M-S bond lengths

Density Function Electronic Structure [Smit and Johnson (67)]. High activity is the result of electron transfer from Co(Ni) to Mo and corresponds to the removal of cr antibonding metal d-sulfur 3p electrons from Co(Ni). Optimal activity is the result of the right oxidation state of the Co(Ni) and the M-S bond length. 

Figure 5. Ranges of average M S bond lengths for bis(dithiolene) transition metal structures.

The longest average M—S bond lengths for structures based on a particular element occur with the dithiosquarate ligand, S2C402 (Table IIC, Entry 52 ... 

The single homoleptic bis(dithiolene) example based on Ag and shown in Fig. 4 is quite remarkable. The structure demonstrates the longest average M—S bond length (2.563 A) of all the homoleptic bis(dithiolene) complexes. The structural unit has a —3 charge relating to a formal oxidation state of Ag(I) . The geometry is distorted tetrahedral with A = 85.2°. 

The report by Henkel and co-workers (140) on [Mn(tdt)2]" complexes (n = 1 and 2 Table IIA, Entry 19) demonstrates the subtle energetic difference between distorted-tetrahedral and square-planar geometry. The dithiolene planes of the Mn(II) complex, [Mn(tdt)2]2, are nearly perpendicular (A, = 89.0°) and the average M S bond length is 2.417 A. Oxidation to the monoanion, [Mn(tdt)2]1, results in a transition to square-planar coordination geometry where the average M—S distance (2.281 A) has decreased by 0.14 A. 

A second to last entry in Table IV, Fig. 19) (368) and [Zr(bdt)3]2 (2.543 A) (7) falling at the outer extremes. Metal centers with higher formal charges and complexes with electron-withdrawing dithiolene substituents tend to result in shorter M—S bond lengths. Ranges for S—C and C=C distances are 1.665-1.785 and 1.304-1.524 A, respectively. 

Average bond length and angle parameters for the homoleptic tris(dithiolene) complexes are less sensitive to the identity of the transition metal or dithiolene ligand than those of bis(dithiolene) structures. Ranges of values are summarized in Fig. 22. Average M—S bond lengths cluster between 2.263 and 2.543 A, with values for two [Fe(mnt)3]2 units (2.263 and 2.269 A) (18), Co CAlCO),, 3... 

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