Syntheses and Crystal Structures of the First Zinc Complex with 1,3,5-Triaza-7-Phosphaadamantane (Pta), [Zncl2(Pta)(2)], and of the Hybrid Organic-Inorganic Salts of N-Methyl-1,3,5-Triaza-7-Phosphaadamantane with Tetrahalozinc [Pta-Me](2)[Zni2X2] (X = I, Cl)