COMPLEXES WITH HETEROCYCLIC NITROGEN LIGANDS .3. CATIONIC RHODIUM(I) DERIVATIVES AND APPLICATIONS IN CATALYSIS

The preparation and spectroscopic properties of mononuclear cationic c omplexes of rhodium(I) coordinated to the diolefin 2,5-norbornadiene ( NBD) and to the heterocyclic nitrogen ligands ihydrodipyrido-[2,3-b:3' ,2'-j]-1,10-phenanthroline (2-4N), o-6H-cyclohepta-[2,1-b:3,4-b]-di-1, 8-naphthyridine (3-4N) and 2,2'-bi-(3-methyl)-1,8-naphthyridine (Me-4N ) are described. The complexes show the characteristic intraligand ban ds of the ligands and an electronic low energy band insensitive to sol vent changes and of low intensity, which may be assigned to a ligand f ield band. The NMR properties agreed with the IR results showing the e quivalence of the two naphthyridine fragments in the complexes. Electr ochemically all the complexes display two reductions and one oxidation waves, in the potential region from +1.5 to -2.4 V vs Fc(+)/Fc. The w ater gas shift reaction (WGSR) and the selective reduction of nitroben zene to aniline under WGSR conditions are effectively catalysed by the se complexes.