Reactivity of the metal-->BX3 dative sigma-bond: 1,2-addition reactions of the Fe-->BX3 moiety of the ferraboratrane complex [kappa4-B(mimBu t)3]Fe(CO)2.

The ferraboratrane [kappa4-B(mim(Bu)t)3]Fe(CO)2 (mim(Bu)t = 2-mercapto-1-tert-butylimidazolyl), the first example of a complex which possesses a retrodative (i.e., metal-to-ligand) Fe-->B bond, is obtained via reaction of the tris(2-mercapto-1-tert-butylimidazolyl)hydroborato complex [Tm(Bu)t]FeCl with LiCH2SiMe3 followed by treatment with CO. Significantly, [kappa4-B(mim(Bu)t)3]Fe(CO)2 exhibits novel reactivity towards a variety of reagents that results in eradication of the Fe-->B bond via a formal 1,2-addition process and the formation of B-functionalized tris(mercaptoimidazolyl)borate derivatives, [XTm(Bu)t]FeY.