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Dichlorophosphoranides featuring N,N-dimethyl-N′-arylformamidine substituents were isolated as individual compounds. Dichlorophosphoranide 9 was prepared by the multicomponent reaction of C-trimethylsilyl-N,N-dimethyl-N′-phenylformamidine and N,N-dimethyl-N′-phenylformamidine with phosphorus trichloride. Its molecular structure derived from a single-crystal X-ray diffraction was compared to the analogous dibromophosphoranide prepared previously by us by the reaction of phosphorus tribromide with N,N-dimethyl-N′-phenylformamidine. It was shown that a chlorophosphine featuring two N,N-dimethyl-N′-mesitylformamidine substituents reacted with hydrogen chloride to form dichlorophosphoranide 11. Its molecular structure was also determined by X-ray analysis and compared with that of closely related dichlorophosphoranide C.

Using DFT and ab initio calculations, we demonstrate that noncyclic formamidines can undergo thermal rearrangement into their isomeric aminocarbenes under rather mild conditions. We synthesized the silylformamidine, for which the lowest activation energy in this process was predicted. Experimental studies proved it to serve as a very reactive nucleophilic carbene. The reactions with acetylenes, benzenes, and trifluoromethane proceeded via insertion into sp, sp

A method for the synthesis of new C-silyl-N,N-dialkyl-N′-arylformamidines was developed. These derivatives were formed by the deprotonation of N-(trimethylsilyl)formamidinium salts to give the corresponding N-trimethylsilyl carbenes followed by a 1,2-migration of the silyl group. The reactions of C-silylformamidines with phosphorus(III) chlorides were then studied. The reactions between chlorodiphenylphosphane and the C-silylformamidines readily afforded C-phosphanylformamidines in high yields. The reactions of dichlorophosphanes and C-silylformamidines yielded previously unknown phosphanes that feature two formamidine substituents. In the reaction with phosphorus trichloride, the sterically least encumbered formamidine gave a stable two-coordinate compound through the formation of an intermediate tris(phosphane). The reactions of the sterically more encumbered formamidines led to the substitution of only two chlorine atoms to give a chlorophosphane or benzazaphosphole. The structures of key compounds were proven by X-ray crystal structure analyses.

International audience; Herein we report on the synthesis of a set of transient N-(PIII)-phosphanyl and N-(PV)-phosphoroselenoyl acyclic diaminocarbenes by deprotonation of the corresponding formamidinium salts. It is shown that N-(PV)-substituted acyclic diaminocarbenes undergo 1,2-phosphorus shift. Transformations of N-(PIII)-substituted acyclic diaminocarbenes result in tetrahydroquinazolines as final products. The proposed mechanism includes the isomerization of the carbenes into transient azomethine ylides followed by their cyclization via electrophilic aromatic substitution. Introduction of the electron-donating dimetylamino group into the phenyl substituent markedly enhances the rate of the reaction and the yield of the final product. In the case of the morpholine derivative, the corresponding azomethine ylide undergoes opening the morpholine ring giving vinyloxazolidin-2-amine. The results are corroborated by DFT calculations.

The deprotonation of N-di-tert-butylphosphanyl-N-aryl-N′-diisopropylformamidinium salts led to a new type of stable acyclic N-phosphanyl-diaminocarbene (PADC). Carbenes 8a–8d were separated as single compounds. The molecular structure of 8c was determined by X-ray diffraction analysis. The PADC 8 possess an optimal substitution pattern at the nitrogen atoms, and the N–Ccarbene–N bond angle is 120.7°. Structural changes near the carbenic carbon atom, such as substitution of phenyl with mesityl, phosphanyl with selenophosphoryl, or the diisopropylamino group with 2,2,6,6-tetramethylpiperidino, rendered them unstable. The PADCs underwent N,C-phosphorus shifts to afford new C-phosphanylformamidines.

The reactions of (di-tert-butylphosphanyl)amines and P,P-di-tert-butylphosphinoselenoic amides with Alder's dimer were studied. For di-tert-butylphosphanylamines, the reaction proceeds by primary electrophilic attack of Alder's dimer at the phosphorus atom to afford a dicationic salt 3. The deprotonation of 3 led to N-phosphanylformamidine 5 (“phosfam”). Alkyl(di-tert-butylphosphanyl)amines reacted with Alder's dimer in a 2:1 molar ratio to give N-phosphanylformamidinium salts; the second equivalent of (alkylamino)phosphane acts as a base. (Arylamino)phosphanes reacted with Alder's dimer to give benzazaphospholium derivatives. To direct the electrophilic attack of Alder's dimer at the nitrogen atom, phosphinoselenoic amides were used. They reacted with Alder's dimer at the selenium atom followed by a selenium–phosphorus shift to give N-(di-tert-butylphosphoroselenoyl)formamidinium salts. The phosphinoselenoic amides with bulky substituents (adamantyl, tBu) underwent cleavage of the N–alkyl bond to afford phosfams. Various key intermediates such as 3 and 22b were isolated and characterized. A convenient method for the synthesis of carbene precursor PIII and PV N-substituted formamidinium salts was developed.

