Thermal Stability of Tetrahydroxydiboron

Despite the widespread application of diboron reagents in Suzuki–Miyaura borylation reactions, the thermal stability of diboron compounds is poorly understood. Seven commonly used diboron reagents were selected to investigate their thermal stability using Differential Scanning Calorimetry (DSC). Tetrahydroxydiboron (BBA) was specifically chosen for comprehensive safety characterization, considering the high thermal risk identified during the DSC screening. The decomposition of BBA was further explored using DSC in conjunction with Advanced Thermokinetics Software (AKTS), as well as Accelerating Rate Calorimetry (ARC) and Differential Accelerating Rate Calorimetry (DARC). Key safety parameters, such as the temperature at which the time to the maximum rate is 24 h (TMR24 and TD24), were estimated. Consistent results for TMR24 were obtained across various methods, affirming the reliability of these techniques in the kinetic analysis. DARC and ARC testing reveal an exceptionally rapid thermal runaway for BBA to the extent that the self-heating rate cannot be tracked within the instrument's limits. Furthermore, BBA was found to be insensitive to impact or friction. This study presents the general methodology and specific findings for BBA, with the aim of providing industry guidance for conducting process safety assessment and ensuring the safe utilization of diboron reagents during process development and scale-up.