Pnictogen‐Functionalised C 1 Ligands: MC‐AR n ( n =0, 1, 2, 3)

The chemistry of transition metal carbynes, L n M≡CR, has historically been dominated by species bearing hydrocarbyl or amino ‘R’ substituents, with other elements appearing only sporadically. In recent years, carbynes and related ‘C 1 ’ species bearing other main‐group substituents, particularly heavier elements of the p‐block, have begun to emerge. This review details the chemistry of heavier pnictogen‐functionalised C 1 ligands, MCAR n (A=P, As, Sb, Bi; n =0–3), including their syntheses, properties and reactivities, and how these are distinguished from more traditional carbyne complexes. Recent developments in the closely related phospha‐isonitrile L n M(CPR), cya‐phosphide and cya‐arside ligands, L n M(C≡A) (A=P, As), are also discussed.