Iridium complexes of an ortho-trifluoromethylphenyl substituted PONOP pincer ligand

Abstract

The synthesis and iridium coordination chemistry of a new pyridine-based phosphinito pincer ligand 2,6- (ArF2PO)2 C5H 3N (PONOP-ArF ; ArF = 2-(CF3)C 6 H4 ) are described, where the P-donors have ortho- trifluoromethylphenyl substituents. The iridium(III) 2,2’-biphenyl (biph) derivative [Ir(PONOP-ArF )(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-ArF )(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-ArF )(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-ArF )(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-ArF )(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.