Synthesis of Titanium and Zirconium Complexes with 2‐Pyridonate and 2, 6‐Pyridinedithiolate Ligands

Treatment of complex [Cp 2 TiCl 2 ] with the lithium salt of 2‐hydroxypyridine afforded complex [Cp 2 Ti(Opy) 2 ] ( 1 ), whereas the same synthetic strategy applied to the analogous zirconium compound [Cp 2 ZrCl 2 ] did not worked. However, the use of the metallocene [Cp tt 2 ZrMe 2 ] with protic ligands allowed directing the reactivity towards protonation of the methyl groups attached to zirconium. To check this approach we reacted [Cp tt 2 ZrMe 2 ] with methanol affording complex [Cp tt 2 ZrMe(OMe)] ( 2 ), which was characterized in situ by NMR techniques. In the same line, the reaction of [Cp tt 2 ZrMe 2 ] with 2‐hydroxypyridine gave complex [Cp tt 2 Zr(Me)(Opy)] ( 3 ); forcing the conditions of this reaction did not lead to the expected complex [Cp tt 2 Zr(Opy) 2 ], most probably due to the steric hindrance exerted by the bulky cyclopentadienyl ligands. Further reactions of complex 3 with ligands having acidic protons also led to the recovery of the starting complex. However, when shifting to the bifunctional ligand 2, 6‐dimercaptopyridine [py(SH) 2 ] a double protonation of the methyl ligands in [Cp tt 2 ZrMe 2 ] occurred, allowing the isolation of mononuclear complex [Cp tt 2 Zr(κ S ,κ S ,κ N ‐pyS 2 )] ( 4 ), upon evolution of methane. The molecular structure of complex 4 was determined by X‐ray methods, showing the zirconium atom in a highly distorted trigonal bipyramidal arrangement; structural parameters indicate a conventional Zr–N bond, but rather weak Zr–S interactions.