N,N′‐Bis(2,6‐diisopropylphenyl)benzamidinates and ‐pivalamidinates of the s‐Block Metals Lithium, Potassium, and Calcium

Abstract

AbstractMetalation of N,N′‐bis(2,6‐diisopropylphenyl)benzamidine (1a) and ‐pivalamidine (1b) in tetrahydrofuran (THF) with n‐butyllithium and potassium bis(trimethylsilyl)amide gives the corresponding N,N′‐bis(2,6‐diisopropylphenyl)benzamidinates and ‐pivalamidinates of lithium, [(thf)2Li{(Dipp‐N)2C‐Ph}] (2a) and [(thf)Li{(Dipp‐N)2C‐tBu}] (2b), as well as of potassium, [(thf)3K{(Dipp‐N)2C‐Ph}] (3a) and [(thf)3K{(Dipp‐N)2C‐tBu}] (3b) (Dipp = 2,6‐diisopropylphenyl). Because metalation of these amidines is not possible with [(thf)2Ca{N(SiMe3)2}2], a metathetical approach has been chosen. Hence, the reaction of 3a with calcium iodide in THF yields (tetrahydrofuran)calcium bis[N,N′‐bis(2,6‐diisopropylphenyl)benzamidinate] (4a). For the bulkier N,N′‐bis(2,6‐diisopropylphenyl)pivalamidinate, heteroleptic [(thf)Ca{(Dipp‐N)2C‐tBu}{N(SiMe3)2}] (4b) forms. Depending on the softness and charge‐to‐radius ratio, syn configuration of the amidinate ligands is observed for 2a, 4a, and 4b, whereas the anti configuration is realized in complexes 2b, 3a, and 3b, the latter being stabilized by intramolecular metal–π interactions.