Phenylcyanamidoruthenium Scorpionate Complexes

Nine [Ru­(Tp)­(dppe)­L] complexes, where Tp is hydrotris­(pyrazol-1-yl)­borate, dppe is ethylenebis­(diphenylphosphine), and L is (4-nitrophenyl)­cyanamide (NO₂pcyd^–), (2-chlorophenyl)­cyanamide (2-Clpcyd^–), (3-chlorophenyl)­cyanamide (3-Clpcyd^–), (2,4-dichlorophenyl)­cyanamide (2,4-Cl₂pcyd^–), (2,3-dichlorophenyl)­cyanamide (2,3-Cl₂pcyd^–), (2,5-dichlorophenyl)­cyanamide (2,5-Cl₂pcyd^–), (2,4,5-trichlorophenyl)­cyanamide (2,4,5-Cl₃pcyd^–), (2,3,5,6-tetrachlorophenyl)­cyanamide (2,3,5,6-Cl₄pcyd^–), and (pentachlorophenyl)­cyanamide (Cl₅pcyd^–), and the dinuclear complex [{Ru­(Tp)­(dppe)}₂(μ-adpc)], where adpc^2– is azo-4,4-diphenylcyanamide, have been prepared and characterized. The crystal structures of [Ru­(Tp)­(dppe)­(Cl₅pcyd)] and [{Ru­(Tp)­(dppe)}₂(μ-adpc)] reveal the Ru^II ion to occupy a pseudooctahedral coordination sphere in which the cyanamide ligand coordinates to Ru^II by its terminal nitrogen atom. For both complexes, the cyanamide ligands are planar, indicating significant π mixing between the cyanamide and phenyl moieties as well as the azo group in the case of adpc^2–. The optical spectra of the nominally ruthenium­(III) species [Ru­(Tp)­(dppe)­L]⁺ were obtained through spectroelectrochemistry measurements and showed an intense near-IR absorption band. Time-dependent density functional theory calculations of these species revealed that oxidation of the ruthenium­(II) species led to species where partial oxidation of the cyanamide ligand had occurred, indicative of noninnocent character for these ligands. The spin densities reveal that while the 3-Clpycd species has substantial Ru^II(3-Clpycd⁰) character, the Cl₅pycd species is a much more localized ruthenium­(III) complex of the Cl₅pycd monoanion. Some bond order and charge distribution data are derived for these ruthenium­(III) species. The near-IR band is assigned as a quite complex mixture of d–d, 4d_π to L­(NCN) MLCT, and L­(NCN) to Ru 4d LMCT with even a scorpionate ligand component. Spectroelectrochemistry was also performed on [{Ru­(Tp)­(dppe)}₂(μ-adpc)] to generate the mixed-valence state. The intense intervalence transition that is observed in the near-IR is very similar to that previously reported for [{Ru­(trpy)­(bpy)}₂(μ-adpc)]²⁺, where trpy is 2,2′:6′,2″-terpyridine and bpy is 2,2′-bipyridine, and by analogy identifies [{Ru­(Tp)­(dppe)}₂(μ-adpc)]⁺ as a delocalized mixed-valence complex

Variable noninnocence of substituted azobis(phenylcyanamido)diruthenium complexes

The synthetic chemistry of substituted 4,4′-azobis(phenylcyanamide) ligands was investigated, and the complexes [{Ru(tpy)(bpy)}2( μ-L)][PF6]2, where L = 2,2′:5,5′-tetramethyl-4,4′-azobis(phenylcyanamido) (Me4adpc2-), 2,2′-dimethyl-4,4′-azobis(phenylcyanamido) (Me2adpc2-), unsubstituted (adpc2-), 3,3′-dichloro-4,4′-azobis(phenylcyanamido) (Cl2adpc2-), and 2,2′:5,5′-tetrachloro-4,4′-azobis(phenylcyanamido) (Cl4adpc2-), were prepared and characterized by cyclic voltammetry and vis-near-IR (NIR) and IR spectroelectrochemistry. The room temperature electron paramagnetic resonance spectrum of [{Ru(tpy)(bpy)}2( μ-Me4adpc)]3+ showed an organic radical signal and is consistent with an oxidation-state description [RuII, Me4adpc•-, RuII]3+, while that of [{Ru(tpy)(bpy)}2( μ-Cl2adpc)]3+ at 10 K showed a low-symmetry RuIII signal, which is consistent with the description [RuIII, Cl2adpc2-, RuII</su

