2,6-Diisopropylphenylamides of Potassium and Calcium: A Primary Amido Ligand in s‑Block Metal Chemistry with an Unprecedented Catalytic Reactivity

Transamination of KN­(SiMe3)2 with 2,6-diisopropylphenylamine
(2,6-diisopropylaniline) in toluene at ambient temperature yields
[K­{N­(H)­Dipp}·KN­(SiMe3)2] (1) regardless of the applied stoichiometry. Recrystallization of 1 in the presence of tetramethylethylenediamine (TMEDA) and
tetrahydrofuran (THF) leads to the formation of [(μ-thf)­K2{N­(H)­Dipp}2]∞ (2), whereas potassium bis­(trimethylsilyl)­amide remains in solution.
Addition of pentamethyldiethylenetriamine (PMDETA) gives [(pmdeta)­K­{N­(H)­Dipp}]2 (3). In contrast to the thf and pmdeta adducts,
which lead to dissociation of 1 into homoleptic species,
addition of bidentate dimethoxyethane maintains the mixed complex
[(dme)­K­{μ-N­(SiMe3)2}­{μ-N­(H)­Dipp}­K]2 (4). A complete transamination of 2,6-diisopropylaniline
with KN­(SiMe3)2 in toluene at 100 °C yields
[K­{N­(H)­Dipp}] (5), which reacts with CaI2 to
give [(thf)nCa­{N­(H)­Dipp}2]
(6), [(pmdeta)­Ca­{N­(H)­Dipp}2] (7), and [(dme)2Ca­{N­(H)­Dipp}2] (8), depending on the solvents and coligands. Excess potassium 2,6-diisopropylphenylamide
allows the formation of the calciate [K2Ca­{N­(H)­Dipp}4]∞ (9). Hydroamination of diphenylbutadiyne
with 2,6-diisopropylaniline in the presence of catalytic amounts of 9 gives tetracyclic 2,6-diisopropyl-9,11,14,15-tetraphenyl-8-azatetracyclo­[8.5.0.01,7.02,13]­pentadeca-3,5,7,9,11,14-hexaene (10). Solid-state structures are reported for 2–4 and 7–10.
Compound 10 slowly rearranges to tetracyclic 5a,9-diisopropyl-2,3,10,11-tetraphenyl-5a,6-dihydro-2a1,6-ethenocyclohepta­[cd]­isoindole (11), which is slightly favored according to quantum chemical studies.