Synthesis of trans-[Mo(N2)2(dippe)2][dippe = 1,2-bis(diisopropylphosphino)ethane] and related derivatives, protonation of co-ordinated dinitrogen and crystal structures of trans-[MoF(NNH2)(dippe)2][BF4] and trans-[MoCl2(dippe)2][BF4]

Abstract
Reduction of [MoCl3(thf)3](thf = tetrahydrofuran) with sodium dispersion or sodium amalgam in the presence of dinitrogen and 1,2-bis(diisopropylphosphino)ethane (dippe) gave low, but reproducible, yields of the bis(dinitrogen) complex trans-[Mo(N2)2(dippe)2]1. This reacted very slowly with H2 to yield the known tetrahydride [MoH4(dippe)2]2, which is more conveniently prepared by reaction of [MoCl4(MeCN)2] with dippe and Na[BH4]. Complex 1 reacted with 2 equivalents of HBF4 in Et2O to give the hydrazido(2–) complex trans-[MoF(NNH2)(dippe)2][BF4], the crystal structure of which has been determined. When the reduction of [MoCl3(thf)3] in the presence of dippe was performed under argon instead of dinitrogen the yellow, 16-electron, paramagnetic complex [MoCl2(dippe)2]4 was obtained. In accordance with its co-ordinatively unsaturated character, 4 reacted with CO in thf yielding seven-coordinate, diamagnetic [MoCl(CO)2(dippe)2]Cl 5. It also underwent one-electron oxidation by reaction with Ag[BF4] in CH2Cl2, furnishing 15-electron [MoCl2(dippe)2][BF4]6, the crystal structure of which was also determined.

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