Three-Coordinate, Cyclic Bent Allene Iron Complexes

Novel three-coordinate Fe complexes featuring 1,2-diphenyl-3,5-bis­(2,6-dimethylphenoxy)­pyrazolin-4-ylidine or “cyclic bent allene” (CBA) have been synthesized. Reaction with FeCl₂(PPh₃)₂ results in the loss of both phosphines to yield monomeric Fe­(CBA)­Cl₂. Treatment with 2 equiv of benzyl Grignard affords the three-coordinate alkylated product Fe­(CBA)­(Bn)₂. Exposure of the alkylated species to an atmosphere of CO results in reductive elimination of 1,3-diphenylpropanone and formation of trigonal-bipyramidal Fe­(CBA)­(CO)₄.