“…The presence of the positive charge on one of the two fragments,c oordinating in its neutral form, clearly excludes the bidentate mode in systems A and B but gives access in both cases to cationic monodentate ligands, the common feature of which is the close proximity of the charget ot he coordinating center.T he chargei st hus located near aP III atom in the carbeniophosphines [10] A,a nd in the vicinity of aC II atom in the phosphoniocarbenes [11] B.T his specificityd istinguishesl igands A and B from most members of the large family of cationic ligands,i nw hich the charge is generally introduced at ar emote positionf rom the coordinating atom for the main purpose of performing catalysis in polar solvents without impairing the electronic properties of the metal center. [12] In systems A,a lso described as donor-acceptor adducts of the carbene-phosphenium type, [13] the positivec hargec onjugated with the P III atom can be introduced by means of a cyclic moietys uch as an imidazolium (A-1)a nd relateds tructures (A-2), [14] ap yridinium (A-3), [15] ac yclopropenium (A-4), [16] or by an acyclic amidinium A-5 [17] (Scheme 1, left). In systems B, the phosphonium group can be attached to the C-4/5 (B-1) [18] or the Np ositions of ah eterocyclic carbene (B-2), [19] or directly bondedtot he C II atom of acyclic amino- [20] (B-3)o rp hosphinocarbenes [21] (B-4)(Scheme 1, right).…”