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Syntheses and Structures of Alkyl and Aryl Halide Complexes of the Type [(PiPr3)2PtH(η1-XR)]BArf and Analogues with Et2O, THF, and H2 Ligands. Halide-to-Metal π Bonding in Halocarbon Complexes

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journal contribution
posted on 27.11.1996, 00:00 by Matthew D. Butts, Brian L. Scott, Gregory J. Kubas
The reaction of Pt(PiPr3)3 with SO2 led to the formation of (PiPr3)2Pt(SO2) (1), isolated in 93% yield. The addition of [H(OEt2)2]+BArf (BArf = B(3,5-(CF3)2C6H3)4) to 1 in ether at −78 °C afforded the solvent complex trans-[(PiPr3)2Pt(H)(OEt2)]BArf (2) in 85% isolated yield. Complex 2 served as a precursor to monodentate halocarbon complexes of the type Pt(η1-XR). The dichloromethane complex trans-[(PiPr3)2Pt(H)(η1-ClCH2Cl)]BArf (3) was isolated in 80% yield by the recrystallization of 2 from CH2Cl2/hexane. IR spectroscopy suggested the existence of dichloromethane binding which was confirmed by X-ray crystallography. The reaction of 2 or 3 with iodo- or bromobenzene led to the isolation of the haloarene complexes trans-[(PiPr3)2Pt(H)(η1-XPh)]BArf, where X = I (4, 87% yield) or Br (5, 60% yield). Both compounds were characterized spectroscopically and by X-ray crystallography. An unexpected steric interaction in 4, suggested by molecular mechanics calculations to be significant, was rationalized in terms of halide-to-metal π bonding. The PhI complex 4 decomposed under harsh conditions to the bridging iodide compound {trans-[(PiPr3)2Pt(H)]2(μ-I)}BArf (6) which was structurally characterized. The THF adduct [(PiPr3)2Pt(H)(THF)]BArf (7), isolated in 78% yield and also characterized by X-ray crystallography, was formed when any of the compounds 2, 3, 4, or 5 was dissolved in THF. The CH2Cl2 complex 3 reacted with H2 to form the dihydrogen complex trans-[(PiPr3)2Pt(H)(η2-H2)]BArf which was characterized by NMR spectroscopy.