84751-23-5Relevant academic research and scientific papers
Synthesis and reactivity of the coordinatively unsaturated methylene complex Ir=CH2[N(SiMe2CH2PPh2)2]
Fryzuk, Michael D.,Gao, Xiaoliang,Joshi, Kiran,MacNeil, Patricia A.,Massey, Roberta L.
, p. 10581 - 10590 (2007/10/02)
The reactions of the coordinatively unsaturated iridium methylene complex Ir=CH2[N(SiMe2CH2PPh2)2] are described. This methylene complex is prepared by the reaction of 2 equiv of KOBut with the methyl iodide derivative Ir(CH3)I[N(SiMe2CH2PPh2) 2] in toluene; the extra equivalent of KOBut serves to coordinate the HOBut that is produced as the precipitate KOBut·-HOBut. The reaction of H2 with the methylene complex generates the trihydride amine IrH3[HN(SiMe2CH2PPh2)2] via a series of oxidative addition and migratory insertion steps; the trihydride derivative loses H2 upon workup to generate the iridium(III) dihydride IrH2[N(SiMe2CH2PPh2)2]. The reaction of the methylene complex with PMe3 produces the square planar PMe3 derivative Ir(PMe3)[N(SiMe2CH2PPh2) 2] and ethylene (0.5 equiv); monitoring this reaction at low temperatures shows the presence of a number of intermediates that suggest the mechanism involves the generation of free H2C=PMe3 which reacts with the methylene complex to ultimately give the observed products. The reaction of the methylene complex with CO results in the formation of Ir(CO)[(CH2PPh2CH2SiMe2NSiMe 2CH2PPh2)], in which the methylene unit has inserted into one of the iridium-phosphine bonds of the ancillary tridentate ligand. Also produced in this reaction is a small and variable amount (≤15%) of the iridium(I) carbonyl complex Ir(CO) [N(SiMe2CH2PPh2)2]; the fate of the coordinated methylene unit for this side reaction could not be determined. Oxidative addition reactions were also examined; addition of Al2Me6 to the methylene derivative resulted in the formation of the hydride-aluminum complex Ir(μ-AlMe2)H[N(SiMe2-CH2PPh 2)2]; this heterobimetallic species has the AlMe2 unit directly bound to iridium and bridged by the amide donor of the backbone. A mechanism is proposed that involves oxidative addition of AlMe3 to the iridium center followed by migratory insertion of the methylene unit and the methyl to generate an ethyl ligand which β-eliminates and releases ethylene to generate the hydride. The methylene complex also reacts with methyl iodide to generate the ethylene hydride iodide complex Ir(η2-C2H4)H(I)[N(SiMe2CH 2PPh2)2]; the proposed mechanism also involves oxidative addition as the first step followed by migratory insertion to generate an ethyl moiety; however, rather than simple β-elimination to the iridium center, the amide unit abstracts the β-hydrogen to form an amine-olefin complex that subsequently inverts at nitrogen and then oxidatively adds the N-H unit to generate the hydride complex. Deuterium-labeling experiments show that the abstraction of the β-hydrogen is reversible since there is scrambling of the label equally into both the α and β positions of the coordinated ethylene.
Stereoselective formation of iridium(III) amides and ligand-assisted heterolytic splitting of dihydrogen
Fryzuk, Michael D.,MacNeil, Patricia A.
, p. 682 - 684 (2008/10/08)
A series of octahedral iridium(III) amides are formed stereoselectively from four- and five-coordinate precursors. In addition, an unusual ligand-assisted heterolytic splitting of dihydrogen is observed.
