Is bipyridine planar in metal complexes?

Deviations from planarity of the bipyridine ligand are discussed in terms of bow and twist angles and an S-shaped deformation. The angle phi between the best-planes through the pyridine moieties is related to the bow and twist angles by phi similar to root(theta(B)(2) + theta(T)(2)). The values are compared with the results of crystal structure determinations. A further deviation from ideality is the in-plane distortion of the ligand that is seen to decrease with increasing metal-nitrogen distances. (C) 2004 Elsevier Ltd. All rights reserved.