Synthesis and Characterization of 4‐, 5‐, and 6‐Coordinate Tris(1‐ethyl‐4‐isopropylimidazolyl‐κ N )phosphine Cobalt(II) Complexes

The synthesis and characterization of [Co(T1Et4 i PrIP)X 2 ] {T1Et4 i PrIP = tris(1‐ethyl‐4‐isopropylimidazolyl)phosphine; X = OTf – ( 1 ), Cl – ( 2 ), Br – ( 3 )} and [Co(T1Et4 i PrIP)(CH 3 CN) 3 ](OTf) 2 ( 4 ) were investigated. In compounds 1 and 4 , T1Et4 i PrIP binds in a tridentate fashion, whereas 2 and 3 feature bidentate ligation. Compound 1 additionally coordinates two triflate ligands to complete a distorted square pyramidal geometry. Compound 4 also binds three acetonitrile ligands to afford a distorted octahedral geometry. Compounds 2 and 3 exhibit a distorted tetrahedral geometry for which the ligands comprise two imidazole nitrogen atoms and two halides. Bidentate coordination by using a tris(imidazolyl)phosphine ligand is unprecedented. Compounds 2 and 3 can be derived from 1 by the addition of either Cl – or Br – salts, respectively, whereas 4 can be generated by dissolving 1 in acetonitrile. DFT studies indicate that the HOMO–LUMO gaps of all compounds are comparable; however, steric factors stabilize the formation of 2 and 3 over 1 in the presence of halide ligands.