The 12-vertex closo-phosphaborane 1,7-P2B10Cl10 (1) has been prepared in low yield from the pyrolysis reaction of B2Cl4 with PCl3 at temperatures above 400 degrees C. A single-crystal X-ray structure determination of 1 (monoclinic space group P2(1)/n with a = 9.239(2) A, b = 16.786(3) A, c = 15.739(3) a, beta = 93.25(3) degrees, and Z = 4) confirmed that, consistent with its 26 skeletal electron count, the phosphaborane adopts a distorted icosahedral structure with the phosphorus atoms in the 1,7-positions. Crystals of 1 contain toluene in a 1:1 molar ratio embedded between each P atom of neighboring cluster molecules. Alteration of the pyrolytic conditions resulted in the formation of the phosphaboranes P4B8Cl6 (2) and P2B8Cl8 (3), which were characterized spectroscopically. Copyrolysis of B2Cl4 with a mixture of PCl3 and AsCl3 at 450 degrees C generated the six-vertex arsaphosphaborane AsPB4Cl4 (4) and traces of the icosahedral arsaphosphaborane AsPB10Cl10. These compounds are examples of heteroboranes which contain two different group-15 atoms within a single molecule.
1 : [Ru"'(Hedta)CI]" was reduced to (Ru"(Hedta)(H20)JB 2 using hydrogen over platinum black under an atmosphere of hydrogen."" The photocatalyst CdS/Pt/RuO> was prepared by the published procedure [IS]. Complex 2 exhibits LMCT peaks at 283, 332, and 296 nm. On passing Nz through dilute solutions of 2 ( = M), the peaks corresponding to 2 decrease with the appearance or a new peak at 221 nm, which was taken as a marker peak for the calculation of the stability constant of 1. The equilibrium constant for the formation of 1 is given by the following expression: [ R~( H e d t a ) ( H , o ) ]~ + N, [Ru(Hedta)(N2)le + H 2 0 2 1From the solubility of N2 in water at 25" (7.81 x mol L-') the equilibrium constant for the formation of 1 at 25" was calculated as log K , = 2.90_+0.02. Complex 1 exhibits the v(M-N,) band at 2040 cm-'. Differential pulse polarography (DPP) of l gives a single peak at -0.48 V corresponding to the redox couple Ru"/Ru'. The cyclic voltammogram of 1 gives reversible peaks at -0.24 and -1.0 V for the Ru"'/Ru" and H"/H potentials, respectively. The peak corresponding to Ru"/Ru' cannot be observed because of the crossover of the cathodic-potential and anodic-potential curves in this region.
Copyrolysis of BzC14 and AsC1, at 330 "C leads to the forma-the products. At temperatures above 400 "C and higher tion of closo-1,2-As2B4C14 (1) and further products the mass B2C14/AsC13 ratios the formation of AszBloCllo is preferred to spectral evidence of which suggests that they are perchlorithat of smaller arsaboranes. A single-crystal X-ray study of 1 nated arsaboranes AsZB5Cl5, As4B8C16, and AszBloCllo. The confirmed that, consistent with its 14-skeletal electron count, pyrolysis temperature and the molar ratio of the reactants the arsaborane adopts a slightly distorted octahedral strucexert an essential influence on the type and distribution of ture with the arsenic atoms in adjacent cis positions.There are only very few boranes known so far containing two arsenic atoms in the polyhedral framework. They were synthesized by a reaction involving two arsenic insertions into decaborane in the presence of a base to yield clos0-1,2-As~B~~H~~['~~~. Derived thereof are closo-1 ,2-As2BloH812[3] and nido-7,8-As,B9H,['l. However, aside from l l -or 12-vertex arsaboranes there are no examples where arsenic atoms are part of frameworks deriving from smaller boron compounds.In this paper we report on the first direct method of combining arsenic and boron species starting from molecules with 2-center 2-electron bonds to yield several previously unknown small-and medium-sized polyhedral diarsaboranes with chlorine ligands attached to the boron atoms. Results and DiscussionRecently, we have reported on the thermal disproportionation of tetrahalodiboranes(4) BzX4 in the presence of the coreactants PX3, CX4, or C2X4 (X = C1, Br). Stable polyhedral heteroboranes such as clos0-1,2-P,B~C1~[~1(2), ~loso-l,2-P~B~Br~[~I, and C2BnXn+2 (n = 5-8)r6] could be obtained in case the reaction took place in the vapor phase. In order to apply this method to the preparation of heteroboranes aside from phospha-and carbaboranes we studied the copyrolyses of B2Cl4 with various other volatile main group halides.Preliminary attempts to prepare arsaboranes via copyrolysis of B2C14 with AsC13 under corresponding conditions in a single-flask reactor failed. Thereby trichloroarsane is reduced almost quantitatively by tetrachlorodiborane(4) to elemental arsenic and trichloroborane (eq. 1). This redox reaction already occurs in the mixture at room temperature. However, if B2C14 and AsCI3 are condensed into two separate flasks which are connected by a tube, and the reactants are transferred into a preheated oven immediately after sealing, simultaneous vaporization and pyrolysis partly suppress the redox reaction to give new arsaborane clusters. The reaction mixture can be sublimed fractionally. The components were identified by mass spectrometry as As2B4CI4 (I), B9C19, AS&Cl6, and -only in traces -as As2BSCIs. The remaining low-volatile residue contains As2BlDCl10 and elemental arsenic.The formation of A s~B~~C I~~ is favored compared to smaller arsaboranes when the pyrolysis is performed at higher temperatures. By increasing both the molar ratio B2Cld...
Bortrihalogenide BX3 (X = F, Cl, Br) setzen sich mit Tris‐(trimethylsilyl)‐amin, (Me3Si)3N, I, (Me CH3—) je nach den Reaktionsbedingungen und dem verwendeten Halogenid zu MeBX2, (Me3Si)2NBMeX, (Me3Si)2NBX2 oder deren Mischungen um; z. B. ergeben BF3 und I (Me3Si)2NBF2 und Me3SiF, während aus BBr3 und I bei 23°C MeBBr2 und (Me3Si)2NSiMe2Br entstehen. Die Aminoborane (Me3Si)2NBMe2 und (Me3Si)2NBMeBr wurden zusätzlich auf anderem Wege synthetisiert.
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