Pentaborane derivatives

The Cd-borane interaction is assumed to be two electron, three centered. The only pentaborane derivative of mercury is represented as Hg(B5Hg)2. 

Scheme 3.2-20. Formation of 1,5-dicarba-c/oso- derivative 39c. Its methylation leads to 39b, pentaborane derivatives 39 (R = CH2CMe3) via and reaction with RC2U to 39d,e (b X = Me c hydroboration of a borylalkyne with HBCI2 to X — Cl, d R — CMe3 e R — Ph). give 40a, which on heating yields the chloro...

Polyhedral Boron Hydrides. Although relatively large quantities of polyhedral boron hydrides and carboranes have been produced under various government contracts, these materials are not currendy produced on a regular commercial basis. Pentaborane(9) nido- and decaborane(14) and carboranes, such as the ortho and meta-carboranes closo-1 1 well as various other derivatives, are... 

Isomers of pentaborane and hexaborane derivatives SnPh2(BsHg)2 and Ph3SnB6H9 were studied by H, nB, 13C, and 119Sn NMR spectroscopy in solution and solid state structures of three isomers were also reported.50-53... 

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]. 

Many derivatives of isomeric 2,3-dicarba-nido-hexaborane(8) are known, available from the reaction of pentaborane(9) with alkynes [59, 60]. In contrast, the carboranes of type 43 with non-adjacent carbon atoms are rare. 

Reduction of the pentaalkyl-1,5-dicarba-closo-pentaboranes(5) 44 with elemental K opens the cluster and subsequent reaction with I2 enforces oxidative fusion of two C2B3 units to give a C4B6 cage (Scheme 3.2-36). The peralkylated hexaboraadamantane derivatives 70 (R = Me, Et X-ray structure analysis for R = Me [89]) rearrange irreversibly into the carboranes 71 with a wido-C4B6 framework [89] (X-ray structural analysis for R = Et [90]). The structure of the nido-C Bf, cluster is fluxional in solution [91]. 

As in the latter example, the same aminosilane employed for the synthesis of the disilaborane (Scheme 3.3-1) was used to incorporate a silicon vertex into a poly-borane cluster skeleton. However, attempts to use pentaborane(9) B5H9 for this method proved not to be successful. Instead, pentaborane(9) undergoes degradation and formation of the tetraborane derivative [B4H8SiMe(NMe2)2BH2] was observed [30],... 

Fig. 3.4-12. Two derivatives of the hypothetical parent diaza-arachno-pentaborane N2B3H7 with an ar-5 and an ar-5 structure in a topological representation and in one with localized bonds.

Pentaborane(9) A Raw Material for the Preparation of Boron Hydrides and Boron Hydride Derivatives. 

Hughes RL, Smith IC, Lawless EW III. Pentaborane (9) and derivatives. In Holzmann RT (ed) Production of the Boranes and Related Research, pp 294—489. New York, Academic Press, 1967... 

Other dicaboranes are derived from the corresponding pentaborane(5), hexa-borare 6), hexaborane(8), heptaborane(7), octaborane 8). nonaborane(9), and deca-... 

Two specifically deuterated tetraborane(lO) derivatives have been prepared. Degradation of pentaborane(ll) by D2O 147.148) gives 95—97% yields of bridge monodeuterated tetraborane(lO). Unsymmetrical cleavage is suggested as a possible mechanism ... 

The synthesis and characterization of the [BsHs]- ion 15,16,17) js one of the most important developments in recent years in the chemistry of pentaborane(9) and its derivatives. Several examples of a new class of pentaborane(9) derivatives have been prepared in which substituents occupy bridging sites 172-175) and significant yields of hexa-borane(lO) 16>17>, hexaborane(12) 17>, or decaborane(14) 16>17> have been obtained from the reaction of B5H8 with B2H6 by careful control of the reaction conditions. 

Prior to 1964, the only halogenated pentaborane(9) derivatives which had been reported were l-IBsHg and 1-BrBsHg isi.isa), but the experimental details of their preparations were sparse. 

A ring current model has been shown to correlate proton and boron-11 chemical shifts in a number of pyramidal boron compounds including pentaborane(9) and its derivatives 180>. This model is analogous to the model used to explain proton chemical shifts in benzene and similar aromatic compounds. 

The structure of decaborane(16) 200> reveals that it should be considered as an apically substituted derivative of pentaborane(9). The bond energy of the unique boron-boron bond which connects the two B5H8 cages has been determined to be 3.2 0.2 e.v. from mass spectrometry 201> the standard heat of formation is 34.8 kcal. per mole 202>. An analysis of the vibrational spectrum of decaborane(16) has been made by Pinson and Lin 203> who note the absence of the strong absorption at 901 cm-1 which was previously reported 204>. 

Conversion of the I-Carba-nracAno-pentaborane( 10) Derivative 7 into a nido-... 

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