Dioxygen-derived peroxo-alkyl complexes of permethyltantalocene.  Structural characterization of (.eta.5-C5Me5)2Ta(.eta.2-O2)(CH2C6H5) and acid-catalyzed rearrangement to oxo-alkoxide derivatives

Asselt, A. Van; Trimmer, Mark; Henling, Lawrence M.; Bercaw, John E.

doi:10.1021/ja00232a058

Cited by 62 publications

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“…1-3 A better understanding of oxygen atom transfer reactions involving transition metal-alkyls is critical to facilitate the design of selective catalytic cycles for alkane and arene functionalization to alcohols and phenols, respectively. 4,5 A firm theoretical underpinning is particularly essential, as experimentally characterized examples of middle to late (non-d 0 ) transition metal complexes undergoing oxyinsertion into metal-carbon bonds are very rare, [6][7][8][9][10][11][12][13][14] and mechanistic details rarer still. Among these examples, a handful of d 0 complexes (i.e., MeReO 3 (MTO), PhReO 3 (PTO), and MeTaCp* 2 ) have been shown to undergo a concerted O-atom transfer akin to the Baeyer-Villiger (BV) oxidation upon reaction with an external oxidant (YO).…”

Section: Introductionmentioning

confidence: 99%

Computational Hammett analysis of redox based oxy-insertion by Pt(ii) complexes

Figg

Cundari

2013

Dalton Trans.

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A computational Hammett analysis of oxy-insertion into platinum-aryl bonds is performed. Modeled transformations involve the two-step conversion of [((X)bpy)Pt(R)(OY)](+) (R = p- or m-X-C(6)H(4); Y = 4- or 3-X-pyridine; (X)bpy = 4,4'- or 5,5'-X-bpy; X = NO(2), H, OMe, NMe(2)) proceeding through a Pt-oxo intermediate to form aryloxide [((X)bpy)Pt(OR)(Y)](+), which contrasts a one-step non-redox (Baeyer-Villiger) oxy-insertion. A structural connection is proposed between redox and non-redox transition states, linked to, among other parameters, oxidant identity. The electronic impact of the catalytic components is compared to previous Hammett studies on OMBV transformations. The Hammett sensitivity for aryl migration is diminished for the migrating group (R) and leaving group (Y), components as compared to OMBV transitions, while the bipyridine supporting ligand (L(n)) has an increased impact. The Hammett impact of R, Y and L(n) upon the aryl migration transition state is small in a global sense, ca. 5 kcal mol(-1); therefore, we conclude that the metal and oxidant are the most important factors in controlling oxy-insertion kinetics for these late metal systems. These results also point to a possible mechanistic advantage for redox over non-redox functionalization of hydrocarbons to alcohols.

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Section: Introductionmentioning

confidence: 99%

Computational Hammett analysis of redox based oxy-insertion by Pt(ii) complexes

Figg

Cundari

2013

Dalton Trans.

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“…The recently reported Pt IV complex with a terminal oxo ligand by Milstein and co‐workers supports the existence of such an intermediate 41. This rearrangement has precedent in the reaction of the tantalum(III)–methylperoxo complex [(Cp*) 2 Ta(η 2 ‐OOMe)] (Cp*=C 5 Me 5 ), which can rearrange to [(Cp*) 2 Ta V O(OMe)] as shown by Bercaw and co‐workers 42. In our case, the subsequent hydrogen abstraction results in the formation of [Pt( 1 )OH][SbF 6 ] and formaldehyde.…”

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confidence: 59%

Towards Photocatalytic Alkane Oxidation: The Insertion of Dioxygen into a Platinum(II)–Methyl Bond

Taylor

Law²,

Sunley³

et al. 2009

Angewandte Chemie

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The selective catalytic oxidation of methane and higher alkanes remains one of the great challenges in catalysis research. Considerable progress has been made during the last three decades regarding the CÀH activation of alkanes, in particular electrophilic activation reactions with late transition metals. [1][2][3][4] Once C À H bond cleavage has occurred at a metal center, a functionalization of the metal-carbon bond is required, followed by release of the product and regeneration of the catalyst. In the case of oxidation reactions, this functionalization of metal-alkyl complexes should be carried out ideally with environmentally benign oxidants such as O 2 or H 2 O 2 . We previously reported the oxidation of dimethylplatinum(II) complexes with H 2 O 2 to generate cis-dihydroxoplatinum(IV) complexes.[5] The unusual cis isomer was obtained by using amino-substituted bipyridine ligands, which stabilize this isomer through hydrogen bonding. When we extended our work to methylplatinum(II) complexes containing tridentate amino-substituted terpyridine (terpy) ligands, we discovered a remarkable reactivity of the complexes towards O 2 .The reaction of 6,6'-diaminoterpyridine (1) (1)]. The rate of the O 2 insertion reaction is affected by light: Whereas the reaction proceeds within several minutes at room temperature in ambient light, the reaction is very slow in the absence of light and only 50 % conversion is obtained after 13 h at room temperature.

