Reactivity of a magnesium diboranate with organic nitriles

Abstract

Reactions of a diboranate with organic nitriles result in B–C bond formation and variable behaviour that is rationalised as due to substituent-dependent modulation in the basicity and electrophilicity of Mg-coordinated nitrile intermediates.

Ring‐Expanded N‐Heterocyclic Copper(I) Boryl Complexes: The Structures of [(6‐Dipp)CuBcat], [(6‐Dipp)CuBneop], and [(6‐Dipp)CuBhex]

“…Cu1À B1: 1, 1.974(3); 2, 1.999(2); 3, 2.0041(18) Å). This expansion in boryl steric bulk is associated with a compression of the CÀ CuÀ B angle (C1À Cu1À B1: 1, 177.27 (13); 2, 171.35 (7); 3, 163.40(7)°). Such deviations could reflect the effect of London dispersion force interactions between the 6-Dipp ligand and boryl fragment.…”

“…[19,22] The metric parameters of 1 (1: C1À Cu1, 1.948(3); Cu1À B1, 1.974(3) Å; C1À Cu1À B1, 177.35 (13); O1À B1À O1, 106.7(2)°) and its analogue, [(IPr)CuBcat], [19] are similar ([(IPr)CuBcat]: C1À Cu1, 1.9309(15); B1À Cu1, 1.978(2) Å; C1À Cu1À B1, 174.22 (7); O1À B1À O2, 106.96(13)°). Similarly, the CÀ CuÀ B core of 2 (2: C1À Cu1, 1.9446(15); Cu1À B1, 1.999(2); B1À O1, 1.393(2); B1À O2, 1.386(2) Å; C1À Cu1À B1, 171.35 (7); O1À B1À O1, 117.58 (16); N1À C1À N2, 116.56(13)°) and the comparative metrics for [(IPr)CuBneop] [22] deviated little, but these two compounds showed vast differences in stability. [(IPr)CuBneop] decomposed within hours at room temperature to IPr, neop 2 B 2 , copper metal, and a number of more remarkable products including [(IPr) 6 Cu 55 ] and [(IPr) 12 Cu 179 ].…”

“…Whilst hydroboration is the most widely applied classical route to CÀ B bonds, the last two decades have seen significant progress in the development of nucleophilic boron fragments which are competent at creating new CÀ B bonds with carbon electrophiles. Boryl anions bonded to groups 1, [1] 2, [2][3][4][5][6][7] and a range of transition metals [8][9] are now known. Copper(I) boryls have seen particular interest owing to their exploitation under catalytically relevant conditions.…”

Synthesis and Reactivity of Calcium Diborane(6) and Diboranate Derivatives

“…Terminally‐bonded magnesium boryl species (e. g. 3 ) are then conveniently accessible through the introduction of an appropriate base such as 4‐dimethylaminopyridine (DMAP), to induce heterolytic activation of the B−B bond (Scheme 1a). Although compounds such as 3 serve as potent sources of nucleophilic boron, we have also observed that the desymmetrised B−B unit of 2 itself behaves as a surrogate source for the formal [Bpin] − anion when treated with multiply bonded C−E (E=O, N) small molecules (e. g. in reaction with organic nitriles, Scheme 1b) [2i] …”

A stable ring-expanded NHC-supported copper boryl and its reactivity towards heterocumulenes

“…Nucleophilic boron fragments are increasingly important "umpolong" reagents applied in the generation of synthetically useful boron-element bonds. [1][2][3][4][5][6][7][8] Copper(I) boryls are, by far, their pre-eminent class, emerging from chemical curiosities to become important synthetic intermediates in the generation of a huge number of new, boron-containing organic molecules. [9][10][11][12][13][14][15] Synthetic access to copper boryls has principally relied upon two synthetic routes; salt metathesis reactions of isolable boryl anions with copper halides [16][17][18] and Cu-O/B-B σ-bond metathesis.…”