Iron and ruthenium organometallic derivatives of spiro-substituted cyclotriphosphazenes bearing nitrile spacer: synthesis and electronic structure

Abstract

The first spiro cyclic phosphazene containing a nitrile pendant coordinating group, N 3P 3(O 2C 12H 8) 2(OC 6H 4CH 2CN) 2 ( 1), has been synthesized by the reaction of the spiro cyclophosphazene N 3P 3(O 2C 12H 8) 2Cl 2 with HOC 6H 4CH 2CN and K 2CO 3 in acetone. The spiro nitrile derivative 1 reacted with CpFe(dppe)I and with CpRu(PPh 3) 2Cl in the presence of NH 4PF 6 in CH 3OH as solvent to give the complexes {[CpFe(dppe)] 2(NCCH 2C 6H 4O) 2N 3P 3(O 2C 12H 8) 2}(PF 6) 2 ( 2) and {[CpRu(PPh 3) 2] 2(NCCH 2C 6H 4O) 2N 3P 3(O 2C 12H 8) 2}(PF 6) 2 ( 3), respectively. The spectroscopic results indicate that the spiro nitrile derivative behaves like their nitrile ligands. These results have been confirmed by extended Hückel molecular orbital calculations which have been carried out on the model complexes [CpFe(PH 3) 2NCCH 3] + ( 4) and [CpFe(PH 3) 2(NCCH 2C 6H 4O)(HO) 5N 3P 3] + ( 5). Two metal-to-ligand charge-transfer bands unprecedented in iron–nitrile complexes were observed in the electronic spectrum, as was predicted by the theoretical calculations. The electronic structures of complexes are discussed.