Dioxygen Splitting by a Tantalum(V) Complex Ligated by a Rigid, Redox Non‐Innocent Pincer Ligand

The reaction of TaMe(3)Cl(2) with the rigid acridane‐derived trisamine H(3)NNN yields the tantalum(V) complex [TaCl(2)(NNN(cat))]. Subsequent reaction with dioxygen results in the full four‐electron reduction of O(2) yielding the oxido‐bridged bimetallic complex [{TaCl(2)(NNN(sq))}(2)O]. This dinuclear complex features an open‐shell ground state due to partial ligand oxidation and was comprehensively characterized by single crystal X‐ray diffraction, LIFDI mass spectrometry, NMR, EPR, IR and UV/VIS/NIR spectroscopy. The mechanism of O(2) activation was investigated by DFT calculations revealing initial binding of O(2) to the tantalum(V) center followed by complete O(2) scission to produce a terminal oxido‐complex.