Cyclometalation of Phosphanes at Iridium(I): Interplay with Intramolecular Reductive Elimination Induced by the Strong π-Acceptor Ligands CO and NO

Reaction of [{Ir(μ‐Cl)(coe)2}2] (1; coe = cis‐cyclooctene) with 4 equiv. of PtBu2Ph in CH2Cl2 at ambient temperature resulted in oxidative addition of one phosphane ligand affording the known cyclometalated IrIII complex [IrCl(H)(PtBu2C6H4‐κ2P,C)(PtBu2Ph)] (2) in high yield. Compound 2 exhibits a coordinatively unsaturated five‐coordinate 16 VE species, and its reactivity towards strong π‐acceptor ligands is investigated. Reaction of 2 with CO resulted in addition of the CO ligand and inversion of cyclometalation to give known IrI complex trans‐[IrCl(CO)(PtBu2Ph)2] (3). In a similar manner, 1 reacted with nitrosonium tetrafluoridoborate affording the new complex salt [IrCl(NO)(PtBu2Ph)2][BF4] (4), which is isoelectronic with 3. Compounds 2 and 4 were characterized by spectroscopic methods as well as by X‐ray crystallography confirming their molecular structures. The synthesis and crystal structure of the cyclometalated unsaturated complex [IrCl(H)(PtBu2C6H4‐κ2P,C)(PtBu2Ph)] (2) is reported. Whereas 2 is quickly formed by oxidative addition of one PtBu2Ph ligand, contrarily, also a facile inversion of the cyclometalation with simultaneous reductive elimination in reactions with strong π‐acceptor ligands such as CO or NO+ was observed.