Synthesis and Reactivity of Monocyclopentadienyl Tantalum Complexes with Pincer Dialkoxide Ligands

Abstract

The new tantalum dialkoxide complexes Cp*TaCl 2 (OCH 2 ) 2 py ( 1 ), trans -Cp*TaMe 2 (OCH 2 ) 2 py ( 2 ), and cis - Cp*TaMe 2 (OCH 2 ) 2 py ( 3 ) (Cp* = η 5 -C 5 Me 5; (OCH 2 ) 2 py = 2,6-pyridinedimethoxide) have been synthesized. The molecular structures of complexes 1 and 2 have been studied by X-ray diffraction methods. The reaction of complex 3 with carbon monoxide renders Cp*Ta(η 2 -Me 2 CO)(OCH 2 ) 2 py ( 4 ), while with isocyanides yields the respective azatantalacyclopropanes Cp*Ta(η 2 -Me 2 CNxylyl)(OCH 2 ) 2 py ( 6 ) (xylyl = 2,6-dimethylphenyl) and Cp*Ta(η 2 -Me 2 CN t Bu)(OCH 2 ) 2 py ( 7 ). The molecular structure of complex 4 has been established by X-ray diffraction. The coordinated ketone in 4 can be reduced to 2-propanol in the presence of water. On the other hand, compound 3 reacts with triflic acid (HOTf) to render the corresponding cationic derivative [Cp * TaMe(OCH 2 ) 2 py]OTf ( 8 ).