The Evolution of [{Ph₂P(CH₂)_nPPh₂}Pt(μ‐S)₂Pt{Ph₂P(CH₂)_nPPh₂}] (n=2, 3) Metalloligands in Protic Acids: A Cascade of Sequential Reactions

Abstract

Given the nucleophilicity of the [Pt(2)S(2)] ring, the evolution of [Pt(2)(mu-S)(2)(P intersection P)(2)] (P intersection P=1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp)) metalloligands in the presence of the simplest electrophilic species, the proton, has been studied. Combined use of experimental and theoretical data has allowed the whole set of reactions ensuing the protonation of the [Pt(2)S(2)] core to be established. The titration of [Pt(2)(mu-S)(2)(P intersection P)(2)] with HCl or HClO(4) was monitored mainly by (31)P[(1)H] NMR and mass techniques. Characterization of all the species involved was completed with the determination of the crystal structure of [Pt(SH)(2)(P intersection P)], for dppe and dppp, and [Pt(3)(mu(3)-S)(2)(dppp)(3)](PF(6))(2). The first protonation step of the [Pt(2)S(2)] core leads to the stable [Pt(2)(mu-S)(mu-SH)(P intersection P)(2)](+) complex, but the second step implies disintegration of the ring, thus giving rise to various mononuclear species. The subsequent evolution of some of these species allows regeneration of [Pt(2)(mu-S)(mu-SH)(P intersection P)(2)](+), evidencing the cyclic nature of this process. Whereas the reaction pathway is essentially common for both phosphine ligands, dppe and dppp, the different coordinating ability of Cl(-) or ClO(4) (-) determines the nature of the final products, [PtCl(2)(P intersection P)], [Pt(3)(mu(3)-S)(2)(P intersection P)(3)]Cl(2) or [Pt(3)(mu(3)-S)(2)(P intersection P)(3)](ClO(4))(2). DFT calculations have corroborated the thermodynamic feasibility of the reactions proposed on the basis of experimental data.

“To Bend or not To Bend?” Both! The Planar and Bent Structures of[(Ph3P)4Rh2(μ‐F)2]

“…We note also that B3LYP calculations have been shown to provide excellent results for the analysis of bending of dinuclear complexes similar to the ones studied here. [18] These results, combined with the structural information of the short contacts between the bridging fluoride ions and the phenyl groups of the phosphanes, suggest that the F···Ph interactions may govern the choice between the planar and bent forms. Therefore, we studied the interaction between [(H 3 P) 4 Rh 2 (µ-F) 2 ] and an independent benzene molecule.…”

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

“…However, as commented below, the presence of HCl is inconvenient as it can cause disintegration of the {Pt(µ-S) 2 Pt} core. [10] Overall, the first pathway offers more advantages and becomes particularly adequate when the solubility of [L 2 Pt(µ-S) 2 PtL 2 ] in the organic solvent used is high, and thus its separation from unreacted Na 2 S·9H 2 O and formed NaCl is feasible. This requirement is best accomplished by the chelating diphosphanes 1,2-bis(diphenylphosphanyl)ethane (dppe) or 1,3-bis(diphenylphosphanyl)propane (dppp) than by PPh 3 .…”

“…Combination of experimental results and theoretical calculations has allowed for a detailed knowledge of the cascade of reactions of [L 2 Pt(µ-S) 2 PtL 2 ] in the presence of either organic electrophiles, such as CH 2 Cl 2 , [9] or the simplest electronacceptor species, the proton. [10] In addition, the influence of {Pt(µ-S) 2 Pt} core on the reactivity of LЈ in [{L 2 Pt(µ 3 -S) 2 PtL 2 } x MLЈ y ] z aggregates has been explored. [11] All these results promise to inspire new approaches that contribute towards the unveiling of the potential of [L 2 Pt(µ-S) 2 PtL 2 ] compounds as nucleophilic agents.…”

“…Our approach has focused on the use of chelating diphosphanes as terminal L ligands, [12] with an emphasis on the chemistry of [L 2 Pt(µ-S) 2 tal electrophiles [9,10] and MLЈ y fragments. [11] This report surveys the present knowledge on the nucleophilicity of the {Pt(µ-S) 2 Pt} core in [L 2 Pt(µ-S) 2 PtL 2 ] compounds; the previous review by Fong and Hor is our starting point.…”

Hydrogen Bonding in Crystalline Alcohol Solvates of the Platinum(II) Sulfido Complex [Pt2(μ‐S)2(PPh3)4]

“…Subsequently, detailed experimental and theoretical studies of the protonation chemistry of complexes with {Pt 2 (µ-S) 2 } cores have been carried out by González-Duarte and co-workers, such that this chemistry is now well understood. [6][7][8] During our investigations into the chemistry of 1, invariably carried out using methanol (occasionally ethanol) sol- 4 ]·6(CF 3 ) 2 CHOH on evaporation. Characterisation by X-ray diffraction shows that the structure contains a [Pt 2 (µ-S) 2 (PPh 3 ) 4 ] hydrogen-bonded to a single (CF 3 ) 2 CHOH molecule, with the additional (CF 3 ) 2 CHOH molecules forming a discrete hydrogen-bonded pentameric cluster in the crystal.…”