Iridium porphyrin complexes with μ-nitrido, hydroxo, hydrosulfido and alkynyl ligands. Issue 23 (21st May 2019)

• Record Type: Journal Article
• Authors: So, Shiu-Chun; Cheung, Wai-Man; Chiu, Wai-Hang; de Vere-Tucker, Matthew; Sung, Herman H.-Y.; Williams, Ian D.; Leung, Wa-Hung
• Is Part Of: Dalton transactions. Volume 48:Issue 23(2019)
• Page Start: 8340
• Page End: 8349
• Publication Date: 2019-05-21
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c9dt00244h
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Iridium porphyrin complexes containing μ-nitrido, hydroxo, hydrosulfido, and alkynyl ligands have been synthesized and structurally characterized, and their oxidation has been studied. Abstract : Iridium porphyrin complexes containing μ-nitrido, hydroxo, hydrosulfido, and alkynyl ligands have been synthesized and structurally characterized, and their oxidation has been studied. The alkyl-Ir III porphyrin complex [Ir(tpp)R] (tpp 2− = 5, 10, 15, 20-tetraphenylporphyrin dianion; R = C8 H13 ;1 ) was synthesized by reaction of [Ir(cod)Cl]2 (cod = 1, 5-cyclooctadiene) with H2 tpp in refluxing monoethylene glycol. Treatment of1 with PPh3 and [(LOEt )Ru(N)Cl2 ] (LOEt − = [(η 5 -C5 H5 )Co{P(O)(OEt)2 }3 ] − ) gave [Ir(tpp)(R)(PPh3 )] (2 ) and the μ-nitrido complex [R(tpp)Ir(μ-N)RuCl2 (LOEt )] (3 ), respectively. The cyclic voltammogram of3 exhibited a reversible oxidation couple at 0.44 V versus Fc +/0 (Fc = ferrocene). The oxidation of3 with [(4-BrC6 H4 )3 N](SbCl6 ) resulted in Ir–C bond homolysis and formation of the chloride complex [Cl(tpp)Ir(μ-N)RuCl2 (LOEt )] (4 ). The short Ir–N(nitrido) bond distances in3 [1.944(3) Å] and4 [1.831(4) Å] are indicative of multiple bond character and thus these two μ-nitrido complexes can be described by the two resonance forms: Ir III –NRu VI and Ir V NRu IV . Similarly, the oxidation of2 with [(4-BrC6 H4 )3 N](SbCl6 ) yielded [Ir(tpp)Cl(PPh3 )] (5 ). Chloride abstraction of5 with TlPF6 in tetrahydrofuran (thf) afforded [Ir(tpp)(PPh3 )(thf)](PF6 ) (6 ) that reacted with CsOH·H2 O and Li2 S to give the hydroxo [Ir(tpp)(OH)(PPh3 )] (7 ) and hydrosulfido [Ir(tpp)(PPh3 )(SH)] (8 ) complexes, respectively. Treatment of6 with phenylacetylene in the presence of CuI and Et3 N yielded the bimetallic complex [Ir(tpp)(PPh3 )(μ-η 1 :η 2 -CCPh)(CuI)] (9 ), whereas the transmetallation of6 with LiCCPh afforded the mononuclear alkynyl complex [Ir(tpp)(PPh3 )(CCPh)] (10 ). The electrochemistry of the Ir porphyrin complexes has been studied using cyclic voltammetry. On the basis of the measured redox potentials of [Ir(tpp)(PPh3 )X], the ability of X − to stabilize the Ir IV state is ranked in the order: R − > PhCC − > Cl − ∼ OH − . Oxidation of8 and9 with [(4-BrC6 H4 )3 N](SbCl6 ) led to isolation of5 and [Ir(tpp)(PPh3 )(H2 O)] +, respectively. The crystal structures of complexes3, 4, and7–10 have been determined.