145312-01-2

Upstream product

• 74364-66-2 [bis(triphenylphosphoranylidene)iminium][Rh(CO)4] 
• 99-54-7 3,4-dichloronitrobenzene 

Downstream Products

• 74364-66-2 [bis(triphenylphosphoranylidene)iminium][Rh(CO)4] 
• 89654-69-3 {(μ-nitrido)bis(triphenylphosphorus)}{Rh(CO)2Cl2} 
• 260403-61-0 [(P(C₆H₅)3)2N]⁽¹⁺⁾*[Rh(CO)2(CH₃COO)2]^(1-)=[(P(C₆H₅)3)2N][Rh(CO)2(CH₃COO)2] 
• 260441-97-2 [(P(C₆H₅)3)2N]⁽¹⁺⁾*[Rh(CO)2((CH₃)3CCOO)2]^(1-) = [(P(C₆H₅)3)2N][Rh(CO)2(C₄H₉COO)2] 

Relevant academic research and scientific papers

Promotion of the [PPN][Rh(CO)4]-catalysed carbonylation of nitrobenzene by 2-hydroxypyridine and related molecules: An apparent bifunctional activation

2-Hydroxypyridine and related molecules have a large activating effect on the previously reported [PPN][Rh(CO)4]-based catalytic system for the reductive carbonylation of nitrobenzene to methyl phenylcarbamate (PPN+=(PPh3)2N+). The effect is not due to the known 2-hydroxypyridine-2-pyridone tautomeric equilibrium, since 4-hydroxypyridine, for which the same tautomeric equilibrium exists, completely inhibits the reaction. A promoting effect of 2-hydroxypyridine is also observed in the reactions of a previously isolated metallacyclic complex, [PPN][Rh(CO)2ON(Ar)C(O)O], believed to be an intermediate in the catalytic reactions. However, the dependence of the rate of the catalytic reactions on the aniline concentration indicates that the effect found for the stoichiometric reaction cannot be the one that is relevant for the acceleration of the catalytic reactions. Thus, two different effects are present, both of which appear to be due to the proximal positions of a basic and an acidic site in the promoter molecules.

Mechanistic study of the carbonylation of nitrobenzene catalyzed by the [Rh(CO)4]-/nitrogen base system. X-ray structure of [PPN][Rh(CO)2ON(C6H3Cl2)C(O)O]

[PPN][Rh(CO)4] (1) reacts with ArNO2 or ArNO to yield the same product (Ar = Ph, 2; Ar = 3,4-Cl2-C6H3, 3). The reaction of 1 with nitrosoarenes also produces the corresponding azoxyarenes. The product was structurally characterized in the case of Ar = 3,4-dichlorophenyl and was shown to be [PPN][Rh(CO)2ON(C6H3Cl2)C(O)O] (3). Crystal data for 3: C45H33-Cl2N2O5P 2Rh·C4H8O, Mr = 989.64, triclinic, space group P1 (No. 2), a = 10.798(4) A?, b = 9.889(6) A?, c = 21.648(6) A?, α = 89.77(1)°, β = 96.00(1)°, γ = 92.71(1)°, V = 2296(2) A?2, Z = 2, Dc = 1.431 g cm-3, Mo Kα radiation (λ = 0.710 73 A?), μ(Mo Kα) = 6.00 cm-1, R = 0.037 (Rw = 0.047) for 5299 independent reflections having I > 3σ(I). Both of the reactions proceed through electron transfer to the nitroso or nitro derivative. Reaction of 2 and 3 with MeOH and CO produced the corresponding amine or the methyl carbamate, depending on the experimental conditions. The reaction of 3 with MeOH/CO was faster in the presence of nitrogen bases, and aniline was shown to be an intermediate in the synthesis of the carbamate. When the same reaction was performed in the presence of a large excess of nitrosobenzene, the two isomeric mixed azoxybenzenes 3,4-Cl2-C6H3N(O)=NPh and 3,4-Cl2-C6H3N=N(O)Ph were the largely dominant products, which strongly suggests the intermediate formation of a nitrene complex.