Using a geminal dianion as precursor, a nucleophilic scandium carbene complex (2) has been synthesized by salt metathesis on ScCl(3)(THF)(3) in 52% isolated yield. The X-ray structure as well as an NBO analysis points to a double interaction between the carbon and the scandium atoms. Quantification of the electron density donation from the carbon to the metal center, from both σ and π symmetry orbitals, predicts a "nucleophilic carbene" behavior. Addition of benzophenone on complex 2 results in the formation of the expected alkene derivative and the trapping of a rare, μ(3)-oxo-Sc species via a "scandia-Wittig" reaction.

Different synthetic strategies are proposed to obtain a family of scandium carbene complexes. Starting either from scandium trichloride, scandium trisbenzyl, or the known scandium bis(diphenylthiophosphinoyl)­methanediide chloride complex 1, the homoleptic bis-carbene complex [Sc{C(PPh2S)2}2Li(THF)2] (3), the alkyl-carbene complex [Sc{C(PPh2S)2}­{CH(PPh2S)2}(THF)] (5), the amido-carbene complex [Sc{C(PPh2S)2}­{N(SiMe3)2}(THF)] (7), and the phosphido-carbene complex [Sc{C(PPh2S)2}­{P(SiMe3)2}(Py)2] (8) were obtained. The influence of the nature of the anionic ligand in trans position to the carbene ligand on the geometries at Sc was probed by DFT calculations in the case of complexes 7 and 8.