49638-64-4Relevant academic research and scientific papers
Experimental and theoretical studies on the mechanism of the C-S bond activation of PdII thiolate/thioether complexes
Kumar, Sushil,Guyon, Fabrice,Knorr, Michael,Labat, Stéphane,Miqueu, Karinne,Golz, Christopher,Strohmann, Carsten
, p. 1303 - 1321 (2017/05/29)
Two equivalents of L (L = 4-methylthio-2-thioxo-1,3-dithiole-5-thiolate or Medmit) react with cis-Pd- (PR3)2Cl2 (R = Ph and Et) to afford Pd(PR3)(η1-L)(η2-L) (R = Et: 1 ; R = Ph: 2) complexes, which have been characterized by X-ray crystallography. These compounds are dynamic in solution due to an exchange of the thiomethyl groups on palladium. Variable-temperature 1H NMR spectroscopy reveals a low coalescence temperature (173 K). Treatment of Pd(diphos)Cl2 (diphos = dppe or dppm) with 2 equiv of L affords thiolato complexes Pd(dppe)(η1-L)2 (3) and Pd(dppm)(η1-L)2 (4). Whereas 3 is rigid in solution with firm η2-coordination of dppe and η1-coordination of the thiolate, two linkage isomers Pd(η2-dppm)(η1-L)2 and Pd(η1-dppm)(η1-L)(η2-L) coexist in a solution of 4. L coordinated on PdII undergoes a S-demethylation reaction leading to dithiolene complexes and MeL. This transformation requires high temperature, and its efficiency depends on the nature of the phosphines as well as the nature of the metal (Pd vs Pt). DFT calculations reveal that the most likely mechanism depends on the lability of phosphines. Starting from M(PR3)2(η1- L)2 (M= Pd and Pt; R = Ph and Et), the favored sequence implies decoordination of one triethyl phosphine (M(PEt3)(η1-L)(η2- L)2 as intermediate) or two triphenylphosphines (Pd(η2-L)2 as intermediate) followed by oxidative addition and reductive elimination (OA/RE) reactions. In the case of PEt3, this OA/RE sequence can also compete with an intramolecular nucleophilic addition (AN), which can be described as an attack of a thiolate sulfur atom on a CH3+ carbocation. An intramolecular SN2 process was found to be the most feasible, starting from M(dppe)(η1-L)2 (M= Pd and Pt), with the nucleophile approaching the thiomethyl group at an angle of 180° with respect to the CCH3-S bond. The influence of the coligand has also been studied experimentally. Structurally characterized disulfide L-L dimer has been isolated upon reaction of 2 equiv of L with MCl2 (M = Pd and Pt).
Synthesis of pyrazinoporphyrazine derivatives functionalised with tetrathiafulvalene (TTF) units: X-ray crystal structures of two related TTF cyclophanes and two bis(1,3-dithiole-2-thione) intermediates
Wang, Changsheng,Bryce, Martin R.,Batsanov, Andrei S.,Howard, Judith A. K.
, p. 1679 - 1690 (2007/10/03)
The pyrazinoporphyrazine system 13 (metal-free, zinc and copper derivatives) has been synthesised by tetramerisation of 2,3-dicyanopyrazine monomer unit 10. The structure of 13a-c has been established by HNMR spectroscopy, UV/Vis spectrophotometry, MALDI-TOF mass spectrometry, cyclic voltammetry and differential pulse voltammetry. The electrochemical redox behaviour of 13a-c is strongly solvent dependent. The expected two-stage oxidation of the tetrathiafulvalene (TTF) units of 13a-c was observed in a range of solvents; in addition, oxidation and reduction of the pyrazinoporphyrazine core of the metal-free derivative 13a was detected in benzonitrile. On excitation of 13 in the Q-band region no fluorescence was observed, which is presumably the consequence of intramolecular charge transfer between the TTF moieties and the excited state of the central porphyrazine. Molecular modelling studies on 13a and 13c are reported. During the course of this work, the novel TTF macrocycles 11 and 20 were synthesised; their X-ray crystal structures reveal severely bent TTF units, the conformations of which are discussed in detail. The X-ray crystal structures of the bis(1,3-dithiole) systems 15 and 18 have also been determined.
