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) 2 BH 2 }] - (R = Me, Ph; [(pz) 2 BH 2 ] - = 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) 2 BH 2 }[R = Me ( 7 ), Ph ( 8 )]. The pallada(IV)cyclic complex ( 6 ) has also been isolated. The first structural analysis of an arylpalladium(IV) complex, Pd(mq)MePh{(pz) 2 BH 2 } ( 8 ), is reported. Complex 8 occurs as two isomers and the one examined by X-ray crystallography has the fac -PdC 3 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)]BF 4 ( 4 ). Structural studies of the dimethylpalladium(IV) complex Pd(mq)Me 2 {(pz) 2 BH 2 } ( 7 ) and the platinum(IV) cation in [Pt(mq)Me 2 (bpy)]BF 4 ·0.75(CH 2 Cl 2 ) ( 5 ) reveal similar structures. The cation [Pd(mq)Me 2 (bpy)] + is less stable than the methyl(phenyl)palladium(IV) analogue ( 2 ), decomposing in (CD 3 ) 2 CO 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 ( 6 ), consistent with mq···CH 2 coupling to give Pd(II) species that undergo further decomposition.