New Monocyclopentadienyl Complexes of Tantalum( V ) and Titanium( IV ) with Chelating Pyrimidinethiolate and Oxypyridine Ligands − Molecular Structure of [Cp*TaCl 3 (SC 6 H 7 N 2 )]

New monocyclopentadienyl species of Ta V , [Cp*TaL 3 (XR)] (L = Cl, Me, X = O, S) bearing 4,6‐dimethyl‐2‐pyrimidinethiolate (SR = SC 6 H 7 N 2 ) or 3‐cyano‐4,6‐dimethyloxypyridine (OR = OC 8 H 7 N 2 ) ligands were prepared, namely [Cp*TaCl 3 (SC 6 H 7 N 2 )] ( 1 ), [Cp*TaCl 3 (OC 8 H 7 N 2 )] ( 2 ), [Cp*TaMe 3 (SC 6 H 7 N 2 )] ( 3 ). In addition, a bis(oxypyridine)titanium( IV ) complex [Cp*TiMe 2 (OC 8 H 7 N 2 ) 2 ] was isolated. The X‐ray structure analysis of 1 revealed that the thiolate group is bonded to the metal center through the sulfur atom and one of the nitrogen atoms in an η 2 ‐fashion. The reactivity of complex 3 with isocyanides (CNR), R = t Bu, Xyl (Xyl = 2,6‐dimethylphenyl) was also studied showing differences depending on the nature of R group. The reaction with 2,6‐dimethylphenyl isocyanide gives the azatantalacyclobutane complex [Cp*TaMe{XylN=CC(Me 2 )NXyl}(SC 6 H 7 N 2 )] ( 5 ) as the final product, whereas in the reaction with tert ‐butyl isocyanide the η 2 ‐imine‐containing complex [Cp*Ta{ t BuNC(Me 2 )}(SC 6 H 7 N 2 )] ( 6 ) is proposed to be formed. The dynamic behavior of [Cp*TaMe 3 (SC 6 H 7 N 2 )] ( 3 ) was also studied by variable‐temperature 1 H NMR spectroscopy. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)