Synthesis of Novel Terminal Iridium Phosphinidene Complexes

Abstract

Stable, crystalline iridium-complexed phosphinidenes, Cp*(L)IrdPR, are readily synthesized by (a) the reaction of Cp*(L)IrCl 2 (2, L) PPh 3) with LiPHMes* and (b) dehydrohalogenation of Cp*(PH 2 R)IrCl 2 (5, R) Mes*, Is, Mes) with in situ capturing of transient Cp*Irt PR (4) with phosphines, phosphites, arsines, isocyanides, and carbon monoxide (L). Cp*Irt PR eluded direct detection. The X-ray crystal structures are reported for Cp*(PPh 3)IrdPMes* (3) and Cp*(CO)IrdPMes* (15). The more congested 3 has an E configuration for its IrdP bond, whereas 15 is obtained in its Z form. The 31 P NMR chemical shifts and 2 J PP coupling constants are diagnostic for the E and Z forms. More shielded phosphinidene resonances and larger coupling constants are typical for the E isomers. These iridium-complexed phosphinidenes react with gem-diiodides to form phosphaalkenes, but not with carbonyl groups.

N‐Heterocyclic Carbene Functionalized Iridium Phosphinidene Complex [Cp*(NHC)IrPMes*]: Comparison of Phosphinidene, Imido, and Carbene Complexes

“…[9] This suggests that the observed shielding of the 31 P NMR resonance arises from the strong s-donor and weak p-acceptor properties of the NHC ligand rather than from geometrical differences. The structure has a two-legged piano stool geometry with a crystallographic mirror plane through C15, C12, Ir1, C18, P1, C1, C4, C9, and C11.…”

“…[9,10] A unique aspect of these novel complexes concerns the facile variation of stabilizing ligand L. So far, established ligands such as phosphines, arsines, phosphites, isocyanides and carbon monoxide have been introduced successfully, leading to stable, isolable complexes with strong metalÀligand bonds. [10] This encouraged us to investigate the availability of phosphinidene complexes that contain an N-heterocyclic carbene ligand, and to study their structural and electronic properties.…”

“…Furthermore, structural and bonding properties for the iridium phosphinidene parent complex that contains the imidazol-2-ylidene ligand is evaluated theoretically, and comparisons are made with analogous alkylidene and imido complexes. The transition metal iridium is used because similar alkylidene, [11,12] imido, [13] phosphinidene, [9] as well as N-heterocyclic carbene complexes [14] are known experimentally for iridium. [14] and confirms the presence of the carbene moiety in 2.…”

Nucleophilic Phosphinidene Complexes: Access and Applicability

“…[25] Treating iridium dichloride complex 9 (a L = PPh 3 , b L = IiPr 2 Me 2 ) with LiPHMes* provided 10 a,b (Scheme 4). [25] NHC-ligated iridium phosphinidene complex 10 b, characterized by an X-ray crystal structure, strongly resembles phosphane analogue 10 a; both show the expected bending (Ir-P-Mes* 10 a 113.73 (7) (5) ).…”

“…[25] Treating iridium dichloride complex 9 (a L = PPh 3 , b L = IiPr 2 Me 2 ) with LiPHMes* provided 10 a,b (Scheme 4). [25] NHC-ligated iridium phosphinidene complex 10 b, characterized by an X-ray crystal structure, strongly resembles phosphane analogue 10 a; both show the expected bending (Ir-P-Mes* 10 a 113.73 (7) (5) ). [25] The difference in the resonances in their 31 P NMR spectra (10 a d = 686.6 ppm, 10 b d = 560.0 ppm) is caused by the strong s-donor and moderate p-acceptor capabilities of the NHC ligand rather than by geometrical differences.…”