Racemic and chiral expanded salen-type complexes derived from biphenol and binaphthol: Salbip and salbin

The reaction of 2-fluoronitrobenzene with 2,2'-biphenol or (R)-binaphthol, followed by reduction and subsequent reaction of the resulting diamine with two equivalents of a salicylaldehyde, affords expanded salen-type ligands having backbones based on biphenol or binaphthol: salbipH(2), (R)-salbinH(2) and (R)-salbin(t-Bu)H-4(2). Deprotonation of these ligands with sodium methoxide or potassium hydride, followed by metallation with M(OAc)(2) (M = Mn, Co, Ni, or Cu), affords the corresponding metal complexes in good yield (61-85%). The species containing Mn, Co, and Ni all have distorted octahedral geometry, as determined by X-ray crystallography. The ethereal oxygen atoms occupy two coordination sites with metal-oxygen distances ranging from 2.19 to 2.36 angstrom. The imine nitrogen atoms are trans to each other in the solid state, an impossible geometry in traditional salen-type complexes. The species containing Cu are distorted square planar and show much longer metal-ethereal oxygen distances ranging from 2.79 to 3.22 angstrom. The manganese complexes are competent catalysts for the epoxidation of olefins. (c) 2005 Elsevier B.V. All rights reserved.