Transition of trigonal-bipyramidal to square-planar geometries by oxidation of a coordinated tripodal polyphosphine in Pd(ii) and Pt(ii) complexes

Abstract

The oxidation reactions of the unusual d 8 trigonal-bipyramidal systems [MX(PP 3 )]X (M = Pd: X = Cl(1), Br(2), I(3); M = Pt: X = Cl(4), Br(5), I(6); PP 3 = tris[2-(diphenylphosphino)ethyl]phosphine) by dissociation of the bound phosphino groups with H 2 O 2 in chloroform and with DMSO-d 6 in the presence of reduced glutathione (GSH) have been explored with emphasis on the factors that influence the number of M-X and PLO functionalities of the resulting products. The oxidations with H 2 O 2 required a higher concentration for Pd than Pt and occurred with formation of both ionic distorted square-planar compounds [MX(PP 2 PO)]X [M = Pd: X = Cl(7); M = Pt: X = Cl(10), Br(11)], that contain one dangling PLO group, and the less common neutral species [MX 2 (PP(PO) 2 ] [M = Pd: X = Br(8), M = Pt: X = I(12)] showing MX 2 P 2 environments and two PLO arms, or with release of all bound phosphorus from 3 to give OP(PO) 3 (9). Although there was no evidence of the formation of neutral species with two Pt-Cl bonds and dissociation of one bound phosphorus by adding H 2 O 2 or M9Cl (M9 = Cu, Ag) to 10, the interaction with [AuCl(tdg)] (tdg = thiodiglycol) afforded [PtAuCl 3 (PP 2 PO)] (10a) containing dangling PLO and PAuCl arms and one chiral central phosphorus. Thus, while the halide anions and ligands allowed both ionic (7, 10, 11) and neutral (8, 9, 10a, 12) systems, the larger anions [S(CH 3 ) 3 (CH 2 ) 3 (SO 3 )] 2 or GS 2 favour only the ionic compounds, namely [PdCl(PP 2 PO)][S(CH 3 ) 3 (CH 2 ) 3 (SO 3 )] (7a), obtained in coexistence with [Pd(GS)(PP 2 PO)]Cl (7a9) from the reaction of 1 + 3 eq. GSH in DMSO-d 6 . The X-ray structure of 7a confirmed the distorted ClPdP 3 arrangement and the presence of a dangling PLO group predicted by LSI-MS and 31 P{ 1 H}NMR data.