Synthesis and characterization of novel ruthenaferracarboranes from photoinsertion of alkynes into a ruthenaferraborane

Abstract

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.