Gottfried Pawelke

Vibrational spectra and normal coordinate analysis of CF3 compounds

Abstract Perfluorotrimethylamine, N(CF 3 ) 3 , has been studied in the liquid and gas state by Raman spectroscopy, and by infrared spectroscopy in the gas state and in a matrix. The assignment of the spectra supports C 3 rather than C 3h molecular symmetry, but the NC 3 pyramid is suggested to be flat. A normal coordinate analysis has been performed. The vibrations of the NC 3 skeleton are strongly mixed with vibrations of the CF 3 ligands and are entirely noncharacteristic. The structure of N(CF 3 ) 3 has been reinvestigated by electron diffraction. The following molecular parameters have been determined: r (CF) 1.323(4) A, r (CN) 1.426(6) A, ∠FCF 108.3°(4), ∠CNC 117.9°(4), τ(CF) 3 26.4° (10). The torsional fundamentals were located near 50 cm −1 both by the diffraction and the spectroscopic results. The CN bond in N(CF 3 ) 3 is shorter and stronger than that in N(CH 3 ) 3 .

Vibrational spectra and normal coordinate analysis of cf3 compounds: Part XLI. Vibrational spectra, normal coordinate analysis and electron diffraction investigation of hexafluoroazomethane and of cis- and trans-1,1,1,4,4,4-hexafluorobut-2-ene

Abstract The structure of hexafluoroazomethane, CF 3 N=NCF 3 , has been reinvestigated by electron diffraction and vibrational spectroscopy and a trans conformation confirmed with r(CF) 1.321(3), r(CN) 1.460(6), r(N=N) 1.235(10)Aand ∡(CNN) 113.4(1.6)°. Similarly, the structures of the but-2-enes trans - and cis -CF 3 CH CHCF 3 have been investigated for comparison, and the following parameters ( trans/cis ) have been determined: r(CF) 1.344(2)/1.343(2), r(CC) 1.481(5)/1.492(5), r(C C) 1.296(20)/1.310(16)Aand ∡(CCC) 125.1(1.6)/126.0(0.5)°. The vibrational spectroscopic data, including those of the butenes-d 2 , verify the observed strengthening of the CF bond in the diazene with respect to that in the butenes. Furthermore, a shortening of the CN/CC and N N/C C bonds upon substitution of CH 3 by CF 3 groups in azomethane and but-2-enes is revealed.

[2 + 4] Cycloaddition reactions of dialkylaminobis(trifluoromethyl)boranes with 1,3-dienes, β-unsaturated carbonyl compounds and methyl methacrylate. Crystal structures of (CF3)2BNR2CH2C(Me)C(Me)CH2, R = Me and Et, and (CF3)2BNEt2CH2CHC(Me)O

Hitherto unknown [2 + 4] addition reactions of aminoboranes were observed when dialkylaminobis(trifluoromethyl)boranes (CF3)2BNR2, R = Me and Et, were treated with a variety of 1,3-unsaturated compounds of the type XCR3CR2CHR1, where X = CH2 or O. The cycloaddition products of the general formula (CF3)2BNR2CHR1CR2CR3X were obtained in high yields. Ring closure was sterically hindered when the enone was OC(Me)CHCMe2, the B-alkylation product (CF3)2B(NHMe2)CH2C(O)CHCMe2 being formed instead by an ene reaction. Twelve novel boracyclohexene derivatives were isolated and characterized by multinuclear NMR spectroscopy and by mass spectrometry, and IR and Raman spectroscopy. The crystal structures of the compounds (CF3)2BNR2CH2-CMeCMeCH2, R = Me and Et, and (CF3)2BNEt2CH2CHCMeO have been determined by X-ray diffraction studies. They show that the BN and BCF3 bonds are somewhat longer than those in acyclic amine adducts of bis(trifluoromethyl)boranes. Furthermore, evidence is presented for steric congestion of the ring substituents.

