Tris(trifluoromethyl)borane Carbonyl, (CF₃)₃BCOSynthesis, Physical, Chemical and Spectroscopic Properties, Gas Phase, and Solid State Structure

Abstract

Tris(trifluoromethyl)borane carbonyl, (CF(3))(3)BCO, is obtained in high yield by the solvolysis of K[B(CF(3))(4)] in concentrated sulfuric acid. The in situ hydrolysis of a single bonded CF(3) group is found to be a simple, unprecedented route to a new borane carbonyl. The related, thermally unstable borane carbonyl, (C(6)F(5))(3)BCO, is synthesized for comparison purposes by the isolation of (C(6)F(5))(3)B in a matrix of solid CO at 16 K and subsequent evaporation of excess CO at 40 K. The colorless liquid and vapor of (CF(3))(3)BCO decomposes slowly at room temperature. In the gas phase t(1/2) is found to be 45 min. In the presence of a large excess of (13)CO, the carbonyl substituent at boron undergoes exchange, which follows a first-order rate law. Its temperature dependence yields an activation energy (E(A)) of 112 kJ mol(-)(1). Low-pressure flash thermolysis of (CF(3))(3)BCO with subsequent isolation of the products in low-temperature matrixes, indicates a lower thermal stability of the (CF(3))(3)B fragment, than is found for (CF(3))(3)BCO. Toward nucleophiles (CF(3))(3)BCO reacts in two different ways: Depending on the nucleophilicity of the reagent and the stability of the adducts formed, nucleophilic substitution of CO or nucleophilic addition to the C atom of the carbonyl group are observed. A number of examples for both reaction types are presented in an overview. The molecular structure of (CF(3))(3)BCO in the gas phase is obtained by a combined microwave-electron diffraction analysis and in the solid state by single-crystal X-ray diffraction. The molecule possesses C(3) symmetry, since the three CF(3) groups are rotated off the two possible positions required for C(3)(v)() symmetry. All bond parameters, determined in the gas phase or in the solid state, are within their standard deviations in fair agreement, except for internuclear distances most noticeably the B-CO bond lengths, which is 1.69(2) A in the solid state and 1.617(12) A in the gas phase. A corresponding shift of nu(CO) from 2267 cm(-)(1) in the solid state to 2251 cm(-)(1) in the gas phase is noted in the vibrational spectra. The structural and vibrational study is supported by DFT calculations, which provide, in addition to the equilibrium structure, confirmation of experimental vibrational wavenumbers, IR-band intensities, atomic charge distribution, the dipole moment, the B-CO bond energy, and energies for the elimination of CF(2) from (CF(3))(x)()BF(3)(-)(x)(), x = 1-3. In the vibrational analysis 21 of the expected 26 fundamentals are observed experimentally. The (11)B-, (13)C-, and (19)F-NMR data, as well as the structural parameters of (CF(3))(3)BCO, are compared with those of related compounds.

29/28, 30/28Silicon, 34/32sulfur and 80/77selenium isotope‐induced fluorine chemical shifts through two bonds

“…Chemical shifts are given in Tables 1-3. The value of 2  19 F 11/10 B given in the literature for [ CF 3 4 B] is 11.1 ppb. 11,12 For oxygen atoms, the percentages of isotopes and spins (in parentheses) are 16 Table 4). Table 1).…”

Trifluormethylborane und ‐borate – neue Synthesestrategien und Anwendungen

“…À -Anion zum bis dahin unbekannten Carbonyltris(trifluormethyl)boran, (CF 3 ) 3 BCO, [21,22] dem einzigen einkernigen Carbonylboran neben der Stammverbindung H 3 BCO, das bislang in Substanz hergestellt wurde. Eine Reihe von Carbonylboranen mit B-B-Bindungen ist dagegen bekannt.…”

“…Eine Reihe von Carbonylboranen mit B-B-Bindungen ist dagegen bekannt. [22][23][24][25][26] Im Folgenden werden für die Salze des [B(CF 3 À . [27] Außerdem bilden wasserfreie HF und (CF 3 ) 3 BCO eine konjugierte Brønsted-Lewis-Supersäure mit dem schwach koordinierenden Anion [(CF 3 ) 3 …”

Die Synthese von B2(SIDip)2 und seine Reaktivität zwischen denen von Diboracumulenen und Diborinen

“…B. : (CO)B(C 3 F 7 ) 3 1.660(3) , (C 2 F 5 ) 3 B(CO) 1.618(2) , 1.623-(2) ). [17,18] Die leicht verlängerte Bindung von C O( 1.173-(2) , 1.173(2) ) gegenüber der in CO,d as an tetraedrisch koordiniertes Bor gebunden ist (1.105-1.124 ), [17,18] lässt ebenfalls auf eine p B !p* CO -Rückbindung schließen. Dies resultiert in einer CO-Streckschwingung bei ñ = 1928 cm À1 , die im Unterschied der von freiem CO (ñ = 2143 cm À1 ) deutlich herabgesetzt ist und in Einklang mit den beobachteten CO-Streckschwingungen in elektronenreichen Komplexen der späten Übergangsmetalle mit beträchtlichen M!…”