Boron–nitrogen coupling in a ruthenium-rich ruthenaborane cluster: synthesis, and molecular and electronic structures of [Ru4H(CO)12BH(µ-NCHMe)]

Abstract

The photolysis of [Ru₃(CO)₉BH₅] in acetonitrile in the presence of [M(CO)₆](M = Cr, Mo or W), with or without Me₃NO, leads to the formation of [Ru₄H(CO)₁₂BH(µ-NCHMe)]1 which is a butterfly cluster containing a semi-interstitial boron atom. The crystal structure of 1 has been determined: monoclinic, space group C2/c, a= 37.642(8), b= 9.340(2), c= 13.923(3)Å, β= 111.19(2)°, Z= 8, R= 0.0278. R′= 0.0390. The formation of 1 represents an example of coupling between a nitrogen atom and a boron atom in a metal-rich metallaborane cluster, and is of interest because of the cluster expansion which accompanies the B–N bond formation. The bonding in compound 1 has been investigated by use of the Fenske–Hall approach. These quantum chemical results are consistent with a picture of localized bonding in the region of the B–N–Ru bridge, a conclusion that is also reached by a consideration of the requirements of the cluster valence electron count of 62.