Reactions of SnMe2-Bridged Bis(cyclopentadienes) with Iron Pentacarbonyl: Migration of the SnMe2 Group

In reactions of the singly bridged bis­(cyclopentadiene) (SnMe2)­(tBuC5H4)2 (1) or the doubly bridged bis­(cyclopentadienes) (SiMe2)­(SnMe2)­(RC5H3)2 (R = H (2), R = tBu (3)) with Fe­(CO)5 in refluxing xylene, the bridging SnMe2 group migrates from the ligand to the iron atoms to give compounds (5, 7, 9a,b) containing the Fe–Sn–Fe units, together with the corresponding destannylated products (6, 8, 10a,b); the bridging SiMe2 group (in 2 and 3) does not migrate. However, in the reaction of the doubly bridged ligand (GeMe2)­(SnMe2)­(C5H4)2 (4) with Fe­(CO)5, the SnMe2 group undergoes a similar migration to produce the complex GeMe2[(η5-C5H4)­Fe­(CO)2]2SnMe2 (12), containing the Fe–Sn–Fe unit, both SnMe2 and GeMe2 groups migrate from the ligand to the iron atoms to yield the product [(GeMe2)­(η5-C5H4)­Fe­(CO)2]­[(SnMe2)­(η5-C5H4)­Fe­(CO)2] (11), containing one Fe–Ge bond and one Fe–Sn bond, or the SnMe2 group is cleaved to afford the destannylation product GeMe2[(η5-C5H4)­Fe­(CO)]2(μ-CO)2 (13). The stability of complexes 5, 7, and 12 containing the Fe–Sn–Fe unit toward heat and light was also studied. The molecular structures of 9a,b, 11, and 12 were determined by X-ray diffraction.