115509-07-4Relevant articles and documents
Pyrazaboles of the type RR′B(μ-pz)2BRR′ and related studies
Das,DeGraffenreid,Edwards,Komorowski,Mariategui,Miller,Mojesky,Niedenzu
, p. 3085 - 3089 (2008/10/08)
Boron-bonded hydrogen or organylthio groups of pyrazaboles, R2B(μ-pz*)2BR2 (Hpz* = pyrazole or C-substituted derivatives thereof), can be replaced by reaction with either (C2H5)2O·BF3 or CH3OH·BF3 to give the corresponding F2B(μ-pz*)2BF2 species. Attempts to replace boron-bonded hydrocarbon groups require much more forcing conditions and usually result in a complete breakdown of the molecule. However, under mild conditions the B-C bond is not attacked and (C6H5)FB(μ-pz)2B(C6H 5)F is readily obtained from the reaction of (C6H5)(C2H5S)B(μ-pz) 2B(C6H5)(SC2H5) with BF3. 4,8-Dihalopyrazaboles, RXB(μ-pz)2BRX, are also obtained from the reaction of dihaloboranes, RBX2, with N-(trimethylsilyl)pyrazole, (CH3)3Si(pz); the halogen of the pyrazabole can be displaced readily by reaction with a Grignard reagent or an alcohol. The compound [(C2H5)2N](pz)B(μ-pz)2B[N(C 2H5)2](pz) was also prepared by the cited procedure. The diethylamino group of the latter species is easily displaced by reaction with pyrazole. Several additional pyrazaboles of the type RR′B(μ-pz)2BRR′ have been prepared. (C6H5)(pz)B(μ-pz)2B(C6H 5)(pz), which is accessible by various preparative routes, was separated into isomers that exhibit distinctly different 1H NMR spectra. The mass spectral fragmentations of such (cis and trans) isomers are significantly different with respect to their loss of the first fragments from the parent ions.
Chemical behavior and structure of triply bridged pyrazaboles of the type RB(μ-pz)2(μ-OBRO)BR
Hsu,Mariategui,Niedenzu,Shore
, p. 143 - 147 (2008/10/08)
Triply bridged pyrazaboles of the type RB(μ-pz)2(μ-OBRO)BR (1, R = C2H5, C6H5; Hpz = pyrazole) are thermally quite stable and can be sublimed without decomposition even under atmospheric pressure. At room temperature they are resistant to water but are not soluble. Dissolution of 1 in protonic solvents occurs with complete breakdown of the molecule. Halogenation of 1 (R = C2H5) with SOCl2 yields the pyrazabole RClB(μ-pz)2BRCl. The latter compound is a valuable material for the preparation of various other pyrazaboles. Thus, reaction with alkali-metal alkoxide or with alcohol in the presence of triethylamine gives access to R(R′O)B(μ-pz)2BR(OR′) (R′ = CH3, C2H5), the first examples of B-alkoxypyrazaboles; with (CX3CO)2O (X = H, F), the species with R′ = CX3CO are obtained. The crystal and molecular structures of 1 with R = C2H5 were determined. The molecule crystallizes in the monoclinic system in space group P21/c with a = 7.587 (2) A?, b = 12.415 (2) A?, c = 16.387 (3) A?, β = 90.50 (2)°, and Z = 4.
