95246-85-8Relevant academic research and scientific papers
Oxidative Addition of Methyl Iodide to Dicarbonylrhodium(I) Complexes
Hickey, Cathryn E.,Maitlis, Peter M.
, p. 1609 - 1611 (1984)
Oxidative addition of MeI to - in aprotic solvents, the 'rate-determining' step in the carbonylation of methyl acetate and methyl halides (to acetic anhydride and acyl halides, respectively), is substantially promoted by iodide and b
Oxidative addition of RCOI to [AsPh4][Rh(CO)2I2]. Synthesis of [AsPh4][RCORh(CO)2I3] (R=Me, Et, n-Pr, i-Pr)
Howe, Laurie A.,Bunel, Emilio E.
, p. 167 - 174 (2008/10/09)
Reaction of [AsPh4][Rh(CO)2I2] (1) with RCOI yields complexes [AsPh4]2[RCORh(CO)I3]2 (2, R=Me; 3, R=Et; 4, R=n-Pr; 5, R=i-Pr). The (13)CO scrambling process for complexes [AsPh4][RCORh((13)CO)(S)I3] (R=Me, Et; S=CD3CN) along with the skeleton isomerizatio
Oxidative addition of alkyl halides to rhodium(I) and iridium(I) dicarbonyl diiodides: Key reactions in the catalytic carbonylation of alcohols
Ellis, Paul R.,Pearson, Jean M.,Haynes, Anthony,Adams, Harry,Bailey, Neil A.,Maitlis, Peter M.
, p. 3215 - 3226 (2008/10/08)
Alkyl iodides (RI) react with [Rh(CO)2I2]- to give acyl species [Rh(CO)(COR)I3]- (R = Et, nPr, iPr) and with [Ir(CO)2]2]- to give alkyl complexes [RIr(CO)2I2]- (R = Et, nPr, iPr, nBu, n-C5H11, n-C6H13). The reactions are analogous to the known reactions of MeI with [Rh(CO)2I2]- and [Ir(CO)2I2]-. The products are characterized spectroscopically and by an X-ray crystal structure determination for Ph4As[(n-C6H13)Ir(CO)2I3] which showed a fac,cis geometry for the anion. [Crystal structure data: monoclinic, a = 9.408(7) ?, b = 19.470(16) ?, c = 19.529(12) ?, β = 94.99(5)°, Z = 4, space group P21/n (a nonstandard setting of P21/c C2h5, No. 14); 2446 independent reflections (of 5197 measured) for which |F|/σ(|F|) > 4.0; R = 0.0966 (Rw = 0.0921, 238 parameters)]. Kinetic data for the reactions of [Rh(CO)2I2] with EtI, nPrI, and iPrI and for [Ir(CO)2I2]- with MeI, EtI, and nPrI show that oxidative addition of RI to [M(CO)2I2]- is first-order in both reactants. For M = Rh, reactions showed clean second-order kinetics below 80°C, though some decomposition occurred at higher temperatures. For M = Ir, clean second-order kinetics were observed with MeI, but reactions with EtI and nPrI showed a more complex kinetic behavior. A competing radical pathway is suggested, which can be quenched by added duroquinone. Second-order rate constants, k2, evaluated over the temperature ranges 70-80°C (M = Rh) and 35-50°C (M = Ir) gave the following activation parameters: (M = Rh) ΔH≠/kJ mol-1 = 50(±1) (R = Me), 56(±10) (R = Et), 51(±10) (R = nPr), 61(±15) (R = iPr); ΔS≠/J mol-1 K-1 = -165(±4) (R = Me), -195(±25) (R = Et), -215(±25) (R = nPr), -180(±30) (R = iPr); (M = Ir) ΔH≠/kJ mol-1 = 54(±1) (R = Me), 66(±5) (R = Et), 66(±3) (R = nPr); ΔS≠/J mol-1 K-1 -113(±4) (R = Me), -123(±15) (R = Et), -132(±11) (R = nPr). Comparisons are made between the reactions of methyl iodide and the higher alkyl iodides with both [Rh(CO)2I2]- (relative rates: Me, 1000, Et, 3; nPr, 1.7) and [Ir(CO)2I2]- (relative rates: Me, 1000; Et, 2.3; nPr, 0.75). The similarity to reactivity trends for organic nucleophiles suggests an SN2 mechanism, but with a competing radical pathway for iridium. Relative rates for the two nucleophiles, kIr/kRh ca. 150 (R = Me), 220 (R = Et), and 140 (R = nPr), are estimated. Alkyl isomerization (iso → n) is observed for both [Rh(CO)(COPr)I3]- and [PrIr(CO)2I3]- and displacement of propene from [Rh(CO)(COPr)I3]- by added ethene gives [Rh(CO)(COEt)I3]- reversibly. A mechanism involving hydridoalkene intermediates is proposed. The data are consistent with the carbonylation of the higher alcohols (ROH) proceeding via rate determining oxidative addition of RI to [Rh(CO)2I2]-, rather than by a route involving a rhodium hydride addition to an olefin derived from the ROH.
Factors influencing the oxidative addition of iodomethane to -, the key step in methanol and methyl acetate carbonylation
Fulford, Anthony,Hickey, Cathryn E.,Maitlis, Peter M.
, p. 311 - 323 (2007/10/02)
The oxidative addition of MeI to A+ - = n-Bu4N, Ph4P, and Ph4As>, the rate determining step in the Rh and I- catalysed conversion of methanol into acetic acid and of methyl acetate into acetic anhydride, is second order overall, first order in both complex and methyl iodide.The reaction is slower in less polar solvents (k2 1.9 * 10-5 M-1 s-1 in MeOAc, 3.1 * 10-5 in THF, and 10.0 * 10-5 M-1 s-1 at 298 K, in MeOH).Protic solvents accelerate the reaction; e.g. addition of ca. 3percent water quadruples the rate in THF.Values of ΔG* have been measured in MeOH and MeOAc between 288 and 318 K, and values of ΔH* -1>, and ΔS* -1 K-1> calculated from them; these numbers are very close to those for the catalytic carboxylation.Iodide also accelerates the reaction in methyl acetate up to two-fold, for addition of 20 equivalents of ->; this may be due to a general salt effect, stabilising the transition rather than the ground state.LiOAc behaves analogously; this is due to the reaction, MeI + LiOAcMeOAc + LiI, which increases the LiI concentration, not to the formation of acetato-complexes of unusual reactivity. n-Bu4NBF4 has no effect on the reaction in methyl acetate.The oxidative addition is insensitive to the nature of the counter-ion except for C12H25NH3+- in less polar solvents, where the IR spectra and also the slower rates of oxidative addition are consistent with some form of interaction, probably a N...H...Rh hydrogen-bond.
