The thermal rearrangement of [Me2Si-η5-C5H4(CO)Fe(CO)2Fe(CO)-η5-C5H4SiMe2] in the presence of phosphorus ligands

Reaction of [Me2Si-η5-C5H4(CO)Fe(CO)2Fe(CO)-η5-C5H4SiMe2] (1) with one equivalent of PR3 in refluxing p-xylene for 9 h leads to rearranged products containing mainly [Me2Si-η5-C5H4Fe(CO)2SiMe2-η5-C5H4Fe(CO)PR3] (3: R=OMe; 4: R=OPh) and a small amount of [Me2Si-η5-C5H4Fe(CO)2SiMe2-η5-C5H4Fe(CO)2] (2). When excess of PR3 is used and/or the time of reaction is shortened, an intermediate product [Me2Si-η5-C5H4(CO)Fe(CO)2Fe(PR3)-η5-C5H4SiMe2] (5: R=OMe; 6: R=OPh) is obtained from the reaction. It is found that 5 and 6 rearrange much faster than 1 under the thermal condition leading to 3 and 4, respectively. Crystal and molecular structures of 3 and 5 have been determined by X-ray diffraction methods.