78610-30-7Relevant articles and documents
Synthesis and 31P NMR studies of platinum complexes of [R2P(O)CHP(O)R2]- ligands, R = Ph or OEt. Crystal and molecular structure of lithium trans-dichloro(triethylphosphine)(bis(diphenylphosphinyl)methyl)platinate(II), an unusual case of chloro bridging between platinum and lithium
Browning, Jane,Bushnell, Gordon William,Dixon, Keith Roger
, p. 3912 - 3918 (2008/10/08)
The anions [CH(PR2O)2]- are formally phosphorus analogues of acetylacetonate. The lithium salts, Li[CH(PR2O)2], react under mild conditions with the chloro-bridged dimers [M2Cl4(PR′3)2] to form trans-[MCl2(PR′3)(CH(PR2O) 2Li)] (5; M = Pd, R = Ph, R′ = Et; M = Pt, R = Ph, R′ = Et or n-Bu; M = Pt, R = OEt, R′ = Et, n-Bu, or Ph). Crystals of 5 (M = Pt, R = Ph, R′ = Et) are orthorhombic, of space group Pbca, with a = 19.247 (8) ?, b = 21.918 (8) ?, c = 15.942 (4) ?, and Z = 8. The structure shows square-planar platinum coordination (Pt-Cl(1) 2.282 (9), Pt-Cl(2) 2.32 (1), Pt-P(3) 2.25 (1), Pt-C(1) 2.14 (3) ?) with the lithiated bis(diphenylphosphinyl)methyl ligand bonded to Pt via the methine carbon. The remarkable feature of the structure is that this six-membered ring ligand adopts a boat conformation with C(1) and Li in the prows so that Li is also coordinated by Cl(2) which is itself bound to Pt. The complex is thus tridentate toward Li within the mononuclear unit, but Li and O(1) lie close to a crystallographic center of symmetry which generates a dimer containing two Pt and two Li atoms. The Li coordination is approximately tetrahedral with Li-O(1) = 2.09 (6), Li-O(2) = 1.84 (6), Li-O(1)′ = 1.98 (7), and Li-Cl(2) = 2.19 (6) ?. The accuracy of the structure refinement was limited by a disorder or thermal motion problem within the PEt3 group, and R = 0.100 and Rw = 0.109 with use of 2123 observations and 331 variables. 31P and 1H NMR data for the complexes 5 are reported and discussed, an important feature being 1J(Pt-PR′3) in the range 2750-2827 Hz trans to the methine carbon. This indicates a comparatively small trans influence for the [CH(PR2O)2Li] ligand relative to normal C-bonded ligands. Other important coupling constants are 3J(P-P) = 11.8-15.4, 2J(Pt-P) = 83.8-99.8, 3J(P-H) = 8.6-14.3, 2J(P-H) = 6.7-22.8, 2J(Pt-H) = 72.5-125 Hz, where H is the methine proton. Comparison of NMR parameters for Na+ and Li+ salts suggests that the Li+ ion in 5 remains intimately associated with the complex in solution. The lithium cations are displaced by reactions of 5 with [M2Cl2(PEt3)4][BF4] 2 to form the unstable cations [(R′3P)Cl2Pt(μ-CH(PR2O) 2)M(PEt3)2]+ (R′ = Et, R = Ph, M = Pd; R′ = n-Bu, R = OEt, M = Pt).
