N-Heterocyclic Carbene Analogues of Nucleophilic Phosphinidene Transition Metal Complexes.

ABSTRACT: Chloride abstraction from the complexes [(?⁶ -p-cymene){(IDipp)P}MCl] (2?a, M=Ru; 2?b, M=Os) and [(?⁵ -C₅ Me₅ ){(IDipp)P}IrCl] (3?b, IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBAr^F ) in the presence of trimethylphosphine (PMe₃ ), 1,3,4,5-tetramethylimidazolin-2-ylidene (^Me IMe) or carbon monoxide (CO) afforded the complexes [(?⁶ -p-cymene){(IDipp)P}M(PMe₃ )]BAr^F ] (4?a, M=Ru; 4?b, M=Os), [(?⁶ -p-cymene){(IDipp)P}Os(^Me IMe)]BAr^F ] (5) and [(?⁵ -C₅ Me₅ ){(IDipp)P}IrL][BAr^F ] (6, L=PMe₃ ; 7, L=^Me IMe; 8, L=CO). These cationic N-heterocyclic carbene-phosphinidene complexes feature very similar structural and spectroscopic properties as prototypic nucleophilic arylphosphinidene complexes such as low-field ³¹ P?NMR resonances and short metal-phosphorus double bonds. Density functional theory (DFT) calculations reveal that the metal-phosphorus bond can be described in terms of an interaction between a triplet [(IDipp)P]⁺ cation and a triplet metal complex fragment ligand with highly covalent ?- and ?-contributions. Crystals of the C-H activated complex?9 were isolated from solutions containing the PMe₃ complex, and its formation can be rationalized by PMe₃ dissociation and formation of a putative 16-electron intermediate [(?⁵ -C₅ Me₅ )Ir{P(IDipp)}I][BAr^F ], which undergoes C-H activation at one of the Dipp isopropyl groups and addition along the iridium-phosphorus bond to afford an unusual ?³ -benzyl coordination mode.

SUBMITTER: Doddi A 

PROVIDER: S-EPMC7756676 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature