Phosphine-based platinum(II) hydroxo and oxo complexes

The platinum(II) hydroxo complexes, [L(2)Pt(mu-OH)](2)(BF4)(2) (1), have been prepared from the reaction of L(2)PtCl(2) with AgBF4 for L(2) = dppm, dppp, dppb, 2PMe(2)Ph, and Bu(2)(t)bpy (dppm = bis(diphenylphosphino)methane, dppe = bis(diphenylphosphino)ethane, dppp = bis(diphenylphosphino)propane, dppb = bis(diphenylphosphino)butane, Bu(2)(t)bpy = 4,4'-di-tert-butyl-2,2'-bipyridine). The trifluoroacetate (L(2) = dppp) and the nitrate (L(2) = Bu(2)(t)bpy) salts were also prepared. Two of these new hydroxo complexes, as well as the previously known PPh(3) complex, were structurally characterized. Crystals of [(PPh(3))(2)Pt(mu-OH)](2)(BF4)(2) from CH2Cl2/ether are monoclinic (C2/m) with a = 17.183(5) Angstrom, b = 18.243(4) Angstrom, c = 13.539(4) Angstrom, beta = 130.66(2)degrees, and Z = 2. Crystals of [(dppm)Pt(mu-OH)](2)(BF4)(2) . 2DMF from DMF/Et(2)O are monoclinic (P2(1)/n) with a = 17.193(6) Angstrom, b = 9.341(5) Angstrom, c = 18.666(7) Angstrom, beta = 98.73(2)degrees, and Z = 2. Crystals of [(dppb)Pt(mu-OH)](2)(BF4)(2) . 4MeOH from MeOH/Et(2)O are triclinic (P (1) over bar) with a = 12.547(13) Angstrom, b = 12.858(14) Angstrom, c = 13.039(20) Angstrom, alpha = 62.89(11)degrees, beta = 63.05(11)degrees, gamma = 60.87(12)degrees, and Z = 1. The structures of the binuclear dications are all similar, having planar P2Pt(mu-OH)(2)PtP2 cores with pseudo-D-2h, symmetry. For all but the dppm complex, addition of 2 equiv of LiN(SiMe(3))(2) results in deprotonation of the hydroxo groups and formation of the oxo complexes [L(2)Pt(mu-O)](2) The isolated oxo complexes are associated with one (L = PPh(3)) or two (L = PMe(2)Ph; L(2) = dppe, dppp, dppb, Bu(2)(t)bpy) LiX units (X = BF4 or CF3CO2) by interaction of the oxo ligands with the Li cations. The structure of [(PPh(3))(2)Pt(mu-O)](2) . LiBF4 (2) was determined. Crystals of 2 . 0.5C(7)H(8) from toluene are monoclinic (C2/c), with (173 K) a = 20.469(8) Angstrom, b = 18.085(9) Angstrom, c = 18.152(8) Angstrom, beta = 90.34(6)degrees, and Z = 4. The structure consists of two edge-shared square planar Pt atoms folded at the edge with cis-phosphines and bridging oxygen atoms. The bridging oxo oxygen atoms are coordinated to the Li cation of a LiBF4 contact ion pair. Two fluorine atoms of the BF4 ion also coordinate to the Li cation, resulting in a flattened tetrahedral environment about the Li cation. The oxo complex [(PMe(2)Ph)(2)Pt(mu-O)](2) .(LiBF4)(2) is unstable in solution and converts to the mu-oxo complex [(L(2)Pt)(3)(mu(3)-O)(2)](BF4)(2) (5) (L = PMe(2)Ph). Crystals of 5 from THF are orthorhombic (Pbna), with (173 K) a = 16.792(4) Angstrom, b = 17.710(5) Angstrom, c = 19.648(6) Angstrom, and Z = 4. The core structure of the dication consists of a dioxo-bicapped Pt-3 triangle. Deprotonation of the dppm hydroxo complex 1 (L(2) = dppm) occurs at the dppm methylene group and not at the hydroxo group. The resulting neutral hydroxo complex [(dppm-H)Pt(mu-OH)](2) (6) (dppm-H = bis(diphenylphosphino)methanide) is further deprotonated in THF at the OH group, giving the structurally characterized anionic oxo complex [(dppm-H)Pt(mu-O)](2)[Li(THF)(2)](2) (7) Crystals of 7 . 4THF from THF are monoclinic (P2(1)/c), with (173 K) a = 10.534(2) Angstrom, b = 21.016(2) Angstrom, c = 18.402(4) Angstrom, beta = 103.41(1)degrees and Z = 2. The structure has a planar core with the deprotonation of the dppm ligand evident from a shortening of the P-C distances. The Li ions are associated with the oxo groups, not the dppm-H groups, and are each coordinated by two THF molecules, giving a trigonal planar Li coordination geometry.