Dynamics of a cis-Dihydrogen/Hydride Complex of Iridium

Abstract

Insertion of CS2 into one of the Ir-H bonds of [Ir(H)5(PCy3)2] takes place to afford the dihydrido dithioformate complex cis-[Ir(H)2(eta2-S2CH)(PCy3)2] accompanied by the elimination of H2. Protonation of the dithioformate complex using HBF4.Et2O gives cis-[Ir(H)(eta2-H2)(eta2-S2CH)(PCy3)2][BF4] wherein the H atom undergoes site exchange between the dihydrogen and the hydride ligands. The dynamics was found to be so extremely rapid with respect to the NMR time scale that the barrier to exchange could not be measured. Partial deuteration of the hydride ligands resulted in a J(H,D) of 6.5 and 7.7 Hz for the H2D and the HD2 isotopomers of cis-[Ir(H)(eta2-H2)(eta2-S2CH)(PCy3)2][BF4], respectively. The H-H distance (d(HH)) for this complex has been calculated to be 1.05 A, which can be categorized under the class of elongated dihydrogen complexes. The cis-[Ir(H)(eta2-H2)(eta2-S2CH)(PCy3)2][BF4] complex undergoes substitution of the bound H2 moiety with CH(3)CN and CO resulting in new hydride derivatives, cis-[Ir(H)(L)(eta2-S2CH)(PCy3)2][BF4] (L = CH3CN, CO). Reaction of cis-[Ir(H)2(eta2-S2CH)(PCy3)2] with electrophilic reagents such as MeOTf and Me3SiOTf afforded a new hydride aquo complex cis-[Ir(H)(H2O)(eta2-S2CH)(PCy3)2][OTf] via the elimination of CH4 and Me3SiH, respectively, followed by the binding of a water molecule (present in trace quantities in the solvent) to the iridium center. The X-ray crystal structures of cis-[Ir(H)2(eta2-S2CH)(PCy3)2] and cis-[Ir(H)(H2O)(eta2-S2CH)(PCy3)2][OTf] have been determined.

A Gallium Hydride as an Oxidizing Agent: Direct Synthesis of IrV Complexes via Ga−H Bond Activation

“…The value obtained for 2 ‐PCy 3 is more consistent with a dihydride/dihydrogen formulation (i.e. [Ir III (H) 2 (H 2 )]), being similar to those measured for fluxional group 9 hydride/dihydrogen systems, for example, [Ir(H)(H 2 )(η 2 ‐S 2 CH)(PCy 3 ) 2 ] + (29 ms), [TpRh(PPh 3 )(H 2 )(H)][BAr f 4 ] (21 ms) . Consistently, 2 ‐PCy 3 undergoes rapid exchange with D 2 —in notable contrast to 2 ‐dppp or 2 ‐dcype (which undergo much slower exchange over a period of several days).…”

“…For comparison, the distinct hydride and dihydrogen ligands in the complex [IrH(H 2 )(bq)(PPh 3 ) 2 ] + (bq=7,8‐benzoquinolinate) show contrasting T 1 values of 390 and 30 ms at 188 K and 500 MHz . Fluxional species undergoing hydride/dihydrogen exchange also tend to show shorter T 1 (min) values, for example, 29 ms for [Ir(H)(H 2 )(η 2 ‐S 2 CH)(PCy 3 ) 2 ] + (at 400 MHz) . These measurements therefore suggest that 2 ‐dppp and 2 ‐dcype are best formulated as Ir V complexes featuring four terminal hydride ligands.…”

Synthesis and characterisation of halide, separated ion pair, and hydride cyclopentadienyl iron bis(diphenylphosphino)ethane derivatives

“…calc'd for C 33 Volatiles were removed in vacuo to yield red solids which were recrystallized from the minimum amount of MeCN with storage at −30°C to afford red crystals.…”

“…The Fe-N bond lengths range from 1.892(7)-1.908(4) Å and are comparable to those found in the literature with complexes containing dppe and Cp ligands (1.881(5)-1.909(8) Å). 17,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] 6 with pertinent bond lengths compiled in Table 1.…”

Activation of heteroallenes by coordinatively unsaturated nickel(ii) alkyl complexes supported by the hydrotris(3-phenyl-5-methyl)pyrazolyl borate (TpPh,Me) ligand

“…[1][2][3][4][5] Apart from CO 2 , other unsaturated small molecules, such as sulfur containing heteroallenes (CS 2 , RNCS, and OCS), can serve as potential building blocks for C 1 chemistry. [8][9][10][11][12][13][14][15][16][17][18] Further transformations of these substrates can be achieved via cleavage of the carbon-sulfur bond, similar to sulfur abstraction observed in low valent transition metal complexes. The activation of these compounds by transition metal complexes with M-C and M-H bonds frequently results in the formation of insertion products.…”