The Heats of Decomposition of Some More Boron Hydrides¹

Quantitative Assessment of B−B−B, B−Hb−B, and B−Ht Bonds: From BH3 to B12H122−

“…The calculated heats of formation obtained from the G4 deviate 0.08 to 9.37 kcal/mol from the experimental values, where the significant deviations are observed for n larger than 6 ( n is the number of boron atoms). It is noteworthy that the experimental heats of formation of B 10 H 14 ( 19 ) range from 4.4 to 11.2 kcal/mol (see Table ) . Moreover, Nguyen and co‐workers argued that the values of a T1 diagnostic (from the CCSD(T)) are small, indicating that boron‐hydrogen compounds do not possess significant multireference character; thus, suggesting the heats of formation of boron‐hydrogen compounds need to be remeasured …”

“…It is noteworthy that the experimental heats of formation of B 10 H 14 (19) range from 4.4 to 11.2 kcal/mol (see Table 2). [140] Moreover, Nguyen and co-workers argued that the values of a T1 diagnostic (from the CCSD(T)) are small, indicating that boron-hydrogen compounds do not possess significant multireference character; thus, suggesting the heats of formation of boron-hydrogen compounds need to be remeasured. [107] Inspection of Table 2 and Figure 3 shows that the highest heat of formation (positive ΔH o f , the amount of energy or heat absorbed during the formation of the substance) is that for B 5 H 2À 5 (8) and the lowest (negative ΔH o f , the amount of energy or heat released during the formation of the substance) is that for B 12 H 2À 12 (21).…”

Diboron(4) Compounds: From Structural Curiosity to Synthetic Workhorse

“…This compound was arduously prepared by the slow passage of B 5 H 9 , in an atmosphere of dihydrogen, through an electric discharge between copper electrodes. Not surprisingly, while several theoretical and physical studies have focused on this complex, − its complicated synthesis has limited the synthetic potential of this unique diboron compound, and its chemistry remains largely unexplored. A different structural isomer of B 10 H 16 , also bearing a central B–B bond where neither boron atom bears a terminal hydride, was prepared by Sneddon and co-workers through the dehydrocoupling of B 5 H 9 …”

Boranes. XXVIII. Reactions of hexaborane(12)

“…The only product which could be detected by nB nmr was boron tribromide. This result is in contrast to direct bromination of both tetraborane(lO) and pentaborane (9).20,21 It is possible that a brominated species was prepared but was unstable under the conditions used and was subject to decomposition and further bromination. Reactions at lower temperatures over a longer period of time may yield the desired product.…”

“…Mass spectral evidence for hexaborane (12) has been reported by several groups,4•5 but only a few chemical and physical studies of the compound have been made. [6][7][8][9] We therefore undertook additional studies of the thermal stability and chemical reactivity of hexaborane (12) including isotopic exchange studies.…”