Electrochemical and theoretical study of the redox properties of transition metal complexes with {Pt₂S₂} cores

Abstract

The oxidation processes undergone by the [Pt2(mu-S)2] core in [Pt2(P[intersection]P)2(mu-S)2](P[intersection]P = Ph2P(CH2)nPPh2, n= 2,3) complexes have been analysed on the basis of electrochemical measurements. The experimental results are indicative of two consecutive monoelectronic oxidations after which the [Pt2(mu-S)2] core evolves into [Pt2(mu-S2)]2+, containing a bridging disulfide ligand. However, the instability of the monoxidised [Pt2(P[intersection]P)2(mu-S)2]+ species formed initially, which converts into [Pt3(P[intersection]P)3(mu-S)2]2+, hampered the synthesis and characterisation of the mono and dioxidised species. These drawbacks have been surpassed by means of DFT calculations which have also allowed the elucidation of the structural features of the species obtained from the oxidation of [Pt2(P[intersection]P)2(mu-S)2] compounds. The calculated redox potentials corresponding to the oxidation processes are consistent with the experimental data obtained. In addition, calculations on the thermodynamics of possible processes following the degradation of [Pt2(P[intersection]P)2(mu-S)2]+ are fully consistent with the concomitant formation of monometallic [Pt(P[intersection]P)S2)] and trimetallic [Pt3(P[intersection]P)3(mu-S)2]2+ compounds. Extension of the theoretical study on the [Pt2Te2] core and comparisons with the results obtained for [Pt2S2] have given a more general picture of the behaviour of [Pt2X2](X = chalcogenide) cores subject to oxidation processes.

Extending The Reaction Landscape of the {Pt(μ‐S)2Pt} Core: From Metal Centers to Non‐Metallic Electrophiles

“…From this orbital analysis it can be inferred that a high electron density is located on the bridging chalcogenide ligand, which will thus be responsible for the nucleophilic character of [L 2 Pt(µ-X) 2 PtL 2 ] compounds. The energy of [25] These energy values are consistent with the lower oxidation potentials found for {Pt 2 Te 2 } than for {Pt 2 S 2 } containing complexes.…”

“…[25,26] Thus, DFT calculations for model complexes using simplified terminal phosphane ligands have revealed that in all cases the highest energy occupied molecular orbital (HOMO) consists of an antibonding combination of the chalcogen p π orbitals (p z ). A 3-D plot of this molecular orbital calculated for the model compound [(PH 3 ) 2 Pt(µ-S) 2 Pt(PH 3 ) 2 ] is shown in Figure 2.…”

“…Assignment of the structure corresponding to the species involved in the cyclic voltammogram peaks relied on the theoretical calculations. [25] The cyclic voltammetric measurements were indicative of two consecutive monoelectronic oxidations. In addition, cyclic voltammetric data showed that the radical cation [L 2 Pt(µ-S) 2 PtL 2 ]…”

Computational electrochemistry: prediction of liquid-phase reduction potentials

“…We begin the survey with inorganic compounds. Recent computations of standard reduction potentials include studies of aqueous metal ions, 268,301,304,305,308,321,322,[342][343][344][345] inorganic clusters containing sulfur and iron in different oxidation states, 346,347 systems of various complexity with the Pt 2 X 2 (X = chalcogenide) cores, 348 and the MFe 2 S 4 clusters (M = Mn, Fe, Co, Ni, Cu, Zn, and Mo) in water by testing four different exchange-correlation functionals (B3LYP, BP86, TPSS, and TPSSh) and the COSMO implicit-solvent model. 349 Houk and co-workers 350,351 computed the standard redox potentials of 36 nitrogen oxides and related species in water using a complete basis set extrapolation method (CBS-QB3) for gas-phase free energies and the PCM implicit-solvent model for solvation free energies with use of the Born-Haber thermochemical cycle (Scheme 2).…”

STRUCTURAL AND MASS SPECTROMETRIC CHARACTERISATION OF THE DINUCLEAR PLATINUM(II) SELENIDO-PHENYLSELENOLATO COMPLEX [Pt2(μ-Se)(μ-SePh)(PPh3)4]PF6

“…Dinuclear platinum(II) sulfide complex [Pt 2 (μ-S) 2 (PPh 3 ) 4 ] 1a [ 1 ] and analogues with alternative phosphine [ 2,3 ] or arsine [ 4 ] ligands have been extensively investigated over a considerable length of time [ 5 ] because of the rich and diverse chemistry they display. Reactivity includes alkylation [ 6,7 ] and arylation [ 8,9 ] reactions (generating platinum-thiolate complexes), redox chemistry [ 10,11 ], metalloligand chemistry (whereupon one or both sulfide ligands coordinate to metal centres generating sulfide-bridged homo- [ 12 ] and hetero- [ 13 ] metallic aggregates), and interesting ligandbased reactivity [ 14 ].…”