Carbene insertion into a P–H bond: parent phosphinidene–carbene adducts from PH₃ and bis(phosphinidene)mercury complexes

PH₃ reacts with the in situ generated N-heterocyclic carbene DippNHC* (DippNHC* = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) to give the phosphanyl–imidazolidine [^DippNHC*-H]-[PH₂]. Upon treatment with an ortho-quinone, [^DippNHC*-H]-[PH₂] is dehydrogenated to give the parent phosphinidene–carbene adduct ^DippNHC*PH. Alternative routes to [^DippNHC*-H]-[PH₂] and ^DippNHC*PH employ NaPH₂ and (TMS)₃P₇ (TMS = trimethylsilyl), respectively, as phosphorus sources. The adduct ^DippNHC*PH and the related adduct ^DippNHCPH (^DippNHC = bis(2,6-diisopropylphenyl)imidazol-2-ylidene) possessing an unsaturated NHC backbone both react with HgCl₂ to give the bis(carbene–phosphinidenyl) complexes [(^DippNHC*P)₂Hg] and [(^DippNHCP)₂Hg].