Discrete and Polymeric Cu(II) Complexes Derived from in Situ Generated Pyridyl-Functionalized Bis(amido)phosphate Ligands, [PO2(NHPy)2]−

Abstract

New examples of Cu(II) complexes containing in situ generated bis(amido)phosphate ligands, [PO2(NHPy)2]−, have been synthesized [(L1)−, where Py = 2-pyridyl, and (L2)−, where Py = 4-pyridyl). These anionic ligands were obtained by the P–N bond hydrolysis reaction of the corresponding phosphonium salts or phosphoric triamides in the presence of Lewis acidic Cu(II) ions in polar solvents. A discrete mononuclear complex {Cu[PO2(NH2Py)2]2} (3) was obtained for the in situ ligand featuring 2-pyridyl substituents, whereas a 1D coordination polymer {[Cu(PO2(NH4Py)2)2(H2O)2]·2DMF·2H2O}∞ (4) was obtained for the ligand containing 4-pyridyl functionalities. The structural analyses show that in 3 the ligand (L1)− is bonded to the metal ion in a chelating tridentate N,N,O coordination and the coordinated P–O group is oriented in a syn fashion with respect to the pyridylamino groups. However, in 4 the ligand (L2)− is bonded in a bridging fashion to two Cu(II) ions via its pyridyl nitrogen donors. The two phosphorus-bound oxygen atoms in (L2)− are anti-oriented and are involved in intermolecular H-bonding interactions with the metal-bound water hydrogen atoms to yield a 3D network. Topology analysis of the H-bonded assembly in 4 shows the presence of a (4-c)2, 8-c binodal scu net as represented by the Schläfli symbol of (44·62)2(416·612) [44·62 for the (L2)− ligand and 416·612 for the Cu atoms]. An interesting 2D Cu(I) coordination polymer {[Cu(PO(NH4Py)3)(PO2(NH4Py)2)]·DMF·2H2O}∞ (5) in uninodal hcb topology was obtained as a minor product along with 4. Formation of the 2D assembly in 5 is mediated by the tridentate coordination of the phosphoric triamide ligand [PO(NH4Py)3]. The role of the anionic (L2)− ligand in 5 is to merely restore the charge balance in the assembly and provide the fourth coordination to the tetrahedral Cu(I) ion. Solvent uptake studies on the activated sample of 4b shows a preferential adsorption of water vapors over aliphatic alcohols.