Isolation and structure of [papH](ClO4) [pap=2-(phenylazo)pyridine]: Its use in the synthesis of M-pap complexes

The salt, [HL](ClO4) [L = 2-(phenylazo)pyridine] has been isolated from its conjugate base, L, in almost quantitative yield (>95%). The X-ray structur e of the above salt is reported. The geometry of [HL](+) is trans about the diaza fragment. The N-N bond length in this compound is 1.258(5) Angstrom which confirms a double bond. This length is elongated in its metal complex es due to extensive d(Pi)-p(Pi) interactions. The use of [HL] as a reagent for the synthesis of M-L complexes from the metal carbonates is explored. I n this respect, the syntheses of [CO(L)(3)](ClO4)(2). [Cu(L)(2)](ClO4), [Ag (L)(2)](ClO4) complexes from the corresponding metal carbonates and [HL](Cl O4) are described.