6533b7defe1ef96bd1275b5e

RESEARCH PRODUCT

Orthometallation reactions of rhodium compounds containing orthohaloarylphosphines

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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 [Rh(cot)2Cl]2, (cot = cyclooctene), with PCCl, sol12 molar ratio, also gives compound 1. Refluxing of a solution of 1 in 96% ethanol gives RhCl2(PC)(η2-PCCl), [PC  (C6H4)PPh2] (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 °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) A, and β 111.62(2)°. The structure consists of a rhodium atom in a square planar environment with the two chlorine atoms from the phosphines 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 bis(diphenylphosphino)methane (dppm), 7, and 1,2-bis(diphenylphosphino)ethane (dppe), 8).