cis‐bond‐producing hydrogenation of polyunsaturates catalyzed by polymer‐complexed Cr(CO)3 catalysts

Abstract cis‐Bond‐producing chromium carbonyl catalysts were prepared by complexing conventional or macroreticular, styrene‐divinylbenzene copolymers or cross‐linked poly (vinyl benzoate) with Cr(CO)6. With one exception, these polymer‐Cr(CO)3 catalysts were as selective as the corresponding homogeneous arene‐Cr(CO)3 complexes for the formation ofcis‐monoenes from methyl sorbate and from conjugated, polyunsaturated fatty esters in cyclohexane. Although several of the polymer catalysts were very active when fresh, they all lost activity on recycling. They could not be recycled more than two times before a marked decrease in activity occurred due to loss of Cr, as shown by elemental analysis and infrared absorption in the recovered catalyst. Thermal analysis indicated instability of the polymer complexes at hydrogenation temperatures.