Structure of 1,1,2-tricarbonyl-μ-(dimethyl 2-butynedioate-μ-C2,μ-C3)-(2-3-η-dimethyl 2-butynedioate)-μ-(1–5:1'–5'-η-fulvalene)-dimolybdenum(Mo–Mo), [Mo2(C10H8)(C6H6O4)2(CO)3

Abstract

M r=687.9, monoclinic, P2Jc, a= 9.6984 (6), b= 15.4379 (21), c= 16.4863 (17)A, fl = 95.880 (7) °, V= 2455.4 (8) A 3, Z = 4, D x = 1.86gem -3, 2(MoKa)=0.7107A, g= 10.6cm -1, F(000)= 1368, T= 298 K, final R = 0.022, wR = 0.029 for 2692 (I > 3e(/)) unique reflections. Impor- tant features include the lack of multiple alkyne coupling, a contracted Mo-Mo distance of 2.906 (1)A, a bridging (4e--donating) alkyne C-C distance of 1.374 (4)A and a singly coordinating (2e--donating) alkyne C-C distance of 1.265 (4)A. The bridging alkyne is slightly displaced towards the singly coordinating alkyne ligand, in the more sterically hindered direction. Introduction. The unusual structural constraints im- posed by a fulvalene ligand anchored to a molybdenum dinuclear center should result in interesting structural and chemical properties relative to analogous r/5- CsHsMo dimers. The multiple alkyne coupling in r/5-CsHsMo dimers (Beck, Knox, Stansfield, Stone, Winter & Woodward, 1982; Green, Norman & Orpen, 1981; Knox, Stansfield, Stone, Winter & Woodward, 1978) is nearly always present with rare exceptions