Structural Variety in Transition Metal Complexes of Tripodal Ligands Containing Mixed Quinolyl and Pyridyl Donors

The syntheses of the tripodal tetraamine ligands 2-(pyridin-2-yl)-N,N-bis(quinolin-2-ylmethyl)ethan-1-amine (DQPEA), N-(pyridin-2-ylmethyl)-2-(quinolin-2-yl)-N-(2-(quinolin-2-yl)ethyl)ethan-1-amine (DQEPMA), 2-(pyridin-2-yl)-N,N-bis(2-(quinolin-2-yl)ethyl)ethan-1-amine (DQEPEA), N,N-bis(pyridin-2-ylmethyl)-2-(quinolin-2-yl)ethan-1-amine (QEDPMA), and 2-(pyridin-2-yl)-N-(2-(pyridin-2-yl)ethyl)-N-(2-(quinolin-2-yl)ethyl)ethan-1-amine (QEDPEA) containing mixed quinolyl and pyridyl moieties are reported, with 2-vinylquinoline being used to attach quinolylethyl arms to the aliphatic N atom. X-ray crystal structures of (Mn(DQPEA))2O22 ⋅ (CH3CN)2, Cu(DQPEA)NCCH32, Zn(DQPEA)NCCH32, [Pd(DQEPEA)Cl]Cl ⋅ 11H2O are detailed, with four, five, and six-coordination observed. In addition, the dimeric complex (DPEA)Co(μ-OH)3Co(DPEA)3 ⋅ 0.5H2O ⋅ MeCN containing the tridentate DPEA ligand formed by N-dealkylation of QEDPEA is reported. Calculations suggest that the very short Co…Co distance of 2.5946(6) Å in this complex is unlikely to be due to a Co-Co bond.