Darstellung, 11 B-NMR- und Schwingungsspektren von cis-Dinitrotetrahydro-closo-hexaborat(2–), cis-[B6H4( NO2)2]2- sowie Kristallstruktur von cis-Cs2[B6H4(NO2)2] / Preparation, 11 B NMR and Vibrational Spectra of cis-Dinitrotetrahydro-closo-hexaborate(2–),cis-[B6H4(NO2)2]2-, and the Crystal Structure of cis-Cs2[B6H4(NO2)2]

1995 ◽  
Vol 50 (7) ◽  
pp. 1030-1034 ◽  
Author(s):  
A. Franken ◽  
W. Preetz

By electrochemical oxidation of [B6H6,]2 in the presence of nitrite ions and of the base DBU in dichloromethane solution apart from [B6H5 (NO2)]2- and [B6H5(NO)B 6H5]3- the dinitro anion cis-[B6H4( NO2)2]2- is formed and can be isolated by ion exchange chromatography on diethylaminoethyl cellulose. The crystal structure of the Cs salt has been determined from single crystal X-ray diffraction analyses. cis-Cs2[B6H4 ( NO2)2] is tetragonal, space group P4̄21 m with a = 10.0656(4), c = 11.0127(13) Å. The 11B NMR spectrum is consistent with a disubstituted octahedral B6 cage with local C2v symmetry. The IR and Raman spectra exhibit characteristic NO2, B - H and B6 vibrations.

1993 ◽  
Vol 48 (12) ◽  
pp. 1727-1731 ◽  
Author(s):  
A. Franken ◽  
W. Preetz ◽  
M. Rath ◽  
K.-F. Hesse

By electrochemical oxidation of [B6H6]2- in the presence of nitrite ions and the base DBU in dichloromethane solution mononitropentahydrohexaborate [B6H5(NO2)]2- ions are formed and can be isolated by ion exchange chromatography on diethylaminoethyl cellulose. The crystal structures of the K and Cs salt were determined from single crystal X-ray diffraction analyses. K2[B6H5(NO2)] is monoclinic, space group P21/m with a = 5.953(1), b = 8.059(4), c = 8.906(1) Å, β = 109.553(9)°; Cs2[B6H5(NO2)] is monoclinic, space group P21/a with a = 9.438(6), b = 9.644(7), c = 11.138(9) Å, β = 101.44(9)°. The B6 octahedron is compressed in the direction of the B—NO2 bond by about 5%, with bond lengths between 1.67 and 1.77 A.


1995 ◽  
Vol 50 (9) ◽  
pp. 1362-1368 ◽  
Author(s):  
A. Franken ◽  
W. Preetz

AbstractBy electrochemical oxidation of [B6H5(CN)]2- in the presence of nitrite ions and of the base DBU in dichloromethane solution cis-[B6H4(CN)(NO2)]2- and cis- [(CN)B6H4(NO)B6H4(CN)]3- are formed and can be isolated by ion exchange chromatography on diethylaminoethyl cellulose. The crystal structure of the tetraphenylarsonium salt has been determined by single crystal X-ray diffraction analysis. [As(C6H5)4]2-cis-[B6H4(CN)(NO2)] is monoclinic, space group P21/a with a = 20.343(5), b = 10.896(2), c = 21.572(5) A and β = 107.30(2)°. The 11B NMR spectra are consistent with disubstituted octahedral B6 cages with local C2v symmetry. The IR and Raman spectra exhibit characteristic NO2, NO, CN, BH, and B6 vibrations.


1994 ◽  
Vol 49 (9) ◽  
pp. 1263-1266 ◽  
Author(s):  
A. Franken ◽  
W. Preetz

By electrochemical oxidation of [B6H6]2- in the presence of nitrite ions and of the base DBU in dichlorom ethane solution the μ-nitroso-bis(pentahydrohexaborate) [B6H5(NO)B6H5]3- ion is formed and can be isolated by ion exchange chromatography on diethylaminoethyl cellulose. The crystal structure of the Cs salt has been determined from single crystal X-ray diffraction analysis. Cs3[B6H5(NO)B6H5] is orthorhombic, space group Pnma with a = 16.2303(13), b = 12.245(6), c = 25.444(2) Å. The unit cell contains three crystallographically independent anions with nearly C2v symmetry but differently distorted B6 cages


