Crystal structure and reactivity of mononuclear cationic palladium(II) and platinum(II) triphos complexes with phenyltin(IV) anions.: The formation of polynuclear platinum-triphos ionic and covalent complexes

The ionic complexes [M(triphos)Cl]X [M = Pd, X = Cl (1), SnCl3 (1a), SnPh2Cl3 (1c); M = Pt, X = Cl (3), SnCl3 (3a), SnPh2Cl3 (3c)], [M(triphos)Cl](2)X [X = SnPh2Cl4, M = Pd (1b), Pt (3b); X = PtCl4, M = Pt (3d)] and [M(triphos)(2)]X-2 [X = SnPh2Cl3, M = Pd (2), Pt (4)] where triphos = bis(2-diphenylphosphinoethyl)phenylphosphine, were synthesised and characterised by microanalysis, mass spectrometry, IR, Sn-119 Mossbauer, NMR (P-31, Pt-195 and Sn-119) spectroscopies and conductivity measurements. The X-ray crystal structures of compounds 1b, 3b and 3c, where tetrachlorodiphenylstannate(IV) and trichlorodiphenylstannate(IV) act as counterions stabilising cationic metal complexes, are reported. These compounds contain the cation [M(triphos)Cl](4) with distorted square-planar geometry at palladium or platinum, triphos acting as a tridentate chelating ligand. The anions [SnPh2Cl4](2-) (1b, 3b) and [SnPh2Cl3](-) (3c) have trans-octahedral and distorted trigonal-bipyramidal environments for the metal, respectively. Although the dinegatively charged [SnPh2Cl4](2-) is counteracted by the presence of two singularly positively charged [M(triphos)Cl](+) species, interanion contacts via hydrogen bonds were found for Ib and 3b but were absent for compound 3c. The crystalline solids [M(triphos)(2)][SnPh2Cl3](2) [M = Pd (2), Pt (4)] were formed via a chelate ring-opening reaction of [M(triphos)Cl](+) induced by triphos. The formation of heterometallic complexes by reaction of AgCl or Au(I) with the complex [Pt(triphos)(2)][SnPh2Cl3](2) (4), followed by P-31 NMR in solution, did not take place. The presence of dangling arm phosphine oxide groups, on oxidation of complex 4 with H2O2, was detected. Other ring-opening reactions were observed by P-31 NMR and conductivity measurements when solutions containing PtC1(2)(PhCN)(2) and triphos in a molar ratio 3:2 were refluxed C,H,. Besides [Pt(triphos)Cl](2)[PtCl4] (3d) and the ionic complex with a dinuclear anion, [Pt(triphos)Cl][Pt-2(triphos)Cl-5] (5). the covalent trinuclear complexes [{PtCl2(Ph2PCH2CH2)(2)PPh-P-1,P-2} (2)(P-3,P-3)PtCl2] (6a, 6b) were formed as minor products. These latter diastereomeric species become the dominant species upon heating, being thermodynamically controlled complexes. Mixtures of 3d, 5, 6a and 6b converted to complex [Pt(triphos)Cl]Cl (3) by addition of triphos, chelate ring-closure reactions of 6a, 6b and the complex anion 5 occurring. With an excess of triphos (Pt:triphos = 3:4 or higher ratio), broad peaks reflecting fast equilibria between ring-opened and ring-closed products were found. (C) 2001 Elsevier Science Ltd. All rights reserved.