Hydrogenation reactions using group III to group VII transition metals

Catalytic hydrogenations using catalysts derived from the following elements are reviewed: scandium, yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, rhenium, and manganese. There are procedures for reducing a wide range of organic compounds using catalysts from this range of non-precious metals. Titanium catalysts have quite an extensive literature and feature some impressive results, although they have not been attracting much recent interest. Mn-based hydrogenation catalysis is only recently established and is showing very promising results, both for pure hydrogenation reaction and other redox type processes. The utility of many of the catalyst systems is compared to precious metal systems; currently the protocols using most of the mentioned non-precious systems are significantly more expensive processes than those using the best precious metal catalysts due to the cost of additives and high catalyst loading. It is envisaged that in the years ahead further research will transform the most promising leads into truly effective and competitive catalysts. It is worth noting that manganese catalysts are very much only just beginning to be researched, yet are already showing utility; Mn catalysts represent the most promising systems discussed in this chapter.