Early-transition-metal-mediated [2+2+2] cycloadditions: formation and fragmentation of a reactive metallacyclopentadiene and its direct conversion to .eta.6-arene and .eta.2-pyridine complexes of tantalum

Smith, David P.; Strickler, Jamie R.; Gray, Steven D.; Bruck, Michael A.; Holmes, Renee S.; Wigley, David E.

doi:10.1021/om00039a037

Cited by 91 publications

(32 citation statements)

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“…[7] Ruthenium catalysts are highly efficient for activated nitriles (e.g., electron-deficient nitriles, dicyanides, and α-halo nitriles) and tethered 1,6-diynes under mild reaction conditions. [8] Nickel, [9] titanium, [10] and tantalum [11] complexes are also effective for this transformation, although stoichiometric amounts of metals are required. Recently, (N-heterocyclic carbene)nickel complexes have been found to catalyze the [2+2+2] cycloaddition of internal alkynes with inactivated nitriles at room temperature.…”

Section: Introductionmentioning

confidence: 99%

Cationic Rhodium(I)/Modified‐BINAP Catalyzed [2+2+2] Cycloaddition of Alkynes with Nitriles

Tanaka¹,

Suzuki²,

Nishida³

2006

Eur J Org Chem

149

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Cationic rhodium(I)/modified‐BINAP complexes catalyze a chemo‐ and regioselective [2+2+2] cycloaddition of a wide variety of alkynes and nitriles leading to highly functionalized pyridines under mild reaction conditions. The asymmetric variant of this reaction, enantioselective desymmetrization of substituted malononitriles, also proceeded to give enantio‐enriched bicyclic pyridines which possess a tertiary or quaternary stereocenter. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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Section: Introductionmentioning

confidence: 99%

Cationic Rhodium(I)/Modified‐BINAP Catalyzed [2+2+2] Cycloaddition of Alkynes with Nitriles

Tanaka¹,

Suzuki²,

Nishida³

2006

Eur J Org Chem

149

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“…The bond lengths of Ta–C(1) (2.054(11) Å) and Ta–C(4) (2.060(10) Å) were similar to those found for (C 4 H 2 t Bu 2 )TaCl(OAr) 2 (Ar = 2,6‐ i Pr 2 C 6 H 3 ) (2.085(5) and 2.166(9) Å). [9b] The short‐long‐short sequence of the bond lengths for C(1)–C(2) (1.367(15) Å), C(2)–C(3) (1.503(15) Å), and C(3)–C(4) (1.367(16) Å) is observed for other structurally characterized tantalacyclopentadiene complexes of (C 4 H 2 t Bu 2 )TaCl(OAr) 2 and (C 4 Et 4 )Ta(OAr) 3 (Ar = 2,6‐ i Pr 2 C 6 H 3 ). [9b] The tantalacyclopentadiene plane is almost flat, as evident from the standard deviation (0.008 Å) from the best plane.…”

Section: Resultsmentioning

confidence: 96%

“…In the 13 C‐NMR spectrum, a singlet signal observed at δ 241.1 was assigned to a quaternary C‐atom at the C( α ) position of the tantalacyclopentadiene, while the C‐atom at the C( β ) position of the tantalacyclopentadiene was observed as a doublet signal centered at δ 108.7, whose directly bonded coupling constant ( 1 J (C–H) = 176 Hz) was typical for an sp 2 ‐hybridized C‐atom. [9] The 13 C‐NMR spectral pattern was essentially the same as that of (C 4 H 2 t Bu 2 )TaCl(OAr) 2 (Ar = 2,6‐ i Pr 2 C 6 H 3 ), reported by Wigley et al . [9b] Although 1,2,4‐ and 1,3,5‐tris( tert ‐butyl)benzenes, which were generated as catalytic cyclotrimerization products by low‐valent Ta species and detected during the formation of complex 2 , we found that the isolated complex 2 was catalytically inert toward cyclotrimerization of 3,3‐dimethylbut‐1‐yne at room temperature, presumably due to the steric hindrance of two t Bu groups at the two α ‐positions of the tantalacyclopentadiene fragment in 2 .…”

