Synthesis and Characterization of Stable Hetereocyclic (Schiff Base) Divalent Tin Species and Photogeneration of Their Transition Metal Carbonyl Complexes

Abstract

New stable divalent heterocyclic species [SnL¹; 1, SnL²; 2] using ONNO and SNNS tetradentate Schiff bases; N,N′-bis(salicylidene)-1,2-bis(o-aminophenoxy)ethane (H₂L¹) and N,N′-bis(2-aminothiophenol)-1,4-bis(2-carboxaldehydephenoxy)butane (H₂L²) were obtained in good yields by alcolysis of the M-N bonds of the divalent precursor Sn[N(SiMe₃)₂]₂ by diols. They have been isolated as solids at ambient temperature and are monomeric. FT-IR, ¹H and ¹¹⁹Sn-NMR spectra are suggestive of N … M intramolecular coordination. Then the synthesis and characterization of the new stable mono and cis-disubstituted Sn(II) chromium and tungsten carbonyl complexes [L¹Sn]M(CO)₅ (M= Cr, 3; W, 4); [L²Sn]M(CO)₅ (M= Cr, 5; W, 6); cis-[L¹Sn]₂M(CO)₄ (M= Cr, 7; W, 8) and cis-[L²Sn]₂M(CO)₄ (M= Cr, 9; W, 10) are described. Pentacarbonyl complexes (3–6) were obtained in high yields by treatment of the M(CO)₅THF (M= Cr, W) intermediates with the divalent species [SnL¹; 1, SnL²; 2] and tetracarbonyl complexes (7–10) were synthesized by the photochemical reactions of [LⁿSn]M(CO)₅ with [LⁿSn] (n = 1, 2). Each of the new carbonyl complexes has been characterized by IR, ¹H, ¹³C, ¹¹⁹Sn-NMR spectroscopy, and mass spectrometry. The sigma donor and pi acceptor ability of the divalent tin species [SnL¹, 1; SnL², 2] as ligands in the transition metal carbonyl complexes (3–10) is discussed by comparing ν(CO) stretching frequencies.

Keywords:

• metal carbonyls
• photochemical reactions
• Schiff base
• tin complexes

Acknowledgments

This work was financially supported by the Scientific Research Foundation of Dokuz Eylul University (project number: 2008.KB.FEN.001). The authors thank TUBİTAK for allocation of time for NMR, mass spectra and elemental analyses. They also thank the Graduate School of Natural and Applied Sciences of Dokuz Eylul University.