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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.

The tetramethyl ester of (hydroxy)(phenyl)methylenebis(phosphonic acid) reacts with morpholinosulfur trifluoride (MOST) to provide, along with the expected product of the substitution of a hydroxy group by fluorine, the adduct of (morpholino)(phenyl)carbene with PF5, compound 3a. Fluorination of dimethyl α-aroylphosphonates with MOST yields adducts of (amino)(aryl)carbene with PF5 (p-XC6H4)(Morph)C:PF5 [3a–f, where Morph is morpholyl, X = H (a), Me (b), OEt (c), F (d), Cl (e), CF3 (f)] as the major reaction products. The reaction mechanism proposed is based on experimental data and DFT calculations. The structure of adduct 3a was determined by X-ray studies. Hydrolysis of compounds 3e and 3f, bearing substituents Cl and CF3 on the phenyl ring, respectively, yields previously unknown benzoylpentafluorophosphates [p-XC6H4–C(=O)PF5]–MorphH+.

A rare example of the addition of sulfur to a phosphaalkene double bond leading to 1,2λ3,σ3-thiaphosphirane 4 is described. The relative accessibility of this compound has allowed the study of some of the chemical properties of the thiaphosphirane ring. The thermodynamic stability of 1,2λ3,σ3-thiaphosphiranes compared with λ5,σ3-phosphoranes has been studied by DFT calculations.

According to quantum chemical calculations at an ab initio level parent 1,2-diphosphete is slightly more stable than its corresponding 1,4-diphosphabutadiene structural isomer. The quantum chemical calculations indicate that substituents at phosphorus and to a much less extent at carbon exert strong influences on the equilibrium geometries of 1,2-diphosphete structures: pi donors at phosphorus strongly elongate the P-P bond while electronegative substituents at phosphorus increase the interflap angle of the four-membered ring systems, bringing an envelope conformation to the fore. The lengthening of the P-P bond gives rise to a Mobius-type delocalization within the ring moiety.