Ligand Linear Structure Formula

The final cu-bonded formulas (3.213), (3.214), and (3.219)-(3.221) bear an obvious resemblance to the usual VSEPR representations of these hypervalent species. Indeed, each cu-bonded structure has the same number of formal bond pairs (bp) and lone pairs (lp) as the VSEPR representation. Furthermore, the predicted angular geometries of the two models are essentially identical, with the linear (or near-linear) cu-bonded ligands occupying axial positions in the SN2-like trigonal bipyramidal motif. 

The linear ditertiary phosphine Ph2PC=CPPh2 (DPPA) forms six complexes of the formula (CuXjalDPPAjg [X = Cl, Br, I, NCS, NO3 (60), BH4 (59, 60)], which are believed to have the structure shown in Fig. 14. It has been assumed in the past that the (CuX)2(diphos)3 complexes [X = Cl, Br, I (237 ), NO3 (10), Ng (128)] had a similar structure. However, recent X-ray structural determinations on the azido (128) (Fig. 15) and chloro (4) complexes show them to contain only one bridging diphos ligand, and the other diphos complexes are almost certainly isostructural. The azido complex can be reacted with... 

The entropies of formation of the 1 1 bivalent metal complexes of the structurally related ligands, Formulas IX-XIII, reported by Martell (10) show a linear correlation with the square of the reciprocal of the effective ionic radius of the metal ions, r , in Equation 8, and with the number of negative carboxylate groups of the ligand that combine with the metal ion. 

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