Organoplatinum(IV) and palladium(IV) complexes containing intramolecular coordination systems based on the 8-methylquinolinyl group (mq), including structures of the cation [Pt(mq)Me2(bpy)]+(bpy=2,2'-bipyridine) and the palladium(IV) complexes Pd(mq)MeR{(pz)2BH2} (R=Me,Ph;[(pz)2BH2]-=bis(pyrazol-1-yl)borate)

Oxidative addition of 8-(bromomethyl)quinoline (mqBr) to PdMeR(bpy) (R = Me, Ph; bpy = 2,2′-bipyridine) and [PdMeR{(pz)2BH2}]- (R = Me, Ph; [(pz)2BH2]- = bis(pyrazol-1-yl)-borate]) has given the first isolable palladium(IV) complexes containing an intramolecular coordination system, [Pd(mq)MeR(bpy)]Br [R = Me (1), Ph (2)] and [Pd(mq)MeR{(pz)2BH2}-[R = Me (7), Ph (8)]. The pallada(IV)cyclic complex [Pd(CH2CH2CH2CH2)(mq)(bpy)]Br (6) has also been isolated. The first structural analysis of an arylpalladium(IV) complex, Pd-(mq)MePh{(pz)2BH2} (8), is reported. Complex 8 occurs as two isomers and the one examined by X-ray crystallography has the fac-PdC3 configuration with the phenyl group trans to the quinoline nitrogen donor. NMR spectra of 8 indicate that the other isomer has the methyl group trans to the quinoline nitrogen donor. Similar geometric isomerism occurs for [Pd-(mq)MePh(bpy)]BF4 (4). Structural studies of the dimethylpalladium(IV) complex Pd(mq)-Me2{(pz)2BH2} (7) and the platinum(IV) cation in [Pt(mq)Me2(bpy)]BF4·0.75(CH2Cl 2) (5) reveal similar structures. The cation [Pd(mq)Me2(bpy)]+ is less stable than the methyl(phenyl)-palladium(IV) analogue (2), decomposing in (CD3)2CO by reductive elimination to form ethane and 8-ethylquinoline in ∼1:2 ratio, together with the Pd(II) products [Pd(mq)(bpy)]Br and PdBrMe(bpy). A complex mixture of 8-substituted-quinolines (saturated and unsaturated substituents) were obtained as the major products of decomposition of [Pd(CH2CH2CH2CH2)-(mq)(bpy)]Br (6), consistent with mq⋯CH2 coupling to give Pd(II) species that undergo further decomposition. © 1999 American Chemical Society.