Two types of imidazoliophosphane with additional electron-withdrawing substituents, such as alkoxy or imidazolio groups, are experimentally described and theoretically studied. Diethyl N,N'-2,4,6-methyl(phenyl)imidazoliophosphonite is shown to retain a P-coordinating ability toward a {RhCl(cod)} (cod = cycloocta-1,5-diene) center, thus competing with the cleavage of the labile C-P bond. Derivatives of N,N'-phenylene-bridged diimidazolylphenylphosphane were isolated in good yield. Whereas the dicationic phosphane proved to be inert in the presence of [{RhCl(cod)}(2)], the monocationic counterpart was shown to retain the P-coordinating ability toward a {RhCl(cod)} center, thus competing with the N-coordinating ability of the nonmethylated imidazolyl substituent. The ethyl phosphinite version of the dication, thus possessing an extremely electron-poor P(III) center, was also characterized. According to the difference between the calculated homolytic and heterolytic dissociation energies, the N(2)C⋅⋅⋅P bond of imidazoliophosphanes with aryl, amino, or alkoxy substituents on the P atom is shown to be of dative nature. The P-coordinating properties of imidazoliophosphanes with various combinations of phenyl or ethoxy substituents on the P atom and those of six diimidazolophosphane derivatives with zero, one, or two methylium substituents on the N atom, were analyzed by comparison of the corresponding HOMOs and LUMOs and by calculation of the IR C=O stretching frequencies of their [RhCl(CO)(2)] complexes. Comparison of the ν(CO)  values allows the family of the electron-poor Im(+) PRR' (Im = imidazolyl) potential ligands to be ranked in the following order versus (R,R'): P(OEt)(3)<(Ph,Ph)<(Ph,OEt)<(OEt,OEt)

The discovery, recent developments and prospects of the carbeniophosphines, and in particular of imidazoliophosphines, are related. The P-conjugated positive charge brought by the stabilized carbenium center gives stable (Im + )R 2 Pmetal dative bonds, while the ligands themselves contain a relatively stable C -P + R 2 dative bond, making imidazoliophosphines, more accurately described as NHC-phosphenium adducts. The preparation methods, structural features, electronic and coordination properties, reactivity, and catalytic properties of carbeniophosphines are reviewed.

The selective separation of benzene (Bz) and cyclohexane (Cy) is one of the most challenging chemical separations in the petrochemical and oil industries. In this work, we report an environmentally...

Carbene→chalcogenophosphenium adducts, which correspond to an intermolecular stabilization mode of the so far elusive, free oxo- and thiooxophosphenium species [R(2)P(+) = X] (X = O, S) by imidazolylidene (NHC) and diaminocyclopropenylidene (BAC) donors, have been isolated and fully characterized. The dative character of the R(2)C:→P(+)(X)Ph(2) bond was confirmed experimentally by nucleophilic displacement of the carbene donor with a chloride ion and by an exchange reaction of the NHC ligand of the NHC:→P(+)(O)Ph(2) adduct with an independently prepared BAC ligand, thereby giving the BAC:→P(+)(O)Ph(2) adduct. This dative character was further characterized by the DFT-calculated preference of carbene→chalcogenophosphenium systems for a heterolytic dissociation mode over a homolytic one.

With the view to enhancing the unique coordinating ability of the known phenyl-tetrakis(diisopropylamino)dicyclopropeniophosphine (Ph-DCP), replacement of the phenyl substituent by a tert-butyl substituent was envisaged. Both α-dicationic R-DCP phosphines, with R = Ph and Bu, were prepared in 54%-55% yield by substitution of RPCl with two equivalents of bis(diisopropylamino)-dicyclopropenylidene (BAC) and metathesis with NaBF. This method is implicitly consistent with the representation of R-DCPs as BAC-phosphenium adducts. The R-DCP salts were found to coordinate hard and soft Lewis acids such as a promoted oxygen atom (in the singlet spin state) in the corresponding R-DCP oxides, and electron-rich transition-metal centers in η-R-DCP complexes with AuCl, PtCl, or PdCl, respectively. Coordination of Ph-DCP with PdCl, which is a more electron-deficient Pd(II) center, leads to pentachlorinated dinuclear complexes [(Ph-DCP)PdCl]Cl, where the dicoordinate Cl bridge screens the repelling pairs of positive charges from each other. The same behavior is inferred for the Bu-DCP ligand, from which addition of an excess of (MeCN)PdCl was found to trigger a heterolytic cleavage of the DCP-Bu bond, releasing Bu and a dicationic phosphide, DCP: the latter is evidenced as a ligand in a tetranuclear complex ion [(μ-DCP)PdCl], which, upon HCl treatment, dissociates to a doubly zwitterionic dipalladate complex. All the complexes were isolated in 82%-97% yield, and five of them were characterized by X-ray crystallography.

Copper‐catalyzed cross‐coupling reactions have found widespread application in carbon–carbon or carbon–heteroatom bond formation. The relatively low toxicity, ease of handling, and low cost of these versatile complexes make them attractive for the elaboration of new methodologies and for the obtaining of new compounds. We focus on recent methods for the copper‐mediated formation of carbon–carbon bonds illustrated by different coupling reactions: cross‐dehydrogenative coupling, decarboxylative cross‐coupling, Sonogashira‐type reactions, Suzuki‐type reactions, and Neigishi‐type reactions. Domino reactions and, finally, more atypical reactions are also illustrated.

Whereas the all-cis tetrahydrofuran framework of the cytotoxic anhydrophytosphingosine jaspine B is considered as a relevant pharmacophore, little is known about the influence of the aliphatic chain of this amphiphilic molecule on its activity. We developed a synthetic strategy allowing flexible introduction of various lipophilic fragments in the jaspine's skeleton. The route was validated with two distinct approaches to jaspine B. Five chain-modified analogues were also prepared. Biological evaluation of these derivatives demonstrated a good correlation between their cytotoxicity and their capacity to inhibit conversion of ceramide into sphingomyelin in melanoma cells. A series of potent and selective inhibitors of sphingomyelin production was thus identified. Furthermore, the good overall potency of an omega-aminated analogue allowed us to dissociate of the pharmacological action of jaspine B from its amphiphilic nature.

In spite of the general oxophilic character and l 5 valence state accessibility of phosphorus centers, the oxidation of phosphanes bearing proximal positive charges remains challenging, in particular for dicationic representatives. Previously described diimidazolo-and diimidazolio-phosphane substrates were first resumed in the P-phenylated series, where the reported absence of coordinating ability of the N,N-dimethylated dication towards a neutral Rh(I) center is here confirmed towards a promoted oxygen atom. By contrast, the P-tert-butylated homologue is shown to undergo P-oxidation to give a stable gem-dicationic phosphine oxide (in 91% yield with m-CPBA). The latter could also be obtained by N,Ndimethylation of the neutral diimidazolo-phosphine oxide precursor. The strict covalent vs. dative character of the N 2 C-P bond in dicationic systems (N 2 C + ) 2 P(X)R (R ¼ Ph, tBu; X ¼ lone pair, :O) has been investigated by DFT calculations on a model series where (N 2 C + ) ¼ 1,3-dimethyl-1H-imidazolio-2-yl. The relative magnitude of Gibbs free energies of the homolytic and heterolytic dissociation modes shows that diamidinio-phosphines and corresponding P-oxides are not N 2 C / P donor-acceptor adducts (as mono(amidinio)phosphines are), but rather true gem-dicationic phosphines and phosphine oxides in the strict sense, respectively.