Synthesis, characterization, X-ray and electronic structures of diethyl ether and 1,2-dimethoxyethane adducts of molybdenum(IV) chloride and tungsten(IV) chloride.

The bis(diethyl ether) and 1,2-dimethoxyethane (dme) adducts of molybdenum(IV) chloride and tungsten(IV) chloride are valuable starting materials for a variety of synthetic inorganic and organometallic reactions. Despite the broad utility and extensive use of these 6-coordinate complexes, their syntheses remain unoptimized, and their characterization incomplete after more than three decades. While exploring the ligand exchange behaviour of trans-MoCl4(OEt2)2, we obtained single crystals of this red-orange complex and subsequently compared its structural parameters with those of the recently reported trans-WCl4(OEt2)2. Significantly improved procedures for both MoCl4(dme) and WCl4(dme) were developed, and X-ray diffraction data were obtained and analysed. The magnetic properties of the dme adducts were probed, both with Gouy and SQUID magnetometry measurements. The magnetic moment of WCl4(dme) was smaller than that of MoCl4(dme), an observation that we attribute to the greater spin-orbit coupling of tungsten. Electronic structure studies were also conducted to probe the preferential trans configuration of the diethyl ether adducts and to assign the UV-Vis spectra of the dme adducts.