Triazenide structure, monodentate triazenides

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... 

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