Substitution Processes in Dimeric Metal Complexes

Ligand Substitution Processes in Dimeric Metal Complexes 

Although the complexation reactions of the vanadyl ion are well known, relatively little is known about such reactions of the preceding 0x0 ion, TiO . This situation has been much improved by a recent study in which it is shown that, in addition to the monomer TiO, the trimers TiaO and TljOsHl , and the tetramer Ti406H4 are formed through the equilibria (50)-(52) in which H2O 

The ability of TiO to undergo this protonation, while does not, is attributed to a higher electron density on the oxo ligand of TiO.  

Kinetics of PR3 substitution on [(Ind)W(CO)3Cl] and Na[(Ind)W(CO)3], Ind = 17 -indenyl, were determined. The rate of substitution on [(Ind)W(CO)3Cl] is orders of magnitude faster than for [CpW(CO)3Cl]. For both [(Ind)W(CO)3Cl] and Na[(Ind)W(CO)3] the rate law for subsitution contains both ligand dependent and independent terms. The rate of substitution on [(Ind)W(CO)3Cl] is also faster than for the molybdenum analog, largely due to the associative pathway. The associative mechanism is more sensitive to the steric properties of L than to electronic properties. The ability of the indenyl ligand to facilitate both associative and dissociative substitution is attributed to the polarizability of the 7r-arene electrons and the ability of the ligand to structurally distort. Kinetic data are presented in Table 10.1.  

Extended Huckel calculations were used to study donor atom exchange in complexes of the type [(N-N)Cr(CO)5], where N-N = cis- and trans-H2N2, pyridazine, naphthyridine, and phen. [(cis-N2H2)Cr(CO)5] was also examined by ab initio calculations. For both isomers of [(N2H2)Cr(CO)5] the favored reaction 

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