Variable Noninnocence of Substituted Azobis(phenylcyanamido)diruthenium Complexes

The synthetic chemistry of substituted 4,4′-azobis­(phenylcyanamide) ligands was investigated, and the complexes [{Ru­(tpy)­(bpy)}₂(μ-L)]­[PF₆]₂, where L = 2,2′:5,5′-tetramethyl-4,4′-azobis­(phenylcyanamido) (Me₄adpc^2–), 2,2′-dimethyl-4,4′-azobis­(phenylcyanamido) (Me₂adpc^2–), unsubstituted (adpc^2–), 3,3′-dichloro-4,4′-azobis­(phenylcyanamido) (Cl₂adpc^2–), and 2,2′:5,5′-tetrachloro-4,4′-azobis­(phenylcyanamido) (Cl₄adpc^2–), were prepared and characterized by cyclic voltammetry and vis–near-IR (NIR) and IR spectroelectrochemistry. The room temperature electron paramagnetic resonance spectrum of [{Ru­(tpy)­(bpy)}₂(μ-Me₄adpc)]³⁺ showed an organic radical signal and is consistent with an oxidation-state description [Ru^II, Me₄adpc^•–, Ru^II]³⁺, while that of [{Ru­(tpy)­(bpy)}₂(μ-Cl₂adpc)]³⁺ at 10 K showed a low-symmetry Ru^III signal, which is consistent with the description [Ru^III, Cl₂adpc^2–, Ru^II]³⁺. IR spectroelectrochemistry data suggest that [{Ru­(tpy)­(bpy)}₂(μ-adpc)]³⁺ is delocalized and [{Ru­(tpy)­(bpy)}₂(μ-Cl₂adpc)]³⁺ and [{Ru­(tpy)­(bpy)}₂(μ-Cl₄adpc)]³⁺ are valence-trapped mixed-valence systems. A NIR absorption band that is unique to all [{Ru­(tpy)­(bpy)}₂(μ-L)]³⁺ complexes is observed; however, its energy and intensity vary depending on the nature of the bridging ligand and, hence, the complexes’ oxidation-state description

Phenylcyanamidoruthenium Scorpionate Complexes

Nine [Ru­(Tp)­(dppe)­L] complexes, where Tp is hydrotris­(pyrazol-1-yl)­borate, dppe is ethylenebis­(diphenylphosphine), and L is (4-nitrophenyl)­cyanamide (NO₂pcyd^–), (2-chlorophenyl)­cyanamide (2-Clpcyd^–), (3-chlorophenyl)­cyanamide (3-Clpcyd^–), (2,4-dichlorophenyl)­cyanamide (2,4-Cl₂pcyd^–), (2,3-dichlorophenyl)­cyanamide (2,3-Cl₂pcyd^–), (2,5-dichlorophenyl)­cyanamide (2,5-Cl₂pcyd^–), (2,4,5-trichlorophenyl)­cyanamide (2,4,5-Cl₃pcyd^–), (2,3,5,6-tetrachlorophenyl)­cyanamide (2,3,5,6-Cl₄pcyd^–), and (pentachlorophenyl)­cyanamide (Cl₅pcyd^–), and the dinuclear complex [{Ru­(Tp)­(dppe)}₂(μ-adpc)], where adpc^2– is azo-4,4-diphenylcyanamide, have been prepared and characterized. The crystal structures of [Ru­(Tp)­(dppe)­(Cl₅pcyd)] and [{Ru­(Tp)­(dppe)}₂(μ-adpc)] reveal the Ru^II ion to occupy a pseudooctahedral coordination sphere in which the cyanamide ligand coordinates to Ru^II by its terminal nitrogen atom. For both complexes, the cyanamide ligands are planar, indicating significant π mixing between the cyanamide and phenyl moieties as well as the azo group in the case of adpc^2–. The optical spectra of the nominally ruthenium­(III) species [Ru­(Tp)­(dppe)­L]⁺ were obtained through spectroelectrochemistry measurements and showed an intense near-IR absorption band. Time-dependent density functional theory calculations of these species revealed that oxidation of the ruthenium­(II) species led to species where partial oxidation of the cyanamide ligand had occurred, indicative of noninnocent character for these ligands. The spin densities reveal that while the 3-Clpycd species has substantial Ru^II(3-Clpycd⁰) character, the Cl₅pycd species is a much more localized ruthenium­(III) complex of the Cl₅pycd monoanion. Some bond order and charge distribution data are derived for these ruthenium­(III) species. The near-IR band is assigned as a quite complex mixture of d–d, 4d_π to L­(NCN) MLCT, and L­(NCN) to Ru 4d LMCT with even a scorpionate ligand component. Spectroelectrochemistry was also performed on [{Ru­(Tp)­(dppe)}₂(μ-adpc)] to generate the mixed-valence state. The intense intervalence transition that is observed in the near-IR is very similar to that previously reported for [{Ru­(trpy)­(bpy)}₂(μ-adpc)]²⁺, where trpy is 2,2′:6′,2″-terpyridine and bpy is 2,2′-bipyridine, and by analogy identifies [{Ru­(Tp)­(dppe)}₂(μ-adpc)]⁺ as a delocalized mixed-valence complex

