Aliphatic pincer-type POCOP ligands and their complexation behaviour with iridium: Crystal structure of an iridium(III) phosphinite complex

Abstract

Reaction of 2 equivalents of 1,3-bis-(di- tert-butylphosphinito)-2-methyl-propane ( 1a) with [Ir(COD)Cl] 2 affords the first aliphatic diphosphinite PCP pincer complex with iridium, Ir(H){( t-Bu 2POCH 2) 2C(Me)}Cl ( 2). The poor yield of 2 is partly explained by the formation of a di-nuclear byproduct [IrCl(COD)] 2( μ 2-{( t-Bu 2POCH 2) 2CH(Me)}) ( 3). Reaction of 1,3-bis-(di- iso-propylphosphinito)-2-methyl-propane ( 1b) under the same condition does not give any cyclometallation, and reaction with IrCl 3·H 2O in DMF leads to complete decomposition of the pincer ligand under the formation of Ir(H)( i-Pr 2P(OH)) 3(CO) ( 4), underpinning the comparatively low thermal stability of aliphatic phosphinite pincer systems.