[2 + 2 Cycloaddition reactions of dialkylaminobis(trifluoromethyl)boranes with isocyanates and isothiocyanates. Crystal structures of (CF32BNMe2CONtBu, (CF32BNMe2CSNtBu, (CF32BNPhC(NMe2)S and (CF3)2BNMeC(NEt2)OCONMe

Abstract The reactions of (CF3)2BNME2 (D1) and (CF3)2BNEt2 (D2) with isocyanates and isothiocyanates have been studied. At or near room temperature the CN bonds of RNCO and RNCS enter into [2+2] cycloadditions with the BN bond of D1 to yield the four-membered rings (CF3)2 BNMe 2 CON R; R = Me (I), tBu (II), Ph (III), CF3 (IV), and (CF3)2 BNMe 2 CSN R; R = Me (V), Et (VI), tBu (VII), Ph (VIII) and p-FC6H4 (IX) respectively. I, V, VI, VIII and IX rearrange at ≈60°C to form the isomers (CF3)2 BNMeC(NMe 2 )O (XI) and (CF3)2 BNRC(NMe 2 )S ; R = Me (XII), Et (XIII), Ph (XIV) and p-FC6H4 (XV), respectively. At room temperature D2 reacts with MeNCO to yield (CF3)2 BNMeC(NEt 2 )O (X) directly. X and XI reversibly incorporate MeNCO to form the six-membered heterocycles (CF3)2 BNMeC(NR 2 )OCON Me; R = Me (XVI) and Et (XVII). The structures of II, VII, XIV and XVII have been established by single crystal X-ray diffraction studies. The bond distances indicate that the π-bonding is delocalized over OCN (sp2), SCN (sp2 and SCN2 (sp2) fragments in II, VII and XIV, respectively. Furthermore, the π-character of the exocyclic CN bonds in XIV and VII, while considerable, is lower than that of the exocyclic CO(S) bonds in II, VII and XVII. The other structural assignments were based on mass spectrometry and vibrational and multinuclear NMR spectra.

Stabilization of tris(trifluoromethyl)borane in complexes with primary, secondary and tertiary amines. Crystal and molecular structure of (CF3)3B·NHEt2 and (CF3)3B·NH2Et

Abstract Various adducts (CF 3 ) 3 B·NHR 1 R 2 of the unknown free Lewis acid tris(trifluoromethyl)borane with secondary amines have been prepared from Cl 2 BNR 1 R 3 by nucleophilic trifluoromethylation with CF 3 Br P(NEt 2 ) 3 and subsequent protonation: R 1 R 2 Me (I), R 1 R 2 Et (II), R 1 + R 2 C 5 H 10 (III), R 1 R 2 cyclo-C 6 H 11 (IV), R 1 Me, R 2 CH 2 Ph (V), R 1 Me, R 2 t-Bu (VI). The primary amine derivatives (CF 3 ) 3 B·NH 2 R 1 , R 1 Et (VII) and Me (VIII), have been isolated as by-products in the preparations of II and VI, respectively. Reactions of I, II and VII with KOH yield the corresponding salts K[(CF 3 ) 3 B·NMe 2 ] (IX), K[(CF 3 ) 3 B·NEt 2 ] (X) and K[(CF 3 ) 3 B·NHEt] (XI). IX and X react with CH 3 I, CH 3 OSO 2 CF 3 and allyl bromide to yield the tertiary amine adducts (CF 3 ) 3 B·NR 1 R 2 R 3 , R 1 R 2 R 3 Me (XII), R 1 R 2 Me, R 3 C 3 H 5 (XIII), R 1 R 2 Et, R 3 Me (XIV), R 1 R 2 Et, R 3 C 3 H 5 (XV). The structure of II and VII were determined by an X-ray diffraction study. The strength of the BN bonds in these compounds is reflected in their comparatively short average length (1.592(5) A). The BC bond lengths average 1.614(4) A, and variations of the bond angles are consistent with considerable F strain in the adducts.

Synthesis of diethyl- and diisopropylamino-trifluoromethylboranes and their reactions with HF, HCl, HBr and H2O. The crystal structure of (CF3)2BN(i-Pr)2, revealing a very short BN bond

Abstract The novel trifluoromethyl-aminoboranes (CF3)(Cl)BNEt2 (I), (CF3)(Br)BNEt2 (II), (CF3)2BNEt2 (III) and (CF3)2BN(i-Pr)2 (IV) have been prepared by the reaction of Cl2BNEt2, Br2BNEt2 and Br2BN(i-Pr)2 with the trifluoromethylating agent P(NEt2)3/CF3Br in CH2Cl2. The reactions of these trifluoromethylboranes with HX (X = F, Cl, Br and OH) have been investigated, and the following 1 1 addition products obtained in high yields: CF3BCl2·NHEt2 (V); CF3BBr2·NHEt2 (VI); (CF3)2BX·NHEt2, X = F (VII), X = Cl (VIII), X = Br (IX), X = OH (X); (CF3)2BX·NH(i-Pr)2, X = F (XI), X = Cl (XII), X = Br (XIII). The structure of aminoborane IV was determined by an X-ray diffraction study. A strong π contribution to the BN bond is suggested by the planarity of the C2BNC2 fragment and the BN bond length, 1.37(1) A.

