Synthesis, Structure, and Reactivities of the Five-Coordinate Molybdenum(0) Mono(acetylene) Complex [Mo(HC⋮CH)(dppe)₂]¹

The reaction of trans-[Mo(N2)2(dppe)2] (1; dppe = Ph2PCH2CH2PPh2) with excess amounts of HC⋮CLi·en (en = H2NCH2CH2NH2) afforded the five-coordinate Mo(0) mono(acetylene) complex [Mo(HC⋮CH)(dppe)2] (2). Treatment of 2 with 2 mol of [Cp2Fe][BF4] (Cp = η5-C5H5) in THF gave the Mo(II) acetylene complex trans-[MoF(HC⋮CH)(dppe)2][BF4], while that in THF−MeCN followed by anion metathesis with NaOTf (OTf = OSO2CF3) led to the formation of the metallacyclopropene complex [Mo(η3-CHCHPPh2CH2CH2PPh2-C,C‘,P)(MeCN)2(dppe)][OTf]2.