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Pt(IV) complexes trans-Pt(PEt3)2(R)(Br)3 (R = Br, aryl and polycyclic aromatic fragments) photoeliminate molecular bromine with quantum yields as high as 82%. Photoelimination occurs both in the solid state and in solution. Calorimetry measurements and DFT calculations (PMe3 analogs) indicate endothermic and endergonic photoeliminations with free energies from 2 to 22 kcal/mol of Br2. Solution trapping experiments with high concentrations of 2,3-dimethyl-2-butene suggest a radical-like excited state precursor to bromine elimination.

The platinum(II) hydroxo complexes, [L2Pt(μ-OH)]2(BF4)2 (1), have been prepared from the reaction of L2PtCl2 with AgBF4 for L2 = dppm, dppp, dppb, 2PMe2Ph, and Bu t 2bpy (dppm = bis(diphenylphosphino)methane, dppe = bis(diphenylphosphino)ethane, dppp = bis(diphenylphosphino)propane, dppb = bis(diphenylphosphino)butane, Bu t 2bpy = 4,4‘-di-tert-butyl-2,2‘-bipyridine). The trifluoroacetate (L2 = dppp) and the nitrate (L2 = Bu t 2bpy) salts were also prepared. Two of these new hydroxo complexes, as well as the previously known PPh3 complex, were structurally characterized. Crystals of [(PPh3)2Pt(μ-OH)]2(BF4)2 from CH2Cl2/ether are monoclinic (C2/m) with a = 17.183(5) Å, b = 18.243(4) Å, c = 13.539(4) Å, β = 130.66(2)°, and Z = 2. Crystals of [(dppm)Pt(μ-OH)]2(BF4)2·2DMF from DMF/Et2O are monoclinic (P21/n) with a = 17.193(6) Å, b = 9.341(5) Å, c = 18.666(7) Å, β = 98.73(2)°, and Z = 2. Crystals of [(dppb)Pt(μ-OH)]2(BF4)2·4MeOH from MeOH/Et2O are triclinic (P1̄) with a = 12.547(13) Å, b = 12.858(14) Å, c = 13.039(20) Å, α = 62.89(11)°, β = 63.05(11)°, γ = 60.87(12)°, and Z = 1. The structures of the binuclear dications are all similar, having planar P2Pt(μ-OH)2PtP2 cores with pseudo-D 2 h symmetry. For all but the dppm complex, addition of 2 equiv of LiN(SiMe3)2 results in deprotonation of the hydroxo groups and formation of the oxo complexes [L2Pt(μ-O)]2. The isolated oxo complexes are associated with one (L = PPh3) or two (L = PMe2Ph; L2 = dppe, dppp, dppb, Bu t 2bpy) LiX units (X = BF4 or CF3CO2) by interaction of the oxo ligands with the Li cations. The structure of [(PPh3)2Pt(μ-O)]2·LiBF4 (2) was determined. Crystals of 2·0.5C7H8 from toluene are monoclinic (C2/c), with (173 K) a = 20.469(8) Å, b = 18.085(9) Å, c = 18.152(8) Å, β = 90.34(6)°, 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 [(PMe2Ph)2Pt(μ-O)]2·(LiBF4)2 is unstable in solution and converts to the μ3-oxo complex [(L2Pt)3(μ3-O)2](BF4)2 (5) (L = PMe2Ph). Crystals of 5 from THF are orthorhombic (Pbna), with (173 K) a = 16.792(4) Å, b = 17.710(5) Å, c = 19.648(6) Å, and Z = 4. The core structure of the dication consists of a dioxo-bicapped Pt3 triangle. Deprotonation of the dppm hydroxo complex 1 (L2 = dppm) occurs at the dppm methylene group and not at the hydroxo group. The resulting neutral hydroxo complex [(dppm-H)Pt(μ-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(μ-O)]2[Li(THF)2]2 (7). Crystals of 7·4THF from THF are monoclinic (P21/c), with (173 K) a = 10.534(2) Å, b = 21.016(2) Å, c = 18.402(4) Å, β = 103.41(1)°, and Z = 2. The structure has a planar core with the deprotonation of t...

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The platinum(II) amido-hydroxo and diamido complexes [(L 2 Pt) 2 (µ-NHR)(µ-OH)](BF 4 ) 2 (1) (L ) PPh 3 , R ) Ph, p-tol, p-Bu t C 6 H 4 , p-NO 2 C 6 H 4 ; L 2 ) dppp, R ) Ph, p-tol) and [L 2 Pt(µ-NHR)] 2 (BF 4 ) 2 ( 2 6) Å, β ) 99.01(1)°, and Z ) 4. The cationic portion consists of two edge-shared square-planar Pt centers folded at the edge with cis-phosphines and bridging hydroxo and amido groups. LiN(SiMe 3 ) 2 , LiNPr i 2 , LiPh, or LiMe addition to 1 (L ) PPh 3 , R ) Ph, p-tol, p-Bu t C 6 H 4 ) or 1a deprotonates the hydroxo group, forming the amido-oxo complexes 5). Crystals of 4 (R ) Ph) from CH 2 Cl 2 /ether are (183 K) orthorhombic (Pna2 1 ) with a ) 38.272(2) Å, b ) 9.2841(5) Å, c ) 15.0099(7) Å, and Z ) 4. The structure consists of two edge-shared square-planar Pt centers folded at the edge with syn-bridging amido groups and chelating dppm-H ligands. Crystals of 5‚5THF from THF are (183 K) monoclinic (P2 1 /n) with a ) 17.669(5) Å, b ) 31.884(3) Å, c ) 14.686(4) Å, β ) 105.03(1)°, and Z ) 4. The structure of the cationic portion shows two edge-shared square-planar Pt centers folded at the edge with syn-bridging NHNH 2 groups and chelating dppm-H ligands. The NHNH 2 groups bridge the Pt centers through the NH portion. The NH 2 portions coordinate to a Li(THF) 2 + group in a "tweezers" fashion resulting in tetrahedral coordination about the Li atom. Further deprotonation of 4 with LiMe yields the anionic diimido complexes [(dppm-H)Pt(µ-NR)] 2 (Li) 2 (6) (R ) H, Ph, p-tol).