Ylide Ph₃PCHP(O)Ph₂ (1) is the hydrolysis product of carbone C(PPh₃)₂ and reacts with MeI to produce the corresponding salt [Ph₃PCH(Me)P(O)Ph₂]I (2). Deprotonation of the cation of 2 with K[N(SiMe₃)₂] in methyl cyclohexane or toluene gives neutral ylide Ph₃PCMeP(O)Ph₂ (7). Addition of AlBr₃ at the oxygen atom of 7 involves simultaneous uptake of a proton along with formation of [Ph₃PCH(Me)P(OAlBr₃)Ph₂][AlBr₄] (9). Small amounts of resultant proton bridged [H{Ph₂(O)PCH(Me)PPh₃}₂][I₃]₃ (10) were isolated during attempts to silylate 2 with trimethylsilytriflate; the main product was found to be [Ph₃PCH(Me)P(O)Ph₂](O₃SCF₃) (8). In the course of our studies several by-products with cation [Ph₃PCH₂P(O)Ph₂]⁺ (4 to 6) were obtained. All compounds were characterized by multiple NMR and X-ray analyses.

Quantum chemical calculations at the BP86/TZVPP//BP86/SVP level of theory have been performed for the isoelectronic series of compounds [(PPh₃)₂CEH₂]^q (E^q=Be, B⁺, C²⁺, N³⁺, O⁴⁺). The equilibrium geometries and bond dissociation energies were calculated and the nature of the CE bond was investigated with charge and energy decomposition methods. The dication [(PPh₃)₂CCH₂]²⁺ could become isolated as a salt compound with two counter ions [AlBr₄]⁻. The X-ray structure analysis of [(PPh₃)₂CCH₂]²⁺ gave bond lengths and angles that are in good agreement with the calculated data. The geometry optimization of [(PPh₃)₂COH₂]⁴⁺ gave [(PPh₃)₂COH]³⁺ as the equilibrium structure. Bonding analysis of [(PPh₃)₂CEH₂]^q shows that [(PPh₃)₂CBeH₂] and [(PPh₃)₂CBH₂]⁺ possess donor–acceptor bonds in which the σ and π lone-pair electrons of (PPh₃)₂C donate into the vacant orbitals of the acceptor fragment. The multiply charged compounds are better described as substituted olefins [(PPh₃)₂CCH₂]²⁺, [(PPh₃)₂CNH₂]³⁺, and [(PPh₃)₂COH]³⁺, which possess electron-sharing σ and π bonds that arise from the interaction between the triplet states of [(PPh₃)₂C]²⁺ and the respective fragment CH₂, (NH₂)⁺, and (OH)⁺. The multiply charged cations [(PPh₃)₂CCH₂]²⁺, [(PPh₃)₂CNH₂]³⁺, and [(PPh₃)₂COH]³⁺ are calculated to be stable toward dissociation.

The reaction of the carbodiphosphorane C(PPh₃)₂ (1) with group 12 MI₂ compounds in THF leads to the salts (HC{PPh₃}₂)[MI₃(THF)] (M = Zn²⁺, 2; Cd²⁺, 3) in good yields upon proton abstraction from the solvent. The salt-like complex (HC{PPh₃}₂)₂[ZnI₄] (4) formed upon reaction of ZnI₂ with 1 in toluene and subsequent heating of the resulting powder in 2-bromofluorobenzene. When this reaction was carried out in 2-bromofluorobenzene as the solvent, no proton transfer occurred, and the colorless addition compounds [I₂Zn1] (5) and [I₂Cd1]₂ (6) were isolated. Compound 5 is monomeric, whereas in 6 the monomeric units are linked by bridging iodine ligands to produce a dimer. All compounds were characterized by X-ray analyses and ³¹P NMR and IR spectroscopy.

The photochemically generated complex [(CO)₅W(thf)] reacts with C(PPh₃)₂ (1) to provide the salt (HC{PPh₃}₂)₂[W₂(CO)₁₀] (5) in high yield by abstraction of a proton from the solvent thf. With [W(CO)₆], a slow reaction in benzene occurs to give a mixture of [(CO)₅W{O₂C₂(PPh₃)₂}] (6) and the heterocumulene (phosphonioacetylide) complex [(CO)₅W(CCPPh₃)] (7) by a Wittig type reaction. Both compounds were characterized by spectroscopic and X-ray diffraction analyses. Theoretical density functional calculations reveal that the ligand CCPPh₃ in 7 and in similar complexes is a strong σ-donor but weak π-acceptor.