DERIVATIVES OF BOROLE .18. TRICARBONYL[ETA-5-(1-PHENYLBOROLE)]IRON - REACTIVITY OF THE COORDINATED LIGANDS

The borole complex (C4H4BPh)Fe(CO)3 (1) undergoes Friedel-Crafts acetylation (MeCOCl/AlCl3) at the meta-position of the phenyl substituent while the derivatives (C4H4BPh)Fe(CO)2L (3, a: L = NMe3, b: L = PMe3) are acetylated at the 2-position of the borole ring. Organolithium reagents (LiMe, LiBu) add to 1 at the boron atom below -50-degrees-C while nucleophilic attack at the carbonyl C atom takes place at higher temperature with formation of acyl anions [(C4H4BPh)Fe(CO)2(COR)]- (6a,b-). The Fischer carbene complex (C4H4BPh)Fe(CO)2[C(OMe)Me] (7) is obtained from 6a-/[Me3O]BF4. Complex 1 reacts with LiN(SiMe3)2 to give [(C4H4BPh)Fe(CO)2(CN)]- (8-) and with 5 M NaOH/C6H6/NBu4HSO4 to produce the hydride NBu4[(C4H4BPh)FeH(CO)2] (NBu4 . 9). A highly reactive dianion [(C4H4BPh)Fe(CO)2]2- (10(2-)) is obtained by deprotonation of 9- or by reduction of 1 or 3 a in THF at - 70-degrees-C. Treatment of 10(2-) with Ph3SnCl gives [(C4H4BPh)Fe(CO)2(SnPh3)]- (11-) which is isolated as NEt4 . 11. Slow reduction of 3a with sodium amalgam in THF at -30-degrees-C produces doubly CO-bridged cis-[{(C4H4BPh)Fe(CO)2}2]2- (12(2-)) which is protonated to the mu-2-hydrido anion [mu-H-{(C4H4BPh)Fe(CO)2}2]- (13-).