1994 ◽  
Vol 49 (4) ◽  
pp. 471-476 ◽  
Author(s):  
A. Franken ◽  
W. Preetz

By reaction of [B6H6]2- with chloroacetonitrile in dichloromethane the cyanomethylhexahy-dro-closo-hexaborate(1-), [B6H6(CH2CN)]- is formed. The com pound has been separated from excess [B6H6]2- by ion exchange chromatography on diethylaminoethyl cellulose. The crystal structure of [P(C6H5)4][B6H6(CH2CN)] has been determined by single crystal X-ray diffraction analysis; triclinic, space group P1 with a = 7.503(3), b = 12.0949(8), c = 14.6572(11) Å α = 79.399(6)°, β = 79.19(2)°, γ = 89.2(2)°. The 11B NMR spectrum is consistent with a mono hetero substituted octahedral B6 cage. In the 13C NMR spectrum of Cs2[B6H5(CH2CN)] a singlet at 131.9 ppm (CN) and a quartet at 2.97 ppm with 1J(C,B) = 54.7 Hz (CH2) are observed. The IR and Raman spectra exhibit a very strong CN stretching band at 2218 cm-1.


1999 ◽  
Vol 54 (6) ◽  
pp. 772-776 ◽  
Author(s):  
C. Drewes ◽  
W. Preetz

By electrochemical oxidation of (n-Bu4N)[B6H5Hfac(C2H5)] in the presence of nitrite ions and of the base DBU in dichloromethane solution cis-[B6H4(C2H5)(NO2)]2- is formed. X-ray diffraction analysis has been performed on a single crystal of cis-(Ph4 As)2[B6H4(C2H5)(NO2)] (triclinic, space group P1; a = 10.673(4). b = 10.907(4), c = 21.237(4) A, α = 80.789(4), β = 83.117(4), γ = 66.548(2)°, Z = 2). The 11B NMR spectrum is consistent with a disubstituted octahedral B6 cage with local Cs symmetry. The IR and Raman spectra exhibit characteristic CH3, CH2, NO2, BN, BH and B6 vibrations


1993 ◽  
Vol 48 (5) ◽  
pp. 598-602 ◽  
Author(s):  
W. Preetz ◽  
A. Franken ◽  
M. Rath

By reaction of Cs2[B6H6] with in situ generated dicyanogen in aqueous alkaline solution the monocyanohydrohexaborate Cs2[B6H5(CN)] and the dicyanohydrohexaborate cis-Cs2[B6H4(CN)2] are formed. The compounds have been separated by ion exchange chromatography on diethylaminoethyl cellulose. The crystal structure of Cs2[B6H5(CN)] was determined from single crystal X-ray diffraction analysis; monoclinic, space group P21/a with a = 9.540(8), b = 9.977(3), c = 10.578(2)Å, β = 105.06(2)°. The B6 octahedron is compressed in the direction of the nearly linear B—CN bond by about 5%, with bond lengths between 1.71 and 1.76Å. The "B NMR spectra of the two compounds reveal the features of substituted B6 cages with C4v and C2v point symmetry. In the 13C NMR spectrum of Cs2[B6H5(CN)] a quartet at -139 ppm with 1J(C,B) 92 Hz is observed. The IR and Raman spectra exhibit very strong CN stretching bands for Cs2[B6H5(CN)] at 2149, and for cis-Cs2[B6H4(CN)2] at 2170 cm-1.


1996 ◽  
Vol 51 (5) ◽  
pp. 609-618 ◽  
Author(s):  
D. Bublitz ◽  
A. Franken ◽  
W. Preetz ◽  
H. Thomsen

