Macrobicyclic Dibridgehead Di(trialkyl)pnictogens E((CH2)n)3E (E/n = As/10, As/12, As/14, Sb/14) and Their Cage-like Metal Complexes: Syntheses, Structures, and Homeomorphic Isomerizations

Photolyses of trans-Fe(CO)₃(As((CH₂)_n)₃As) (n = a, 10; b, 12; c, 14) in the presence of PMe₃, or reactions of trans-[Fe(CO)₂(NO)(As((CH₂)_n)₃As)]⁺ BF₄^– and n-Bu₄N⁺ Cl^–, afford the air stable title complexes As((CH₂)_n)₃As (8a–c) in 79–34% yields. With 8a, the in, in and out, out isomers are separable and each is crystallographically characterized. With 8b,c, the isomers rapidly interconvert by homeomorphic isomerization, but each crystallizes (contrathermodynamically) as an out, out isomer. Reactions of 8c with H₂O₂ or 8b with BH₃ give 8c·2O or 8b·2BH₃, respectively (85–94%). Reactions of 8c with MCl₂ (M = Pt, Pd, Ni), Rh(CO)(Cl), and Fe(CO)₃ sources afford the corresponding cage-like complexes trans-ML_n(As((CH₂)₁₄)₃As) (86–51%). The crystal structures of 8c·2O and the PtCl₂ and PdCl₂ adducts are determined and compared to those of 8a–c and diphosphorus analogs. The corresponding distibine Sb((CH₂)₁₄)₃Sb is analogously prepared, but precursors necessary for the bismuth analog could not be accessed due to the diminished BiR₃ Lewis basicity.