Reactivity of an Iron Carbonyl Dianion Dictated by a Lewis Basic Appendant

Abstract

Studies toward transition metals in negative oxidation states are much less explored compared to those in zero or positive oxidation states. In this study, we present the synthesis and reactivity studies of an Fe(‐II) carbonyl dianion (3) featuring an appended Lewis base, [(L)Fe(CO)3]2‐ (L=Ph2PCH2CH2NMe2). Unlike the well‐known reactivity of [Fe(CO)4]2‐ with common electrophiles (E+) which typically forms [(E)2Fe(CO)4], 3 reacted with 2 equiv. of Ph3SnCl to afford a mixture of two products: one being an Fe(II) bis(triphenylstannyl) product (4), and the other an Fe stannylene product (5). Further insights into the reactivity of 3 was elucidated through its reactions with 2 equiv. of Cy3SnCl or Me3SiCl, producing an Fe(II) bis(tricyclohexylstannyl) product (8) and a zwitterionic complex (11), respectively, the latter emerging via THF ring‐opening. Intermediates generated from reactions of 3 with 1 equiv. of each electrophile were isolated to shed light on the reaction mechanisms, highlighting the influence of appended Lewis base on the reactivity of metal carbonyl dianions, especially the generation of the novel stannylene complex 5. The electronic structure of this paramagnetic stannylene complex was also investigated by computational studies.