Copper triazenide complexes

Although monodentate triazenide ligands were first proposed (erroneously) by Meunier in 1900 150,152) for the copper(I) complex Cu(PhNNNPh), this mode of coordination was not finally confirmed until 1976 when Brown and Ibers 21, 22) reported the X-ray crystal structure of c/s-Pt(PhNNNPh)2(PPh3)2 C6H6 (Fig. 1). Monodentate triazenide ligands remain relatively rare and are mainly confined at present to the four-coordinate d metal ions, Rh(I), Ir(I), Pd(II), and Pt(II). To date only six examples have been characterized by diffraction methods (see Table I). In some of these, notably trans-PtH(p-tol-NNN-tol-pXPPh3)2, there is a short nonbonded contact (2.91 A) between the metal and the terminal (N-3) nitrogen atom 109). Variable-temperature proton NMR studies (see Section... 

Studies of electronic spectra are confined almost exclusively to derivatives of silver(I) (236, 237) and mercury(II) (79, 194, 234), both of which have been investigated extensively. Data have also been recorded for copper(II) triazenide complexes (79, 236) and nickel(II) (84). 

The ability of copper(I) and silver(I) salts to react with triazenes was first noted by Peter Griess in 1866 (90), and triazenide complexes of these metals have attracted considerable attention during the intervening years. In marked contrast the first gold triazenide complexes have only recently been reported. 

Finally, copper(I), silver(I), and mercury(II) triazenides react with selected rhodium(I), iridium(l), and platinum(II) halide complexes to afford metal-metal bonded binuclear triazenide-bridged species 129). 

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