Dicubane-like Tetrameric Cobalt(II)−Pseudohalide Ferromagnetic Clusters

Abstract

Three tetrameric cobalt(II)-pseudohalide complexes have been structurally and magnetically characterized. Compounds 1 and 2 are isomorphous and exhibit the general formula [Co2(dpk-OH)(dpk-CH3O)(L)(H2O)]2A2-4H2O where dpk = di-2-pyridyl ketone, L = N3(-) and A = BF4(-) for 1, and L = NCO(-) and A = ClO4(-) for 2. The ligands dpk-OH(-) and dpk-CH3O(-) result from solvolysis and ulterior deprotonation of dpk in water and methanol, respectively. Both compounds exhibit cationic tetramers consisting of a dicubane-like core with two missing vertexes where the Co(II) ions are connected through end-on pseudohalide and oxo-bridges. A similar tetranuclear core has been found for 3 whose formula is [Co2(dpk-OH)(dpk-CH3O)(NCO)2]2. In this case, the tetramers are neutral and exhibit a terminal cyanate in place of the coordinated molecule of water for 1 and 2. The tetrameric units for 2 and 3 represent the first examples of any kind of cubanes exhibiting cyanate bridges as well as the first Co(II) compounds exhibiting intermetallic bridges through these pseudohalide groups. Measurements of the magnetic susceptibility indicated the presence of ferromagnetic Co(II)-Co(II) interactions in the three compounds.

Reactions of Dipyridylketone With Group 8 Metal Carbonyls in Different Media

“…Ru 3 (CO) 12 , Os 3 (CO) 12 and di-2-pyridylketone were supplied from Aldrich. All the solvents were reagent grade and purified prior to use.…”

“…A mixture of Ru 3 (CO) 12 (0.10 g, 0.16 mmol) and dpk (0.10 g, 0.44 mmol) were mixed in 30 ml dioxane. The mixture was degassed with one freeze-thaw cycle and refluxed for 8h where a brown precipitate was formed.…”

“…In a previous study, reaction of Ru 3 (CO) 12 , with 2-(2'-pyridyl)benzimidazole (HPBI) resulted in the formation of Ru(CO) 3 (HPBI) complex. In presence of pyridine or bipyridine, the two derivatives [Ru(CO) 3 12 reacted with 2,3-bis(2´-pyridyl)quinoxaline (dpq) in benzene in presence of either 2,2´-dipyridine (dpy) or pyridine (py) to give the mononuclear complex [Ru(CO) 3 (dpq)] or [Ru(CO) 2 (dpq)(py)] [24]. In this article, we report the synthesis and characterization of some ruthenium and osmium complexes of dpk.…”

“…It has been found that copper(I)-PPh 3 -dpk complexes are efficient photocatalysts for norbornadiene-quadricyclane conversion [6], which is important as a solar energy storage process [7,8]. On the other hand, the metal promoted hydration of dpk has been of interest for some time since the ligand has the ability to undergo a reaction after initial coordination to a transition metal ion [9][10][11][12][13]. Frequently the coordinated dpk undergoes nucleophilic addition of water or an alcohol at the carbonylic carbon atom to form the diol or the corresponding hemiacetal, (NC 5 H 4 ) 2 C(OR)(OH), which deprotonated and acts as a mononegative, tridentate N,O,N-donor ligand (Fig.1).…”

“…

AbstractReaction of di-(2-pyridyl)ketone (dpk) with [M 3 (CO) 12 ], M =Ru or Os in dioxan under reduced pressure gave the tricarbonyl derivative [Ru(CO) 3 (dpk)] (1) and [Os(CO) 3 (dpk)] (2). When these reactions were carried out in benzene/ethanol 1:1 (v:v) under reflux and reduced pressure gave the binuclear ruthenium complex [Ru 2 (CO) 4 (-CO)( 3 -dpkO,Oeth) 2 ] (3), where  3 -dpkO,Oeth is N,O,N-ethoxybis(2-pyridyl)-methanolato and the mononuclear [Os(CO) 3 ( 3 -dpkO,Oeth) (4).

…”