Wolfgang Einholz

Borylierung von Sulfamiden, Sulfoniminen und Sulfondiiminen/Borylation of Sulfamides, Sulfonimines and Sulfonediimines

Abstract The diborylated sulfamide 6a can be obtained from 2-chloro-1,3-dimethyl-1,3,2-diazaborolidine and the silylated sulfamide la , whereas (Me2N)2BCl and 1a yield the dithia-tetrazadiborocine 7b. Similarly, (Me2N)2BCl reacts with a) the sulfonimine 2a, b) the sulfonediimine 3a to give a) B(NMe2)3, and the bis-and tris(sulfonimino)boranes 10b and 11, b) B(NMe2)3 and the dithiatetrazadiborocine 15b. The diborylated sulfamide 6c (R2B = Ph2B) cannot be isolated. The synthesis of the monoborylated sulfonimines 9c, 9e and sulfonediimines 13, 14 is described.

Redox reactions of the boron subhalide clusters BnCln0/˙–/2– (n = 8 or 9) investigated by electrochemical and spectroscopic methods†

The redox properties of the electron hyperdeficient boron subhalide clusters octachlorooctaborane(8), B8Cl8, and nonachlorononaborane(9), B9Cl9, were investigated in solution by cyclic voltammetry at platinum or glassy carbon electrodes, and by 11B NMR as well as ESR spectroscopy. The neutral compounds undergo a spontaneous reduction by traces of moisture usually present even in dried solvents, and the voltammetric experiment starts from B8Cl8˙– or B9Cl9˙–. The radical anions were identified by ESR spectroscopy. Their formation leads to line broadening in NMR spectra of BnCln. Electrochemically, they are quasireversibly reduced to the dianions, but oxidized in an ECcat (electrochemical step, catalytic chemical step) reaction with an essentially reversible electron transfer step to the neutral compounds. The potential ordering for the two redox processes is “normal” in both clusters, being in accordance with the fact that structural changes accompanying the electron transfer are minor. The radical anion B8Cl8˙– is even more stable against disproportionation than B9Cl9˙–.

Zwölfgliedrige Heteroborancluster durch Copyrolyse von Tetrachlordiboran(4) mit Elementhalogeniden/ Twelve-Vertex Heteroborane Clusters by Copyrolysis of Tetrachlorodiborane(4) and Element Halides

Abstract The perchlorinated arsaboranes closo-1,2-As2B10Cl10 and As4B8C16 are formed in the co pyrolysis of B2C14 and AsCl3 at temperatures of 330-450°C. The icosahedral structure of closo-1,2-As2B10Cl10 is confirmed by 11B-11B-COSY-NMR spectroscopy. As4B8Cl6 is suppo sed to be a conjuncto-borane (As2B4Cl3)2 with two boron-boron linked As2B4Cl3 octahedra. The copyrolysis of B2Cl4 andSbCl3 or SbCl5 yields Sb2B10Cl10, and the corresponding reaction of B2Cl4 with S2Cl2 gives the icosahedral thiaborane cluster SB11Cl11 .

Kristall-und Molekülstruktur von N,N'-Bis(1,3-dimethylbenzo[b]-1,3,2-diazaboroIidin-2-yl)carbodiimid

Abstract Crystals of the title compound (2) are monoclinic with a = 905.5(3), b = 593.6(2). c - 3243.5(8) pm, β = 95.63(2)°, Z = 4, space group P21/n. The molecule 2 neither has a C2-symmet-rical allene-type nor a D2d -symmetrical cumulene-type structure, but it has a non-linear B-N = C= N - B arrangement and is nearly planar. The central N = C= N angle has a value of 171.9(3)°, the B - N = C angles are 145.9(2)° and 163.1(3)°.

Adducts of trichloroborane with cyanamides. Thermal degradation to boron nitride

Abstract H 2 NCN reacts with BCl 3 at low temperatures to give the complex H 2 NCNBCl 3 ( 1 and the dimeric iminoborane [H 2 NC(Cl)NBCl 2 ] 2 ( 3 ), whereas Me 2 NCN and BCl 3 yield mainly [Me 2 NC(Cl)NBCl 2 ] 2 ( 4 ). The cyanamide complex 1 and the iminoborane 3 release HCl when heated above 100°C, and the pyrolysis of 1 or 3 at 1000°C in the presence of NH 3 leads to the formation of boron nitride. Promising results concerning resistance of graphite against oxidation were obtained when graphite was covered with a layer of dissolved 3 and pyrolysed under NH 3 at 1000°C with additional heating in vacuo at 1350°C.

Ligandenaustauschreaktionen zwischen Halogenboranen und Alkylsilanen/Ligand Exchange Reactions between Haloboranes and Alkylsilanes

Abstract In a ligand exchange reaction between BHal3 (Hal = Cl, Br) and the tetraalkylsilanes Et4Si, (Me3Si)2CH2 or Ph2CHSiMe3 the alkylhaloboranes EtBBr2 or MeBHal2 and the alkylhalosilanes Et3SiBr, HalMe2Si-CH2-SiMe3, (HalMe2Si)2CH2, and Ph2CHSiMe2Br, respectively, are formed. Similarly, the methyloligosilanes (Me3Si)2 (1) and (Me3Si)2SiMe2 (2) react with BHal3 (Hal = Cl, Br, I) via methyl-halogen-transfer to give HalMe2Si-SiMe3 (Hal = Cl, Br, I), (HalMe2Si)2 (Hal = Br, I), HalMe2Si - SiMe2-SiMe3, (Me3Si)2SiMeHal, HalMe2Si - SiMeHal -SiMe3, (HalMe2Si)SiMe2 (Hal = Cl, Br) or (BrMe2Si)2SiMeBr besides MeBHal2 (Hal = Cl, Br, I) and Me2BI, respectively.