Use any oxophilic system, say TiCl4 or WCl6 and "hope" that it works. There is no mechanistic evidence to anything that is proposed, so this is more of a "hit or miss" recipe. You could just use TaCl5 and say that "it performs poorly than NbCl5" or go for any of the above systems. Or say Ti(OiPr)4 and see how that works relative to the NbCl5 system. Protic / wet solvents are a no-no.