Redox Multifunctionality in a Series of Pt^II Dithiolene Complexes of a Tetrathiafulvalene‐Based Diphosphine Ligand

Abstract

The redox-active and chelating diphosphine, 3,4-dimethyl-3',4'-bis(diphenylphosphino)-tetrathiafulvalene, denoted as P2, is engaged in a series of platinum complexes, [(P2)Pt(dithiolene)], with different dithiolate ligands, such as 1,2-benzenedithiolate (bdt), 1,3-dithiole-2-thione-4,5-dithiolate (dmit), and 5,6-dihydro-1,4-dithiin-2,3-dithiolate (dddt). The complexes are structurally characterized by X-ray diffraction, together with a model compound derived from bis(diphenylphosphino)ethane, namely, [(dppe)Pt(dddt)]. Four successive reversible electron-transfer processes are found for the [(P2)Pt(dddt)] complex, associated with the two covalently linked but electronically uncoupled electrophores, that is, the TTF core and the platinum dithiolene moiety. The assignments of the different redox processes to either one or the other electrophore is made thanks to the electrochemical properties of the model compound [(dppe)Pt(dddt)] lacking the TTF redox core, and with the help of theoretical calculations (DFT) to understand the nature and energy of the frontier orbitals of the [(P2)Pt(dithiolene)] complexes in their different oxidation states. The first oxidation of the highly electron-rich [(P2)Pt(dddt)] complex can be unambiguously assigned to the redox process affecting the Pt(dddt) moiety rather than the TTF core, a rare example in the coordination chemistry of tetrathiafulvalenes acting as ligands.

Oxidative access to flexible {Pt2(μ-SAr)2} square motifs from platinum thiolato complexes with chelating diphosphine

“…This result contrasts strongly with those described earlier for (P2)Pt(dithiolene) complexes incorporating a chelating 1,2-dithiolate moiety, where the intensity of the (M þ þ 1) peak was reported to be 100% [10]. This behavior also indicates that the bis(monothiolate) complexes described herein are less stable than their corresponding dithiolate analogs, which is a consequence of the absence of the chelate effect.…”

“…The thiolate (P2)Pt(SAr) 2 complexes where SAr is benzenethiolate (BT), or 3,5-dimethylbenzenethiolate (DMBT), were prepared as previously described for dithiolene complexes [10,11], by the metathesis reaction of (P2)PtCl 2 [9g] with the corresponding arylthiols (ArSH) in the presence of NEt 3 (Scheme 4). Purification by column chromatography afforded the products in 60% yield.…”

“…Similarly, in tetrathiafulvalenyl-based (P2)Pt(dithiolene) complexes such as (P2)Pt(dmit) or (P2)Pt(dddt) (Scheme 3) [10,11], up to four oxidation waves were identified, which were attributed to the sequential oxidation of the independent redox moieties, namely the TTF core on the one hand and the Pt(dddt) moiety on the other hand.…”

“…Mononuclear systems with {P 2 PtS 2 } coordination motifs are especially attractive in this respect, specifically those with chelating dithiolate ligands or with redox active diphosphines such as 1,1 0 -bis(diphenylphosphino)ferrocene (dppf) [7,8] or 3,4-dimethyl-3 0 ,4 0 -bis(diphenylphosphino) tetrathiafulvalene (hereafter, abbreviated as P2) [9e11]. Indeed, the 16-electron (diphosphine)Pt(dithiolene) complexes, for example, (dppe)Pt(dmit) [12] (dmit: 2-thio-1,3-dithiole-4,5-dithiolato; dppe: 1,2-bis(diphenylphosphino)ethane) or (dppe)Pt(dddt) [10] (dddt: 4,5-dihydro-1,4-dithiine-2,3-dithiolato) (Scheme 1), have shown reversible oxidation as the cation radical state. This is attributed to the non-innocent character of the dithiolene ligands.…”

Ambipolar Discotic Liquid Crystals Built Around Platinum Diimine‐Dithiolene Cores

“…[2,2′‐Bipyridine]‐4,4′‐dicarboxylic acid, 3,4,5‐tris(dodecyloxy)aniline, bis[1,2‐bis(3′,4′‐di‐ n ‐dodecyloxyphenyl)ethane‐1,2dithiolene]nickel (complex 6 ), 4′‐[(10‐bromodecyl)oxy]‐4‐carbonitrile‐[1,1′‐biphenyl], dichloro(4,4′‐di‐ tert ‐butyl‐2,2′‐bipyridine)platinum(II) ([PtCl 2 ( t bu 2 bpy)]) (complex 4 c ), dichloro(2,2′‐bipyridine)platinum(II) ([PtCl 2 (bpy)]) (complex 4 d ), 2,2‐dibutyl‐5,6‐dihydro‐1,3,2‐dithiastannolo[4,5‐ b ][1,4]dithiin (complex 5 ), and PtCl 2 (DMSO) 2 were synthesized as previously described. All the other reagents were purchased from commercial sources and used as received.…”