Molecular mechanics amine metal complexes

This section would not be complete without a brief mention of the use of molecular mechanics calculations in coordination chemistry, as these have been applied mainly to amine complexes 46,47 While most calculations relate to complexes of Co111, these are now being extended to complexes with other metal centres, e.g. Ni11.48... 

Bernhardt and Comba have combined molecular mechanics and the angular overlap model (AOM) to predict the d-d electronic spectra of several hexaamine compounds.The force field used, which had been described earlier, is appropriate for the modeling of Cu(II), Ni(II) (S = 1), Co(III), Fe(III), Cr(III), Zn(II), and Rh(III) complexes of amines, carboxylates, pyridines, and thia ethers. The AOM requires several parameters including metal-ligand cr-and TT-bonding terms [e and e ), interelectronic repulsion terms P- and F" ), and spin-orbit coupling terms Q. The current application uses the empirical relationship e r) = C/r to determine the value of e, where r is the bond distance and C is a constant whose value increases with alkyl substitution. This choice is consistent with the view that N-alkylation increases donor strength. The d-d electronic spectra of a variety of Cr(III), Co(III), and Ni(Il) hexaamine complexes are predicted to within 1000 cm. ... 

More accurate force constants for a number of transition metal complexes with amine ligands have been derived by normalinfrared spectra [187, 188], The fundamental difference between spectroscopic and molecular mechanics force constants (see Section 3.4) leads to the expectation that some empirical adjustment of the force constants may be necessary, even when these force constants have been derived by full normal-coordinate analyses of the infrared data. This is even more important for force constants associated with bond-angle deformation (see below). It is unusual for bond-length deformation terms to be altered substantially from the spectroscopically derived values. 

A series of l-(isoquinolin-l-yl)naphthalen-2-amines 239 was prepared. The atropisomers of the NH2, N-Me and N,N-diMe2 derivatives were separated on various CSPs and the barriers to racemization in toluene were experimentally determined AG = 125.4, 130.8, and 124.5 kj mol respectively. Molecular mechanics calculation showed that the most favorable transition state is the anti one in which the amino group is opposite to the isoquinoline nitrogen (04H223). When racemic 239 (R = Me, = H) and zirconium tetrakis(dimethylamide) were combined in a 2 1 ratio. X-ray data of the complex showed that a selection of identical ligand antipodes by the metal had occurred (homochiral complex) (02AG(IE)345). 

In addition, complexes with low- and high-molecular weight amines (ethylene-diamine, triethylenetetramine, butylamine, poly(ethyleneimine)) were tested as catalase models [75]. The examined polymer-metal catalysts were nearly as effective as the catalase models. Pshezhetskii et al. [76] studied the mechanism of hydrogen peroxide decomposition by PAA-Fe complex in the presence of diethylenetriamine as a cofactor (see the lower scheme on p. 12). 

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