Platinum(II) and Platinum(IV) Acyl and Formyl Complexes

Reinartz, Stefan; Brookhart, Maurice; Templeton, Joseph L.

doi:10.1021/om010772j

Cited by 36 publications

(40 citation statements)

References 49 publications

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“…[23] Thus, under a CO atmosphere the platinum complex that separates from the medium as a solid contains the acyl moiety trans to the chloro atom. We supposed that, in fact, the formation of the SnCl 3 ligand is reversible, so we decided to add one equivalent of SnCl 2 to the acyl chloro complex.…”

Section: Characterisation Of An Acylplatinum Speciesmentioning

confidence: 99%

Hydride Route for the Palladium‐Catalysed Cyclocarbonylation of Monoterpenes

et al. 2005

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This paper focuses on the mechanism by which a monoterpene undergoes a cyclocarbonylation reaction catalysed by a palladium complex. Evidence is provided, based on intermediate species observed under pressure or with various ligands, that the catalytic cycle follows a hydride route starting from [Pd(H) ( IntroductionPalladium chemistry is currently the workhorse of organic chemistry and is a versatile tool to perform carboncarbon coupling.[1] When appropriate building blocks are introduced the substrate can follow a multistep functionalisation so that tandem reactions open the way for the preparation of rather sophisticated organic molecules.[2] A number of interesting compounds that show biological activity contain a lactone moiety. [3] During the last few years we have explored the introduction of a CO building block into an unsaturated substrate to obtain such a backbone in a one-pot synthesis.[4] We chose to follow an hemisynthetic way starting from an abundant and cheap raw material like monoterpenes. Thus, we functionalised isopulegol and dihydromyrcenol into the corresponding lactones, [4] and then extended this type of tandem reaction to the cyclocarbonylation of isolimonene, which produces a cyclopentanone. [5] All these reactions are an extension of the classical alkoxycarbonylation reaction by which a terminal alkene is carbonylated in the presence of an alcohol to provide an ester. Generally, this reaction is catalysed by a palladium complex containing a phosphane or a diphosphane ligand, and most [a] [1,7] The copolymerisation of ethylene and carbon monoxide catalysed by the cationic [Pd(diphos)] 2+ complexes in the presence of methanol perfectly interconnects the two catalytic pathways [8] such that polymers with -CH 2 COOCH 3 and -CH 2 CH 3 terminal functions are produced in equal proportions. For the alkoxycarbonylation reaction of an alkene, Knifton has reported the [PdCl 2 (PPh 3 ) 2 ]/SnCl 2 catalytic system, with which he detected the presence of a ν(Pd-H) stretching frequency. [7] In the literature, several papers deal with evidence that the palladium hydride pathway operates preferentially. [9,10] Results and DiscussionCarbonylation of isopulegol A or isolimonene B, under a CO pressure of 40 bar, in the presence of [PdCl 2 L 2 ]/SnCl 2 provides the lactone C or the cyclopentanone D, irrespective of whether the medium contains methanol or not (Scheme 1). [4,11,12] Scheme 1. Cyclocarbonylation of isopulegol A and isolimonene B.After catalysis, we never detected any alkoxycarbonylpalladium complex containing the isopulegyl moiety among the organometallic compounds. However, starting from isolimonene, small amounts of dehydro-D have previously been identified corresponding to a cyclopentenone resulting from the sacrificial formation of the palladium hydride species. [5,11,13] During the present study, we carefully analysed the products resulting from the cyclocarbonylation of isopulegol by GC/MS and we identified small amounts of the unsaturated lactone dehydro-C, which leads to Equation (...

