Tantalum Complexes Containing a Tridentate [NSN]-Type Ligand: Unusual Reactivity of a Dihydride Complex with an Isocyanide to Give an Azatantallaziridine Moiety

A series of new tantalum complexes containing a [NSN]-type amide ligand (2,2′-diamidophenyl sulfide) have been synthesized and characterized. The complexes [TaCp*Cl2{(N-C6H4)2S-κ3-N,S,N}] (1) and [TaCp*Me2{(N-C6H4)2S-κ3-N,S,N}] (2) were prepared by reaction of 2,2′-diaminophenyl sulfide with [TaCp*Cl4] and [TaCp*Me2Cl2], respectively. In addition, [TaCp*MeCl{(N-C6H4)2S-κ3-N,S,N}] (3) and [TaCp*(H)2{(N-C6H4)2S-κ3-N,S,N}] (4) were synthesized by reaction of 1 with AlMe3 and NaBEt3H, respectively. The reactivity of these complexes with nucleophiles and electrophiles was also studied, and complexes [TaCp*(tBuNCH2-κ2-C,N){(N-C6H4)2S-κ3-N,S,N}] (5) and [TaCp*Me{(N-C6H4)2S-κ3-N,S,N}][MeB(C6F5)3] (6) were isolated and characterized. The single-crystal structures of 1 and 4 were determined by X-ray diffraction methods. The NMR chemical shifts of the amidic protons in the complexes allowed us to evaluate the influence that the other ligands in the coordination sphere have on the electronic density of the metal.