Abstract The reactions of tin(II) chloride in tetrahydrofuran with the η 1-allyl systems, [η 5-Cp(CO) 2Fe allyll, have been reexamined, and an extension made to SnBr 2 and GeCl 2.dioxan. The insertion compounds, [η 5-Cp(CO) 2FeMX 2 allyl], which contain the Group IVB element bound to iron, are the major products, but, in the presence of excess metal dihalide, these slowly react to form the trihalometal compounds [η 5-Cp(CO) 2FeMX 3]. The insertion reactions are inhibited by small amounts of a radical scavenger, and occur initially with allylic rearrangement. In methanol, the process is more complex; an unknown species, possibly an iron-olefin dipolar intermediate, and substantial amounts of trihalometal-iron compounds are formed additionally. A mechanistic scheme for the processes is discussed.