Heterobimetallic and Heterotrimetallic Clusters Containing a Redox‐Active Metalloligand

Abstract

A new multimetallic construct has been developed utilizing a redox-active metalloligand. The molybdenum complex, Mo[SNS] 2 {1; [SNS]H 3 = bis(2-mercapto-p-tolyl)amine}, has been shown to coordinate to Ni(dppe) {dppe = 1,2bis(diphenylphosphanyl)ethane} through two cis thiolate donors to generate heterobimetallic Mo[SNS] 2 Ni(dppe) (2) and heterotrimetallic Mo[SNS] 2 {Ni(dppe)} 2 (3). X-ray diffraction studies confirm the presence of formal metal-metal bonds between [a] 5574 electron distribution. Given the evidence for a direct communication pathway between the two nickel centers in neutral 3, it is surprising that 3 + shows localized behavior. Current efforts are aimed at understanding the communication pathways resulting in this non-coupled mixed-valent system.

Hydrogen-Atom Noninnocence of a Tridentate [SNS] Pincer Ligand

“…For both PCy 3 and PPh 3 derivatives, these anionic nickel complexes contained diamagnetic, square-planar, nickel­(II) centers. The [SNS] ligand in [ 2a ] ⊖ and [ 2b ] ⊖ is consistent with a trianionic pincer-type ligand, as has been previously observed when the ligand is coordinated to tungsten or molybdenum. ,− When metalation of the [SNS] ligand platform was carried out in air, oxidized versions of the nickel complexes were obtained. In the case of the PCy 3 derivative, 3a , the product was a square-planar, S = 1 / 2 nickel complex.…”

Molybdenum imidazole citrate and bipyridine homocitrate in different oxidation states – balance between coordinated α-hydroxy and α-alkoxy groups

“…Until now, a number of citrate or imidazole molybdenum complexes have been reported, while there is less interest on the mixed-ligand complexes of citrate and imidazole. 45,47,[56][57][58][59] Most of the mixed-valence molybdenum complexes focus on Mo(VI)/ Mo(V) and Mo(V)/Mo(IV), [47][48][49][50][51][52][53][54] fewer examples of Mo(VI)/Mo(IV) have been reported. 55 2were obtained from an aqueous solution.…”

“…44 The latter also contains octanuclear molybdenum complexes [Mo 8 O 26 (im) 2 ] 4À with imidazole from histidine residue as polyoxometalates. [44][45][46] It is noted that most of the mixed-valence molybdenum complexes are in VI/V and V/IV, [47][48][49][50][51][52][53][54] while molybdenum(VI/IV) complex is less common. 55…”

Heterodinuclear Ni/M (M = Mo, W) Complexes Relevant to the Active Site of [NiFe]-Hydrogenases: Synthesis, Characterization, and Electrocatalytic H2 Evolution

“…Although the electrochemical properties of some dinuclear Ni II /M 0 (M = Mo, W), ,, Ni I /Mo V or Ni 0 /Mo VI , and Ni I /W V complexes were previously studied by means of CV techniques, the electrochemical and electrocatalytic properties of dinuclear Ni II /M II (M = Mo, W)-based [NiFe]-H 2 ase models have not been systematically investigated, so far. To know the electrochemical properties of our Ni II /M II complexes, we chose 2a , b and 4b , c as representatives (note that 2a , b and 4b , c are suitable representatives of 2a – c and 4a – c since they contain all the different metals Mo/W and different substituents R 1 /R 2 included in 2a – c and 4a – c ) to determine their cyclic voltammograms by using n -Bu 4 NPF 6 as the supporting electrolyte in MeCN at a scan rate of 100 mV s –1 .…”

“…45 Electrochemical Properties of Dinuclear Ni II /M II (M = Mo, W) Complexes 2a,b and 4b,c. Although the electrochemical properties of some dinuclear Ni II /M 0 (M = Mo, W), 40,43,46 Ni I /Mo V or Ni 0 /Mo VI , 47 48,49 In addition, since the first reduction wave of stronger electron-donating group p-MeC 6 H 4 CH 2 -substituted complex 2a (−1.36 V) is remarkably shifted negatively up to 50 mV relative to that of weaker Table 1. Electrochemical Data of 2a,b and 4b,c 54,55 To compare the electrocatalytic activity of 2a,b and 4b,c, we determined the ratio of the catalytic current (i cat ) to reductive peak current (i p ) in the absence of TFA as well as the corresponding turnover frequencies (TOFs); note that a higher i cat /i p or TOF value means faster catalysis.…”