7318-78-7Relevant articles and documents
Schlesinger, H. I.,Brown, H. C.,Horvitz, L.,Bond, A. C.,Tuck, L. O.,Walker, A. O.
, p. 222 - 224 (1953)
Reactions of the diboron tetrahalides B2Cl4 and B2Br4 with B5H9: Preparation and properties of the (dihaloboryl)pentaborane derivatives 1-BX2B5H8, (X = Br, Cl, F, OCH3, t-Bu, H) and synthesis of (BCl2)3B5H6
Saulys,Morrison
, p. 4174 - 4179 (2008/10/08)
The reactions of B2Cl4 with excess B5H9 yield 1-BCl2B5H8 (73%) while those of B2Br4 generate 1-BBr2B5H8 (80%). Ligand exchange of 1-BCl2B5H8 with excess BBr3 forms 1-BBr2B5H8 (86%), that with Hg(CF3)2 results in 1-BF2B5H8 (96%), that with CH3OH generates 1-B(OCH3)2B5H8 (46%), and that with Li(t-Bu) prepares B(t-Bu)(Cl)B5H8 (23%) and B(t-Bu)2B5H8 (20%). The relative thermal stabilities of these products are BF2B5H8 > BCl2B5H8 > BBr2B5H8 > B(OCH3)2B5H8 > B(t-Bu)2B5H8. All of these BX2B5H8 compounds (X = F, Cl, OCH3, t-Bu) decompose to form BX3 and B5H9 as the volatile products. Reactions of BCl2B5H8 with excess B2Cl4 yield (BCl2)3B5H6, a compound of limited thermal stability, but no evidence for further BCl2 substitution on the pentaborane cage was obtained. Reductions of BCl2B5H8 with LiBH4 in C6H5Cl or C6H4Cl2 form apparent equilibrium mixtures of 1:1′,2′-[B5H8][B2H5] and 1:1′-[B5H8][B2H5]. One or both of these compounds decompose with the evolution of B2H6, B5H9, and coupled pentaborane cages (B5H7)n, where n can be at least as large as 8. The 11B NMR and mass spectrometric evidence from the last reaction is consistent with the initial dimerization of the hexaborane 1-BH2B5H8, which is rapidly followed by the formation of 1:1′-[B5H8][B2H5], the cross product arising from the interaction of B2H6 with (BH2B5H8)2, and then isomerization of this heptaborane to 1:1′,2′-[B5H8][B2H5].
Relative reactivities of the small closo carboranes 1,6-C2B4H6 and 2,4-C2B5H7 and of closo-1,10-C2B8H10 toward electrophilic reagents
Nam, Wonwoo,Onak, Thomas
, p. 1581 - 1586 (2008/10/08)
The relative reactivities of the closo carboranes C2BnHn+2 (n = 4, 5, 8), and some of their derivatives, toward electrophilic reagents of the type RX/AlCl3 (RX = CH3Cl, C2H5Cl, Cl2, Br2) are reported from competition studies. Among the three parent carborane compounds, closo-2,4-C2B5H7 is the most reactive toward an electrophilic type of substitution. Alkyl substituents on closo-2,4-C2B5H7 enhance the reactivity of the compound toward an electrophilic substitution, whereas halogen substituents decrease the reactivity. However, in the closo-1,6-C2B4H6 system, the reactivity of the chloro-substituted compound, 2-Cl-1,6-C2B4H5, toward an electrophilic substitution is greater, at the 4-position, than that of the parent carborane. The nature (halogen or alkyl) and cage position of a substituent on closo-2,4-C2B5H7 appear to have little or no influence on the site of electrophilic substitution.
