Dinuclear iridium and rhodium complexes with bridging arylimidazolide-N(3),C(2) ligands: synthetic, structural, reactivity, electrochemical and spectroscopic studies

Visible-Light-Responsive Polyoxometalate@Metal-Organic Frameworks Involving Ir Metalloligands for Highly Selective Photocatalytic Oxidation of Sulfides to Sulfoxide

The synthesis of highly efficient visible-light-responsive photocatalysts is fundamental to solving the problems of low efficiency and poor selectivity in photocatalytic organic synthesis reactions. We synthesized a crystalline polyoxometalate @metal-organic framework material {Zn4 (H2 O)8 [Ir(ppy)2 (dcbpy)]4 [SiW12 O40 ]} ⋅ 4H2 O (Ir-SiW) by self-assembly of Ir metalloligands with POMs. The introduction of Ir metalloligands extends the light absorbing range to visible light, improving the efficient utilization of solar energy. The transfer of photogenerated electrons from Ir metalloligands to SiW12 was observed under visible light irradiation, which boosted the carrier separation efficiency. The synergistic effect of the two components increased the photocatalytic thioether oxidation activity, and the product methyl phenyl sulfoxide for 2.5 h under visible light irradiation (λ >400 nm) reached 99.5 %, which was higher than those of other POM-based photocatalysts. Meanwhile, the yield of methyl phenyl sulfoxide was still higher than 97 % after three cycles, demonstrating the high stability and reusability of Ir-SiW.

Cu(i), Ag(i), Ni(ii), Cr(iii) and Ir(i) complexes with tritopic NimineCNHCNamine pincer ligands and catalytic ethylene oligomerization

Potentially pincer-type tritopic N^imineC^NHCN^amine ligands with a variable length of the spacer connecting N^imidazole to the amine donor are evaluated.

Tetra-, Hexa-, Dodeca-Nuclear Ir Supramolecules via Bridge-Driven Self-Assembly of Tetrazolyl Ligands

Herein, we report the formation of multinuclear Ir4, Ir6, and Ir12 supramolecular complexes via the bridge-driven self-assembly of tetrazolyl ligands. The synthesis of dimeric half-sandwich Ir units was made by the reaction of half-sandwich Ir units and tetrazolyl ligands in a molar ratio of 1:2. The use of different ligands containing multiple tetrazolyl units resulted in the formation of different Ir supramolecular architectures. The reaction of [Cp*IrCl2]2, AgOTf, and 1,2- or 1,3-ditetrazolyl benzene in a molar ratio of 1:3:1 resulted in the formation of rectangular tetranuclear or truncated trigonal pyramidal hexanuclear Ir complexes, respectively. On the other hand, the reaction of [Cp*IrCl2]2, AgOTf, and 1,3,5-tritetrazolyl benzene in a molar ratio of 6:18:4 produced a supramolecular dodecanuclear iridium complex. The molecular structure of the complex resembled a truncated tetrahedral structure with a large inner cavity, as determined by X-ray crystallography.

Half-sandwich iron(ii) complexes with protic acyclic diaminocarbene ligands: synthesis, deprotonation and metalation reactions

A variety of half-sandwich iron(ii) complexes with diprotic acyclic diaminocarbene ligands (pADCs) have been obtained by reaction of the cationic complexes [Fe(Cp)(CO)₂(CNR)]⁺ and [Fe(Cp)(CO)(CNR)₂]⁺ with methylamine, and their acid-base behaviour was studied, revealing an easy reversible deprotonation reaction of both N-H moieties of the carbene ligands. The deprotonation process is frequently followed by a nucleophilic attack of the nitrogen atom on a vicinal carbonyl or isocyanide ligand, affording the corresponding metallacycles. Metalation of one or two N-H groups of the pADC ligands can be accomplished by reaction of the carbene complexes with either [AuCl(PPh₃)] or [Ru(p-cym)Cl₂]₂ in the presence of KOH or LiHMDS as deprotonating agents. A number of Fe(ii)/Au(i) and Fe(ii)/Ru(ii) heterometallic complexes have been prepared in this way, some of them formally containing unique metalla-N-heterocyclic carbene ligands.

