Reactions of the Allenylidenestrans-[IrCl{=C=C=C(Ph)R}(PiPr3)2] with Electrophiles: Generation of Butatriene-, Carbene-, and Carbyne-Iridium Complexes

Abstract

The allenylidenciridium(I) complexes trans-[IrX(=C=C-CPh2)(PiPr3)2] (X = Cl: 1; X = I: 2) react with excess methyl iodide by C-C coupling and elimination of HI to give the eta2-butatriene compounds trans-[IrX-(eta2-CH2=C=C=CPh2)(PiPr3)2] (3, 4), of which 3 (X = Cl) was characterized by X-ray crystallography. Treatment of 1 and 5 (containing C=C=C(Ph)tBu as the allenylidene ligand) with HCI leads to the formation of the six-coordinate hydridoiridium(III) complexes [IrHCl2[= C=C=C(Ph)R](PiPr3)2] (6, 7) by oxidative addition at the metal center. In contrast, the reactions of 1 and 5 with both CF3CO2H and CF3SO3H afford the four-coordinate vinylcarbene compounds trans-[IrCl[=C(X)-CH=C(Ph)R[(PiPr3)2] (8-10). For X= CF3CO2, in nitromethane a dissociation of the C-X bond occurs and the cationic iridium carbynes trans-[IrCl[=C-CH=C(Ph)R](PiPr3)2]+ are generated. Upon addition of NaBPh4, the stable carbyne complexes 11b (R= Ph) and 12b (R = tBu) with BPh4 as the counterion were isolated in almost quantitative yields. The X-ray crystal structure analysis of 6 reveals that the chloro ligands are cis and the phosphane ligands trans disposed.

Carbene Iridium(I) and Iridium(III) Complexes Containing the Metal Center in Different Stereochemical Environments

“…An alternative route to 26 consists of the oxidative addition of gaseous HCl to 14 in benzene. If this reaction is monitored by 31 P NMR spectroscopy (in C 6 D 6 ), after 1 min the signal of the starting material at δ 4.2 disappeared and is replaced by a new signal at δ 1.7, which in analogy with the related allenylidene compound [IrHCl 2 (CCCPh 2 )(P i Pr 3 ) 2 ] can be assigned to the six-coordinate hydridoiridium(III) complex 26 . The presence of an Ir−H bond is indicated by the high-field resonance in the 1 H NMR spectrum at δ −19.23, the chemical shift of which is similar to that of [IrHCl 2 (CCCPh 2 )(P i Pr 3 ) 2 ] (δ −17.63).…”

Synthesis of ruthenium phenylindenylidene, carbyne, allenylidene and vinylmethylidene complexes from (PPh3)3−4RuCl2: A mechanistic and structural investigation

“…Also the addition of nonnucleophilic acid converted Ru [35,36] and Ir [37] allenylidene complexes into vinylcarbyne complexes. The formation of a dicationic carbyne complex from a diphenylallenylidene moiety was also observed by Dixneuf et al via 31 P NMR spectroscopy when converting a 18-electron (p-cymene)Ru diphenylallenylidene complex into the phenylindenylidene analogue with triflic acid at low temperatures [31].…”

Repercussion of a 1,3-Hydrogen Shift in a Hydride-Osmium-Allenylidene Complex

“…The P(1)− Os−P(2) angle of 109.51( 9) compares well with that of 7, as expected, since the same coordination mode for the etherdiphosphine is observed in both complexes. The alkyne coordinates to the osmium atom with Os−C( 16) and Os− C( 17) distances of 2.065 (10) and 2.098( 9) Å, respectively. The coordination produces a slight elongation of the triple bond, according to the usual Chatt−Dewar−Ducanson bonding model.…”

“…Thus, the C( 16)−C( 17) bond length of 1.280 (13) Å is intermediate between triple and double bond. The osmium-carbyne bond length Os−C(1) of 1.708 (10) Å and the C(1)−C(2) and C(2)−C(3A) distances of 1.441 (13) and 1.313( 16) Å, respectively, are similar to those of 2. The 1 H, 13 C{ 1 H}, and 31 P{ 1 H} NMR spectra, in dichloromethaned 2 at 253 K, are consistent with the structure shown in Figure 7.…”

“…The main problem for the development of the stoichiometric chemistry of these bifunctional compounds, which enables to understand the catalytic performance, is their low stability, since they are thermodynamically unstable with regard to the 1,2-insertion products (eq ). As a consequence, only a scarce number of hydride-vinylidene complexes of 8 group metals have been isolated and fully characterized so far, mainly osmium derivatives, − ,− whereas the known hydride-allenylidene compounds are reduced to the cations [OsH­(CCCPh 2 )­(CH 3 CN) 2 (P i Pr 3 ) 2 ] + and [OsH­(CCCPh 2 )­(η 2 -HCCH)­(P i Pr 3 ) 2 ] + and the neutral iridium­(III) complexes IrHCl­(CCCPhR)­(P i Pr 3 ) 2 (R = Ph, t Bu), although only some reactivity of the first of them has been investigated …”