363136-93-0Relevant academic research and scientific papers
Substitution and migratory insertion reactions of square-planar allenylidene iridium complexes
Ilg, Kerstin,Werner, Helmut
, p. 3782 - 3794 (2008/10/08)
A series of (allenylidene)iridium(I) complexes of general composition trans-[IrX{=C=C=C(Ph)R}(PiPr3)2] [X = Br (5), I (6), NCO (7, 8), NCS (9, 10), OH (11, 12), N3 (13, 14)] was prepared from the corresponding chloro derivatives trans-[IrCl{=C=C=C(Ph)R}(PiPr3)2] (3, 4) by salt metathesis. An X-ray crystal structure analysis of 4 (R = Ph) confirmed the almost linear arrangement of the Ir-C-C-C chain. The azido compounds 13 (R = Ph) and 14 (R = tBu) react with CO by migratory insertion of the allenylidene ligand into the Ir-N3 bond. While the product trans-[Ir{C≡C-CR(Ph)N3}(CO)(PiPr3)2] with R = tBu (16) is thermally stable, the related complex with R = Ph (15) rearranges slowly in benzene to the metalated acrylonitrile derivative trans-[Ir{C(CN)=CPh2}(CO)(PiPr3)2] (17) by elimination of N2. Treatment of the phenolato compound trans-[Ir(OPh){=C=C=C(Ph)tBu}(PiPr3)2] (19), obtained from the analogous hydroxo derivative 12 and phenol, with CO also proceeds by migratory insertion and affords the functionalized (alkynyl)iridium(I) complex trans-[Ir{C≡C-CtBu(Ph)OPh}(CO)(PiPr3)2] (20) in excellent yield. The Lewis basicity of the hydroxo compounds 11 and 12 was also illustrated by the reactions with CF3CO2H, NEt3·3HF, and [pyH]BF4, which gave the substitution products trans-[Ir(κ1-O2CCF3){=C=C=C(Ph)tBu}-(PiPr 3)2] (21), trans-[IrF(=C=C=CPh2)(PiPr3)2] (22), and trans-[Ir{=C=C=C(Ph)tBu}(py)-(PiPr3)2]BF4 (23), respectively. In methanol solution, both 11 and 12 react by complete fragmentation of 1 equiv of CH3OH to afford the octahedral (allenyl)dihydridoiridium(III) complexes [IrH2{CH=C=C(Ph)R}(CO)(PiPr3)2] (24, 25). An unprecedented type of insertion reaction occurs by treating the hydroxo derivatives 11 and 12 with an excess of 1-alkynes R′C≡CH (R′ = Ph, CO2Me), which leads to the formation of the novel five-coordinate iridium(III) compounds [Ir(C≡CR′)2{η1-(E)-CH=CR′-CH=C=C(Ph) R}(PiPr3)2] (26-29). From 26, 27 (R′ = Ph), and CO, the octahedral 1:1 adducts 30 and 31 are formed. The molecular structures of 22 and 26 have been determined by X-ray crystallography.
