Solid-State and Solution Structures of a Series of [(HBPz3Me2)Rh(CO)(PR3)] and [(HBPz3Me2,4Cl)Rh(CO)(PR3)] Complexes

Abstract

Addition of 1 equiv. of a phosphane or phosphite ligand to the κ3-bonded [TpMe2Rh(CO)2] and [TpMe2,4ClRh(CO)2] dicarbonyl precursors gives the monosubstituted complexes [TpRh(CO)L]. The X-ray crystal structures show that the three complexes [TpMe2Rh(CO)(PMe3)], [TpMe2Rh(CO)(PMePh2)], and [TpMe2,4ClRh(CO)(PMePh2)] adopt square-planar geometries. The X-ray crystal structure of [TpMe2Rh(CO){P(OPh)3}] is consistent with an interaction between the dangling pyrazolyl group and the rhodium centre, the Rh−N distance being 2.762(3) A. Analysis of ν(BH) and ν(CO) stretching frequencies shows that all the phosphane-containing complexes are square planar in solution as well as in the solid state. According to infrared analyses, the phosphite complexes [TpMe2,4ClRh(CO){P(OPh)3}] and [TpMe2,4ClRh(CO){P(OMe)3}] adopt a pentacoordinated geometry both in the solid state and in solution. However, the infrared data for [TpMe2Rh(CO){P(OPh)3}] and [TpMe2Rh(CO){P(OMe)3}] indicate that the TpMe2 ligand is in a κ3 coordination mode in the solid state, as already evidenced by the X-ray crystal structure, but in a κ2 mode in solution. We also describe an exchange phenomenon between dangling and coordinated pyrazolyl groups, as studied by NMR.