Diplatinum-(II) and -(III) complexes with bridging µ-diphosphonito-P,P′ or µ-methylenebis(phosphonito)-P,P′ ligands. Synthesis, structure, and nuclear magnetic resonance analysis of the ‘lantern’ complexes. Crystal structures of K4[Pt2{µ-CH2[P(O)OH]2}4]·6H2O and K4[Pt2{µ-CH2[P(O)OH]2}4Cl2]·8H2O

Abstract

The complex K4[Pt2{µ-CH2[P(O)OH]2}4]·6H2O {K4[Pt2(pcp)4]} has been prepared by treating K2[PtCl4] with CH2[PH(O)OH]2. The structure shows a ‘lantern’ arrangement of phosphorus ligands about the two platinum(II) centres, with a Pt–Pt separation of 2.980 1(2)A. This complex, K4[Pt2(pcp)4], reacts with halogens X2(X = Cl, Br, or I) to give diplatinum(III) complexes K4[Pt2(pcp)4X2] The structure of the dichloro complex K4[Pt2{µ-CH2[P(O)OH]2}4Cl2]·8H2O shows long Pt–Cl distances of 2.442(1)A and a short Pt–Pt separation of 2.750 0(3)A. The complexes [Pt2(pcp)4X2]4– show X→PtIII ligand to metal charge transfer bands at 298 (X = Cl), 326 (X = Br), 354 and 454 nm (X = I). The 31P-{1H} and 195Pt-{1H} n.m.r. spectra of the complexes [Pt2(pcp)4]4–, [Pt2(pcp)4X2]4–, [Pt2(pop)4]4–, and [Pt2(pop)4X2]4–{X = Cl, Br, or I; pop =µ-O[P(O)OH]22–} have been solved by second-order analysis of the nine-spin Pt195Pt and ten-spin 195Pt2 isotopomer mixtures in the solutions. The spectra have been simulated as the [A4][X]2[A′4] spin system using the program PANIC, and as the [A]4[X]2[A′]4 spin system using DSYMPLOT. In the diplatinum(II) complexes 1J(PtPt) < 1 000 Hz, but in the diplatinum(III) complexes 1J(PtPt)≈ 7 000–11 000 Hz.