A Novel Pt(II)-Pt(IV) Mixed Valence Complex: The Crystal and Molecular Structure of [LPt(μ-l)(μ-Me2PCH2PMe2)2PtMe3] [h], L = 0.451 + 0.55Me

X-ray structure determination of the title compound has shown that iodination of [Pt2Me4 (,u-Me2PCH2PMe2)2] involves an oxidative addition reaction accompanied by methyl group transfer between the two platinum atoms. The crystal structure is built of symmetrical, linear [Isl- anions and partially disordered cations, in which I- or CH3- ligands occupy the L sites with nearly equal propability. In the cations the Pt(II) and Pt(IV) centres are characterised by square planar and octahedral coordination geometries; they are locked into close proximity [Pt ... Pt 386.3(1) pm] by two bridging Me2PCH2PMe2 ligands. The L-shaped LPt(μ -I)PtMe fragment [Pt-I-Pt 91.2(1)0 ] is perpendicular to the Pt(l)P2L(μ -I) and Pt(2)P2C2 coordination planes. The overall geometry of the cation approximates to C8 symmetry. Crystals of the title compound are triclinic, space group Pl, with two formula units in a unit cell of dimensions a = 924.0(2), b = 932.8(4), c = 1804.4(7) pm, a = 102.39(4), fl = 94.63(3) and y = = 96.93(3)0 . Lecrst-squares refinement of the structural model defined by 221 parameters converged at a conventional R index on F of 0.049 for 5045 reflections with I ~ 3 a (I)

Conformations of diphosphinoamines; variable-temperature nuclear magnetic resonance and <i>X</i>-ray crystallographic studies

The variable-temperature 31P-{1H} n.m.r. spectra of a series of diphosphinoamines, X2PN(R)PX2(R = H, Me, Et, or Pri, X = Ph; R = Me, But, or CH2But, X = Cl; R = Me or But, X = F; R = Et, X = NMe2) have been studied. Complementary information on these compounds has been obtained from 1H, 13C, and 19F n.m.r., including double and triple resonance experiments. The coupling constant, 2J(PNP), covers the range –23.9 to 731.9 Hz, and its magnitude and sign can be related to the proportion of molecules in which the local symmetry of the P–N–P skeleton is C2v rather than Cs. Diphosphinoamine conformers of the latter type have been clearly identified for the first time both in solution (for R = Et or Pri, X = Ph, and R = But or CH2But, X = Cl) and also in the solid phase. X-Ray analysis of Ph2PN(Pri)PPh2, based on 1 269 diffractometric intensities refined to R = 0.035, shows that the symmetry of the P–N–P skeleton is close to Cs in the solid, with P–N = 1.706(4) and 1.711(4) Å, and PNP = 122.8(3)°