Homo- and Heterodinuclear Ir and Rh Imine-functionalized Protic NHC Complexes: Synthetic, Structural Studies, and Tautomerization/Metallotropism Insights

The influence of the potentially chelating imino group of imine-functionalized Ir and Rh imidazole complexes on the formation of functionalized protic N-heterocyclic carbene (pNHC) complexes by tautomerization/metallotropism sequences was investigated. Chloride abstraction in [Ir(cod)Cl{C3 H3N2 (DippN=CMe)-κN3}] (1 a) (cod=1,5-cyclooctadiene, Dipp=2,6-diisopropylphenyl) with TlPF6 gave [Ir(cod){C3 H3N2 (DippN=CMe)-κ(2) (C2,Nimine )}](+) [PF6 ](-) (3 a(+) [PF6 ](-)). Plausible mechanisms for the tautomerization of complex 1 a to 3 a(+) [PF6 ](-) involving C2-H bond activation either in 1 a or in [Ir(cod){C3 H3 N2 (DippN=CMe)-κN3}2](+) [PF6 ](-) (6 a(+) [PF6 ](-)) were postulated. Addition of PR3 to complex 3 a(+) [PF6 ](-) afforded the eighteen-valence-electron complexes [Ir(cod)(PR3){C3 H3N2 (DippN=CMe)-κ(2) (C2,Nimine )}](+) [PF6 ](-) (7 a(+) [PF6 ](-) (R=Ph) and 7 b(+) [PF6 ](-) (R=Me)). In contrast to Ir, chloride abstraction from [Rh(cod)Cl{C3H3N2 (DippN=CMe)-κN3}] (1 b) at room temperature afforded [Rh(cod){C3 H3N2 (DippN=CMe)-κN3}2](+) [PF6 ](-) (6 b(+) [PF6 ](-)) and [Rh(cod){C3 H3N2 (DippN=CMe)-κ(2) (C2,Nimine )}](+) [PF6 ](-) (3 b(+) [PF6 ](-) ) (minor); the reaction yielded exclusively the latter product in toluene at 110 °C. Double metallation of the azole ring (at both the C2 and the N3 atom) was also achieved: [Ir2 (cod)2 Cl{μ-C3H2N2 (DippN=CMe)-κ(2) (C2,Nimine ),κN3}] (10) and the heterodinuclear complex [IrRh(cod)2 Cl{μ-C3H2N2 (DippN=CMe)-κ(2) (C2,Nimine ),κN3}] (12) were fully characterized. The structures of complexes 1 b, 3 b(+) [PF6 ](-) , 6 a(+) [PF6 ](-) , 7 a(+) [PF6 ](-), [Ir(cod){C3HN2 (DippN=CMe)(DippN=CH)(Me)-κ(2) (N3,Nimine )}](+) [PF6 ](-) (9(+) [PF6 ](-)), 10⋅ Et2 O⋅toluene, [Ir2 (CO)4 Cl{μ-C3H2N2 (DippN=CMe)-κ(2) (C2,Nimine ),κN3}] (11), and 12⋅2 THF were determined by X-ray diffraction.

Versatile deprotonated NHC: C,N-bridged dinuclear iridium and rhodium complexes

Bearing the versatility of N-heterocyclic carbene (NHC) ligands, here density functional theory (DFT) calculations unravel the capacity of coordination of a deprotonated NHC ligand (pNHC) to generate a doubly C2,N3-bridged dinuclear complex. Here, in particular the discussion is based on the combination of the deprotonated 1-arylimidazol (aryl = mesityl (Mes)) with [M(cod)(μ-Cl)] (M = Ir, Rh) generated two geometrical isomers of complex [M(cod){µ-C₃H₂N₂(Mes)-κC2,κN3}]₂). The latter two isomers display conformations head-to-head (H-H) and head-to-tail (H-T) of C_S and C₂ symmetry, respectively. The isomerization from the H-H to the H-T conformation is feasible, whereas next substitutions of the cod ligand by CO first, and PMe₃ later confirm the H-T coordination as the thermodynamically preferred. It is envisaged the exchange of the metal, from iridium to rhodium, confirming here the innocence of the nature of the metal for such arrangements of the bridging ligands.

Transition metal (Rh and Fe) complexes and main-group (Se and B) adducts with N,N′-diphosphanyl NHC ligands: a study of stereoelectronic properties

The reactions ofN,N′-bis(di-tert-butylphosphanyl)-imidazole-2-ylidene (PCNHCP) with [Rh(μ-Cl)(COD)]₂, [Rh(μ-Cl)(CO)₂]₂, [Fe₄Cl₈(THF)₆], elemental Se and [(C₆F₅)BO]₃, have been investigated to evaluate the stereoelectronic properties of this hybrid ligand.