A Nitrido-bridged Heterometallic Ruthenium(IV)/Iron(IV) Phthalocyanine Complex Supported by A Tripodal Oxygen Ligand, [Co(η5-C5H5){P(O)(OEt)2}3]-: Synthesis, Structure, and Its Oxidation to Give Phthalocyanine Cation Radical and Hydroxyphthalocyanine Complexes

DFT Quantum-chemical prediction of molecular structure of iron(VI) macrocyclic complex with phthalocyanine and two oxo ligands

The possibility of the existence of the unknown iron complex containing phthalocyanine and two oxygen atoms in the inner coordination sphere was predicted using DFT quantum chemical calculation (OPBE/TZVP and B3PW91/TZVP levels). The structural parameters, the ground state multiplicity, the NBO analysis results, and the standard thermodynamic parameters for complex formation (standard enthalpy [Formula: see text], entropy [Formula: see text] and Gibbs’s energy [Formula: see text] are represented.

Properties and reactivity of μ-nitrido-bridged dimetal porphyrinoid complexes: how does ruthenium compare to iron?

Methane hydroxylation by metal-oxo oxidants is one of the Holy Grails in biomimetic and biotechnological chemistry. The only enzymes known to perform this reaction in Nature are iron-containing soluble methane monooxygenase and copper-containing particulate methane monooxygenase. Furthermore, few biomimetic iron-containing oxidants have been designed that can hydroxylate methane efficiently. Recent studies reported that μ-nitrido-bridged diiron(IV)-oxo porphyrin and phthalocyanine complexes hydroxylate methane to methanol efficiently. To find out whether the reaction rates are enhanced by replacing iron by ruthenium, we performed a detailed computational study. Our work shows that the μ-nitrido-bridged diruthenium(IV)-oxo reacts with methane via hydrogen atom abstraction barriers that are considerably lower in energy (by about 5 kcal mol^‒1) as compared to the analogous diiron(IV)-oxo complex. An analysis of the electronic structure implicates similar spin and charge distributions for the diiron(IV)-oxo and diruthenium(IV)-oxo complexes, but the strength of the O‒H bond formed during the reaction is much stronger for the latter. As such a larger hydrogen atom abstraction driving force for the Ru complex than for the Fe complex is found, which should result in higher reactivity in the oxidation of methane.

Iridium porphyrin complexes with μ-nitrido, hydroxo, hydrosulfido and alkynyl ligands

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-IrIII porphyrin complex [Ir(tpp)R] (tpp2- = 5,10,15,20-tetraphenylporphyrin dianion; R = C8H13; 1) was synthesized by reaction of [Ir(cod)Cl]2 (cod = 1,5-cyclooctadiene) with H2tpp in refluxing monoethylene glycol. Treatment of 1 with PPh3 and [(LOEt)Ru(N)Cl2] (LOEt- = [(η5-C5H5)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 of 3 exhibited a reversible oxidation couple at 0.44 V versus Fc+/0 (Fc = ferrocene). The oxidation of 3 with [(4-BrC6H4)3N](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 in 3 [1.944(3) Å] and 4 [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: IrIII-N[triple bond, length as m-dash]RuVI and IrV[double bond, length as m-dash]N[double bond, length as m-dash]RuIV. Similarly, the oxidation of 2 with [(4-BrC6H4)3N](SbCl6) yielded [Ir(tpp)Cl(PPh3)] (5). Chloride abstraction of 5 with TlPF6 in tetrahydrofuran (thf) afforded [Ir(tpp)(PPh3)(thf)](PF6) (6) that reacted with CsOH·H2O and Li2S to give the hydroxo [Ir(tpp)(OH)(PPh3)] (7) and hydrosulfido [Ir(tpp)(PPh3)(SH)] (8) complexes, respectively. Treatment of 6 with phenylacetylene in the presence of CuI and Et3N yielded the bimetallic complex [Ir(tpp)(PPh3)(μ-η1:η2-C[triple bond, length as m-dash]CPh)(CuI)] (9), whereas the transmetallation of 6 with LiC[triple bond, length as m-dash]CPh afforded the mononuclear alkynyl complex [Ir(tpp)(PPh3)(C[triple bond, length as m-dash]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 IrIV state is ranked in the order: R- > PhC[triple bond, length as m-dash]C- > Cl- ∼ OH-. Oxidation of 8 and 9 with [(4-BrC6H4)3N](SbCl6) led to isolation of 5 and [Ir(tpp)(PPh3)(H2O)]+, respectively. The crystal structures of complexes 3, 4, and 7-10 have been determined.

Reactions of cerium complexes with transition metal nitrides: synthesis and structure of heterometallic cerium complexes containing bridging catecholate ligands

Heterometallic cerium complexes containing bridging catecholate ligands have been synthesized from cerium complexes with Kläui's tripodal ligand and metal catecholates.