Three-dimensional hydrogen-bonded supramolecular assembly in tetrakis(1,3,5-triaza-7-phosphaadamantane)copper(I) chloride hexahydrate

The structure of the title compound, [Cu(PTA)4]Cl·6H2O (PTA is 1,3,5-triaza-7-phosphaadamantane, C6H12N3P), is composed of discrete monomeric [Cu(PTA)4]+ cations, chloride anions and uncoordinated water molecules. The CuI atom exhibits tetrahedral coordination geometry, involving four symmetry-equivalent P–bound PTA ligands. The structure is extended to a regular three-dimensional supramolecular framework via numerous equivalent O—H⋯N hydrogen bonds between all solvent water molecules (six per cation) and all PTA N atoms, thus simultaneously bridging each [Cu(PTA)4]+ cation with 12 neighbouring units in multiple directions. The study also shows that PTA can be a convenient ligand in crystal engineering for the construction of supramolecular architectures.

The structure of the title compound, [Cu(PTA) 4 ]ClÁ6H 2 O (PTA is 1,3,5-triaza-7-phosphaadamantane, C 6 H 12 N 3 P), is composed of discrete monomeric [Cu(PTA) 4 ] + cations, chloride anions and uncoordinated water molecules. The Cu I atom exhibits tetrahedral coordination geometry, involving four symmetry-equivalent P-bound PTA ligands. The structure is extended to a regular three-dimensional supramolecular framework via numerous equivalent O-HÁ Á ÁN hydrogen bonds between all solvent water molecules (six per cation) and all PTA N atoms, thus simultaneously bridging each [Cu(PTA) 4 ] + cation with 12 neighbouring units in multiple directions. The study also shows that PTA can be a convenient ligand in crystal engineering for the construction of supramolecular architectures.
This work has been supported by the FCT, Portugal, and its POCI 2010 programme (FEDER funded).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: DN2329).

metal-organic compounds
Three-dimensional hydrogen-bonded supramolecular assembly in tetrakis(1,3,5-triaza-7phosphaadamantane)copper (I) chloride (Phillips et al., 2004). Besides, PTA and its derivatives can also be convenient building blocks for the construction of polymeric networks (Lidrissi et al., 2005;Frost et al., 2006;Mohr et al., 2006) due to several potentially available coordination sites, protonation ability of N atoms, and strong affinity towards hydrogen bonds. Nevertheless, the use of PTA ligands in crystal design and engineering has remained little explored. Hence, in pursuit of our recent studies directed towards the synthesis of new copper compounds including PTA complexes  and various coordination polymers, supramolecular frameworks and host-guest systems with other ligands (Karabach et al., 2006;Di Nicola et al., 2007;Kirillov et al., 2008), we have prepared compound (I) whose crystal structure and supramolecular features are reported herein.
The moiety formula of (I) consists of the [Cu(PTA) 4 ] + cation (Fig. 1), one chloride anion and six symmetry equivalent crystallization water molecules. The [Cu(PTA) 4 ] + unit possesses a very high symmetry, being generated from only five symmetry nonequivalent atoms (Cu1, P1, N1, C1 and C2). The Cu I atom lies on -43m site symmetry and its coordination environment is filled by four equivalent P-bound PTA ligands, arranged in a perfect tetrahedral coordination geometry with the corresponding P-Cu-P angles of 109.47 (2)°. The Cu-P bond distances of 2.2598 (6) Å as well as other bonding parameters within the cage-like PTA cores are comparable to those reported for tetrahedral PTA complexes of Cu , Au (Forward et al., 1996), Pt (Darensbourg et al., 1999) and Ni (Darensbourg et al., 1997).
An interesting feature of (I) consists in the extensive intermolecular hydrogen bonding that arises from only one type of O-H···N H-bond (Table 1). Hence, each crystallization water molecule (O10) repeatedly acts as a double H-bond donor bridging to two N1 atoms of two different [Cu(PTA) 4 ] + units. This results in the extensive interlinkage in multiple directions of every monomeric copper unit with twelve neighbouring ones (Fig. 2), thus leading to the formation of a regular three-dimensional supramolecular framework (Fig. 3). That framework has the shortest Cu···Cu separation of 13.977 (1) Å and possesses the repeating channels (ca 4.8 Å diameter) filled by water molecules.

Experimental
To the ethanolic solution (5 ml) of CuCl 2 (27 mg, 0.20 mmol) was added solid PTA (126 mg, 0.80 mmol). The obtained mixture was refluxed for 3 h resulting in a white suspension. This was filtered off and the colourless filtrate was left to evaporate in a beaker in air and at ambient temperature. A small crop of the colourless X-ray quality crystals of (I) was formed in several days. 1 H NMR data are similar to those reported for [Cu(PTA) 4 ]NO 3 .

Refinement
All H atoms attached to C atoms were fixed geometrically and treated as riding with C-H = 0.97 Å and U iso (H) = 1.2U eq (C).
H atom of the water molecule were located in difference Fourier maps and included in the subsequent refinement using restraint (O-H= 0.82 (1)Å) with U iso (H) = 1.5U eq (O). In the last stage of refinement,it was treated as riding on the O atom.  tetrakis(1,3,5-triaza-7-phosphaadamantane)copper(I) chloride hexahydrate Crystal data [Cu(C 6  Geometric parameters (Å, °)