Dehydrocoupling of catecholborane catalyzed by group 4 compounds

Formation and Reactivity of Electron‐Precise B−B Single and Multiple Bonds

“…[34] Thereaction, however, remains limited to this one specific substrate. [37] Through stoichiometric studies,u sing am odel [{(CyCH 2 ) 3 P} 2 Pt] precursor designed to provide flexible steric bulk, two catalytic intermediates could be identified: a trans-hydridoboryl Pt II complex, 11,r esulting from the reversible oxidative addition of HBCat, and a cis-bis(boryl) Pt II complex, 12,obtained by the reversible reaction of 11 with excess HBCat (Scheme 5b). [35] Prior to this,M arder and co-workers had already observed the formation of small amounts of B 2 Pin 2 from HBPin as ab y-product during the rhodium-catalyzed synthesis of boronate esters.…”

The Catalytic Dehydrocoupling of Amine–Boranes and Phosphine–Boranes

“…In 2013, Weller and MacGregor reported the first well-characterised example of the B-B homocoupling of an amine-borane to yield the diborane (4) Me 3 N · BH 2 BH 2 · NMe 3 ligand sigma bound to rhodium [62]. B-B homocoupling of boranes has been otherwise limited to B-B bond formation in polyhedral boranes [73,74], guanidine bases [75] and catechol-and pinacolboranes [76][77][78] Sigma complexes of aminoboranes have also been isolated, where donation from the B-H bonds into a vacant metal orbital is reinforced by π back-donation from the metal into the π* B-N orbital of the aminoborane [80]. Various examples have been characterised with rhodium [13,66,80,81], iridium [17,19,80,82] and ruthenium [24,80,83,84], and a selection is presented in Fig.…”

Dehydrogenative Boron Homocoupling of an Amine‐Borane

“…By contrast, the homocoupling [5] of amine-boranes to form welldefined products with BÀB single bonds has not been reported, although dehydrogenation of H 3 4 ] has been reported to form insoluble polymeric materials with B À B bonds. Well-defined homocoupling of boranes, as mediated by transition metals, is essentially limited to B À B bond formation in polyhedral boranes, for example pentaborane(9) (A), [7,8] guanidine bases (B), [9] and most recently the homocoupling of HBCat and related derivatives to give the corresponding diboranes (C) [10][11][12] (Scheme 1). Well-defined homocoupling of boranes, as mediated by transition metals, is essentially limited to B À B bond formation in polyhedral boranes, for example pentaborane(9) (A), [7,8] guanidine bases (B), [9] and most recently the homocoupling of HBCat and related derivatives to give the corresponding diboranes (C) [10][11][12] (Scheme 1).…”