Computational Study of B(4)H(10) Addition to Ethene. Baskets from Boranes

Area of Science:

• Computational Chemistry
• Organoboron Chemistry
• Reaction Mechanisms

Background:

• Decaborane (B(4)H(10)) is a key boron hydride.
• Ethene (C(2)H(4)) is a fundamental alkene.
• Understanding reaction pathways is crucial for synthesis.

Purpose of the Study:

• To investigate three distinct reaction pathways from B(4)H(10) and C(2)H(4) to (CH(2)CH(2))B(4)H(8).
• To determine the preferred reaction mechanism and kinetics.
• To identify potential intermediates and byproducts.

Main Methods:

• Theoretical calculations using the MP4/6-311+G(d,p)//MP2/6-31G(d) + ZPC level of theory.
• Analysis of reaction barriers and transition states.
• Evaluation of entropic contributions to reaction favorability.

Main Results:

• The 'addition' pathway is identified as the preferred route, featuring transient intermediates and a rate-determining barrier of 33.0 kcal/mol.
• 'Indirect hydroboration' is entropically disfavored.
• 'Direct hydroboration' has a lower overall energetic barrier (26.9 kcal/mol) but is entropically hindered, making the 'addition' path dominant at experimental temperatures.
• Direct hydroboration can lead to side reactions forming byproducts like Et-(CH(2)CH(2))B(4)H(7).

Conclusions:

• The 'addition' pathway is the main synthetic route to (CH(2)CH(2))B(4)H(8) under typical experimental conditions.
• Entropic factors play a significant role in determining the preferred reaction mechanism.
• Alternative pathways and potential side reactions need consideration in organoboron synthesis.