Synthesis, structures and characterization of the calcium pyrrolates [Ca{(2-(dimethylaminomethyl)pyrrolyl}₂ donor_n] (donor = THF and pyridine, n = 2; DME and TMEDA, n = 1) as potential precursors for solid-state applications

The synthesis and characterization of novel alkaline earth metal pyrrolyl derivatives is described. The target molecules were synthesized using transamination and metallation protocols, involving either the treatment of calcium bis[bis(trimethylsilyl)amide with two equivalents of 2-(dimethylaminomethyl)pyrrole (2-DMAMP) or the reaction of elemental calcium with two equivalents of 2-DMAMP. Different donors, namely THF, pyridine (py), DME (dimethoxyethane), and TMEDA (N,N,N′,N′ -tetramethylethylenediamine) were utilized to study their influence on the structural chemistry of the target compounds. In order to compare the influence of the metal coordination on the pyrrole ligand, we included the crystal structure of the free 2-DMAMP ligand. All new compounds were characterized using ¹H, ¹³C NMR and IR spectroscopy in addition to X-ray crystallography. Crystal data with Mo-K_α radiation (λ = 0.71073 Å) are as follows: 1: [Ca(2-DMAMP) ₂(THF)₂], a = 15.440(2) Å, b = 14.992(2) Å, c = 10.175(1) Å, β = 94.9(3)° V = 2346.6(6) ų, Z = 4, monoclinic, space group P2₁/c, R1(all data) = 0.0981; 2: [Ca(2-DMAMP)₂(py)₂], a = 9.168(6) Å, b = 10.418(7) Å, c = 13.329(8) Å, α = 85.9(1)°, β = 72.9(1)°, γ = 86.2(1)°, V = 1212.2(1) ų, Z = 2, triclinic, space group P1, R1 (all data) = 0.0711; 3: [Ca(2-DMAMP)₂(DME)], a = 10.814(1) Å, b = 12.907(1) Å, c = 15.170(1) Å, V = 2117.3(3) ų, Z = 4, orthorhombic, space group P2₁2 ₁2₁, R1 (all data) = 0.0729; 4: [Ca(2-DMAMP) ₂(TMEDA)], a = 9.403(6) Å, b = 15.810(1) Å, c = 15.417(1) Å, V = 2292.0(3) ų, Z = 4, orthorhombic, space group Pbcn, R1 (all data) = 0.0997; 5: 2-DMAMP, a = 10.8820(7) Å, b = 15.2186(10) Å, c = 9.7578(6) Å, β = 109.736(2)°, V = 1521.05(17) ų, Z = 2, monoclinic, space group Cc, R1 (all data) = 0.0382.