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

Metalation 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) 2 Li{(Dipp‐N) 2 C‐Ph}] ( 2a ) and [(thf)Li{(Dipp‐N) 2 C‐ t Bu}] ( 2b ), as well as of potassium, [(thf) 3 K{(Dipp‐N) 2 C‐Ph}] ( 3a ) and [(thf) 3 K{(Dipp‐N) 2 C‐ t Bu}] ( 3b ) (Dipp = 2,6‐diisopropylphenyl). Because metalation of these amidines is not possible with [(thf) 2 Ca{N(SiMe 3 ) 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) 2 C‐ t Bu}{N(SiMe 3 ) 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.