Synthesis and Characterization of Novel Ruthenaferracarboranes from Photoinsertion of Alkynes into a Ruthenaferraborane

Photolysis of [{(μ3-BH)­(Cp*Ru)­Fe­(CO)3}2(μ-CO)] (1; Cp* = η5-C5Me5) in the presence of various alkynes such as 1,2-diphenylethyne, 1-phenyl-1-propyne, 2-butyne, and 1-(diphenylphosphino)-2-phenylacetylene led to the formation of four types of novel heterometallic metallacarboranes, [1,1,1-(CO)3-μ-2,3-(CO)-2,3-(Cp*)2-4,6-Ph2-closo-1,2,3,4,6-FeRu2C2BH] (2), [1,8-(Cp*)2-2,2,7,7-(CO)4-μ-2,8-(CO)-μ-7,8-(CO)-4-Me-5-Ph-pileo-1,2,7,4,5-RuFe2C2(BH)2] (3), [1,8-(Cp*)2-2,2,7,7-(CO)4-μ-2,8-(CO)-μ-7,8-(CO)-4,5-Me2-pileo-1,2,7,4,5-RuFe2C2(BH)2] (4), and [1,2-(Cp*)2-6,6,7,7-(CO)4-μ-2,7-(CO)-exo-μ-5,6-(PPh2)-μ3-1,2,6-(BH)-4-Ph-pileo-1,2,6,7,4,5-Ru2Fe2C2BH] (5). Cluster compound 2 exhibits an octahedral structure with adjacent carbon atoms consistent with its skeletal electron pair (sep) count of 7. The cage geometry of 3 and 4 is based on a pentagonal bipyramid with one additional {Cp*Ru} vertex capping one of its faces. The solid-state X-ray diffraction results of 5 suggest that the core geometry is a capped pentagonal bipyramid, with an Fe–C bridging PPh2 group. All the cluster compounds 2–5 have been characterized by IR and 1H, 11B, and 13C NMR spectroscopy, and the geometries of the structures were unequivocally established by crystallographic analysis.