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Exploratory Synthetic Studies of the Praseodymium/Di-2-Pyridyl Ketoxime System Leads to Unusual Reactivity and Interesting New Molecules

Year: 2025

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Reactions of lanthanoid(III) ions with di-2-pyridyl ketoxime, dpkoxH, have been studied. Full synthetic investigation of the Pr(NO 3 ) 3 ·6H 2 O/dpkoxH reaction system has provided access to complexes [Pr 2 III (NO 3 ) 4 (L) 2 ] (isolated as MeCN and MeNO 2 solvates; 1 and 2 ), [Pr 4 III (OH) 2 (NO 3 ) 4 (dpkox) 6 (EtOH) 2 ] ( 3 ) and [Pr 8 III Pr IV O 4 (OH) 4 (NO 3 ) 4 (dpkox) 12 (H 2 O) 4 ] ( 4 ). A novel Pr III -assisted/promoted ligand transformation has occurred in the dinuclear complexes, where L – is the anion of di(pyridin-2-yl)methanone O -(1-hydroxy-1,1-di(pyridin-2-yl)) methyl oxime (HL). Mechanistic schemes have been proposed. In 1 and 2, the two Pr III centers are bridged by two deprotonated oxygen atoms of two “head-to-head” 2.2011110 (Harris notation) L – ligands. The tetranuclear molecule 3 is held together by two μ 3 -hydroxido groups, two 2.2110, two 2.1110 and two 3.2110 dpkox – ligands. The {Pr 4 III (μ 3 –OH) 2 } 10+ unit of the {Pr 4 III (μ 3 –OH) 2 (μ 2 -oximato) 4 } 6+ core comprises four coplanar Pr III ions in a “butterfly”-type disposition. In the highly symmetrical cluster 4, the nine Pr ions are held together by four μ 3 -O 2– and four μ 3 –OH – groups, as well as four 2.1110, four 3.2111 and four 2.2110 dpkox – ligands. The inorganic {Pr 8 III Pr IV (μ 3 -O) 4 (μ 3 –OH) 4 } 16+ unit of the core can be described as four fused “butterflies”, the Pr IV center being the common site at one of their “body” positions. The X-band (∼9.5 GHz) EPR spectrum of 4 at 4.2 K shows a sharp peak at 630 G, a derivative feature at 1340 G, and a multitude of weaker signals; the data are compatible with the presence of the half-integer spin expected for the 4f 1 Pr IV center.

Source: Inorganic Chemistry

DOI: 10.1021/acs.inorgchem.5c04100