Structure and Reactivity Relationships in Methyl and Hydrido Complexes of Platinum(II) by Group 15 Donor Atom Ligands

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 ∆H≠ = 60.4 ± 1.4 and 53.7 ± 0.3 kJ mol−1, and ∆S≠ = −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.