NHC adducts of tantalum amidohalides: the first example of NHC abnormally coordinated to an early transition metal.

The reaction of Ta(NMe) with NHC·HBF (NHC = IMes and SIMes) leads to new carbene adducts of the mixed Ta amidofluoride, [(NHC)TaF(NMe)]. On the contrary, the reaction of Ta(NMe) with IMes·HCl gives a complex mixture, where [(aIMes)TaCl(NMe)] is identified as one of the products. This is the first example of abnormal NHC coordination to an early transition metal.