Synthesis and oxidation reactions of mono- and di-nuclear rhodium carbonyl complexes of (o-diphenylphosphinophenyl)amine, H₂L; X-ray structure analysis of a rhodium(<scp>II</scp>) amido-bridged dimer, [{Rh(µ-HL)(CO)Cl}₂]·EtOH

Abstract

Reaction of cis-[NBun4][Rh(CO)2Cl2] or [{Rh(CO)2Cl}2] with one or two molar equivalents of (o-diphenylphosphinophenyl)amine (H2L) respectively gives the mononuclear halogenocarbonylrhodium(I) complexes [Rh(H2L)(CO)X][X = Cl (2a), Br (2b), or I (2c)]. These new compounds were found to react with air to give the novel amido-bridged rhodium(II) metal–metal bonded dimers [{Rh(µ-HL)(CO)X}2][X = Cl (5a), Br (5b), or I(5c)]. The chloro species (2a) was also shown to react with base in an inert atmosphere to generate the rhodium(I) amido-bridged dimer [{Rh(µ-HL)(CO)}2](4), which reacts with one molar equivalent of halogen to produce (5) or with excess halogen to give the monomeric rhodium(III)mer-trihalogeno complexes [Rh(H2L)(CO)X3][X = Cl (7a), Br (7b), or I (7c)]. The chloro rhodium(II) dimer (5a) has been characterised by X-ray structure analysis. Crystals of (5a)·EtOH are monoclinic, space group P21/c, with a= 14.669(3), b= 14.754(3), c= 18.233(4)Å, β= 92.46(4)°, and Z= 4. Full-matrix refinement of 3 498 unique data with I 3σ(I)(3 < θ < 25°) gave R= 0.045 and R′= 0.042.