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

摘要

The ionic complexes [M(triphos)CI]X [M = Pd, X= CI (I), SnCl_3 (la), SnPh_2Cl_3 (Ic); M = Pt, X= CI (3), SnCI, (3a), SnPh,CI, (3c)], [M(triphos)CI]_2X [X = SnPh_2Cl_4, M = Pd (Ib), Pt (3b); X= PtCl_4, M = Pt (3d)] and [M(triphos)_2]X_2 [X = Sn-Ph_2CI:I, M ;. pd (2), Pt (4)] where triphos = bis(2-diphenylphosphinoethyl)phenylphosphine, were synthesised and characterised by microanalysis, mass spectrometry, IR, 119Sn Mossbauer, NMR (3IP, '9Sptand 119Sn) spectroscopies and conductivity measurements. The X-ray crystal structures of compounds 1b, 3b and 3c, where tetrachlorodiphenylstannate(IV) and trichlorodiphenylstal1nate(IV) act as counterions stabilising cationic metal complexes, are reported. These compounds contain the cation [M(triphos)CI]+ with distorted square-planar geometry at palladium or platinum, triphos acting as a tridentate chelating ligand. The anions [SnPh_2Cl_4]~(2-) (Ib, 3b) and [SnPh_2Cl_3]- (3c) have trans-octahedral and distorted trigonal-bipyramidal environments for the metal, respectively. Although the dinegatively charged [SnPh_2Cl_4]~(2-) is counteracted by the presence of two singularly positively charged [M(triphos)CI]+ species, interanion contacts via hydrogen bonds were found for Ib and 3b but were absent f;)r compound 3c. The crystalline solids [M(triphos)_2][SnPh_2Cl_3]_2 [M = Pd (2), Pt (4)] were formed via a chelate ring-opening reaction of [M(~riphos)CI]+ induced by triphos. The formation of heterometalic complexes by reaction of AgCI or Au(I) with the complex [Pt(t- riphos)_2][SnPh_2Cl_3]_2 (4), followed by 31p NMR in solution, did not take place. The presence of dangling arm phosphine oxide groups, on oxidation of complex 4 with H_2O_2, was detected. Other ring-opening reactions were observed by 31p NMR and conductivity measurements when solutions containing PtCl_2(PhCN)_2 and triphos in a molar ratio 3:2 were refluxed C6H6. Besides [Pt(triphos)Cl]_2[PtCI~] (3d) and the ionic complex with a dinuclear anion, [Pt(triphos)C.I][Pt_2(triphos)CI~] (5), the covalent trinucle~r complexes [ {PtC.2(Ph_2PCH_2CH_2)_2PPh-P1,P_2}_2(P_3,P_1ptCl_2] (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)C.I]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-i:losed products were found.