Neutral dinuclear gold(I) complexes having general formula [Au2Cl2(NHCP)] (NHCP = N-phosphanyl N-heterocyclic carbene) have been synthesized by two different synthetic procedures: i) transmetalation of the NHCP ligand from the corresponding dinuclear silver(I) complex; ii) deprotonation of the corresponding N-phosphanyl azolium/tetrahydropyrimidinium salt in the presence of the gold(I) precursor. Interestingly, although the silver complexes are invariably dinuclear dicationic species of formula [Ag2(NHCP)2](OTf)2, both stoichiometries [Au2(NHCP)2](OTf)2 and [Au2Cl2(NHCP)] are potentially accessible with gold. Preference for either stoichiometry is dictated by the steric properties of the NHCP ligand as well as by a proper choice of the experimental conditions. On the other hand, preparation of copper(I) compounds with [Cu2Cl2(NHCP)] stoichiometry leads to product mixtures and has not led up to now to pure neutral compounds. Both the silver(I) and gold(I) complexes have been structurally characterized.

Dinuclear silver(I) complexes with bridging N-phosphorylated azolylidene ligands have been synthesized. Subsequent transfer of the ligands to other group 11 metal centers (Cu, Au) has been accomplished, highlighting the usefulness of the silver complexes as an easy to handle, air- and moisture-stable source of these ligands. Preliminary results indicate that dinuclear copper(I) complexes with N-phosphorylated imidazolylidene ligands display notable catalytic efficiency in nitrene transfer reactions.

Synthetic routes to novel N-phosphorylated 1,2,4-triazolium salts have been developed. Treatment of the specified salts with strong base produces new stable N-phosphorylated 1,2,4-triazol-5-ylidenes, which add Se in two stages (first at the carbene carbon and then at phosphorus) and rearrange to C-phosphorylated triazoles with heating. The capacity of such N-phosphorylated triazol-5-ylidenes to act as bidentate ligands toward transition-metal centers has also been demonstrated; in particular, the formation of two dinuclear silver carbene complexes is described herein. The structures of one representative carbene and of one carbene complex were determined by an X-ray study.

The first annelated bis- and mono-3H-1,3-azaphosphole ferrocene sandwich compounds have been synthesized from aminoferrocenes, and their X-ray structures are compared to those of their selenide-protected P═Se analogues, showing net discrepancies both in metallocene backbone conformation and in fused-ring planarity.

C -Phosphorylated (P V ) arylformamidines have been prepared by the reaction of N -arylamidotrichloromethyl derivatives of phosphorus, thiophosphorus, and selenophosphorus acids with secondary amines. Dependence of the reaction on the nature of chalcogene, electronic and steric factors has been studied. By reduction of N -arylformamidinophosphonoselenides the corresponding C -phosphorylated (P III ) arylformamidines have been synthesized.

Complexes of palladium(II) with newly disclosed, N-phosphanyl acyclic diaminocarbene ligands are synthesized for the first time and structurally characterized. The ligands coordinate palladium(II) in a chelating fashion, yielding remarkably stable complexes which can be stored without special precautions in the solid state. Related palladium(II) complexes with an isomerized chelating ligand, formed upon 1,2-migration of the phosphanyl group from the nitrogen to the adjacent carbon atom, have also been isolated in some instances and structurally characterized. The complexes efficiently act as precatalysts for Suzuki coupling reactions of aryl chlorides, where their productivity compares favourably with that of related palladium complexes with acyclic diaminocarbene ligands. In addition, the complexes show a distinct tendency to form as the byproduct the reductive homocoupling product of aryl chloride. This observation, together with ad hoc performed control tests, suggests that Pd colloids are involved in the formation of catalytically competent species.

A direct synthetic approach to C-phosphanyl-N,N-dialkyl-N′-aryl(alkyl)-formamidines was developed. It was shown that phosphorylation of the formamidines proceeds at the nitrogen atom affording N-phosphanylformamidinium salts. Upon deprotonation, these salts gave C-phosphanylformamidines via formation of carbenes followed by a 1,2-phosphorus shift.

A direct synthetic approach to C-phosphanyl-N,N-dialkyl-N′-aryl(alkyl)-formamidines was developed. It was shown that phosphorylation of the formamidines proceeds at the nitrogen atom affording N-phosphanylformamidinium salts. Upon deprotonation, these salts gave C-phosphanylformamidines via formation of carbenes followed by a 1,2-phosphorus shift.

N-phosphorylated, N-heterocyclic carbenes (NHC) based on the imidazoline skeleton have been prepared for the first time. The free carbenes feature good stability and in best cases they can be stored in the solid state for months at ambient temperature without decomposition. The carbenes are capable of acting as ligands towards late transition metal centres such as silver(I). The resulting complexes are stable and can be employed as reagents for the preparation of complexes of other group 11 metals upon transmetallation. The complexes, one carbene ligand and related compounds have all been structurally characterized.

A synthesis of 3H-1,3-benzazaphospholes starting from C-phosphorylated P(III) arylformamidines has been developed. Electron-donating substituents were found to enhance markedly the rate of the cyclization, with substituents at the meta position having the greatest effect. A plausible mechanism of the cyclization was proposed based on DFT calculations. (C) 2011 Elsevier Ltd. All rights reserved.

Correction for ‘Palladium(ii) complexes with chelating N-phosphanyl acyclic diaminocarbenes: synthesis, characterization and catalytic performance in Suzuki couplings’ by Anatoliy Marchenko et al., Dalton Trans., 2016, DOI: 10.1039/c5dt02250a.