Coinage Metal Complexes of Tris(pyrazolyl)methanide-Based Redox-Active Metalloligands

Abstract

A series of coinage metal complexes containing the redox-active metalloligands [RuCp X (κ 3 N-Tpmd)] {κ 3 N-Tpmd = κ 3 N-[C(pz) 3 ] with pz = pyrazolyl; [RuCp(Tpmd)] (2a) and [RuCp*(Tpmd)] (2b)} are presented. 2a and 2b are isolable, relatively stable compounds, despite the fact that they feature a "naked" carbanion at the bridgehead position of the κ 3 N-coordinated tris(pyrazolyl)methanide ligand scaffold. As expected, both complexes act as κ 1 C ligands toward coinage metal fragments to yield dinuclear complexes of the general formulaAll complexes under study were fully characterized by common spectroscopic techniques; the structural parameters of 2a, 3a, 5a, 6a, 7a, and 10a were determined by X-ray diffraction. Coordination of the {MX} fragment leads to electronic effects on the metalloligand unit, as reflected by the corresponding 1 H and 13 C NMR spectra. Density functional theory calculations were performed in order to elucidate a conceivable interplay between the metal atoms. The bonding characteristics within the {MX} fragment are only marginally affected upon electronic excitation of the ruthenium-based metalloligand. However, some effect of the influence of {MX} on the E 0 1/2 (Ru II /Ru III ) value was detected with the aid of cyclic voltammetry measurements. A strong Lewis-acidic metal fragment such as GaCl 3 (11a) leads to an E 0 1/2 value of 0.37 V, while electron-richer coinage metal fragments facilitate the oxidation of the ruthenium center significantly (E 0 1/2 = 0.14−0.23 V). This dependence suggests an interaction between both metals due to their close spatial proximity.

Synthesis, Spectroscopy, and Redox Studies of Ferrocene-Functionalized Coinage Metal Alkyne Complexes

“…Supporting ligands are mostly organic compounds exhibiting two or more donor sites or, as shown in this work, derivatives of acetylene . Because of their ability to coordinate to metal ions via both σ- and π-bonding modes, acetylenes allow a close proximity of the metal centers; thus, the formation of strong metal–metal interactions is promoted. , In coinage metal compounds, metallophilicity is regarded as an important criterion for photoluminescence, molecular recognition, optical switches, and catalysis. − Furthermore, metal alkyne complexes are believed to be key intermediates in metal-catalyzed transformations of alkynes. − However, to date, comparably few redox studies dealing with coinage metal complexes have been carried out. ,− Investigation of the redox properties of copper complexes, in particular, is beneficial for the development and understanding of copper-promoted cross-couplings (e.g., Chan–Lam coupling). , Therefore, an in-depth understanding of the cooperative interaction between metals, including the rationalization of structures and varying bonding modes, is essential. Ferrocene is the epitome of an organometallic moiety that displays a well-behaved, reversible, one-electron redox process.…”

Tris(pyrazolyl)methanide Complexes of Trivalent Rare-Earth Metals

“…Tris­(pyrazolyl)­methanide (Chart a) is as a cousin of the widely used tris­(pyrazolyl)­borate (Tp) (Chart b), by replacing the apical [BH] − moiety with the [C] − moiety. Recently, tris­(pyrazolyl)­methanide has received growing attention due to its feature of bearing an anionic κ 3 -coordinating six-electron-donor pocket, and an increasing number of tris­(pyrazolyl)­methanide metal complexes have been reported . Although several rare-earth-metal complexes bearing neutral tris­(pyrazolyl)­methane have been reported, to the best of our knowledge, only one trivalent rare-earth-metal complex, L ScCl 2 (THF) ( L = tris­(3,5-dimethylpyrazolyl)­methanide), and one divalent rare-earth-metal complex, L ′YbI­(THF) ( L ′ = tris­(3-(1-adamantyl)-5-methylpyrazolyl)­methanide), have been synthesized by the groups of Mountford and Jones .…”

Switching of the redox centers of a tris-2-mercaptophenolato chromium(iii) metalloligand by a guest metal ion

“…[10][11][12][13][14][15][16] As an alternative approach, redox-active metalloligands (MLs) are designable molecular building blocks having various redox properties on their central metals, ligands, and guest metals. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] Recently, fac-[Cr III (mp) 3 ] 3− (mp: 2-mercaptopheno-lato), which represent the first example of ligand-centered redox activity in mp complexes, has been reported. 37 Almost all the reported tris-mp complexes adopt a facial-[O 3 S 3 ] geometry around the metal center because of the trans influence of the three oxygen and three sulfur atoms.…”