Complexes of Zirconium and Hafnium in Oxidation State iii

Unusually Strong Long-range Electronic Coupling Across Redox-Active Bridges in M3+/M4+ Mixed-Valence Complexes of Group 4 Congeners

“…[116][117] On the other hand, the Zr 4+/3+ and Hf 4+/3+ redox couples occur at very similar potentials to the TIP 0/-1 (typically observed between -1.70 V and -2.12 V) and consequently, they are extremely rare. [118][119][120][121][122][123] This suggests that titanium is more energetically mismatched with the ligand, and upon reduction it may be more favorable for the electron to sit at the metal rather than travel across the higher energy bridge. The energetic similarity of the respective 4d and 5d , where ΔE is the pulse amplitude.…”

Unusually Strong Long-range Electronic Coupling Across Redox-Active Bridges in M3+/M4+ Mixed-Valence Complexes of Group 4 Congeners

“…[116][117] On the other hand, the Zr 4+/3+ and Hf 4+/3+ redox couples occur at very similar potentials to the TIP 0/-1 (typically observed between -1.70 V and -2.12 V) and consequently, they are extremely rare. [118][119][120][121][122][123] This suggests that titanium is more energetically mismatched with the ligand, and upon reduction it may be more favorable for the electron to sit at the metal rather than travel across the higher energy bridge. The energetic similarity of the respective 4d and 5d ions with TIP Me results in better orbital overlap and consequently, increased delocalization is observed.…”

Reverse Regioselectivity in Reductive Ring Opening of Epoxide Enabled by Zirconocene and Photoredox Catalysis

“…To this end, we set out to investigate a catalytic protocol for the ring opening of epoxides using zirconocene with photocatalysts even though Zr (III) has been scarcely utilized in organic synthesis. [26][27][28][29][30][31][32] Since the reduction of zirconocene typically requires high reducing power (-E1/2 (Cp2ZrCl2) = -1.85 V vs SCE) 33 , we commenced with strongly reducing photocatalyst Ir[(4-MeO)ppy]3 (P1, E1/2 Ir(IV)/Ir(III)* = -1.95 V vs SCE in MeCN). 34 Visible light irradiation of 1A in the presence of zirconocene dichloride, P1, and 1,4-cyclohexadiene (CHD) resulted in no product formation (Table 1, entry 1).…”