Polycyclic Borazines

Submitted by D. T. HAWORTH and G.-Y. LIN KIEL Checked by LEE J. TODDf and MARK W. BAIZEf 

In earlier volumes of Inorganic Syntheses the preparation of borazine, 2,4,6-trichloroborazine, l,3,5-trimethylborazine, J and l,3,5-trimethyl-2,4,6-trichloroborazine are given. We report here the details of procedures for the preparation of several polycyclic borazines using the three-step synthesis shown above. The procedures described here are based on the original 

Lead thiolates are obtained in near quantitative yield from the reaction of the thiol with a 95% ethanol solution of lead acetate. To a stirred solution of 

0 g (0.13 mol) of Pb(OCOCH3)3 3H2O in a mixture of 350 mL of 95% ethanol plus 35 mL H2O, 18.3 g (0.30 mol) of ethanethiol is slowly added. Filtration after 0.5 h affords a yellow solid that is washed with water, then ethanol- and vacuum-dried, yielding 38.2 g (89% yield) of Pb(SC2H5)2.  

The corresponding Pb(SC3H,)2 (42.4 g, 91% yield) is prepared in an analogous manner from 50.0 g (0.13 mol) of Pb(0C0CH3)2-3H20 and 

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Fused Rings and Polymers. Borazine analogues of naphthalene and substituted phenalenes are known the latter compound is formed by reaction of distannylamine and a large excess of tris(methylthio)borane (137). A general method for the preparation of the polycyclic borazines using fused carbon—heteroatom rings, where X = O, NR and n = 2,3, has been given (137). 

Polycyclic borazines (55) X = 0, NH, or NMe, n = 2 or 3) result from the reaction of a trisalkylthioborane with hydroxyamines or amines. Their i.r. and mass spectra, with possible mechanisms of formation, were reported. Photochemical reactions of borazine in the presence of (photochemically generated) radicals derived from hexafluoroacetone have led to the formation of B-(2H-hexafluoro-2-propoxy- and B-(perfluoro-butoxy)-borazine. ... 

Copolymerization reactions also yield polycyclic borazines with directly linked rings. The reaction of N-lithiated borazines with B-chloroborazines gives polymers ... 

Because of the extreme moisture sensitivity of the tris(alkylthio)boranes and the subsequent polycyclic borazines, all the manipulations made during their synthesis should be executed with the exclusion of water. 

Polycyclic Borazines. All the following operations are performed under a pure dry nitrogen atmosphere. A double necked, round-bottomed, 120-mL... 

Polycyclic B—N chains have been formed by the direct attachment of borazine rings or by the attachment of boron atoms of successive rings to an intervening NR group. There are also examples of cyclic species joined by other atoms, but only B—N-linked polymers are considered here. 

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