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

Abstract

Abstract A new scorpionate ligand, Na[HB(mim) 2 (Pn t Bu )] (Na[ Pn Bm]), with one pyridazinyl‐3‐thione and two methimazolyl (mim) substituents was prepared by mixing 6‐ tert ‐butylpyridazine‐3‐thione (HPn t Bu ) and sodium dihydridobis(methimazolyl)borate (Na[Bm]) in boiling xylene. Addition of CuCl to a solution of Na[ Pn Bm] in methanol in the presence of PR 3 gave the monomeric copper(I) complexes [Cu{ Pn Bm}(PR 3 )] (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 κ 3 ‐ S , S , H fashion, exhibiting a 3‐center‐2‐electron B–H ··· Cu interaction. Reaction of the ligand Na[ Pn Bm] with CuCl in the absence of phosphane yielded a copper(I) complex, which was determined to be [Cu{ Pn Bm}] ( 3 ). Variable‐temperature 1 H 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 κ 3 ‐ S mim , S mim , H or a κ 3 ‐ H mim , S Pn , H coordination mode have very similar energies with a low energy barrier (25.4 kJ/mol) for their interconversion.