Orthometallation reactions of rhodium compounds containing orthohaloarylphosphines. V. Synthesis and reactivity of orthometallated rhodium(III) compounds. Crystal structure of RhCl(CO)2

Article abstract of DOI:10.1016/0022-328X(88)83152-8

The reaction of RhCl3*3H2O with a 3-molar proportion of P(o-ClC6H4)Ph2, (PCCl) at room temperature gives RhCl(PCCl)2 (1), in high yield.Reaction of 2, (cot = cyclooctene), with PCCl, 1/2 molar ratio, also gives compound 1.Refluxing of a solution of 1 in 96percent ethanol gives RhCl2(PC)(η²-PCCl), (2).Complex 1 reacts with CO to give RhClCO(PCCl)2 (3). 31P NMR studies reveal that 1 exhibits a fluxional behaviour in solution in the temperature range -50 to 0 deg C.The low temperature spectrum is consistent with the formulation RhCl(η²-PCCl)(η¹-PCCl).In cyclic voltammetry complex 2 shows two two-electronic reduction processes, at -0.98 and -1.56 V.Electrochemical or chemical reduction of 2 under carbon monoxide give compound 3.Crystal structure of 3 was solved in the P2₁/n space group, Z = 2, with cell parameters a 9.394(2), b 17.194(4), c 10.948(2) Angstroem, and β 111.62(2) deg.The structure consists of a rhodium atom in a square planar environment with the two chlorine atoms from the phophines orientated towards the apical positions.Replacement of chlorine or PCCl in compound 2 has enabled isolation of several orthometallated derivatives, RhCl(hp)(PC)(PCCl) (hp 2-oxypyridinate, 4; 6-Clhp, 5 and 6-CH3hp, 6) and RhCl2(PC)(P-P) (P-P bis(diphenylphosphino)methane (dppm), 7, and 1,2-bis(diphenylphosphino)ethane (dppe),8).