Synthesis and Structural Characterization of a New Tetranuclear Nickel(II) Sulfato Complex Containing the Anionic Form of Di-2-Pyridyl Ketone Oxime

Eleni Moushi,Spyros P Perlepes,Constantinos G Efthymiou,Constantina Papatriantafyllopoulou

doi:10.1155/2011/606271

Abstract

The preparation and crystal structure of a tetranuclear Ni(II) sulfato cluster containing the anion of di-2-pyridyl ketone oxime, (py)2CNO−, are reported. Treatment of NiSO4·6H2O with one equivalent of (py)2CNOH and one equivalent of NEt3 in MeOH leads to the compound [Ni4{(py)2CNO}4(SO4)2(MeOH)4] (1) in moderate yield. The metal ions are linked together by two 3.2111 and two 2.1110 (Harris notation) (py)2CNO− ligands, as well as two 2.1100 SO42− ions to create a rare metallacrown-type (12-MC-4) ring. Strong H-bond intermolecular interactions in 1 lead to the formation of a 1D chain along the axis. Characteristic IR bands are discussed in terms of the known structure of 1.

Highlights

There is currently a renewed interest in the coordination chemistry of oximes [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]. 2-pyridyl oximes (Scheme 1) are popular ligands in coordination chemistry [21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36]. The anions of these molecules are versatile ligands for a variety of research objectives, including μ2 and μ3 behaviour [21, 22]; the activation of 2-pyridyl oximes by 3d-metal centers towards further reactions is becoming a fruitful area of research [21, 22, 26]
Analogues of 1 with 2-pyridinealdoxime [(py)C(H)NOH], methyl(2-pyridyl)ketone oxime [(py)C(Me)NOH], or phenyl(2-pyridyl)ketone oxime [(py)C(ph)NOH] (Scheme 1) are not known, until to date, and further research efforts are in progress to determine the appropriate reaction conditions that could possibly favor such species
We are currently working on the chemistry of the NiSO4·6H2O/(py)C(R)NOH (R=H, Me, Ph) reaction systems

Summary

Introduction

There is currently a renewed interest in the coordination chemistry of oximes [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]. 2-pyridyl oximes (Scheme 1) are popular ligands in coordination chemistry [21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36]. Carboxylates are able to deprotonate the oxime group of 2-pyridyloximes under mild conditions (the use of external hydroxides often perplexes the reactions) Besides their deprotonating ability, the R CO2− ions are flexible ligands, a consequence of their ability to adopt a number of different ligation modes, both terminal and bridging as well as both bidentate and tridentate. The additional inorganic monoanions in the ternary “ligand blends” often behave as terminal ligands and help the formation of clusters (and not coordination polymers). The initial employment of the sulfate ion in NiII/(py)C(R)NOH (R = Me, Ph, NH2) chemistry has led to the isolation and characterization of high-nuclearity NiII compounds, such as Ni12 [50] and Ni6 [51, 52] clusters which possess interesting structural properties. The IR data are discussed in terms of the nature of bonding and the structure of the complex

Experimental

Ni4 C48 H48 N24 O16 S2

Compound Preparation

Results and Discussion

Conclusions