Boratocarbyne Complexes: Li[Mo{CB(OMe)3}(CO)2{HB(pzMe2)3}] and [K(18-crown-6)][Mo(CBF2OMe)(CO)2{HB(pzMe2)3}] (pz = pyrazol-1-yl)

The successive treatment of [Mo( CBr)(CO)(2){HB(pzMe(2))(3)}] (1; pz = pyrazol-1-yl) with (BuLi)-Bu-n and B(OR)(3) (R = Me, Pr-i) affords, via the lithiocarbyne complex [Mo( CLi)(CO)(2){HB(pzMe(2))(3)}] (2), the boratocarbynes Li[Mo{ CB(OMe)(3)}(CO)(2){HB(pzMe(2))(3)}] (R = Me, Li[3a]; R = Pr-i, Li[3b]). The salt Li[3b] readily eliminates (LiOPr)-Pr-i to afford the neutral boryl carbyne [Mo{ CB((OPr)-Pr-i)(2)}(CO)(2){HB(PzMe(2))(3)}] (4b). The analogous boryl carbyne [Mo{ CB(OMe)(2)}(CO)(2){HB(pzMe(2))(3)}] (4a) on treatment with K[HF2] and 18-crown-6 (18C6) provides the structurally characterized difluoro(methoxy)boratocarbyne salt [K(18C6)][Mo( CBF2OMe)(CO)(2){HB(pzMe(2))(3)}] ([K(18C6)][6]).