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

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-Bu2POCH2)2C(Me)}Cl (2). The poor yield of 2 is partly explained by the formation of a di-nuclear byproduct [IrCl(COD)]2(μ2-{(t-Bu2POCH2)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 IrCl3·H2O in DMF leads to complete decomposition of the pincer ligand under the formation of Ir(H)(i-Pr2P(OH))3(CO) (4), underpinning the comparatively low thermal stability of aliphatic phosphinite pincer systems.