Copper Complexes with a Hybrid Scorpionate Ligand Containing Pyridazine-3-thione

• Published in: European journal of inorganic chemistry 2012-10, Vol.2012 (29), p.4701-4707
• Main Authors: Nuss, Gernot, Ozwirk, Anja, Harum, Bastian N., Saischek, Gerald, Belaj, Ferdinand, Mösch-Zanetti, Nadia C.
• Format: Article
• Language: English
• Subjects: Borates; Copper; COPPER COMPOUNDS; Diffraction; Isomers; LIGANDS; MATHEMATICAL ANALYSIS; Methyl alcohol; NMR spectroscopy; Phenyls; S ligands; Sodium; Sulfur; Tripodal ligands
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201200158

A new scorpionate ligand, Na[HB(mim)2(PntBu)] (Na[PnBm]), with one pyridazinyl‐3‐thione and two methimazolyl (mim) substituents was prepared by mixing 6‐tert‐butylpyridazine‐3‐thione (HPntBu) and sodium dihydridobis(methimazolyl)borate (Na[Bm]) in boiling xylene. Addition of CuCl to a solution of Na[PnBm] in methanol in the presence of PR3 gave the monomeric copper(I) complexes [Cu{PnBm}(PR3)] (R = cyclohexyl 1, phenyl 2) in good yields. They were characterized by NMR spectroscopy and in the case of 2 also by single‐crystal X‐ray diffraction analysis. The latter revealed a compound in which the ligand is coordinated in a κ3‐S,S,H fashion, exhibiting a 3‐center‐2‐electron B–H···Cu interaction. Reaction of the ligand Na[PnBm] with CuCl in the absence of phosphane yielded a copper(I) complex, which was determined to be [Cu{PnBm}] (3). Variable‐temperature 1H NMR spectroscopy points to the occurrence of two dimeric isomers in solution, which interconvert in a fluxional behavior at room temperature. DFT calculations show that two isomers with a κ3‐Smim,Smim,H or a κ3‐Hmim,SPn,H coordination mode have very similar energies with a low energy barrier (25.4 kJ/mol) for their interconversion. A new hybrid scorpionate ligand, Na[HB(mim)2(PntBu)] (Na[PnBm]), containing the methimazole and pyridazine moieties was prepared. Reaction of the ligand with CuCl and phosphane donors gave complexes [Cu{PnBm}(PR3)] (R = cyclohexyl 1, phenyl 2), whereas without phosphane donors dimeric complex [Cu{PnBm}]2 (3) was formed. The fluxional behavior was further investigated by theoretical calculations.