Di- and trinuclear Pd(II) and Pt(II) complexes containing bridging 2,7-disubstituted naphthyridines

Dinuclear complex cations of the type cis-[M2L2(bpy)(2)](2+) (1, 2, M = Pd, L = onp(-), monp(-): 5, 6, M = Pt, L = onp(-), monp(-)) contain mu-1 kappa N':2 kappa N-8 bridging monoanionic naphthyridine ligands (Honp = 1,8-naph thyridin-2-one, Hmonp = 7-methyl-1,8-naphthyridin-2-one) in a head/tail arr angement and exhibit short M M distances in the range 2.794-2.804 Angstrom. The analogous reaction of [MCl2(bpy)] with the dibasic 2,7-disubstituted n aphthyridine H(2)donp (1,8-naphthyridin-2,7-dione) in the presence of LiOH leads to the trinuclear complexes cis-[M-3(donp)(2)(bpy)(3)](2+) (3) (M = P d) and 9 (M = Pt) with similar short M ... M distances (2.801-2.807 Angstro m). A head/tail arrangement is once again adopted by the mu(3)-1 kappa O-2: 2 kappa N-1:3 kappa N-8 bridging donp(2-) dianionic ligands. Blue-green col oured 9 exhibits reversible one-electron transfer waves at E-1.2 0.65 and 1 .30 V (in CH3CN versus Ag/AgCl) accompanied by a colour change from. blue-g reen (lambda(max) = 725 nm) to violet (lambda(max) = 695, 540 nm) and corre sponding to oxidation to [Pt-3(donp)(2)(bpy)(3)](3+) and [Pt-3(donp)(2)(bpy )(3)](4+). 9 can be reduced to green coloured [Pt-3(donp)(2)(bpy)(3)](+) at E-1/2 = - 0.82 V. The structures of the above compounds and [Pt(mbznnp)(bp y)(H2O)]ClO4 (4, Hmbznnp = 2-benzylamino-7-methyl-1,8-naphthyridine [Pt(don p)(bpy)] (7) and [Pt2Cl2(donp)(bpy)(2)] (8) were established by X-ray struc tural analysis. (C) 1999 Elsevier Science S.A. All rights reserved.