Transition-metal promoted hydroborations of alkenes, emerging methodology for organic transformations

Unsupported boron–carbon σ-coordination to platinum as an isolable snapshot of σ-bond activation

“…Isolable σ-complexes range from complexes with weak agostic (that is, supported by a stronger secondary point of ligation) C-H 10,11 , C-C 12,13 and Si-Si 14,15 ligation to strong, unsupported σ-dihydrogen 1,2 and σ-borane complexes [16][17][18][19][20][21][22][23] , whose stability (significantly enhanced in the latter by retrodonation interaction III, Fig. 1a) has led to advances in our understanding of catalytic hydrogenation, hydroboration [24][25][26] , and reversible hydrogen storage by amine-boranes [27][28][29] .…”

Synthese von ansa‐[2]Boracyclopentadienylcycloheptatrienylchrom und Reaktion zum ansa‐Platinabis(boryl)‐Komplex durch oxidative Addition der Bor‐Bor‐Bindung

“…[17] Darüber hinaus ist die umgekehrte Reaktion, also die reduktive Eliminierung der B-C-Bindung vom späten Übergangs-metallzentrum, thermodynamisch bevorzugt und tritt bekanntermaßen als ein Schlüsselschritt in der metallkatalysierten Hydroborierung auf. [18] Demgegenüber gehen B-B-Bindungen bereitwillig oxidative Additionen mit einer Vielzahl von niedervalenten Über-gangsmetallkomplexen [18d, 19] unter Bildung von Bisborylkomplexen M(BR 2 ) 2 ein. [20] Daher wurden Diborane(4) bereits sehr erfolgreich zur übergangsmetallkatalysierten Diborierung von Alkenen, [21] Alkinen [22] und 1,3-Dienen eingesetzt.…”

The Development of Enantioselective Rhodium-Catalysed Hydroboration of Olefins

“…[2,50] The dissociation of a triphenylphosphine ligand from Wilkinsons catalyst (2) generates the catalytically active species 4 to which the B À H bond of the borane reagent oxidatively adds to give 5. The analogous complex with P(i-Pr) 3 rather than PPh 3 has been isolated and structurally characterised by Westcott and co-workers.…”

“…[11,87] "Asymmetric amplification" experiments provided no evidence to suggest there was more than one phosphine ligand per catalyst molecule but did not conclusively rule out that possibility either. [94] Subsequently, Burgess [95] prepared a series of hybrid ligands 51 -53, Figure 5, which were chiral not only in the carbon backbone like (R,R)-DIOP (24), but also at phosphorus, like DIPAMP (50).…”