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The masked Ti( ii ) synthon ( Ket guan)(η 6 -Im Dipp N)Ti ( 1 ) oxidatively adds across thiophene to give ring-opened ( Ket guan)(Im Dipp N)Ti[κ 2 - S (CH) 3 C H] ( 2 ). Complex 2 is photosensitive, and upon exposure to light, reductively eliminates thiophene to regenerate 1 – a rare example of early-metal mediated oxidative-addition/reductive-elimination chemistry. DFT calculations indicate strong titanium π-backdonation to the thiophene π*-orbitals leads to the observed thiophene ring opening across titanium, while a proposed photoinduced LMCT promotes the reverse thiophene elimination from 2 . Finally, pressurizing solutions of 2 with H 2 (150 psi) at 80 °C leads to the hydrodesulphurization of thiophene to give the Ti( iv ) sulphide ( Ket guan)(Im Dipp N)Ti(S) ( 3 ) and butane. 

Abstract Vacancy‐ordered double perovskites are attracting significant attention due to their chemical diversity and interesting optoelectronic properties. With a view to understanding both the optical and magnetic properties of these compounds, two series of Ru^IVhalides are presented;A₂RuCl₆andA₂RuBr₆, whereAis K, NH₄, Rb or Cs. We show that the optical properties and spin‐orbit coupling (SOC) behavior can be tuned through changing theAcation and the halide. Within a series, the energy of the ligand‐to‐metal charge transfer increases as the unit cell expands with the largerAcation, and the band gaps are higher for the respective chlorides than for the bromides. The magnetic moments of the systems are temperature dependent due to a non‐magnetic ground state withJ_eff=0 caused by SOC. Ru‐Xcovalency, and consequently, the delocalization of metald‐electrons, result in systematic trends of the SOC constants due to variations in theAcation and the halide anion.