Di- and tripalladium(II) and -platinum(II) complexes containing 7-amino-1,8-naphthyridin-2-one as a bridging ligand - Oxidation of a [Pt-3](6+) core to [Pt-3](8+)

All three dinuclear complexes [Pd-2(donp)(2)(bpy)(2)] (1) (H(2)donp = 1,8-n aphthyridin-2,7-dione), [Pd-2(H(2)nonp)(2)(bpy)(2)](ClO4)(2) (2), and [Pt-2 (H(2)nonp)(2)(bpy)(2)](PF6)(2) (3) (H(3)nonp = 7-amino-1,8-naphthyridin-2-o ne) exhibit the mu-1 kappa N-1:2 kappa N-8 bridging mode for their head/tai l orientated naphthyridine Ligands. Whereas 1 and 3 may be prepared by dire ct reaction of the dinucleating ligand with [MCl2(bpy)], formation of compe ting tripalladium(II) complexes must be avoided for 2 by employment of the precursor H(2)acnonp (7acetamido-1,8-naphthyridin-2-one), which affords [H( 2)nonp](-) on cleavage of its original acetyl group. A mixture of the head/ tail (4a) and head/head (4b) isomers of [Pd-3(Hnonp)(2)(bpy)(3)] (ClO4)(2) is obtained when H(3)nonp is treated with [PdCl2(bpy)] and LiOH at room tem perature for 2 d, followed by precipitation with LiClO4. Contrastingly excl usive formation of 4a is observed upon refluxing this reaction mixture for 3 d in aqueous solution. The [Hnonp](2-) ligands exhibit a mu(3)-1 kappa N- 1:2 kappa N-8:3 kappa N-7 bridging mode that leads to short Pd...Pd interac tions of 2.781(2) and 2.775(2) Angstrom. Similar metal-metal distances of 2 .771(3) and 2.816(3) Angstrom are observed in head/head-[Pt-3(acnonp)(Hnonp )(bpy)(3)]Cl-2 (5). An in situ 2e(-)-oxidation (Ag+/Ag) of the [Pt-3](6+) c ore in triplatinum(II) species such as 5 formed by the reaction of [PtCl2(b py)] with H(2)acnonp allows the isolation of diamagnetic dark-brown head/he ad-[Pt-3(Hnonp)(2)(NO3)(bpy)(3)](ClO4)(2) (NO3) (6) with an average oxidati on state of Pt (2.67+). The Pt-Pt distances of 2.723(2) and 2.670(2) A are markedly shorter than in 5.