LIGAND STEREOCHEMISTRY OF METAL CLUSTERS CONTAINING PI-BONDED LIGANDS

摘要

The dummy atom formalism, originally proposed by Doman, Landis, and Bosnich for metallocenes, has been generalized in order to deal with any kind of pi-bonding ligands and cluster faces (which can also be seen as polyhapto moieties). A modified VESCF approach has been used to derive a general force field for eta(n)-coordinated pi-bonding ligands whose performances are comparable with those of the best current force fields for cyclopentadienyl derivatives but can be used also for mu(3)-eta(2):eta(2):eta(2) complex coordination modes. This approach, which can be considered a further step in the building up of a general force field for metal (carbonyl) clusters, has been tested by rationalizing the dynamic stereochemistry in solution of two classes of triangular clusters: M(3)L(3)(CO)(3) (M=Co, Rh, Ir; L=eta(5)-Cp, eta(5)-Cp*, eta(5)-Ind) and Co-3(eta(5)-Cp)(3)(mu(3)-eta(2):eta(2):eta(2)-RR'C6H4) (R=R'=H, Me, Et and R=Me, Et, Pr-i; R'=H).