The complexes, PtCl(diene)R (diene = hexa-1,5-diene (hex) or norbornadiene (nbd), R C6F5, p-HC6F4, or p-MeOC6F4; diene = diene = dicyclopentadiene (dcy), R = C6F5) have been prepared by reaction between equimolar amounts of PtCl2(diene) and Me3SnR in dichloromethane. Most reactions also gave some of the corresponding PtR2(diene) complex, which was readily separated by chromatography, and Pt(p-MeOC6F4)2(nbd) was obtained in high yield from PtCl2(nbd) and Me3Sn(p-MeOC6F4) when a 1 2 mole ratio was used. Attempts to prepare PtCl(dcy)R (R p-HC6F4 or p-MeOC6F4) from Me3SnR gave only PtR2(dcy) in boiling CH2Cl2 despite the use of 1 1 reactant stoichiometry, and Pt(p-MeOC6F4)2(dcy) or no reaction (R p-HC6F4) at room temperature. Alternative reagents, R′3 SnR (R′ Bu or Et, R C6F5 or p-MeOC6F4) had a variable effect on the selectivity of monoarylation. Thus, Bu3SnC6F5 was more selective and Et3SnC6F5 less selective in formation of PtCl(hex)C6F5 than Me3SnC6F5. With Et3SnR (R C6F5 or p-MeOC6F4) and an equimolar amount of PtCl2(dcy), PtCl(dcy)R was the major product. The crystal structure of ptCl(dcy)C6F5 shows near square planar stereochemistry for platinum and steric congestion. The double bond from the six-membered ring of dcy is unsymmetrically coordinated to platinum trans to C6F5 and is further from the metal than the other double bond, which is symmetrically bonded trans to chlorine. The pentafluorophenyl group is approximately normal to the coordination plane, and gives two ortho-fluorine resonances in the 19F NMR spectrum.