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

The reaction of Pt(PiPr 3 ) 3 with SO 2 led to the formation of (PiPr 3 ) 2 Pt(SO 2 ) ( 1 ), isolated in 93% yield. The addition of [H(OEt 2 ) 2 ] + BAr f (BAr f = B(3,5-(CF 3 ) 2 C 6 H 3 ) 4 ) to 1 in ether at −78 °C afforded the solvent complex trans -[(PiPr 3 ) 2 Pt(H)(OEt 2 )]BAr f ( 2 ) in 85% isolated yield. Complex 2 served as a precursor to monodentate halocarbon complexes of the type Pt(η 1 -XR). The dichloromethane complex trans -[(PiPr 3 ) 2 Pt(H)(η 1 -ClCH 2 Cl)]BAr f ( 3 ) was isolated in 80% yield by the recrystallization of 2 from CH 2 Cl 2 /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 -[(PiPr 3 ) 2 Pt(H)(η 1 -XPh)]BAr f, 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 -[(PiPr 3 ) 2 Pt(H)] 2 (μ-I)}BAr f ( 6 ) which was structurally characterized. The THF adduct [(PiPr 3 ) 2 Pt(H)(THF)]BAr f ( 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 CH 2 Cl 2 complex 3 reacted with H 2 to form the dihydrogen complex trans -[(PiPr 3 ) 2 Pt(H)(η 2 -H 2 )]BAr f which was characterized by NMR spectroscopy.