Di-2-pyridyl ketone in lanthanide(III) chemistry: Mononuclear and dinuclear erbium(III) complexes

The use of di-2-pyridyl ketone ((py)2CO)/SCN_ ‘‘blend’’ in erbium(III) chemistry has yielded mononuclear and dinuclear complexes. The ErIII/SCN_/(py)2CO reaction mixture in alcohols (MeOH, EtOH) gives complexes [Er(NCS)3{(py)2C(OR)(OH)}3] (R = Me (1), Et (2)), where (py)2C(OR)(OH) is the neutral hemiacetal derivative of (py)2CO. Incorporation of hydroxides in the methanolic reaction system leads to the isolation of [Er2(NCS)3{(py)2C(OMe)O}3(MeOH)] (3).

 

Complex 3 can also be isolated by the reaction of 1 with three equivalents of NMe4OH in MeOH. The crystal structures of 2 Ζ0.3EtOH Ζ0.4H2O and 3 ΖMeOH have been solved by single-crystal X-ray crystallography. The ErIII atom in the former is in a nine-coordinate, tricapped trigonal prismatic ligand environment. The (py)2C(OEt)(OH) molecules adopt the novel N(2-pyridyl), O(hydroxyl)-bidentate chelating mode, while three isothiocyanate ligands complete the coordination sphere of ErIII. In complex 3 ΖMeOH the two ErIII atoms are triply bridged by the deprotonated hydroxyl oxygen atoms of the g1:g2:g1:l2(py)2C(OMe)O_ ligands; three 2-pyridyl nitrogen atoms belonging to three different ligands and two isothiocyanate anions complete eight-coordination at one ErIII atom, while eightcoordination at the other ErIII atom is completed by three 2-pyridyl nitrogen atoms, one isothiocyanate ligand and one MeOH molecule. The coordination polyhedra of the eight donor atoms about both ErIII atoms are best described as distorted dodecahedra. The complexes were studied by room-temperature effective magnetic moments and spectroscopic (IR, solid-state f–f) methods. All data are discussed in terms of the nature of bonding and known (2, 3) or assigned (1) structures.

 

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