From the parent phosphinidene-carbene adduct NHC = PH to cationic P4-rings and P2-cycloaddition products.

Reactions of the parent phosphinidene-carbene adduct (Dipp)NHC = PH with chlorophosphanes are reported herein. The obtained (Dipp)NHC-substituted chlorodiphosphanes, (Dipp)NHC = P-PClR, and the formation of their cationic derivatives, [(Dipp)NHC-P = PR](+), were also explored. Depending on the steric demand of their substituents, these cations were found to be monomeric [(Dipp)NHC-PP-N(i)Pr2][GaCl4] or to dimerise to cyclotetraphosphanes [(Dipp)NHC-PP-R]2[GaCl4]2 (R = Ph, NMe2). For R = NMe2, this dication is the first isolated example of a tetrasubstituted all-σ(3) cyclotetraphosphane. Finally, the hetero-Diels-Alder reactivity of these cations was studied with 2,3-dimethylbuta-1,3-diene and cyclopentadiene, resulting in the isolation of a number of cationic 1,2-diphosphinanes.