Tungsten Compounds

Oxidation Chemistry of Axially Protected Mo2 and W2 Quadruply Bonded Compounds

“…For example, the generation of binuclear systems employing (N,N) donor-ligands is significantly easier for Mo than for W: Mo 2 (N,N) 4 species are immediately accessible either by a direct reaction of commercially available Mo(CO) 6 , or by a ligand substitution reaction of the easily prepared Mo 2 (OAc) 4 and the desired ligand . The preparation of an analogous W 2 (N,N) 4 compound typically involves a series of steps starting from comproportionation of W(CO) 6 and WCl 6 to produce WCl 4 , which is further reduced by an electron-donor such as NaHBEt 3 and subsequently reacted with a ligand salt to produce the quadruply bonded target W 2 (N,N) 4 . Even though one-pot reactions between W(CO) 6 and hydroxy-pyridines in high-boiling solvents (diglyme) at elevated temperatures have been shown to produce W 2 (N,O) 4 species, − the analogous reactions with (N,N)-ligands, such as formamidines, yield either incomplete substituted species (e.g., W 2 (N,N) 4 (CO) 2 ) or furnish compounds with only triply bonded W 2 6+ cores .…”