Unsymmetrical Platinum(II) Phosphido Derivatives: Oxidation and Reductive Coupling Processes Involving Platinum(III) Complexes as Intermediates

Abstract

Reaction of the trinuclear [NBu 4] 2[(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(R F) 2] ( 1, R F = C 6F 5) with HCl results in the formation of the unusual anionic hexanuclear derivative [NBu 4] 2[{(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(mu-Cl)} 2] ( 4, 96 e (-) skeleton) through the cleavage of two Pt-C 6F 5 bonds. The reaction of 4 with Tl(acac) yields the trinuclear [NBu 4][(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(acac)] ( 5, 48 e (-) skeleton), which is oxidized by Ag (+) to form the trinuclear compound [(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(acac)][ClO 4] ( 6, 46 e (-) skeleton) in mixed oxidation state Pt(III)-Pt(III)-Pt(II), which displays a Pt-Pt bond. The reduction of 6 by [NBu 4][BH 4] gives back 5. The treatment of 6 with Br (-) (1:1 molar ratio) at room temperature gives a mixture of the isomers [(PPh 2R F)(R F)Pt(mu-PPh 2)(mu-Br)Pt(mu-PPh 2) 2Pt(acac)], having Br trans to R F ( 7a) or Br cis to R F ( 7b), which are the result of PPh 2/C 6F 5 reductive coupling. The treatment of 5 with I 2 (1:1 molar ratio) yields the hexanuclear [{(PPh 2R F)(R F)Pt(mu-PPh 2)(mu-I)Pt(mu-PPh 2) 2Pt(mu-I)} 2] ( 8, 96 e (-) skeleton), which is easily transformed into the trinuclear compound [(PPh 2R F)(R F)Pt(mu-PPh 2)(mu-I)Pt(mu-PPh 2) 2Pt(I)(PPh 3)] ( 9, 48 e (-) skeleton). Reaction of [(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(NCMe) 2] ( 10) with I 2 at 213 K for short reaction times gives the trinuclear platinum derivative [(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(I) 2] ( 11, 46e skeleton) in mixed oxidation state Pt(III)-Pt(III)-Pt(II) and with a Pt-Pt bond, while the reaction at room temperature and longer reactions times gives 8. The structures of the complexes have been established by multinuclear NMR spectroscopy. In particular, the (195)Pt NMR analysis, carried out also by (19)F- (195)Pt heteronuclear multiple-quantum coherence, revealed an unprecedented shielding of the (195)Pt nuclei upon passing from Pt(II) to Pt(III). The X-ray diffraction structures of complexes 4, 5, 6, 9, and 11 have been studied. A detailed study of the relationship between the complexes has been carried out.

Reactivity of the phosphinito bridged Pt(i) complex [(PHCy2)Pt(μ-PCy2){κ2P,O-μ-P(O)Cy2}Pt(PHCy2)](Pt–Pt) towards Au(i) and Ag(i) electrophiles

“…S18 ‡) showed an intense peak at m/z: 1567.5285, corresponding to the 10 + cation (exact mass = 1567.5179 Da). The 31 P{ 1 H} NMR spectrum of [10]OTf (Fig. S19 ‡) resembles that of [9]OTf, apart from the additional presence of two signals at δ 7.5 and δ 16.2 which gave an intense exchange peak in the 31 P{ 1 H} EXSY spectrum recorded at 230 K (Fig.…”

“…The Pt 2 -μP bond of 1 constitutes the attack site also for [Au-(PPh 3 )OTf ] (independently from the solvent) and for AgX (X = OTf, BF 4 , ClO 4 , Cl) or [Ag(PPh 3 )OTf ] with formation of the trinuclear clusters [10]X and [10]OTf, respectively, all displaying the [AgX] or [AgPPh 3 ] + group bridging the μ-P-Pt 2 . A covalent nature of the Ag-Cl bond in 9-Cl is suggested by the HRMS Scheme 8 Reaction of 1 with Ag(PPh 3 )OTf.…”

“…‡ Electronic supplementary information (ESI) available: 31 P{ 1 H} NMR spectrum of 4, 7, [9]X (X = OTf, ClO 4 , BF 4 , Cl), [10]OTf; 31 P NMR spectrum of 4, 31 P{ 1 H} NOESY-EXSY of [10]OTf, 195 Pt{ 1 H} NMR spectrum of 4, [6]OTf, 7, [9]OTf; HRMS data of 4, hydride, except in the case of HF (conc) for which a dicationic protonation product containing a bridging hydride (and having structure B) obtained in the first stage of the reaction spontaneously evolves into the more stable monocationic species 2′ + and 2 + having a terminal hydride on Pt 2 (Scheme 1). 4 From the mechanistic point of view, for all studied protonations the reactions start with the proton attack at the oxygen of 1, formation of a six-membered cyclic species and transfer of the proton from the PO to the Pt-Pt bond.…”

“…The reaction of coinage metal based electrophiles with transition metal complexes has long been used for the synthesis of small-size clusters. 7 As far as the reaction of group 11 electrophiles with platinum phosphanido bridged complexes is concerned, most cases deal with platinum(II) compounds and result in (i) the oxidation of the metal [from Pt(II) to Pt(III)] [8][9][10][11] or of the phosphorus ligands; 12,13 (ii) the formation of adducts in which M + bridges two Pt atoms; 11,14 (iii) the formation of adducts in which M + bridges the Pt-μ-P bond; 11,15 (iv) the formation of adducts displaying a single M-Pt bond; 11 (v) halide abstraction. [16][17][18] The reported examples of reactions of Pt(I) dimers with group 11 electrophiles comprise coordination of an [Au(PPh 3 )] + fragment at a Pt-μ-P bond 19 as well as coordination of the electrophile at the Pt-Pt bond.…”

“…Spectroscopic and spectrometric data of[10]OTf. In an NMR tube, solid [Ag(PPh 3 )OTf ] (0.042 g, 0.035 mmol) was added to a toluene-d 8 solution of 1 (0.018 mg, 0.035 mmol in 0.5 mL) at 230 K and the resulting solution was monitored by 31 P NMR at 230 K and used for ESI-MS analysis.HR ESI-MS(+), exact mass for the cation C 66 H 105 AgOP 5 Pt 2 : 1567.5179 Da; measured: m/z: 1567.5285 [M + ].…”