By reaction of [B6H6]2- with dibenzoylperoxide in dichloromethane conjuncto-[B6H6- B6H6]2- is formed. The product could be separated from excess [B6H6]2- by ion exchange chromatography on diethylaminoethyl cellulose. The crystal structure of [P(C6H5)4]2 -conjuncto- [B6H6-B6H6] has been determined by single crystal X-ray diffraction analysis; triclinic, space group P1̄ with a = 10.8315(10), b = 11,2422( 12), c = 20.340(2) Å, α = 91.278° (9), β = 90.178° (9), γ = 105.662°(9). The 11B NMR spectrum reveals three signals with the intensity ratio 1:1:4, for two equivalent moieties of the conjuncto molecule ion with local C4v symmetry. The IR and Raman spectra of the deprotonated Cs salts of the 10B, 11B and their respective D isotopomers of conjuncto-[B6H5-B6H5]4- exhibit characteristic shifts. Using averaged crystallographic data and assuming idealized D4h symmetry, normal coordinate analyses have been performed based on a modified valence force field. With a set of eleven force constants (e.g. fd(BB)conjuncto = 2.9, fd(BB)cage = 1.6 mdyn/Å) very good agreement between observed and calculated frequencies has been achieved. From strong vibrational coupling with the B6 clusters two vibrations result for the conjuncto B-B bond at 1142/1198 and 292/304cm-1 for 11B/10B species, respectively. They can be assigned as anti-phase and in-phase motions of the conjuncto B atoms related to the equatorial B4 planes.


1996 ◽  
Vol 51 (4) ◽  
pp. 545-550 ◽  
Author(s):  
W. Lübbe ◽  
W. Preetz

Abstract By reaction of [B6H6]2- with dibromomethane in acetonitrile μ-Methylene-bis-hexahydro-closo-hexaborate, [B6H6(CH2)B6H6]2-, is formed which can be separated from excess [B6H6]2- by ion exchange chromatography on diethylaminoethyl cellulose. The crystal structure of [As(C6H5)4]2[B6H6(C H2)B6H6] · (CH3)2CO has been determined by single crystal X-ray analysis: triclinic, space group P1 with a = 10.779(2), b = 10.8003(12) and c = 23.077(3) Å, a = 99.147(10), β = 91.569(13) and y = 91.288(11)°. The 11B NMR spectrum reveals the features of a monosubstituted octahedral B6 cage. The 13C NMR spectrum exhibits a multiplet at -5.44 ppm. In the 1H NM R spectrum a singlet of the methylene protons at 0.23 ppm and two singlets at 1.97 and -4.52 ppm of the BH fragments are observed. The IR and Raman spectra exhibit strong CH stretching bands between 2873 and 2762 cm-1, BH stretching bands between 2443 and 2403 cm-1, and a BC stretching vibration at 1138 cm-1 in the Raman spectrum.


1999 ◽  
Vol 54 (10) ◽  
pp. 1219-1221 ◽  
Author(s):  
C. Drewes ◽  
W. Preetz

By electrochemical oxidation of (n-Bu4N)[B6H5Hfac(CH2Ph)] in the presence of nitrite ions in dichloromethane solution cis-[B6H4(CH2Ph)(N O2)]2- is formed. X-ray diffraction analysis has been performed on a single crystal of cis-(Ph4P)2[B6H4(CH2Ph)(NO2)] HO2CH3CN (triclinic, space group Pl̅ a = 11.338(5), b = 11.377(5), c = 21.081 (5) Å, α = 93.727(5), ß = 98.872(5), γ = 105.926(5)°, Z = 2). The 11B NMR spectrum is consistent with a disubstituted octahedral B6 cage with local C2v symmetry. The IR and Raman spectra exhibit characteristic CH, NO2, BN, BH and B6 vibrations.


1995 ◽  
Vol 50 (7) ◽  
pp. 1025-1029 ◽  
Author(s):  
J. Baurmeister ◽  
A. Franken ◽  
W. Preetz

By reaction of [N(C4H9 )4]2 [B6H6] with iodomethyl-trimethylsilane in acetonitrile a solution with trimethylsilylm ethyl-closo-hexaborate(1-)anions, [B6H6 (CH2Si(CH3)3)]-, is formed. The crystal structure of [P(C6H5 )4][B6H6(CH2Si(CH3)3)] has been determined by single crystal X-ray diffraction analysis; monoclinic, space group P21/n with a = 16.140(2), b = 11.646(8), c = 16.731(3) Å, β 109.664(11)°. The 11B NMR spectrum reveals features of a mono hetero substituted octahedral B6 cage. The 13C NMR spectrum exhibits a quartet at +0.18 ppm with 1J(C,H) = 118 Hz for the three methyl groups and a weak multiplet at -0.65 ppm for the methylene bridge due to quadrupole coupling with the boron atoms. In the 29Si NMR spectrum a decet at +2.25 ppm with 2J(C,H ) = 6.9 Hz is observed. The B -C stretching vibration is observed at 1155 cm-1 in the IR and Raman spectrum.


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