ISSN:
0009-2940
Keywords:
Azadiboracyclobutanes
;
Azadiboracyclopentanes
;
Azadiboriridine, ring-opening of
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Tri-tert-butylazadiboriridine: Ring Prolongation by the Action of Isonitriles, α-Bromolithioalkanes, and AzidesIsonitriles ArNC are 1,1-boroborated by the B-B bond of the azadiboriridine (-BR-BR-NR-) (1; R = tBu) to form the four-membered ring [-BR-C(NAr)-BR-NR-] (2b; Ar = 2,6-C6H3Me2). Corresponding rings undergo [3 + 3] cyclodimerization of the B-C=N chain to give the tricyclic products 6a, b when isonitriles RNC with the small ligands R = Me, Et are boroborated by 1. Two molecules of tBuNC open the B-B bond of 1; the resulting five-membered ring 7a may add excess tBuNC to yield 7a · 2 CNtBu (8). The results strongly support a mechanistic hypothesis set up for the multistep reaction of 1 and CO. The carbene units, which are present in the α-bromolithioalkanes [-C(Br)Li-CMe2-CH2-], LiC(Br)H2, and LiC(Br)Me2, are also 1,1-boroborated by 1 to give the corresponding four-membered ring 2c, or by a 2:1 reaction to afford the five-membered ring 7b, or by a 1:1 reaction and subsequent rearrangement to yield the five-membered ring 7c. The nitrene units, which are present in the azides PhN3 and PhCH2N3, are also boroborated by 1; the diazadiboretidines 5b, c are formed with evolution of N2. The bis(diazadiboretidinyl)borane RB(N2B2R3)2 (5d) is the corresponding product from the reaction of RB(N3)2 with 1 in the ratio 1:2. The azide Me3SiN3 reacts differently yielding the N-boryl diazadiboretidine 5e and the iminoborane RB≡N̊. The B-B bond length of 187.6 pm in 5e indicates a transannular bonding interaction. The products 5d, 5e, and 6a were characterized by a crystal structure analysis.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19951281011
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