The first member of a second generation family of ligands derived from metal-ion assisted reactivity of di-2,6-(2-pyridylcarbonyl)pyridine: Synthesis and characterization of a MnII/III4 rhombus

Nucleophilic attack by the carbanion −CH2COCH3 at the carbonyl carbon atoms of 2,6-di-(2-pyridylcarbonyl)pyridine, pyCOpyCOpy, in the presence of Mnn+ ions under basic conditions has yielded the cationic cluster [Mn4(OH)2(L)2(H2O)2](ClO4)4 (1), where L2− is the (py)C(CH2COCH3)(O−)(py)C(CH2COCH3)(O−)(py) dianion. The cluster cation possesses a planar {MnII2MnIII2(μ3-OH)2(μ-OR)4}4+ rhombus core, resulting from two μ3-OH− ions and two η1:η2:η1:η1:η1:η2:η1:μ3 bridging L2− groups from the in situ formed ligand. Complex 1 is antiferromagnetically coupled with an unusual S = 2 ground state resulting from spin frustration effects within the triangular Mn3 subunits of the cluster.

Nucleophilic attack by the carbanion −CH2COCH3 at the carbonyl atoms of 2,6-di-(2-pyridylcarbonyl)-pyridine, pyCOpyCOpy, in the presence of Mnn+ ions under basic conditions has yielded the cationic cluster [Mn4(OH)2(L)2(H2O)2](ClO4)4, where L2− is the (py)C(CH2COCH3)(O−)(py)C(CH2COCH3)(O−)(py) dianion; the latter is the first member of a second generation family of ligands derived from pyCOpyCOpy.Figure optionsDownload as PowerPoint slideHighlights
► The ligand pyCOpyCOpy undergoes a metal-assisted nucleophilic attack.
► The dianion (py)C(CH2COCH3)(O−)(py)C(CH2COCH3)(O−)(py) acts as a bridging group.
► The {MnII2MnIII2} cluster possesses a rare, planar [Mn4(μ3-OH)2(μ-OR′)4]4+ core.
► The Mn4 cluster is antiferromagnetically coupled and has an S = 2 ground state.
► Spin frustration effects stabilize the obtained, intermediate ground state.