The past quarter century has witnessed an enormous transformation in the use of soluble transition metal complexes as catalysts in the chemical process industries. Until the mid-1950s, industrial use of homogeneous catalysis was largely confined to reactions of acetylene [1]. As indicated in Fig. 1, a large family of acetylene-based reactions was used to produce polymer intermediates such as vinyl acetate, vinyl chloride, acrylonitrile, chloroprene, and 1,4-butanediol. The processes were simple but they were relatively expensive because they were based on an expensive raw material. The large energy content of the acetylene molecule (ΔF°=50.84 kcal/mol) made it both hazardous to handle and expensive even in times when energy was cheaper.