On the Road to MM′X Polymers: Redox Properties of Heterometallic Ni···Pt Paddlewheel Complexes

Abstract

On the quest of heterometallic mixed-valence MM'X chains, we have prepared two stable discrete bimetallic compounds: the reduced (PPN)[ClNi(μ-OSCPh)4Pt] (PPN = bis(triphenylphosphine)iminium; OSCPh = benzothiocarboxylato) and the oxidized [(H2O)Ni(μ-OSCPh)4PtCl] species. The role of the aqua and chlorido axial ligands is crucial to facilitate oxidation of the {Ni(μ-OSCPh)4Pt} core. Experimental and theoretical analyses indicate that a NiPt-Cl/Cl-NiPt isomerization process occurs in the oxidized species. The electronic structure of the reduced system shows two unpaired electrons, one located in a d(x(2)-y(2)) orbital of the Ni(II) ion and a second in the antibonding d(z(2)-dz(2)) combination from the Ni(II) and Pt(II) centers. Oxidation occurs by removing one electron from this second multicenter molecular orbital. Although the mixed-valence character of the oxidized species makes the isolation of MM'X chains very attractive, such polymeric structure is prevented by the low Pt-Cl···Ni interaction energy and the high tendency of Ni centers to coordinate water molecules. Thus, this work offers valuable insights and hints to engage the production of heterometallic mixed-valence MM'X chains, which still is a challenging task.

Thiocyanate-Ligated Heterobimetallic {PtM} Lantern Complexes Including a Ferromagnetically Coupled 1D Coordination Polymer

“…The two monothiocarboxylate lantern compounds related by a redox couple and ligand rearrangement, namely (PPN)[PtNi(tba) 4 Cl] and [ClPtNi(tba) 4 (OH 2 )], were studied. 49 Oxidation of the former did not allow formation of a {PtNiCl} chain because the Cl ligand migrated to Pt, whereas Ni remained five coordinate by coordinating one H 2 O. Herein, we report the synthesis and characterization of eight isothiocyanate-ligated heterobimetallic lantern complexes, including the first example of a Pt−Mn lantern complex, a highly rare example of an isothiocyanate-bridging lantern complex, 50 and the first example of isothiocyanate bridges between Cr and Pt in any structure. The {PtCr(NCS)}containing compound demonstrates a heterobimetallic mixedvalent chain.…”

“…Thiocyanate has previously been shown to bridge metal centers into 1D, − 2D, − and 3D − arrays and has been used as a terminal axial ligand for lantern complexes, including homometallic Cr and Ru , cores, a trinuclear {FeCr 2 } species, and extended metal atom chains (EMACs). − The same hard–soft interactions that ensure homoleptic coordination in our lantern complexes should facilitate directional binding in a 1D system with the harder 3 d metal favoring coordination to N and the softer Pt favoring coordination to S, producing a repeating {PtM-NCS} unit. The two monothiocarboxylate lantern compounds related by a redox couple and ligand rearrangement, namely (PPN)­[PtNi­(tba) 4 Cl] and [ClPtNi­(tba) 4 (OH 2 )], were studied . Oxidation of the former did not allow formation of a {PtNiCl} chain because the Cl ligand migrated to Pt, whereas Ni remained five coordinate by coordinating one H 2 O.…”

Ionic-caged heterometallic bismuth–platinum complex exhibiting electrocatalytic CO2 reduction

“…-0.28 and -0.64 V vs. NHE come from the dissociation of the solvent molecule from the Pt ion and the dimerization process, respectively. 16 The pair centered at ca. -0.80 V vs. NHE were assigned to the redox reactions of [BiPt(SAc)4] + ↔ [BiPt(SAc)4]on the basis of the theoretical value of -0.78 V vs. NHE as determined using the model shown in Figure S9.…”

Paramagnetic Metal–Metal Bonded Heterometallic Complexes

“…The Doerrer and Zamora groups have used thiocarboxylate ligands tba and SAc, while the Berry group has used 2-thiopyridone (PyS). 109,110,[112][113][114][115]123 Interestingly, Vargaftik and co-workers have shown conclusively that HSAB ligand design is not absolutely necessary to support heterobimetallic compounds containing Pd or Pt−their group has utilized the simple acetate ligand. 99−104…”

“…Both Doerrer and Berry laboratories have taken advantage of similar HSAB principles to form C 4 symmetric compounds using the ligands shown in Figure . The Doerrer and Zamora groups have used thiocarboxylate ligands tba and SAc, while the Berry group has used 2-thiopyridone (PyS). ,,− , Interestingly, Vargaftik and co-workers have shown conclusively that HSAB ligand design is not absolutely necessary to support heterobimetallic compounds containing Pd or Pt–their group has utilized the simple acetate ligand. − …”