Diborane(2)

Diborane(2) is a highly reactive molecule that rapidly decomposes, making it a challenge to study experimentally under ambient conditions. To observe diborane(2) experimentally, high-vacuum and low temperature conditions using matrix isolation techniques are required, such as trapping the molecule in inert matrices like neon or argon. As a result of these difficult synthesis conditions, its properties and behaviour have been predominantly studied using theoretical models and computational simulations.

Diborene also refers to a series of molecules with the formula R:(BH)=(BH):R or R-B=B-R where R is an organic group. Diborene derivatives are relatively stable and can be stored at room temperature under inert conditions. They have been synthesized and characterized experimentally, and have shown potential in a variety of applications.

Synthesis

The first experiment that lead to the synthesis of diborane(2) was via pulsed laser ablation of boron in a mixed hydrogen-argon gas atmosphere. Upon cooling the mixture, the argon gas changed into a solid, thereby stabilizing the trapped diboranes. The reaction involved two boron monohydrides coming together to form diborane(2), with the reaction being exothermic by 117kcal/mol. The diborane(2) was characterized by a broad band with a sharp peak at 2679.9 cm^–1, corresponding to the antisymmetric stretching mode of B-H.

Following this experiment, there have been other methods of diborane(2) preparation by decomposition of gaseous B₂H₆ via photoionization, electron bombardment, X-irradiation, high-temperature reactions, and pulsed laser vaporization.

Since diborene derivatives are more stable than diborane(2), various methods have been used to synthesize them. They have been primarily made by reacting diboron compounds with organic molecules and the reduction of boron-containing precursors. Additionally, the diborene group can be protected by a suitable ligand, which prevents other side reactions.