Ligand-Assisted Volatilization and Thermal Stability of Bis(imido)dichloromolybdenum(VI) ([(t‑BuN)₂MoCl₂]₂) and Its Adducts

Volatile molybdenum-containing compounds have successfully been utilized for the atomic layer deposition of MoN_x, MoO₃, MoS₂, and MoC_xN_y. Most of the reported volatile molybdenum-containing compounds have been prepared via salt metathesis reactions of bis­(tert-butylimido)­dichloromolybdenum­(VI) with anionic nitrogen-based ligands. Herein we describe the preparation of several adducts of [(t-BuN)₂MoCl₂]₂ (2) via ligand exchange reactions, which include the isolation and characterization of (t-BuN)₂MoCl₂·2THF, (t-BuN)₂MoCl₂·(tetramethylethylenediamine), (t-BuN)₂MoCl₂·(2,2′-bipyridine), (t-BuN)₂MoCl₂·(trimethylphosphine), (t-BuN)₂MoCl₂·(1,2-bis­(dimethylphosphino)­ethane), and (t-BuN)₂MoCl₂·(1,3-bis­(tert-butyl)­imidazolin-2-ylidene). These compounds have been characterized using NMR spectroscopy and elemental analysis, and the solid-state structures have been determined using single-crystal X-ray crystallography. The volatility and thermal stability of all compounds have been assessed using TGA and DSC, showing that the coordinated ligands can improve the volatility, but in many cases the gas-phase species reverts to 2. This highlights a strategy for using coordinative ligands that are easily thermolyzed during evaporation and delivery yet improve the volatility of a key precursor.