Secondary Coordination Sphere Alkylation Promotes Cyclometalation

09 February 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Diphosphines have taken on a dominant role as supporting ligands in transition metal chemistry. Here, we describe complexes of the type [Cp*Fe(diphosphine)(X)] (X = Cl, H) where for diphosphine = tetraallylphosphinoethane (tape), a Lewis-acidic secondary coordination sphere (SCS) was installed via allyl group hydroboration using dicyclohexylborane (HBCy2). The resulting chloride complex, [Cp*Fe(P2BCy4)(Cl)] (P2BCy4 = 1,2-bis(di(3-cyclohexylboraneyl)propylphosphino)ethane), was treated with n-butyllithium (1-10 equivs.), resulting in SCS butylation, followed by cyclometalation at iron. This reactivity is contrasted with [Cp*Fe(dnppe)(Cl)] (dnppe = 1,2-bis(di-n-propylphosphino)ethane), whereby addition of n-butyllithium provides a mixture of products. Overall, transmetalation is a common elementary transformation in organometallic chemistry, and here we describe how its outcome is altered due to Lewis acid SCS incorporation.

Keywords

boron
phosphorus
iron
secondary coordination sphere
cyclometalation

Supplementary materials

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