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Section: Characterisation Of An Acylplatinum Speciesmentioning

confidence: 99%

Hydride Route for the Palladium‐Catalysed Cyclocarbonylation of Monoterpenes

et al. 2005

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“…[14][15][16][17] Such platinum(IV) species are proving to be of increasing interest, including use as sensors 18 and as models for the Fischer-Tropsch synthesis. 19 Even though the reductive elimination of hydrocarbons from platinum(IV), which can be seen as analogous to the reverse of a C-H activation, has been widely studied, 20-25 and the Pt(II)/Pt(IV) redox cycle has been investigated as a model for the activation of C-H bonds, 26, 27 there have been few reports of C-H activation by a platinum(IV) centre to date. [28][29][30][31] Here we report the synthesis of some cyclometallated platinum(II) compounds derived from substituted phenylpyridines and discuss the reactivity of these complexes with respect to oxidation.…”

Section: Introductionmentioning

confidence: 99%

Cyclometallated platinum(ii) complexes: oxidation to, and C–H activation by, platinum(iv)

et al. 2007

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A series of cyclometallated phenylpyridine platinum(II) complexes have been synthesised with a systematic variation in both the phenylpyridine and the ancillary ligand. Oxidation of one of the cyclometallated species leads to a number of isomeric platinum(IV) complexes, all of which eventually isomerize to a single compound. The route to these new compounds has been demonstrated to involve an initial slow oxidation followed by a rapid C-H activation to give doubly cyclometallated complexes. The solid state structures of a number of both the platinum(II) and the platinum(IV) species have been solved; many of the structures exhibited extended interactions that result in complex three dimensional packing.

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“…[29] Methylation of acyl complex 5 under similar conditions to those used for methylation of complexes 3a-d preceded cleanly, but slowly, requiring 24 hours to go to completion. The addition of excess methyl triflate (10 equiv.)…”

Section: (1)mentioning

confidence: 99%

Cationic Pt(IV) Tp' carbenes

Lavoie

Frauhiger

White

et al. 2015

Journal of Organometallic Chemistry

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This article is dedicated to the memory of Professor A.E. Shilov, the founder of platinum-alkane chemistry. Abstract: A series of Pt(IV) carbene complexes of the form [(Tp′)Pt(=C(X)(Y))(Me) 2 ] + (Tp′ = hydridotris(3,5-dimethylpyrazolyl)borate) was synthesized. Methylating a series of Ptcarboxamido precursors allowed isolation of [(Tp′)Pt(=C(OMe)NHR)Me 2 ][OTf] (R = Et, n Pr, i Pr, Bn). The solid-state structures of the Pt-carbene complexes reveal resonance-stabilized cationic carbene complexes. The method for generating these rare Pt(IV) carbenes was extended to synthesize a methoxy stabilized Pt carbene complex, [Tp′Pt(=C(OCH 3 )CH 3 )Me 2 ][OTf], from a Pt-acyl precursor. Preparation of an alkylidene analog proved more challenging, but low temperature protonation (-80 o C) of a Pt-vinyl complex, (Tp′)Pt(CH=CH 2 )(Me) 2 , generated a small amount of an ethylidene Pt complex as monitored by NMR. Low temperature NMR indicated the presence of the Pt=CH(CH 3 ) unit in [(Tp′)Pt(=CH(CH 3 )Me 2 ][B(Ar F ) 4 ]. The 13 C labeling studies revealed the carbene carbon signal at 500 ppm, a dramatic downfield chemical shift. Warming the reaction to -40 o C results in isomerization accompanied by protonation of a Tp′ nitrogen and reductive elimination to form a new C-C bond in a Pt(II) propylene adduct, [κ 2 (Tp′ (NH) )Pt(η 2 CH 2 =CHCH 3 )Me][B(Ar F ) 4 ]. Abstract GraphicIntroduction:

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Platinum(II) and Platinum(IV) Acyl and Formyl Complexes

Abstract: An unprecedented monomeric platinum(IV) formyl complex has been prepared by analogy to the synthetic route used to form platinum(IV) acyl complexes.

Cited by 36 publications

References 49 publications

Hydride Route for the Palladium‐Catalysed Cyclocarbonylation of Monoterpenes

Hydride Route for the Palladium‐Catalysed Cyclocarbonylation of Monoterpenes

Cyclometallated platinum(ii) complexes: oxidation to, and C–H activation by, platinum(iv)

Cationic Pt(IV) Tp' carbenes

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