A Novel Family of Triangular CoII2LnIII and CoII2YIII Clusters by the Employment of Di-2-Pyridyl Ketone

Abstract

The synthesis, structural characterization and magnetic study of novel Co II /4f and Co II /Y III clusters are described. In particular, the initial employment of di-2-pyridyl ketone, (py) 2 CO, in mixed metal Co/4f chemistry, provided access to four triangular clusters,is the monoanion of the hemiketal form of (py) 2 CO. Clusters 1-4 are the first reported Co/4f (1-3) and Co/Y (4) species bearing (py) 2 CO or its derivatives, despite the fact that over 200 metal clusters bearing this ligand have been reported so far. Variable-temperature, solid-state dc and ac magnetic susceptibility studies were carried out on 1-4 and revealed the presence of weak ferromagnetic exchange interactions between the metal ions (J Co-Co = +1.3 and +0.40 cm −1 in 1 and 4, respectively; J Co-Gd = +0.09 cm −1 in 1). The ac susceptibility studies on 2 revealed nonzero, weak out-of-phase (χ" M ) signals below~5 K.

Indium(III) in the “Periodic Table” of Di(2-pyridyl) Ketone: An Unprecedented Transformation of the Ligand and Solid-State 115In NMR Spectroscopy as a Valuable Structural Tool

“…The spectra do not display a band/peak in the carbonyl stretching vibration ν­(CO) (1680–1630 cm –1 ) region; this is anticipated since carbonyl-containing (py) 2 CO ligands in the complexes are absent (this band appears at 1680 cm –1 in the IR spectrum of free di­(2-pyridyl) ketone, Figure S5). The nearest band at ∼1600 cm –1 is attributed to a pyridyl stretching vibration, whereas the bands at 610 and 402 cm –1 in the IR spectrum of (py) 2 CO are assigned to the in-plane, δ­(py), and out-of-plane, γ­(py), deformations of the 2-pyridyl ring; their shifts to higher wavenumbers (∼650 and 415 cm –1 , respectively) in the spectra of 1 – 3 , in comparison with these bands in the spectrum of (py) 2 CO, indicate the involvement of the ring-N atoms in coordination . The IR bands/Raman peaks in the spectra of 1 – 3 at ∼1560 and ∼1375 cm –1 are assigned , to the ν as (NO 2 ) and ν s (NO 2 ) vibrations of the NO 2 group of (py) 2 C­(CH 2 NO 2 )­(O) − , respectively, the former overlapping with a 2-pyridyl stretch.…”

“…Our group − and others − have had an intense interest over two decades or so in the reactions of coordinated ligands represented as A-CO-A, A-CO-CO-A, A-CO-A-CO-A, and A-CO-B, with A and B being donor and nondonor groups, respectively. The ligand studied most in depth is di­(2-pyridyl) ketone, (py) 2 CO, shown in Scheme . − ,− …”