Asymmetric by Design: Heteroleptic Coordination Compounds with Redox-Active Dithiolene and 1,2,4,5-Tetrakis(isopropylthio)benzene Ligands

Che Wu; Lakshmi Nishanth Kakarla; Chandru P Chandrasekaran; Xiaodong Zhang; Joel T Mague; Stephen Sproules; James P Donahue

doi:10.1021/acs.inorgchem.3c02928

Asymmetric by Design: Heteroleptic Coordination Compounds with Redox-Active Dithiolene and 1,2,4,5-Tetrakis(isopropylthio)benzene Ligands

Inorg Chem. 2024 Jan 8;63(1):173-183. doi: 10.1021/acs.inorgchem.3c02928. Epub 2023 Dec 22.

Authors

Che Wu¹, Lakshmi Nishanth Kakarla², Chandru P Chandrasekaran², Xiaodong Zhang¹, Joel T Mague¹, Stephen Sproules³, James P Donahue¹

Affiliations

¹ Department of Chemistry, Tulane University, 6400 Freret Street, New Orleans, Louisiana 70118-5698, United States.
² Department of Chemistry and Biochemistry, Lamar University, Beaumont, Texas 77710, United States.
³ WestCHEM, School of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom.

Abstract

The 1,2,4,5-tetrakis(alkylthio)benzenes are redox-active organosulfur molecules that support oxidation to a stable radical cation. Their utility as ligands for the assembly of multimetal complexes with tailored functionality/property is unexamined. Here, 1,2,4,5-tetrakis(isopropylthio)benzene (tptbz, 1) is shown to bind PdCl₂ at either one end, leaving the other open, or at both ends to form centrosymmetric [Cl₂Pd(tptbz)PdCl₂], 4. Ligand metathesis between Na₂[(N≡C)₂C₂S₂] (Na₂mnt) and [Cl₂M(tptbz)] (M = Pd, 2; M = Pt, 3) yields [(mnt)M(tptbz)] (M = Pd, 5; M = Pt, 6), but an alternative route involving transmetalation with [(mnt)SnMe₂] delivers substantially greater yield. The mixed dithiolene-dithioether compound [(Ph₂C₂S₂)Pt(tptbz)] (8) is formed by a similar transmetalation protocol using [(Ph₂C₂S₂)SnⁿBu₂]. Compounds 5, 6, and 8 are the first such heteroleptic complexes prepared by deliberate synthesis. The cyclic voltammetry of 8 reveals anodic waves at +0.14 and +0.97 V vs Fc⁺/Fc, which are attributed to successive dithiolene oxidation processes. While oxidized at +0.73 V as a free ligand, the redox-active MO of tptbz is pushed to a higher potential upon coordination to Pt²⁺ and is inaccessible. Calculations of the structures of [8]⁺ and of [((Cl₂-3,5-C₆H₃)₂C₂S₂)Pt(tptbz)]⁺ show that, in the latter, the dithiolene MOs are drawn down in energy into proximity with the tptbz MOs.