Boron Compounds - Advances in Chemistry (ACS Publications)

---

16 Boron Compounds VI. New Compounds with Boron-Nitrogen Bonds R. KOSTER and K. IWASAKI

Downloaded by UNIV OF LEEDS on August 19, 2014 | http://pubs.acs.org Publication Date: January 1, 1964 | doi: 10.1021/ba-1964-0042.ch016

Max-Planck-Institut

für Kohlenforschung,

Mulheim/Ruhr,

Germany

Compounds with B - N - Β bonds have been pre­ pared through interaction of bisborolanes with primary amines or ammonia. The elimination of hydrogen from BH- and NH- groups is cata­ lyzed by amines. The reaction of bisborolanes with amines is compared with the behavior of alkyldiboranes — for instance, B H R — to­ ward amines. The preparation of novel boron­ -and nitrogen-containing ring compounds from alkyldiboranes and amines is described, and transboronation reactions of compounds with B - N and B - N - Β bonds are discussed. In addi­ tion, novel Β-Ν heterocycles of the naphthalene and indene types were prepared. 2

2

4

R ecently it was reported that bisborolanes (Table I), in contrast to the tetraalkyldiboranes, B H R , are stable at room temperature to­ ward hydrolysis, alcoholysis, and oxidation (3). 2

Table I.

2

4

Properties of Bisborolanes

B. P., °C.(Mm.) Bisborolane Bis(3-methyl borolane)

Μ. P.,

76-77(10)

ê 20

95(12)

a

t D

n

4

1.4894 0.8541 20 0. 8307 1.4762

a

Bis(3,4-dimethyl borolane)^

°C.

120-124(12)

- 30

1.4683

25

20

-

Mixture of isomers 148

In Boron-Nitrogen Chemistry; Niedenzu, K.; Advances in Chemistry; American Chemical Society: Washington, DC, 1964.

20

16

KOSTER AND IWASAKI

Figure

1.

Compounds

Infrared

with B-N Bonds

spectrum

of

149

bisborolane

Downloaded by UNIV OF LEEDS on August 19, 2014 | http://pubs.acs.org Publication Date: January 1, 1964 | doi: 10.1021/ba-1964-0042.ch016

d = 0.05 mm., NaCl prism Undiluted 4% solution in cyclohexane The B - H bonds of the five-membered boron heterocycle (compare Figure 1) react only at elevated temperatures (above 100° C.) with olefins and alkines to the corresponding alkyl and alkenylborolanes. D i az omethane is not decomposed by bisborolanes at room temperature. This leads to the conclusion that borolanes are dimeric compounds, since even traces of alkylboranes catalyze the decomposition of diazomethane into nitrogen, polymethylene, and organoboron compounds of higher molecular weighty, 8, 9). Hence the B - H bondsof bisborolanes at room temperature have no catalytic effect on the alkyl group exchange of trialkylboranes (4, 7). Only at about 100 C . does an equilibrium exist containing the monomeric form, and only then can the e

2

B - H bonds of these compounds react with alcohols, with elimination of hydrogen and formation of alkoxyborolanes. A l l other reactions usually

typical of organoboron compounds — for instance, hydroboration and oxidation — are possible with bisborolanes only at elevated temperatures. The following exchange reactions belong in this group. A mixture of different bisborolanes can be separated at room temperature. Only above 100 C . can the organic radicals exchange until equilibration is achieved. e

In Boron-Nitrogen Chemistry; Niedenzu, K.; Advances in Chemistry; American Chemical Society: Washington, DC, 1964.

A D V A N C E S IN

150

C H E M I S T R Y SERIES

The equilibration can be followed by gas chromatography (11). Analo­ gously, when bisborolanes and bis(l-deuteroborolane) are heated, equilibrated mixtures are formed in which the starting materials are partially preserved and a compound with B ^ B is formed.

0