Containing Boron and Nitrogen

Six-membered Rings containing Boron and Nitrogen 1.21.8.3.1 Synthesis... 

The second major type of sigma-bonded boron-nitrogen-carbon heterocycles contains boron and nitrogen as annular atoms of saturated ring systems. Though several types of such azaboracycloalkanes are known 7>... 

AH = 2.9 kJ mol-1 at 300 K and 1 atm. Diamond is the hardest material known, although a compound containing boron and nitrogen, borazon, has almost equal hardness. Because of this property, diamond has a great many industrial uses in tools and abrasives. Because gem quality diamonds are prohibitively expensive for such uses, there has been a great deal of interest in producing diamonds synthetically. Industrially, this process is carried out under extreme conditions (3000 K and 125 kbar) to produce several tons of diamond annually. 

A detailed account of the chemistry of the fully conjugated rings containing boron and nitrogen was given in the first edition of Comprehensive Heterocyclic Chemistry <84CHEC-I(1)629>, and systems of the type (7) and (8) are not discussed here. Also excluded are compounds of the type (9), i.e., heterocycles containing a noncoordinative bond between boron and another heteroatom such compounds are only occasionally mentioned in this chapter for comparison. 

We also performed C02-laser heating experiments on borane-dimethylamine BH3 NH(CH3)2 to check if organic materials containing boron and nitrogen can be used for synthesis of ternary BNC compounds with diamond-like structure. Borane-dimethylamine was heated at 23 GPa to about 3000 K. Raman spectra from the heated sample area revealed the presence of cubic BN, and of liquid H2 at pressures below the solidification point of hydrogen (5.5 GPa at room temperature [71]) (Fig. 17). A Raman spectrum of the recovered white agglomerate showed a weak line of diamond in addition to the Raman bands of cubic BN. Thus, borane-dimethylamine transformed to cubic BN, diamond and hydrogen... 

As usual, the largest number of publications dealing with heterocyclic organoboron compounds have concerned molecules containing boron and nitrogen and, in many cases, at least one other heteroatom. Phosphiniminoboranes (21), prepared from iV-trimethylsilyl-triphenylphosphinimine and diorganylhalogeno-boranes, have been found to be dimeric in solution but monomeric in the vapour state. ... 

Boron nitride may be obtained in three primary crystalline modifications (2) a, j3, and y. The most commonly encountered a form has a graphitic structure (hexagonal cell, a = 2.504 A, c = 6.661 A). For many years, this modification has been prepared from combinations of cheap boron and nitrogen containing reagents, e.g. B(0H)3 and (NH2)C0, B(0H)3, C and N2 or KBH4 and NH4C1 (3-5). More... 

Boron- and Nitrogen-Containing Polymers for Advanced Materials 103... 

Boron-containing nonoxide amorphous or crystalline advanced ceramics, including boron nitride (BN), boron carbide (B4C), boron carbonitride (B/C/N), and boron silicon carbonitride Si/B/C/N, can be prepared via the preceramic polymers route called the polymer-derived ceramics (PDCs) route, using convenient thermal and chemical processes. Because the preparation of BN has been the most in demand and widespread boron-based material during the past two decades, this chapter provides an overview of the conversion of boron- and nitrogen-containing polymers into advanced BN materials. 

There is a great deal of potential interest in borazine as a precursor of boron nitride, since it offers the advantages of being a single source of boron and nitrogen with the correct B/N ratio and a high ceramic yield. In addition, borazine contains the elementary BN building block as its substituted derivatives. This is described later. 

Ring Systems Containing Boron and Two Nitrogen Atoms 646... 

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