A study of the thermal and photochemical reactions of group 6 metal carbonyl compounds when bound to organic polymer supports

摘要

This work follows the general thrust for the development ofudhybrid phase catalysts in which the active site maintains theudstereochemistry which occurs in homogeneous solution, while the bulk solubility of the material can be controlled by varying the nature of the polymer backbone. In particular, we wish to examine the effect of polymer binding on the chemistry of group 6 metal carbonyls, with a view to the synthesis of polymers in which active coordinatively unsaturated species could be generated, either by thermal or photochemical means.ududThe polymers of interest contain pendant donor atoms, inudparticular nitrogen or phosphorus, to which metal carbonyls of the type [M(CO) L ] (M = Cr, Mo, or W; L = vinylpyridine, 6 -n n 2,2'-bipyridyl, or p-styryldiphenylphosphine) are anchored. The preparation and characterisation of these materials is discussed. The synthesis of the polymer-bound metal carbonyls can be achieved by two routes. The first involves the preparation of the polymer and subsequent complex forming reaction to bind the metal carbonyl moiety to it. The second pathway involves the synthesis of the metal carbonyl complex containing a polymerisable group which can later be copolymerised with suitable comonomers. The polymer-bound systems were characterised by UV/visible and infrared spectroscopy. The polymer materials exhibit similar spectroscopic behaviour to their monomeric analogues. The position of the metal-to-1igand charge transfer (MLCT) bands in the UV/visible was found to depend on the nature of the polymer backbone. Laser flash photolysis studies investigating the mechanism and kinetics of binding of the metal carbonyl fragment to the polymer is reported.ududThe thermal reactions of a variety of the polymer-bound metal carbonyl compounds when cast as films is also presented, as is evidence for the thermal decarbonylation of these materials resulting in polymers which contain fully decarbonylated metal centres. Preliminary photochemical investigations indicate the generation of active coordinatively unsaturated metal carbonyl species in polymer matrices at low temperatures.