Polycyclic bis(tert-butylamido)cyclodiphosph(III)azane complexes of lithium and magnesium: Their syntheses, molecular structures, and relationships to isoelectronic cyclodisilazane derivatives

Syntheses and single-crystal X-ray diffraction studies of the bis(tert-butylamino)cylodiphosphazane cis-[((BuNP)-Bu-t)(2)-((BuNH)-Bu-t)(2)], 1a, and its lithium and magnesium salts are described. The pristine molecule has crystallographic C-2 symmetry, both N-H groups being disposed in an endo fashion, and crystallizes in the monoclinic space group P2/c with unit cell dimensions (193 K) a = 9.600(4) Angstrom, b = 5.904(4) Angstrom, c = 18.97(1) Angstrom, beta = 101.09(3)degrees, and Z = 2. Treatment of 1a with (BuLi)-Bu-n or (Bu-n)(2)Mg in refluxing THF yielded the heterocubic cis-[((BuNP)-Bu-t)(2)((BuNLi)-Bu-t . THF)(2)], 2a, and the seco-heterocubic {[((BuNP)-Bu-t)(2)((BuN)-Bu-t)(2)]Mg .(THF)(2)}, 3a, respectively. The crystal data (223 K) for the dilithio compound are monoclinic, space group P2(1)/c, a = 10.691(1) Angstrom, b = 15.827(2) Angstrom, c = 19.424(4) Angstrom, beta = 105.617(7)degrees, and Z = 4, and those for the magnesium derivative (213 K) are monoclinic, space group P2(1)/n, a = 10.6272(4) Angstrom, b = 17.6643(7) Angstrom, c = 16.3625(6) Angstrom, beta = 90.46(3)degrees, and Z = 4. The lithium and magnesium complexes are shown to be isostructural with isoelectronic cyclodisilazane species, and the development of a parallel coordination chemistry for both ligands is proposed.