The monodeprotonation of [CH2(PPh2→BH3)­(PPh2E)] (E = S (6), O (7)) afforded [CH­(PPh2→BH3)­(PPh2E)]− (E = S (6 ‑ ), O (7 – )), whose structures were confirmed by X-ray crystallography. The kinetics of the second deprotonation appeared to be crucial in efficient synthesis of the corresponding dianions. Thus, the double deprotonation of 6 only led to 6 2– ; the analogous reaction with 7 was slower and resulted only in the partial formation of 7 2– . Double deprotonation of the compound [CH2(SiMe3)­(PPh2S)] (8) also resulted in the partial formation of [C­(SiMe3)­(PPh2S)]2‑ (8 2– ), whose structure was confirmed by X-ray crystallography. The rare monomeric Mg carbene compound [MgC­(PPh2→BH3)­(PPh2S)] (9) was obtained by the reaction of 6 with Mg­(nBu)2. The X-ray structure of 9 is presented.