Structure and reactivity relationships in methyl and hydrido complexes of platinum(II) by group 15 donor atom ligands

Abstract

Square-planar substitution reactions (chlorido for iodide, trans to methyl and hydrido as non-labile ligands) was kinetically investigated in chloroform solution in a series of platinum(II) trans-[PtRCl(L)2] complexes (R = Me: L = PPh3, 1; PPh2Fc, 2; P(NMe2)3, 3; AsPh3, 5; As(4-Me-Ph)3, 6; R = H: L = PPh3, 7) and cis-[PtMeCl(Ph2PFcPPh2)], 4. The reactions follow the normal associative mode of activation, but with equilibria present in all steps, with rate constants for the direct substitution pathway, k12, of (9.1 × 1.0) × 10-4, 0, (1.389 × 0.016)×10-2, (1.51 × 0.15), (2 × 4) × 10-3, (2.79 × 0.04) × 10-2 and 0 mol-1 dm3 s-1 at 298 K for 1 to 7 respectively. The corresponding second order rate constants for the solvent assisted pathway, k13′, were also determined. The activation parameters for the direct and solvent assisted pathways for 3 were determined as ΔH≠ = 60.4 × 1.4 and 53.7 × 0.3 kJ mol-1, and ΔS≠ = -78 × 4 and -142 × 1 J mol-1 K-1. A significant more than four orders-of-magnitude reactivity range was observed. Crystal structures of trans-[PtMeCl(PPh2Fc)2].2CHCl3.2H2O, trans-[PtMeCl{P(NMe2)3}2], cis-[PtMeCl(Ph2PFcPPh2)].2CHCl3 and trans-[PtHCl(PPh3)2].CH3OH are reported.