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“…[41] This rearrangement has precedent in the reaction of the tantalum(III)-methylperoxo complex [(Cp*) 2 Ta(h 2 -OOMe)] (Cp* = C 5 Me 5 ), which can rearrange to [(Cp*) 2 Ta V = O(OMe)] as shown by Bercaw and co-workers. [42] In our case, the subsequent hydrogen abstraction results in the formation of [Pt(1)OH][SbF 6 ] and formaldehyde. This process is probably also related to the insertion of O 2 into a chromium(II)-phenyl bond, reported by Theopold and co-workers, which results in the formation of a Cr IV = O(OPh) complex.…”

mentioning

confidence: 77%

Towards Photocatalytic Alkane Oxidation: The Insertion of Dioxygen into a Platinum(II)–Methyl Bond

Taylor

Law²,

Sunley³

et al. 2009

Angew Chem Int Ed

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Keywords: singlet oxygen, platinum, photosensitiser, alkane oxidation 2 The selective catalytic oxidation of methane and higher alkanes remains one of the great challenges in catalysis research. Considerable progress has been made during the last three decades regarding the C-H activation of alkanes, in particular electrophilic activation reactions with late transition metals. [1][2][3][4] Once C-H bond cleavage has occurred at a metal centre, a functionalisation of the metal carbon bond is required, followed by release of the product and regeneration of the catalyst. In the case of oxidation reactions, this functionalisation of metal alkyl complexes should be carried out ideally with environmentally benign oxidants such as O 2 or H 2 O 2 . In a previous study, we reported the oxidation of dimethyl Pt II complexes with H 2 O 2 to generate cis-dihydroxo Pt IV complexes. [5] The unusual cis isomer was obtained by using amino-substituted bipyridine ligands, which stabilise this isomer through hydrogen bonding. When we extended our work to Pt II methyl complexes containing tridentate amino-substituted terpyridine ligands, we discovered a remarkable reactivity of the diamino substituted terpy Pt II methyl complex towards O 2 .The reaction of 6,6'-diaminoterpyridine (1) Figure 1 and the supporting material for further information). [6] This dimer formation is quite common for terpy Pt II complexes and arises from metal-metal and π-π interactions. [7] It is for example also observed in the solid state structure of [Pt ( Pt II complexes. [9][10][11] Excitation of the charge transfer region at 388 nm results in an emission spectrum with maxima at 580 and 654 nm (see Supplementary Information).Noteworthy, the diamino substituted terpyridine ligand itself also shows photoluminescence. [12,13] The luminescent behaviour of [Pt (1) [14] In addition, several Pt II and Pt IV complexes containing alkylperoxo ligands other than methylperoxo have been reported previously, but none of these have been prepared via an O 2 insertion reaction. [15][16][17][18][19][20] The O 2 insertion reaction into the Pt II -Me bond in the complex [(PN)Pt(Me)(OOMe)] is also affected by light and the authors have proposed a radical mechanism for their insertion reaction. [14] Similarly, the insertion of O 2 into a Pt IV -H bond has been reported to involve a radical pathway, [21] and insertions of O 2 into other transition metal methyl bonds such as Co and Fe methyl complexes proceed via methyl radicals. [22,23] In contrast, two reports on the direct insertion of O 2 into Pd II -H bonds have shown that these insertion reactions are not affected by light. [24,25] Mechanistic investigations suggest that these reactions proceed by a Pd I /HO 2 (triplet) radical pair intermediate or via a stepwise pathway initiated by reductive elimination of HX to form an O 2 -reactive Pd 0 intermediate. [26,27] Dioxygen, in its triplet ground state, is rather unreactive because reactions are spinforbidden and require a triplet-singlet surface crossing on the reaction c...

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Dioxygen-derived peroxo-alkyl complexes of permethyltantalocene. Structural characterization of (.eta.5-C5Me5)2Ta(.eta.2-O2)(CH2C6H5) and acid-catalyzed rearrangement to oxo-alkoxide derivatives

Cited by 62 publications

References 0 publications

Computational Hammett analysis of redox based oxy-insertion by Pt(ii) complexes

Computational Hammett analysis of redox based oxy-insertion by Pt(ii) complexes

Towards Photocatalytic Alkane Oxidation: The Insertion of Dioxygen into a Platinum(II)–Methyl Bond

Towards Photocatalytic Alkane Oxidation: The Insertion of Dioxygen into a Platinum(II)–Methyl Bond

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