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 cydic bent allene (CBA) have been synthesized. Reaction with FeCl2(PPh3)(2) results in the loss of both phosphines to yield monomeric Fe(CBA)Cl-2. 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).