Cyclodimerisierung eines Oxoborylkomplexes durch trans‐Ligandabstraktion

Comparison of Anionic and Lewis Acid Stabilized N‐Heterocyclic Oxoboranes: Their Facile Synthesis from a Borinic Acid

“…Remarkably, the B À O bond lengths of 1.296(3) and 1.287(4) (1.2915 average) in the two independent molecules are almost equal to the calculated value of 1.292 for the BÀO double bond in the unknown oxoborane [HC(CMe) 2 (NC 6 F 5 ) 2 ]BO at the B3LYP/6-311 + G(d) level [5] and even marginally shorter than that in the acid-stabilized oxoborane [HC(CMe) 2 (NC 6 F 5 ) 2 ]BOAlCl 3 (1.304 (2) ). The average B À O bond length in 3 b is 6.1 % shorter than that found in the borinic acid 2 (1.370 (6) , Figure S1 in the Supporting Information), while the B À N bonds (1.492(3) and 1.494(3) ) in 3 b are noticeably longer than those (1.433 (5) and 1.436(5) ) in 2, thus indicating the pronounced electronic effects of the OH hydrogen atom on the boron bonding in the system. The short BÀO bond observed in 3 b, along with the almost trigonal-planar geometry of the boron atom (sum of angles 359.98 (18)8), is indicative of a B À O double bond.…”

“…[4] In 2005, Cowley and co-workers reported the first isolable Lewis acid stabilized oxoborane supported by a b-diketiminato ligand. [6] It has been shown that three-coordinate anionic boron species may also possess double-bonding character, as demonstrated by the anionic (Mes 2 BCH 2 ) À and dianionic (R 2 BBR 2 ) 2À species reported by Power and others, which contain a boroncarbon and a boron-boron double bond, respectively. [6] It has been shown that three-coordinate anionic boron species may also possess double-bonding character, as demonstrated by the anionic (Mes 2 BCH 2 ) À and dianionic (R 2 BBR 2 ) 2À species reported by Power and others, which contain a boroncarbon and a boron-boron double bond, respectively.…”

“…[5] More recently, Braunschweig and co-workers reported the platinum oxoboryl complex trans-[(PCy 3 ) 2 PtBr(BO)] (Cy = cyclohexyl), in which the low-coordinate boron center is stabilized by a late-transition-metal fragment. [6] It has been shown that three-coordinate anionic boron species may also possess double-bonding character, as demonstrated by the anionic (Mes 2 BCH 2 ) À and dianionic (R 2 BBR 2 ) 2À species reported by Power and others, which contain a boroncarbon and a boron-boron double bond, respectively. [7] Inspired by the pioneering work on the stabilization of elusive oxoboranes and anionic boron p-bonding species, we anticipated that free monomeric oxoboranes (R 2 BO) À would be accessible and may exhibit boron-oxygen double-bond character if suitable ligand frameworks are employed.…”

Anorganische Chemie 2010

“…Die Ag+‐Ionen‐induzierte Abspaltung eines Bromidions aus dem Oxoborylkomplex [(R3P)2PtBr(B'O)] liefert den cyclischen Komplex [(R3P)2PtB(µ2‐O)2BPt(PR3)]2+ (4), in dem eine Dioxodiboryleinheit zwei kationische Platinfragmente überbrückt 1_5. Dass auch Bor alleine eine äußerst interessante Koordinationschemie mit Übergangsmetallen zeigt, macht die Synthese neutraler und anionischer übergangsmetallfragmentstabilisierter Metalloborylene deutlich (5, 6) 1_6…”

“…Die Verbindung ist bei Raumtemperatur bemerkenswert stabil. Bei der Abstraktion des Bromoliganden mit Ag+‐Ionen kommt es jedoch zur Cyclodimerisierung, und es bildet sich ein beispielloser Dioxodiboretandiyl‐Komplex (Abbildung 6) 2_16…”