Phenylcyanamidoruthenium Scorpionate Complexes

Nine [Ru­(Tp)­(dppe)­L] complexes, where Tp is hydrotris­(pyrazol-1-yl)­borate, dppe is ethylenebis­(diphenylphosphine), and L is (4-nitrophenyl)­cyanamide (NO₂pcyd^–), (2-chlorophenyl)­cyanamide (2-Clpcyd^–), (3-chlorophenyl)­cyanamide (3-Clpcyd^–), (2,4-dichlorophenyl)­cyanamide (2,4-Cl₂pcyd^–), (2,3-dichlorophenyl)­cyanamide (2,3-Cl₂pcyd^–), (2,5-dichlorophenyl)­cyanamide (2,5-Cl₂pcyd^–), (2,4,5-trichlorophenyl)­cyanamide (2,4,5-Cl₃pcyd^–), (2,3,5,6-tetrachlorophenyl)­cyanamide (2,3,5,6-Cl₄pcyd^–), and (pentachlorophenyl)­cyanamide (Cl₅pcyd^–), and the dinuclear complex [{Ru­(Tp)­(dppe)}₂(μ-adpc)], where adpc^2– is azo-4,4-diphenylcyanamide, have been prepared and characterized. The crystal structures of [Ru­(Tp)­(dppe)­(Cl₅pcyd)] and [{Ru­(Tp)­(dppe)}₂(μ-adpc)] reveal the Ru^II ion to occupy a pseudooctahedral coordination sphere in which the cyanamide ligand coordinates to Ru^II by its terminal nitrogen atom. For both complexes, the cyanamide ligands are planar, indicating significant π mixing between the cyanamide and phenyl moieties as well as the azo group in the case of adpc^2–. The optical spectra of the nominally ruthenium­(III) species [Ru­(Tp)­(dppe)­L]⁺ were obtained through spectroelectrochemistry measurements and showed an intense near-IR absorption band. Time-dependent density functional theory calculations of these species revealed that oxidation of the ruthenium­(II) species led to species where partial oxidation of the cyanamide ligand had occurred, indicative of noninnocent character for these ligands. The spin densities reveal that while the 3-Clpycd species has substantial Ru^II(3-Clpycd⁰) character, the Cl₅pycd species is a much more localized ruthenium­(III) complex of the Cl₅pycd monoanion. Some bond order and charge distribution data are derived for these ruthenium­(III) species. The near-IR band is assigned as a quite complex mixture of d–d, 4d_π to L­(NCN) MLCT, and L­(NCN) to Ru 4d LMCT with even a scorpionate ligand component. Spectroelectrochemistry was also performed on [{Ru­(Tp)­(dppe)}₂(μ-adpc)] to generate the mixed-valence state. The intense intervalence transition that is observed in the near-IR is very similar to that previously reported for [{Ru­(trpy)­(bpy)}₂(μ-adpc)]²⁺, where trpy is 2,2′:6′,2″-terpyridine and bpy is 2,2′-bipyridine, and by analogy identifies [{Ru­(Tp)­(dppe)}₂(μ-adpc)]⁺ as a delocalized mixed-valence complex