An iridium(iii/iv/v) redox series featuring a terminal imido complex with triplet ground state

Abstract

An iridium(iii–v) imido series has been isolated that features an iridium complex with an unprecedented triplet ground state.

A Terminal Iridium Oxo Complex with a Triplet Ground State

“…SOC stabilizes the lowest spin-free state by 24 kJ mol À1 and splits the triplet root into aground state that is 744 cm À1 below two almost degenerate states.T he computed axial zero-field splitting parameter (D QDPT = 775 cm À1 )i si n good agreement with the experimentally determined value. Thes ame picture evolved for imide complex 1,y et with as maller energetic separation of the spin-orbit ground state (450 cm À1 ), [13] supporting the covalencya rguments discussed above to rationalize the magnetic properties.…”

“…This comparison suggests ar educed Ir À Ob ond order for 8 due to an electronic (yz) 2 (z 2 ) 2 (p* 1 ) 1 (p* 2 ) 1 configuration with half-filled IrÀO p* orbitals,i na nalogy to the isoelectronic imido complex 1. [13] Accordingly,t he IrÀOs tretching frequencyo f8 (n = 743 cm À1 ), which was assigned by comparison with the 18 Olabeled isotopologue,i sc onsiderably lower than that of [Ir V O(Mes) 3 ](n = 802 cm À1 ). [8b] In analogy to imido complex 1,t hree sharp,y et strongly paramagnetically shifted 1 HNMR signals between + 21 and À75 ppm in [D 8 ]THF at room temperature (d H (1): + 20 to À60 ppm) and no 31 PNMR signals were found.…”

Electrochemical and Kinetic Insights into Molecular Water Oxidation Catalysts Derived from Cp*Ir(pyridine‐alkoxide) Complexes

“…For instance, quasi‐reversible pre‐catalytic features around 0.9 V vs. NHE often assigned to a molecular Ir III–IV redox couple are more characteristic of amorphous, hydrated iridium‐oxyhydroxide deposites which may form on the surface of the working electrode . The recent electrochemical characterization of well‐defined and stable model complexes showing Ir III–IV redox couples at potentials below 0.7 V vs. NHE and even reversible Ir IV–V transitions around 1.0–1.2 V vs. NHE, call for a revision of the electrochemistry of Cp*Ir based water oxidation precatalysts.…”

A Terminal Iridium Oxo Complex with a Triplet Ground State

“…X-ray crystallographic characterization confirmed the formation of the dimeric, sodium-bridged iridium(I) hydroxyl contact ion pair [{Na(thf)Ir I (OH)(PNP)} 2 ]( 6;F igure 2). [13] Accordingly,t he IrÀOs tretching frequencyo f8 (n = 743 cm À1 ), which was assigned by comparison with the 18 Olabeled isotopologue,i sc onsiderably lower than that of [Ir V O(Mes) 3 ](n = 802 cm À1 ). The molecular structure of 8 ( Figure 2) exhibits approximate square-planar coordination with an almost linear N-Ir-O axis (173.68 8).…”

“…Salt metathesis of [IrCl(PNP)] (4) [13] with NaOH in THF/ H 2 O( 2:1) afforded the iridium(II) hydroxide complex [Ir-(OH)(PNP)] (5)i n9 1% isolated yield (Scheme 1). [14] Characterization of 5 by ESI-MS and X-ray crystallography ( Figure 2) confirmed the formation of arare,terminal iridium hydroxide complex.…”