Reactions of Borazines with Pyrazole and Some Related Studies.
Abstract
The reaction of borazines, (-BR-NR'-)3, with pyrazole, Hpz, gives mu-pyrazolato-mu-amido diboron species of the type R-(pz)B(mu-pz)mu-NHR')BR(pz) containing a central B2N3 ring system; four compounds of this type with R = C2H5 or C6H5 and R' = H or CH3, respectively, were prepared. Identical species can be obtained on interaction of bis(dimethylaminoboryl)amines of the tyep R'N(BR-N(CH3)2)2 with Hpz; they are closely related to the pyraxabloes, R2B(mu-pz)2BR2, which contain a central B2N4 ring. A pathway for the formation of the novel species is postulated and supported by NMR data; conformational isomers could be identified but not separated. In contrast, RB(N(CH3)2)2 (R = C2H5) reacts with Hpz at room termpeature to give (CH3)2HN-BR(PZ)2, and in refluxing toluene to yield the pyrazabole R(pz)B(mu-pz)2BR(pz). the latter compound was also obtained from (-BR-NR'-)3 (R = H, CH3) or the mu-pyrazolato-mu-amido diboron species (R = C2H5, R' = H) and boiling Hpz (at temperatures near 180-200 C) The compound could be separated into conformational isomers: The lower melting one with the terminal pz groups in cis (equatorial) position crystallizes tetragonal in space group I41/acd: a = b = 14.876 A, c = 34.932 A, Z = 16; with the central B2N4 ring in boat conformation. The higher melting trans isomer crystallizes monoclinic in space group P21/c; a = 8.156 A, b = 14.720 A. c = 7.501 A, beta = 95.58 deg, Z = 2, with the central B2N4 ring in chair conformation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1986
- Accession Number
- ADA171883
Entities
People
- E. Hanecker
- H. Noeth
- J. Bielawski
- Kurt S. Niedenzu
- M. K. Das
Organizations
- University of Kentucky