Reactivity of M(ArN-N=NAr)(CO)(PPh3)2 with aryldiazonium salts (M=Rh(I), Ir(I); Ar=p-CH3C6H4, p-FC6H4)

The title complexes [M(ArN-N=NAr)(CO)(PPh3)2] (M=Rh(I), Ir(I); Ar = p-CH3C6H4, p-FC6H4) obtained from MCl(CO)(PPh3)2 by substitution of Cl- with (ArN3Ar)-, easily react with aryldiazonium salts [ArN2][BF4] both in benzene-acetone or –ethanol medium. The i.r. spectrum of [Ir(ArN3Ar)(CO)(PPh3)2][BF4] shows one band for v(CO) at ca. 2060 cm-1 typical of an iridium(III) arydiazenido- or aryldiazene-complex. The i.r. spectrum of the product of [Rh(OC-N(Ar)-N=NAr)(N2Ar)(PPh3)2][BF4] shows no band in the 2300-1950 cm-1 region (for v(NN) and v(CO) whilst it show bands of strong intensity at ca. 1690, 1630 and 1590 cm-1 and several band in the 1320-1160 cm-1 region. The band at 1690 cm-1 is assignable to vCO of an acyltriazenido ligand yielded by (formal) CO insertion into a Rh-N bond of the triazenido ligand.