Metallosupramolecular chemistry of novel chiral closo-o-carboranylalcohol pyridine and quinoline ligands: Syntheses, characterization, and properties of cobalt complexes

Abstract

The cobalt(II) complexes CoCl 2(LOH) 2 (LOH = 1-[R(hydroxy)methyl]-2-R′-1,2-dicarba-closo-dodecaborane (R′ = H or Me; R = 2-pyridyl 3a or 4a, 3-pyridyl 3b or 4b, 4-pyridyl 3c or 4c, 2-quinolyl 3d or 4d, 4-quinolyl 3e or 4e)) and CoCl 2(LOH) 4 (5, R′ = H; R = 4-pyridyl) were synthesized and characterized. Deprotonation of alcohol in 3a afforded the square-planar complex Co II(LO) 2 (6) that oxidized slowly in solution and under air to give the cobaltacarborane complex Co III{(η 5-C 2B 9H 10)(CHOH)(η 1-NC 5H 4)}(η 2-NC 5H 4COO) (7). Crystal structures for 3a, 3a·2MeOH, 3b, 3e, 4c, 4e, 5, 6, and 7 have been determined by X-ray diffraction (XRD). Molecular structures show octahedral (3a, 3a·2MeOH, 5), tetrahedral (3b, 3e, 4c, 4e), and square-planar (6) coordination around Co II centers, whereas 2-pyridyl and quinolyl ligands favor a bidentate N,O-coordination mode and 3- and 4-pyridyl and quinolyl ligands favor a monodentate N-coordination. The supramolecular structures are dominated by intermolecular O-H⋯Cl/O hydrogen bonds and π-π interactions in the case of tetrahedral complexes. The magnetic properties of 3a-c were investigated in the temperature range 2-300 K by means of X MT, which corroborated coordination numbers and geometries as well as provided information on the supramolecular interactions among neighboring molecules for all three compounds. Complex 3a shows solvent accessible channels running parallel to the hydrogen bonding network and is able to uptake methanol vapors to convert into 3a·2MeOH. The structure of 3a is related to that for 3a·2MeOH by rotation of complex molecules within the 1D O-H⋯Cl hydrogen bonding networks and insertion of methanol into it. © 2012 American Chemical Society.