Supramolecular networks of silver(i) and iron(ii) complexes of the third generation tris(pyrazolyl)methaneligand Ph2(O)POCH2C(pz)3 (pz = pyrazolyl ring)

Abstract

The new ligand Ph₂(O)POCH₂C(pz)₃ (pz = pyrazolyl ring), prepared from the reaction of HOCH₂C(pz)₃ and Ph₂P(O)Cl in the presence of base, reacts with either AgBF₄ or Fe(BF₄)₂·6H₂O in a 2/1 molar ratio to yield {[Ph₂(O)POCH₂C(pz)₃]₂Ag}(BF₄) (1) and {[Ph₂(O)POCH₂C(pz)₃]₂Fe}(BF₄)₂ (4), respectively. In the structure of 1, the silver is in an unusual planar geometry with each of the ligands in a κ²–κ⁰ coordination mode. Slow evaporation of a thf solution of 1 yields crystalline [Ph₂(O)POCH₂C(pz)₃Ag]₂(thf)₂}(BF₄)₂ (2). In each cationic unit of 2, the two Ph₂(O)POCH₂C(pz)₃ ligands coordinate to the same two silver(I) centers in a κ²–κ¹ bonding mode, with a silver atom separation of 3.36 Å. The supramolecular structure of both 1 and 2 is dominated by a pair of cooperative hydrogen bonding interactions between the Ph₂P(O) secondary tecton and a hydrogen atom from a methylene group situated on a neighboring building block, which arranges the cations in chains. The reaction of HC(pz)₃ and AgO₃SCF₃ (AgOTf) yields {[HC(pz)₃]₂Ag₂}(OTf)₂ (3). The cationic unit in 3 has a structure very similar to that of 2, but with a much shorter distance between the silver atoms at 2.86 Å. The supramolecular structure of 3 is dominated by an unusual pyrazolyl embrace interaction where the acceptor ring in the C–H⋯π interaction is the pyrazolyl ring κ¹-bonded to silver in the adjacent dimeric unit rather than the other ring in a κ²-bonded Cpz₂ unit. This interaction arranges the cations in chains which are further organized into sheets by the triflate anions that link the chains via combined Ag⋯O/CH⋯O interactions. The iron in 4 is octahedral with each tris(pyrazolyl)methane unit in the κ³-tripodal coordination mode. The supramolecular structure is sheets formed by hydrogen bonding between the Ph₂P(O) oxygen and a meta-position hydrogen on one of the diphenylphosphine rings from an adjacent cation.