POLYENE-ML2 AND POLYENE-ML4 COMPLEXES - CONFORMATIONAL PREFERENCES AND BARRIERS OF ROTATION

Rotational barriers in acyclic and cyclic polyene-ML2 and -ML4 complexes are analyzed by subdividing the molecules into polyene and MLnfragments. In CnHn-ML2 the inherently small rotational barrier may be strongly perturbed by substitution patterns which create an electron density asymmetry. Slipping and geometrical deformations of the coordinated polyene may also occur. In acyclic polyene-ML2complexes generally large barriers are to be expected, with well-defined equilibrium conformations. The analysis of ML4 complexes follows similar lines, but is complicated by a geometrical degree of freedom which relates C4vand C2v, ML4fragment geometries. © 1979, American Chemical Society. All rights reserved.