The synthesis of abd-trichloro-f-phenyl-ce-bis(triethylphosphine)platinum (1a) and novel reactions involving the aryl ligand of this complex are described. Lewis acid-catalysed chlorination of complex (1a) formed exclusively the p-chlorophenyl analogue leaving the aryl–metal bond intact. Taft substituent parameters for the (PEt3)2PtCl3 group, viewed as an aryl substituent, were determined from 19F n.m.r. studies on the p- and m-fluorophenyl analogues of (1a). In a novel rearrangement the complex gave phenyltriethylphosphonium trichloro(triethylphosphine)platinate (2) when heated in polar solvents. The possible mechanisms of this rearrangement are discussed.