Insertion reactions of β-diketiminate-stabilised calcium amides with 1,3-dialkylcarbodiimides

Abstract

A series of heteroleptic β-diketiminate-stabilised calcium amides of the form [{ArNC(Me)CHC(Me)NAr}Ca{NR¹R²}(THF)] (Ar = 2,6-diisopropylphenyl; R¹ = H, R² = Ar; R¹ = H, R² = CH₂CH₂OMe; R¹ = R² = Ph) react with 1,3-dialkylcarbodiimides, R³NCNR³ (R³ = Cy, ⁱPr), to yield the corresponding insertion products [{ArNC(Me)CHC(Me)NAr}Ca{(R³N)₂CNR¹R²}(THF)] at room temperature in hydrocarbon solutions. These latter compounds contain both β-diketiminate and guanidinate ligands bound to calcium. Solid-state data are consistent with the guanidinate ligands adopting a number of binding modes including κ² through κ³ coordination, with varying degrees of delocalisation of the non-bound guanidinate nitrogen lone-pair across the π-framework of the ligand. DFT computational studies have been conducted to address these variations in coordination behaviour.