PHOTOCHEMICALLY REACTIVE POLYMERS - PHOTOCHEMICAL-REACTIONS OF POLYURETHANES CONTAINING CP2MO2(CO)6 OR CP2FE2(CO)4 MOLECULES ALONG THE POLYMER BACKBONE

The photochemistry of the [-OCH2C(O)C5H4(CO)3Mo-Mo(CO)3C5H4C(O)CH2OC(O)NH(CH2)6NHC(O)-]n (1), [-OCH2CH2C5H4(CO)3Mo-Mo(CO)3C5H4CH2CH2OC(O)NH(CH2)6NHC(O)-]n (2), [-(O(CH2)4OC-(O)NH(CH2)6NHC(O))m-OCH2CH2C5H4(CO)3Mo-Mo(CO)3C5H4CH2CH2OC(O)NH(CH2)6NHC(O)-]n (3), and [-OCH2CH2C5H4(CO)2Fe-Fe(CO)2C5H4CH2CH2OC(O)NH(CH2)6NHC(O)-]n (4) oligomers was investigated. Because of the metal-metal bonds along the oligomer backbone, these polyurethanes are photochemically reactive, undergoing reactions similar to the Cp2Mo2(CO)6 and Cp2Fe2(CO)4 dimers. Irradiation leads to homolysis of the metal-metal bonds, as evidenced by formation of Cl-(CO)3MoC5H4-R-C5H4Mo(CO)3Cl or Cl(CO)2FeC5H4-R-C5H4Fe(CO)2Cl (R = CH2CH2OC(O)NH(CH2)6NHC(O)OCH2CH2 or C(O)CH2OC(O)NH(CH2)6NHC(O)OCH2C(O)) when the oligomers are irradiated in the presence of CCl4. In the presence of triethyl phosphite, disproportionation of the Mo-Mo and Fe-Fe bonded units occurred to give a fragmentation product containing (C5H4R)Mo(CO)3- and (C5H4R)Mo(CO)2(P(OEt)3)2+ or (C5H4R)Fe(CO)2- and (C5H4R)Fe(CO)(P(OEt)3)2+ groups, respectively. Photochemical decomposition of the polyurethanes also occurred over several weeks to months in the solid state. Both light and oxygen are necessary for this decomposition in the solid state. It is proposed that cleavage of the metal-metal bonds leads to oligomer fragmentation and the formation of metal oxide species in these solid state reactions. Oligomer 2, containing the singly bonded Cp(CO)3Mo-Mo(CO)3Cp unit, was converted (photochemically or thermally) to a polymer containing triply bonded Cp(CO)2Mo = Mo(CO)2Cp groups.