Crystal structures of two unusual, high oxidation state, 16-electron irida-benzenes

Treatment of carbon-yl(1,2-diphenylpenta-1,3-dien-1-yl-5-yl-idene)bis-(tri-phenyl-phosphane)iridium, [IrCO(-C(Ph)=C(Ph)-CH=CH-CH=)(PPh3)2], with either bromine or iodine produced di-bromido-(1,2-diphenylpenta-1,3-dien-1-yl-5-yl-idene)(tri-phenyl-phosphine)iridium(III), [IrBr2{-C(Ph)=C(Ph)-CH=CH-CH=}(PPh3)], (I), and (1,2-diphenylpenta-1,3-dien-1-yl-5-yl-idene)di-iodido-(tri-phenyl-phosphane)iridium(III), [IrI2{-C(Ph)=C(Ph)-CH=CH-CH=}(PPh3)], (II), respectively, which are two rare examples of 16-electron metalla-benzenes. Structural elucidation of (I) and (II) reveals that these isotypic irida-benzenes are unusual, not only in their electron count, but also in their coordination sphere of the Ir(III) atom where they contain an apparent open coordination site. The crystal structures of (I) and (II) confirm that the mol-ecules are complexes containing five-coordinated Ir(III) with only one tri-phenyl-phosphine group bound to the iridium atom, unambiguously proving that the mol-ecules are indeed 16-electron, high-oxidation-state irida-benzenes. The coordination geometry of the Ir(III) atom in both structures can be best described as a distorted square pyramid with the P, two Br (or I) and one C atom in the basal plane and another C atom in the apical position.