Expanding the Scope of Ligand Substitution from [M(S₂C₂Ph₂] (M = Ni²⁺, Pd²⁺, Pt²⁺) To Afford New Heteroleptic Dithiolene Complexes

Abstract

The scope of direct substitution of the dithiolene ligand from [M(SCPh)] [M = Ni (1), Pd (2), Pt (3)] to produce heteroleptic species [M(SCPh)L] (n = 1, 2) has been broadened to include isonitriles and dithiooxamides in addition to phosphines and diimines. Collective observations regarding ligands that cleanly produce [M(SCPh)L], do not react at all, or lead to ill-defined decomposition identify soft σ donors as the ligand type capable of dithiolene substitution. Substitution of MeNC from [Ni(SCPh)(CNMe)] by L provides access to a variety of heteroleptic dithiolene complexes not accessible from 1. Substitution of a dithiolene ligand from 1 involves net redox disproportionation of the ligands from radical monoanions, SSCPh, to enedithiolate and dithione, the latter of which is an enhanced leaving group that is subject to further irreversible reactions.

A Mixed-Valence Tetra-Nuclear Nickel Dithiolene Complex: Synthesis, Crystal Structure, and the Lability of Its Nickel Sulfur Bonds

“…In 2011, Neves et al [35] reported an interesting mixed-valence tetra-nuclear nickel dithiolene complex [K(18-crown-6)] 2 [Ni 4 (α-tpdt) 4 ] (α-tpdt = 2,3-thiophenedithiolate) with a structure that was unique at that time and constitutes the only known analog of the novel tetrameric complex which is presented here. The originally targeted nickel dithiolene complex in the present investigation was initially merely of interest as a dithiolene ligand transmitter to a molybdenum center in a procedure, which typically works rather well and is commonly applied in our group [21,[23][24][25]50,51]. With the specific ligand system used (a dithiolene with one phenyl substituent on one carbon of the ene function and one carboxylic acid ethyl ester group on the other), the reaction did not turn out as expected.…”

“…From the very beginning of dithiolene chemistry, nickel has always been an integral part of many respective investigations, either in the course of the synthesis of dithiolene ligands [21,22] as a dithiolene ligand transmitter to other metal ions (e.g., molybdenum or tungsten) [21,[23][24][25][26][27] or as a central metal of interest for potential applications [7,[28][29][30][31][32][33]. Such applications of dithiolene-bearing compounds include molecular materials with conducting [34], magnetic [35,36], and optical [37] properties on account of their unique electronic structure.…”

Group 10 Metal Dithiolene Bis(isonitrile) Complexes: Synthesis, Structures, Properties, and Reactivity

“…The following is a better-yielding alternative to a preparation reported earlier . A solution of [Et 4 N] 2 [Ni­(CN) 4 ] (0.035 g, 0.083 mmol) in 10 mL of MeCN (10 mL) was added to a solution of 4a (0.030 g, 0.078 mmol) in 10 mL of MeCN, which produced a change in color from dark blue to maroon.…”

“…As detailed in a recent account, we were motivated to survey the generality of dithiolene extrusion from [(R 2 C 2 S 2 ) 2 M] to form [(R 2 C 2 S 2 )­ML 2 ] beyond the limited bounds of Schrauzer’s work because of the potential we saw for the use of [(R 2 C 2 S 2 )­ML 2 ] compounds in the targeted synthesis of complex multimetal dithiolene complexes. The syntheses of [(Ph 2 C 2 S 2 )­M­(CNR) 2 ] (M = Ni 2+ , Pd 2+ , Pt 2+ ; R = Me, Cy, t Bu, 1-Ad, Ph) were disclosed in that report as well as a preliminary study of the further reactivity of [(Ph 2 C 2 S 2 )­Ni­(CNMe) 2 ].…”

Diradical Character of Neutral Heteroleptic Bis(1,2-dithiolene) Metal Complexes: Case Study of [Pd(Me2timdt)(mnt)] (Me2timdt = 1,3-Dimethyl-2,4,5-trithioxoimidazolidine; mnt2– = 1,2-Dicyano-1,2-ethylenedithiolate)

“… 37 − 39 Notably, different optical properties in the visible–near-infrared (vis–NIR) region are associated with the differently charged forms of bis(1,2-dithiolene) complexes (electrochromism). 16 , 40 , 56 Neutral complexes [M L 2 ] show a peculiar intense absorption in the region above 800 nm. 2 , 5 , 30 This band, attributed to a π–π* HOMO → LUMO (H → L) one-electron excitation, 5 , 6 is shifted to lower energies and lowered in intensity in the corresponding monoreduced forms [M L 2 ] − , 41 while the dianions [M L 2 ] 2– do not show any vis–NIR absorption.…”