Synthesis and characterisation of a series of ruthenium scorpionate complexes with B–H ⋯ M agostic interactions. Crystal structure of [RuH(κ2-N,BH TpTn)(PMe3)(cod)] (TpTn = hydrotris[3-(2-thienyl)pyrazol-1-yl]borate)

A series of monohydrides of RuII of formula RuH(TpR)(cod) 1–3 have been synthesized from the reaction of [RuH(NH2NMe2)3(cod)]BPh4 with the corresponding TpR ligand {hydrotris(7-methylindazol-2-yl)borate, TpBo,7Me, 1; hydrotris[3-(2-thienyl)pyrazol-1-yl]borate, TpTn, 2; tris[3-(2,4-dimethoxyphenyl)pyrazol-1-yl]hydroborate, Tp(2,4(OMe)2Ph), 3}. In these compounds the Tp ligand is κ3N,N′,BH coordinated with a B–H ⋯ Ru agostic interaction. Reactions of 1 and 2 with two-electron donor ligands, L = PMe3, PMe2Ph and CN-t-Bu, led to the formation of complexes of formula RuH(TpR)(L)(cod) (TpR = TpBo,7Me, L = PMe34, PMe2Ph 5 or CN-t-Bu 6; TpR = TpTn, L = PMe37, PMe2Ph 8 or CN-t-Bu, 9). In this new series the incoming ligands replace one of the coordinated pyrazole rings instead of the stated B–H ⋯ Ru interaction which remains and consequently the TpR ligands are κ2N,BH coordinated. The molecular structure of 7 was determined by an X-ray diffraction study. The ruthenium atom has a distorted octahedral environment with the ligand TpTn coordinated through only one pyrazole ring and an agostic B–H group. The two hydrides are in a mutually trans disposition with an angle of 166°. The Ru ⋯ H distance is 2.07(5) and Ru–Hterminal 1.33(5) A. The molecular structure of the model complex [RuH(κ2-N,BH-Tp)(PH3)(H2CCH2)2] has been optimised with the aid of ab initio calculations in order to compare the structural parameters with those of the experimentally determined structure.