Tetraborane lO

B4H10 forms slowly by decomposition of diborane, B2H6, in a slightly exothermic reaction (AH = -14 kj mol 1) and it is produced in a hot-cold-reactor (120 °C/ -78 °C). At present the best method is to react Bu4N[B3H8] with BC13 or A1C13 in the presence of toluene as shown in Eq. (26)  

It is most likely that unstable B3H7 is generated in a first step. Its dimerization leads to unstable B6Hi4 [32] which decomposes to tetraborane(lO) and non-characterized additional boron compounds, denoted in Eq. (26) as B2H4.  

Tetraborane(lO) is a very weak acid. Therefore, deprotonation requires a very 

Tetraborane(lO) reacts, as does diborane, readily with unsaturated hydrocarbons. Alkenes give access to B2,B4-alkylene bridged B4H8(RCH-CHR) organo-boranes [37] while alkynes, allenes and l-ene-3-ynes lead to a variety of carba-boranes [38-40]. 

2 Derivatives of nido-Tetraborane(8), B4Hg, and closo-Tetraborane(6), B4H6 

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The tetra alkyl amm onium salts of [B Hg] , formed by ion-exchange reactions, have proven to be useful synthetic reagents because of their thermal and air stabihties. The stmcture of the [B Hg] ion has been determined by an x-ray study (66) and shown to have the 2013 styx stmcture, C2 symmetry. Mechanisms for the formation of this ion have been proposed (67). Tetraborane(lO) can be easily obtained from salts of [B Hg] (eq. 9). 

The reported ignition of diborane and tetraborane(lO) in contact with air or oxygen is due to the presence of traces of silicon hydrides [1]. The lower members of the latter class ignite or explode in air or oxygen, especially at reduced pressure [2], Phosphine is also sensitive [3],... 

Phosphacarba- f6>-pentaborane [2-/Bu-l,2-PCB3Fl5] 25 was synthesized by gas-phase reaction of phosphaalkyne with tetraborane(lO) (see Figure 11). In the 31P NMR spectrum a signal at —501 ppm was detected for the apical phosphorus atom and confirmed by quantum mechanical calculations.120... 

Most of these reactions are reversible. Thus, heating tetraborane(lO) in the presence of a large excess of hydrogen reforms diborane. Pentaborane(ll) is thermally... 

Carbaboranes with an arachno-CB4 skeleton, that is derivatives of 1-carba-arachno-pentaborane(lO), were identified as side products (Scheme 3.2-11) 18 in the reaction of dichloroethylborane with elemental Li [29], and 19 was obtained from pro-pyne and tetraborane(lO) [30], The reaction of dimethyl(dipropyn-l-yl)silane with a large excess of tetraethyldiborane(6) [ hydride bath which contains Et2BH2BEt2, other ethyldiboranes(6) and triethylborane] [31, 32] resulted in the formation of 20 in good yield [33]. 

Phosphorus azide dilluoride-borane, 4316 Poly[borane(l)], 0134 Tetraborane(lO), 0181... 

Diborane(6) and tetraborane(lO) are colorless gases at ambient temperature and pressure. Diborane has a repulsive odor. Higher boranes up to nine boron atoms are colorless hquids. Decaborane(14) is a colorless crystalline solid. Pentaborane(ll) andhexaborane(12) are unstable compounds. The densities and melting and boiling points of selected boron hydrides are shown in the following table ... 

There, are at least six definitely characterized boron hydrides, as follows diborane(6), B H tetraborane(lO), B4 H, pentaborane(9) (stable), B3 H pentaborane( 11) (unstable). B5 Hu hexaborane(lO). H10 and decaborane(14). Bio H14. In these names, note that the prefix denotes the number of boron atoms, while the figure in parentheses denotes the number of hydrogen atoms. In addition to these compounds, which are all gases or volatile liquids except decaborane(L4), decomposition of the lower boron hydrides yields colorless or yellow solid boron hydrides, ranging in composition from (BItysty to (BII). This readiness to polymerize is evidence of the reactivity of these borane compounds, which readily form additional products with ammonia, with the amalgams of the active metals, and with many otganic compounds, as well as with CO. 

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