Iridium complexes of an ortho-trifluoromethylphenyl substituted PONOP pincer ligand

The synthesis and iridium coordination chemistry of a new pyridine-based phosphinito pincer ligand 2,6-(Ar(F)(2)PO)(2)C(5)H(3)N (PONOP-Ar(F); Ar(F) = 2-(CF(3))C(6)H(4)) are described, where the P-donors have ortho-trifluoromethylphenyl substituents. The iridium(iii) 2,2′-biphenyl (biph) derivative [Ir(PONOP-Ar(F))(biph)Cl] was obtained by reaction with [Ir(biph)(COD)Cl](2) (COD = 1,5-cyclooctadiene) and subsequent halide ion abstraction enabled isolation of [Ir(PONOP-Ar(F))(biph)](+) which features an Ir ← F–C bonding interaction in the solid state. Hydrogenolysis of the biphenyl ligand and formation of [Ir(PONOP-Ar(F))(H)(2)](+) was achieved by prolonged reaction of [Ir(PONOP-Ar(F))(biph)](+) with dihydrogen. This transformation paved the way for isolation and crystallographic characterisation of low valent iridium derivatives through treatment of the dihydride with tert-butylethylene (TBE). The iridium(i) π-complex [Ir(PONOP-Ar(F))(TBE)](+) is thermally stable but substitution of TBE can be achieved by reaction with carbon monoxide. The solid-state structure of the mono-carbonyl product [Ir(PONOP-Ar(F))(CO)](+) is notable for an intermolecular anagostic interaction between the metal centre and a pentane molecule which co-crystallises within a cleft defined by two aryl phosphine substituents.