Organometallic chemistry of ethynyl boronic acid MIDA ester, HC≡CB(O2CCH2)2NMe.

The reactions of HC CBMIDA (BMIDA = B(O2CCH2)(2)NMe) with a range of ruthenium complexes afford the first isolated examples of sigma-alkynyl, sigma-alkenyl and vinylidene complexes bearing 4-coordinate boron substituents. Specifically, the reactions of HC CBMIDA with [RuH(S2CNR2)(CO)(PPh3)(2)] (R = Me, Et) and [Ru(CO)(2)(PPh3)(3)] afford the alkynyl complexes [Ru(C CBMIDA)(S2CNR2)(CO)(PPh3)(2)] and [RuH(C CBMIDA)-(CO)(2)(PPh3)(2)], the latter being converted to [Ru(C CBMIDA)Cl(CO)(2)(PPh3)(2)] on treatment with chloroform. With [RuCl(dppe)(2)]PF6 the vinylidene salt [RuCl(=C=CHBMIDA)(dppe)(2)]PF6 is obtained, which reacts with Et3N to afford the neutral alkynyl derivative [Ru(C=CBMIDA)Cl(dppe)(2)]. Hydrometallation of HC CBMIDA by [RuHCl(CO)(PPh3)(3)] affords the coordinatively unsaturated s-alkenyl complex [RuCl-(CH=CHBMIDA)(CO)(PPh3)(2)] which in turn reacts with CO, CNC6H2Me3-2,4,6, [Et2NH2][S2CNEt2] or K[HB(pz)(3)] (pz = pyrazol-1-yl) to afford the coordinatively saturated complexes [Ru(CH=CHBMIDA) Cl(CO)(2)(PPh3)(2)], [Ru(CH=CHBMIDA)Cl(CO)(CNC6H2Me3)(PPh3)(2)], [Ru(CH=CHBMIDA)(S2CNEt2)(CO)(PPh3)(2)] and [Ru(CH=CHBMIDA)(CO)(PPh3){HB(pz)(3)}]. In all cases, the transannular N -> B dative bond is retained in the BMIDA substituent.