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