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[CH2OCH2(pz)(3)](2)[Mn(CO3](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)(5)Br 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 kappa(3)-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 pi-pi and C-H...pi interaction involving the pyrazolyl rings. The double pi-pi/C-H...pi 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 pi-pi/C-H...pi interaction is intramolecular between adjacent (ortho) side arms. These supramolecular structures are also supported by weak C-H...F hydrogen bonds. For 3, classic pi-pi 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. (C) 2002 Elsevier Science B.V. All rights reserved.