Preparation and characterization of rhodium(III) complexes containing 1,1,1-tris(dimethylphosphinomethyl)ethane (tdmme). Structures of [RhX3(tdmme)](X = Cl, Br or I), [Rh(NH3)3(tdmme)]3+ and [{Rh(tdmme)}2(µ-X)3]3+(X = Cl or OH) in the solid state and in solution

Abstract

Several new rhodium(III) complexes containing a tripodal tridentate phosphine, MeC(CH₂PMe₂)₃(tdmme), have been synthesized and their structures investigated both in the solid state and in solution. Single-crystal X-ray analyses revealed the smaller steric requirement and stronger trans influence of tdmme than those of the phenyl-substituted analogue, MeC(CH₂PPh₂)₃(tdpme). The long Rh–Cl bond in the mononuclear trichloro complex, [RhCl₃(tdmme)]1, due to the strong trans influence of tdmme, made the complex reactive in water; the structure of 1 in solution and its reaction products with some acids or bases were characterized. The triply chloro-bridged dinuclear complex, [{Rh(tdmme)}₂(µ-Cl)₃][BF₄]₃, also showed structural change in water, while the mononuclear triammine complex, [Rh(NH₃)₃(tdmme)][BF₄]₃, and the triply hydroxo-bridged dinuclear complex, [{Rh(tdmme)}₂(µ-OH)₃][BF₄]₃, were stable. The absorption spectra of the tdmme complexes suggested a stronger ligand field of tdmme to the rhodium(III) centre than those of corresponding didentate diphosphine ligands, in accordance with the short Rh–P bond lengths in 1 found by single-crystal X-ray analysis.