New outcomes of Lewis base addition to diboranes(4): electronic effects override strong steric disincentives

Abstract

(2016) New outcomes of Lewis base addition to diboranes(4): electronic effects override strong steric disincentives. Chemical Communications, 52

Controlling Regiochemistry in the Syntheses of Boraindanes from Diborane(4) Starting Materials

“…The crystallographically determined structure of 12 (Figure 8) showedt he two boron atoms of the diborane to have been movedt oo pposite ends of the molecule, with aB Mes unit chelated by as elf-assembled b-diketiminato ligand (nacnac). The exo-cyclic C3ÀC4 bond (1.333 (3) ) and only slightly bent C3-C4-N2 angle (163.50(19)8)r esemble the isonitrileÀcarbenoid bonds in the trapped intermediates 5a, 8, and 9,s uggesting that in the formation of 12 C3 is as imilarly (2), C2-N1 1.463(2),C 1-N2 1.397 (2); B1-C1-C21 14.13(14), C1-C2-N1172.98 (17), C1-N2-B21 15.51 (13), C1-N2-C3 117.01 (12), C2-N1-C41 32.06 (15) . For 8:B 1-C1 1.503(3), C1-C21 .345 (3), C2-N1 1.191(3), C1-N2 1.465 (2), N2-B21.394 (3);B1-C1-C21 14.39 (16), C1-C2-N1173.…”

“…For clarity,h ydrogen atoms and ellipsoidsoft he carbon atoms have been omitted. Selectedb ond lengths []and bond angles [8] (2), C3-C2 1.510 (2), B1-N1-C1 119.81 (14),C 4-B2-C1 107.88 (15),C 4-B2-Br2 128.57 (14), C4-C3-C2 113.64 (15), C2-C1-B2 103.41 (14), C3-C2-C1 105.47 (14),C 3-C4-B2106.58 (15). at al ocal energetic minimum (À13.8 kcal mol À1 ,X = Cl; À11.2 kcal mol À1 ,X = Br).…”

“…The similarity between 11 and Yamashita's 2-boraindanes speak for al ikely resemblance in the respective reaction pathways for the unsymmetrical diboranes tarting materials, which is different from the pathway proposed in Figure 3. Ac ritical (2), B2-C1 1.580 (2), N2-C1 1.283 (2), B2-N21.548 (2), B1-Cl1 1.614 (3), B2-Cl2 1.8972(19), B1-C2 1.624(3);B1-C2-N1173.32 (17), B1-C1-B21 49.28 (15), B2-C1-N264.52 (12), C1-N2-B2 67.07 (12), N2-B2-C1 48.40(10).…”

“…For 8:B 1-C1 1.503(3), C1-C21 .345 (3), C2-N1 1.191(3), C1-N2 1.465 (2), N2-B21.394 (3);B1-C1-C21 14.39 (16), C1-C2-N1173. 16(19), C1-N2-B2 118.90 (15),C 1-N2-C31 13.23 (14),C 2-N1-C4132.0 (2). For 9:B1-C1 1.525(2), C1-C2 1.359(2), C2-N1 1.187(2), C1-N2 1.4763(19), N2-B2 1.418 (2);B1-C1-C21 13.24 (13), C1-C2-N1 172.35 (16), C1-N2-B21 19.87 (12),C 1-N2-C3 115.18 (11), C2-N1-C41 37.34 (14).…”

Reactivity of highly Lewis acidic diborane(4) towards pyridine and isocyanide: formation of boraalkene–pyridine complex and ortho-functionalized pyridine derivatives

“…Despite the coordination of pyridine, the B–B bond (1.717(3) Å) of 7 was identical to that of 1 (1.722(4) Å). 23 , 24 The hybridization of the B1 atom is slightly distorted (B2–B1–C6 = 94.31(16)°) from ideal sp 3 hybridization as observed in similar sp 2 –sp 3 diborane(4) derivatives that contain a BMes 2 moiety, 25 which is probably due to the steric demand of the Mes groups.…”