This sequence is supported by the observations that W2(NMe2)6 does not react with Me3SiCl in the absence of amine and that W2Cl2(NMe2))4 reacts rapidly with HN(CD3)2 to give W2(NMe2)6 with complete scrambling of dimethylamine. In solution W2Cl2(NMe2)6 and W2(NMe2)6 exist in equilibrium with W2Cl(NMe2)5 (K approx. 1 at 30 C). The compounds M2Cl2(NMe2)4 have been characterized by variable temperature nmr studies, infrared and mass spectroscopy and single crystal X-ray crystallography.
Prepared in cooperation with Texas A and M Univ., College Station. Dept. of Chemistry.