Hydrogen-halide versus alkyl-halide oxidative addition in dimethyl platinum(II) complexes: Crystal structure of [PtBr2(bpy)]

摘要

Dimethyl platinum(II) complexes [PtMe2(NN)] {NN = bu(2)bpy (4,4'-di-tert-butyl-2,2'-bipyridine) (1a), bpy (2,2'-bipyridine) (1b), phen (1,10-phenanthroline) (1c)} reacted with commercial 3-bromo-l-propanol in the presence of 1,3-propylene oxide to afford cis, trans-[PtBrMe2{(CH2)(3)OH}(NN)] (NN = bu(2)bpy (2a), bpy (2b), phen (2c)). On the other hand, [PtMe2(NN)] (1a)-(1b) reacted with the trace of HBr in commercial 3-bromo-1-propanol to give [PtBr2(NN)] (NN = bu(2)bpy (3a), bpy (3b)). The reaction pathways were monitored by H-1 NMR at various temperatures. Treatment of 1a-1b with a large excess of 3-bromo-l-propanol at -80 degrees C gave the corresponding methyl(hydrido)platinum(IV) complexes [PtBr(H)Me-2(NN)] (NN = bu(2)bpy (4a), bpy (4b)) via the oxidative addition of dimethyl platinum(II) complexes with HBr. The complexes [PtBr(H)Me-2(NN)] decomposed by reductive elimination of methane above -20 degrees C for bu2bpy and from -20 to 0 degrees C for bpy analogue to give methane and platinum(II) complexes [PtBrMe(NN)] (5a)-(5b) and then decomposed at about 0 degrees C to yield [PtBr2(NN)] and methane. When the reactions were performed at a molar ratio of Pt:RX/1:10, the corresponding complexes [PtBrMe(NN)] (5a)-(5b) were also obtained. The crystal structure of the complex 3b shows that platinum adopts square planar geometry with a twofold axis through the platinum atom. The Pt center dot center dot center dot Pt distance (5.164 angstrom) is considerably larger than the interplanar spacing (3.400 angstrom) and there is no platinum-platinum interaction. (C) 2007 Elsevier B.V. All rights reserved.