Thermal Stability and Decomposition Pathways in Volatile Molybdenum(VI) Bis-imides

Michael A Land; Goran Bačić; Katherine N Robertson; Seán T Barry

doi:10.1021/acs.inorgchem.1c03817

Thermal Stability and Decomposition Pathways in Volatile Molybdenum(VI) Bis-imides

Inorg Chem. 2022 Mar 28;61(12):4980-4994. doi: 10.1021/acs.inorgchem.1c03817. Epub 2022 Mar 15.

Authors

Michael A Land¹, Goran Bačić¹, Katherine N Robertson², Seán T Barry¹

Affiliations

¹ Department of Chemistry, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada.
² Department of Chemistry, Saint Mary's University, 923 Robie Street, Halifax, Nova Scotia B3H 3C3, Canada.

PMID: 35289589
DOI: 10.1021/acs.inorgchem.1c03817

Abstract

The vapor deposition of many molybdenum-containing films relies on the delivery of volatile compounds with the general bis(tert-butylimido)molybdenum(VI) framework, both in atomic layer deposition and chemical vapor deposition. We have prepared a series of (^tBuN)₂MoCl₂ adducts using neutral N,N'-chelates and investigated their volatility, thermal stability, and decomposition pathways. Volatility has been determined by thermogravimetric analysis, with the 1,4-di-tert-butyl-1,3-diazabutadiene adduct (5) found to be the most volatile (1 Torr of vapor pressure at 135 °C). Thermal stability was measured primarily using differential scanning calorimetry, and the 1,10-phenanthroline adduct (4) was found to be the most stable with an onset of decomposition of 303 °C. We have also investigated molybdenum compounds with other alkyl-substituted imido groups: these compounds all follow a similar decomposition pathway, γ-H activation, with varying reaction barriers. The tert-pentyl, 1-adamantyl, and a cyclic imido (from 2,5-dimethylhexane-2,5-diamine) were systematically studied to probe the kinetics of this pathway. All of these compounds have been fully characterized, including via single-crystal X-ray diffraction, and a total of 19 new structures are reported.