Reaction of perfluorotrimethylamine with antimony pentafluoride. Synthesis and X-ray structure of perfluorinated hexahydro-triazinedione derivative

Abstract Perfluorotrimethylamine and SbF 5 at an elevated temperature slowly eliminate CF 4 to form the cation (III). (III) is also obtained from the reaction of CF 3 NCF 2 with SbF 5 in nearly quantitative yield. The hexahydrotriazinedione (IV) has been obtained by hydrolysis of (III). The constitution and structure of (IV) are established by X-ray crystallography.

Hexa-, hepta- und octafluortrimethylamin

Abstract The electrofluorination of N(CH 3 ) 3 yields, along with fragmentation and recombination products and N(CF 3 ) 3 (I), minor quantities of the hitherto unknown compounds (CF 3 ) 2 NCF 2 H (II), CF 3 N(CF 2 H) 2 (III) and N(CF 2 H) 3 (IV). I –IV have been isolated and characterized by their 1 H, 13 C and 19 F nmr and their E I and C I mass spectra.

The reaction of (trifluoromethyl)dialkylaminoboranes with HF, HCl and HBr. X-ray structure investigation of the amineboranes (CF3)2B(X)NHMe2, X = F and OH

Abstract The reactions of CF 3 B(NMe 2 ) 2 (I) and (CF 3 ) 2 BNMe 2 (II) with HX (X  F, Cl and Br) have been investigated. Additions with preservation of the BC bonds to yield species with tetracoordinate boron, along with some BN cleavage, were observed. While I formed boronium salts CF 3 B(X)(NHMe 2 ) 2 + X − with X  Cl and Br, CF 3 BF 2 · NHMe 2 (V) was obtained with HF. On the other hand, reactions of II with HX yielded the 1 : 1 adducts (CF 3 ) 2 B(X) · HNMe 2 in each case. Of these, the species with X  F (VI) and X  OH (IX) (obtained by hydrolysis) were examined by single crystal X-ray diffraction. Surprisingly, no difference was found between the average BC bond lengths of these borates (VI 1.612(8), IX 1.624(4) A) and that of II. The implications of this observation for BCF 3 bonding are discussed.

BC bond formation by ene-type reactions of dimethylaminobis(trifluoromethyl)borane with nitriles and carbonyl compounds. Crystal structure of (NCCH2)(CF3)2B · NHMe2

Abstract Dimethylaminobis(trifluoromethyl)borane, (CF3)2BNMe2 (A), reacts with nitriles RCH2CN | to yield triorganoboron adducts | NCCHR)(CF3)2B · NHMe2 (R  H (I), Cl (II), Me (III) and Et (IV)). Analogously carbonyl compounds of the general formula R2C(O)CH2R1 form the respective complexes (R2C(O)CHR 1)(CF3)2B · NHMe2: R1  H, R2  tBu (V), R1  H, R2  Ph (VI), R1  H, R2  CCHCHC(Me)O (VII), R1  H, R2  Me (VIII), R1  H, R2  CHCMe2 (IX), R1  H, R2  OMe (X), R1  H, R2  OtBu (XI), R1  H, R2  OSiMe3 (XII), R1  H, R2  OC(Me)CH2 (XIII), R1  H, R2  OCH2CHCH2 (XIV), R1  H, R2  OtBu (XI), R1  OSiMe3 (XII), R1  H, R2  OC(Me)CH2 (XIII), R1  H, R2  OCH2CH CH2 (XIV), R1  H, R2  NMe2 (XV), R1  H, R2  NEt2 (XVII), R1  Cl,R2  OEt (XVIII), R1  Me, R2  OMe (XIX), R1  Et, R2  OMe (XX), R1  C(O)OMe, R2  OMe (XXI), R1  C(O)OtBu, R2  OtBu (XXII), R1, R2  CH2OCH2 (XXIII). Their identities have been confirmed by multinuclear NMR, IR, and mass spectroscopy. The crystal and molecular structure of I has been determined by an X-ray diffraction study. Individual molecules are linked to form infinite chains through hydrogen bonding. The BC (1.627(3) A (BCF3) and 1.629(4) A (BCH2CN)) and BN bond lengths (1.600(3) A are normal.