15367-52-9Relevant academic research and scientific papers
Imidazoliophosphines are true N-heterocyclic carbene (NHC)-phosphenium adducts
Abdellah, Ibrahim,Lepetit, Christine,Canac, Yves,Duhayon, Carine,Chauvin, Remi
experimental part, p. 13095 - 13108 (2011/02/24)
Whereas the external nucleophilic reactivity of α-amidiniophosphines has been previously illustrated by their complexation to transition-metal centers, their internal electrophilic reactivity is herein investigated by using BIMIONAP (BIMIONAP=N-methylated BIMINAP cation, BIMINAP=formal contraction of the acronyms BIMIP=2,2′-bis(diphenylphosphino)-1,1′-bibenzimidazole and BINAP=2,2′-bis(diphenylphosphino)-1,1′-binaphthyl). Reaction of tetraethylammonium chloride with free BIMIONAP is found to induce heterolytic cleavage of the N2C-P bond to give chlorodiphenylphosphine and a transient phosphine-N-heterocyclic carbene (NHC) species that is trapped in situ by protonation to the corresponding phosphine-benzimidazolium cation. When the chloride anion reacts with the cationic [Pd(η2-BIMIONAP)Cl 2] complex, the same cleavage occurs and the phosphine-NHC moiety is trapped in the corresponding [PdCl2(η2-phosphine-NHC)] complex. When the chloride anion reacts with the dicationic [Pd(π-allyl)(η2-BIMIONAP)]+ complex, allyldiphenylphosphine is produced, and the [PdCl(η2-phosphine- NHC)(PPh2CH2CH=CH2)]+ complex is obtained. Reaction of free BIMIONAP with the harder n-butyllithium nucleophile also induces heterolytic cleavage of the N2C-P bond, from which the phosphine-NHC moiety is trapped by hydrolysis of the benzimidazole ring or by P,C-sulfurization. Cleavage of a C-P bond with the weak Cl- nucleophile to release the reactive NHC moiety (according to the unusual scheme C-P+Cl-→C:+Cl-P) is a definite experimental indication of the dative nature of the N2C-P bond of amidiniophosphines, which are, therefore, better described as NHC→phosphenium adducts. This interpretation is supported by the calculation, at the DFT level, of a heterolytic dissociation mode of the N2C-P bond lower in energy than the homolytic one. A mesomeric description of the NHC→phosphenium entity is also proposed on the basis of electron localization function (ELF) and atoms in molecules (AIM) analyses. Finally ELF and AIM-based Fukui indices, molecular orbitals, and MESP analyses show that the initial attack of Cl- takes place at the carbenic atom of BIMIONAP. Addition of anionic nucleophiles (Cl-, nBu-) to free BIMIONAP and BIMIONAP-containing palladium complexes results in selective cleavage of the N2C-P bond, from which the released N-heterocyclic carbene (NHC) fragment can be trapped by protonation, hydrolysis, sulfurization, or coordination to PdII centers (see scheme).
Reactivity of X3P compounds with elemental sulfur, carbon disulfide or both, to yield X3PS, X3RCS2 or X3P.Sn.CS2 adducts
Demarcq, Michel C.
, p. 307 - 320 (2007/10/03)
Kinetic constants k2 have been obtained for the reaction of sulfur with 25 PIII compounds in toluene or hexane. In the series PhnMe3-nP (n = 1-3) or PhnBu3-nP (n = 0-3), log k2 decreases linearly with Σχi (χi=Tolman's electronic parameter of each ligand on P), taken as a gauge for the donor strength of P. Dramatic deviations from additivity are observed for the series PhnP(OEt)3-n, PhnP(OEt)3-n, and BunP(OEt)3-n(n = 0-3); the deviation is smaller for PhnPCl3-n, and even smaller for PhnP(NEt2)3-n . The results are discussed in terms of P-coordination (PIV vs. PV), stability and geometry of the intermediate X3P.S8 or of the transition state leading to this adduct, emphasis being laid on the donor/acceptor character of the P site. A similar dependence on X governs the reactivity of X3P with S8, CS2 or both, to give X3PS, X3P.CS2 (binary red adduct) or X3P.Sn.CS2 (ternary yellow adduct) respectively; an explanation for this parallelism is proposed.
PHASE-TRANSFER CATALYTIC ALKYLATION OF HYDROTHIOPHOSPHORYL COMPOUNDS. IV. REACTIONS WITH PRIMARY ALKYL HALIDES
Aladzheva, I. M.,Odinets, I. L.,Petrovskii, P. V.,Mastryukova, T. A.,Kabachnik, M. I.
, p. 431 - 437 (2007/10/02)
A convenient general method for the synthesis of compounds containing a thiophosphoryl group was elaborated on the basis of the Michaelis-Becker reaction with the use of the method of phase-transfer catalysis. The influence of the nature of the hydrothiophosphoryl compounds, of the alkylating agents, and of the reaction conditions on the yields of alkylated products was investigated in detail.
