Structurally adaptive multitopic ligands containing tris(pyrazolyl)methane units as supramolecular synthons: manganese carbonyl complexes

The compounds {p-C6H4[CH2OCH2C(pz)3]2[Mn(CO)3]2}(BF4)2 (1, pz=pyrazolyl ring), {p-C6H4[CH2OCH2C(pz)3]2[Mn(CO)3]2}(OTf)2 (2, OTf−=CF3SO3−), {m-C6H4[CH2OCH2C(pz)3]2[Mn(CO)3]2}(BF4)2 (3) and {1,2,4,5-C6H2[CH2OCH2C(pz)3]4[Mn(CO)3]4}(BF4)4 (4) have been prepared by reaction of the respective ligands with ‘Mn(CO)5+’, prepared ‘in situ’ from the reaction of Mn(CO)5Br and AgBF4 or AgOTf in refluxing acetone. In the structures of all four complexes, the environment around the manganese atom is a slightly distorted octahedron, with the distortion caused by the restricted bite angle of the κ3-bonded tris(pyrazolyl)methane ligand. The structurally adaptive ligands in all four complexes support extended three-dimensional (3D) supramolecular structures. An important organizational feature for the three BF4− complexes is a double π–π and CH⋯π interaction involving the pyrazolyl rings. The double π–π/CH⋯π interaction is intermolecular in 1 and 3 leading to the formation of chains and sheets. In the case of the tetratopic ligand in complex 4, the π–π/CH⋯π interaction is intramolecular between adjacent (ortho) side arms. These supramolecular structures are also supported by weak CH⋯F hydrogen bonds. For 3, classic π–π interactions of the central arene rings are also involved in organizing the 3D network. For 2, the structure is organized solely by CH⋯O hydrogen bonding.