The reaction of NaBH4 with the bis-nitrile compound [Mo2Cp2(μ-SMe)3(MeCN)2](BF 4) 1 unexpectedly gives rise to the rare, stable μ-(η1-H):(η1-H) tetrahydroborato complex [Mo2Cp2(μ-SMe)3(μ-BH4)] 2, in addition to the expected azavinylidene product [Mo2Cp2(μ-SMe)3(μ-η1 -NCHMe)] 3.
