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 (CH2Cl2)(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.