Catalytic Properties and Chemical Transformations of CIS-W(CO)4(C5H5N)2 Initiator in Ring Opening Metathesis Polymerization

The six-coordinate W0 complex cis- W(CO)4(C5H5N)2 has been found to be active in the in situ formation of a carbene species from norbomene generating a typical ring opening metathesis product of the substrate. A mechanism of initiation is proposed illustrating the reaction follows the course of a 1,2-hydrogen shift in the coordinated norbornene (η2→η1). The initiating carbenoid group is identified from the products of the spontaneous carbene-CO coupling and Wittig reactions test. Formation of W(CO)5(C5H5N) and W(CO)3(η6-C6H5CH3) is blamed for catalyst deactivation.