Salt-Free Reducing Reagent of Bis(trimethylsilyl)­cyclohexadiene Mediates Multielectron Reduction of Chloride Complexes of W(VI) and W(IV)

We developed a salt-free reduction of WCl6 using 1-methyl-3,6-bis­(trimethylsilyl)-1,4-cyclohexadiene (MBTCD) in toluene to give a low-valent trinulcear tungsten complex involving W­(II) and W­(III) centers, while in the presence of redox active ligands such as α-diketone and α-diimine the same reduction produced W­(IV) complexes with the corresponding redox-active ligands, (α-diketone)­WCl4 and (α-diimine)­WCl4. A W­(VI) complex with two α-diketone ligands, (α-diketone)2WCl2, was found to be synthetically equivalent to low-valent W­(IV) species that trapped azopyridine to give (α-diketone)­WCl2(azopyridine).