Binuclear Intermediates in Oxidation Reactions: [(Me₃SiC≡C)Me₂(bipy)Pt−PtMe₂(bipy)]⁺ in the Oxidation of Pt^IIMe₂(bipy) (bipy = 2,2′-Bipyridine) by IPh(C≡CSiMe₃)(OTf) (OTf = Triflate)

Abstract

A study of the reaction of PtMe(2)(bipy) with IPh(C[triple bond]CSiMe(3))(OTf) at low temperature in acetone, leading to detection of the Pt-Pt-bonded cation [Pt(2)Me(4)(C[triple bond]CSiMe(3))(bipy)(2)](+), an intermediate in the oxidation of Pt(II) to Pt(IV), is reported. The cation is assessed as Pt(III)-Pt(III) <--> Pt(IV)-Pt(II), and at the other extreme may be regarded as a cationic alkynylplatinum(IV) center, "[Pt(IV)Me(2)(C[triple bond]CSiMe(3))(bipy)](+)", stabilized by "Pt(II)Me(2)(bipy)" as a donor ligand. The detection and isolation of the [Pt(2)Me(4)(C[triple bond]CSiMe(3))(bipy)(2)](+) cation provides a number of insights into the mechanisms of oxidation reactions.

Diacetylplatinum(II) and ‐platinum(IV) Complexes Bearing κ2‐ and κ3‐Coordinated Tris(pyrazolyl)methane Ligands: Investigations on the Synthesis, Fluxionality, and Reactivity in Relation to the Substitution Pattern of the Ligands

“…[28] To obtain more thermally stable complexes, the sixth coordination site of the platinum(IV) center has to be occupied by an additionally added anionic donor like iodide [28] or an neutral N donor like pyridine [29] because the anionic part of the alkynyliodonium salts requires the incorporation of nonnucleophilic anions like triflate, tetrafluoridoborate, or tosylate. [30] The use of diacetylplatinum(II) complexes with κ 2 -coordinated tris(pyrazolyl)methane ligands in such reactions should open the possibility to synthesize cationic alkynyl platinum(IV) complexes when the pendant pyrazolyl ring coordinates to the sixth coordination site.…”

“…Synthesis of alkynyl(dimethyl)platinum(IV) complexes. [28] yl)platinum(IV) complexes 8 (Scheme 5). The reactions were performed at -78°C in dichloromethane, and after addition of the first drops of the alkynyliodine(III) reagent, the color of the reaction mixture immediately turned dark red.…”

Oxidation of Half-Lantern Pt2(II,II) Compounds by Halocarbons. Evidence of Dioxygen Insertion into a Pt(III)–CH3 Bond

“…5,6 However, these reactions very often follow an S N 2 pathway, 7−11 with the metal center acting as nucleophile through the filled d z 2 orbital. In addition, Puddephatt and Canty have shown that OA to Pt(II) complexes of planar diimines follow a binuclear stepwise mechanism, with two π−stacked units involved in the initial oxidation step, 12,13 providing evidence of the role of metallophyllic interactions on the chemical reactivity of mononuclear d 8 complexes.…”

Alkynylation with Hypervalent Iodine Reagents

“…Stang and co-workers also demonstrated that reaction of platinum(0) complex 20 with alkynyliodonium triflate yielded alkynyl platinum(II) complexes after careful optimization of the reaction conditions (Scheme 2.10, A [92]). Canty and co-workers then further used the strong oxidizing properties of alkynyliodonium salts to access alkynyl-metal complexes in high oxidation states [93][94][95][96][97][98]. They first demonstrated that platinum(II) pincer complex 21 could be oxidized to platinum(IV) alkynyl complex 22 in 91% yield using alkynyliodonium triflate 14 as reagent (Scheme 2.10, B [93]).…”

“…They were also able to synthesize the corresponding palladium(IV) complex 25 and characterize it at low temperature, as it decomposed readily at room temperature [94]. In 2009, Canty and co-workers were also able to characterize a rare Pt dimer complex 27 at -80 °C, obtained by reacting Pt(II) bipyridine complex 26 with half an equivalent of alkynylodonium triflate 14 (Scheme 2.11) [98]. In principle, 27 can be considered as either a Pt(III) or a Pt(II)-Pt(IV) dimer.…”