Facile Access to Unprecedented Electron‐Precise Monohydrodiboranes(4), cis‐1,2‐Dihydrodiboranes(4), and a 1,1‐Dihydrodiborane(5)

Abstract

2,3-Bis(dimethylamino)-substituted B N C heterocycles underwent selective dimethylamino/hydride exchange with either one or two equivalents of BH ⋅SMe to give the corresponding cyclic monohydrido- or (cis)1,2-dihydridodiboranes(4), respectively. Upon either heating or irradiation in solution, the latter underwent ring contraction to the corresponding five-membered BN C heterocycles, whereas irradiation of the 1,2-dimethylaminoethene-supported 1,2-dihydridodiborane(4) in the presence of PEt gave an unprecedented unsymmetrical 1,1-dihydrodiborane(5) phosphine adduct.

Three‐Coordinate Boron(III) and Diboron(II) Dications

“…Given the synthesis of 4 2+ it was at hand that 1 might also be suitable for the stabilization of a three‐coordinate diboron(II) dication complex as a congener to four‐coordinate III and IV , as well as Braunschweig's diboron(II) dication (Figure ) . Reminiscent to the synthesis of III and that of a related uncharged cyclic bisamido diborane(4) compound, also reported by Braunschweig and co‐workers ( VI ), bisimine 1 was reacted with (B(Cl)NMe 2 ) 2 (Scheme ). A colorless precipitate was collected and identified as 1 ⋅(B(Cl)NMe 2 ) 2 by ESI‐HRMS and NMR spectroscopic analysis.…”

“…is processed). The related diborane(4) compound VI that bears a bisamido ligand . Synthesis of the aluminum dihydride salt 7 [A] (A − =AlB 2 H 8 − , BH 4 − ).…”

“…In the solid state 6 [SbCl 6 ] 2 ⋅0.5(1,2‐F 2 ‐C 6 H 4 ) is marked by a six‐membered B 2 N 2 C 2 ring which assumes a twist boat conformation and resembles the hexacycle in the structurally related but uncharged congener VI (Figure , Scheme ). The sum of the bond angles around each boron atom confirms the trigonal planar structure motif.…”

Facile Access to Substituted 1,4‐Diaza‐2,3‐Diborinines

“…To this end, we initially developed a more convenient protocol for the synthesis of mesityl‐substituted DADB 1 a (Ar=Mes=2,4,6‐Me 3 ‐C 6 H 2 ), which does not require the isolation and purification of Li 2 [ Mes dab] (Scheme ) . Through this, DADB 1 a was readily obtained in moderate yields of 42 % even on a larger scale.…”

“…Short exocyclic B−N ( 1 a : 1.436(2), 1.433(2); 1 b : 1.449(3), 1.430(3); 1 c : 1.409(2); 1 d : 1.406(2), 1.412(2) Å) and rather long B−B bond lengths ( 1 a : 1.719(2); 1 b : 1.719(3); 1 c : 1.708(2); 1 d : 1.704(2) Å; calculated parent DADB B 2 N 2 C 2 H 6 1.6514 Å) are reminiscent of strong conjugative effects arising from the pendant NMe 2 groups, observations that have been interpreted earlier for 1 a in terms of aromaticity loss …”