Section: Resultsmentioning

confidence: 99%

“…[9] The 13 C‐NMR spectral pattern was essentially the same as that of (C 4 H 2 t Bu 2 )TaCl(OAr) 2 (Ar = 2,6‐ i Pr 2 C 6 H 3 ), reported by Wigley et al . [9b] Although 1,2,4‐ and 1,3,5‐tris( tert ‐butyl)benzenes, which were generated as catalytic cyclotrimerization products by low‐valent Ta species and detected during the formation of complex 2 , we found that the isolated complex 2 was catalytically inert toward cyclotrimerization of 3,3‐dimethylbut‐1‐yne at room temperature, presumably due to the steric hindrance of two t Bu groups at the two α ‐positions of the tantalacyclopentadiene fragment in 2 .…”

Section: Resultsmentioning

confidence: 99%

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Synthesis and Characterization of Heterobimetallic Tantalum–Rhodium and Tantalum–Iridium Complexes Connected by a Tantalacyclopentadiene Fragment

Yamamoto

Higashida

Nagae

et al. 2016

Helvetica Chimica Acta

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We report the synthesis of heterobimetallic Ta-Rh and Ta-Ir complexes bridged by a 2,5-di-tertbutyltantalacyclopentadiene fragment. A mononuclear 2,5-di-tert-butyltantalacyclopentadiene complex 2 was prepared by the reaction of (g 2 -Me 3 SiCCSiMe 3 )TaCl 3 (dme) (1) with excess amounts of 3,3-dimethylbut-1-yne in the presence of AlCl 3 . The tantalacyclopentadiene moiety of complex 2 served as a g 4 -diene unit for coordinating the Rh and Ir centers; treatment of 2 with [M(l-Cl)(cod)] 2 (M = Rh and Ir; cod = cycloocta-1,5-diene) in toluene gave TaRh(l-C 4 H 2 t Bu 2 )Cl 4 (cod) (3) and [TaIr(l-C 4 H 2 t Bu 2 )Cl 4 ] 2 (5), respectively. The X-Ray diffraction study of 3 revealed a dative bond from an electron-rich Rh toward an electron-deficient Ta. Upon dissolving 3 in THF, [(thf)TaRh(l-C 4 H 2 t Bu 2 ) Cl 3 ] 2 (l-Cl) 2 (4) was isolated together with free cycloocta-1,5-diene. When complex 5 was treated with 1,2-bis-(diphenylphosphino)ethane (dppe), a monomeric Ta-Ir complex, TaIr(l-C 4 H 2 t Bu 2 )Cl 4 (dppe) (6), was isolated. Ta-Rh and Ta-Ir heterobimetallic complexes 3 and 6 were reduced by a two-electron process upon reaction with 2,3,5,6tetramethyl-1,4-bis(trimethylsilyl)-1,4-dihydropyrazine (7a: Si-Me 4 -DHP) or 2,5-dimethyl-1,4-bis(trimethylsilyl)-1,4dihydropyrazine (7b: Si-Me 2 -DHP) to afford the corresponding complexes TaM(l-C 4 H 2 t Bu 2 )Cl 2 (L) (8: M = Rh, L = cod; 9: M = Ir, L = dppe), where the metallacycle moiety was assigned to have a tantalacyclopentadiene fragment with a large contribution of a tantalacyclopentatriene canonical form.Bu 2 )TaCl 3 (2), as a unique precursor for reacting with Rh and Ir cyclooctadiene complexes, giving the corresponding Ta-Rh and Ta-Ir heterobimetallic complexes. In these complexes, the diene moiety of the tantalacyclopentadiene served as the

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“…On the other hand, previous investigations demonstrate that the reactivity of metallacyclopentadienes occurs at the M-C  and C  =C  bonds 35 in most cases. So far, the reactions involving C  -C ' bond cleavage and recombination have been only reported in thermally induced isomerization of Ta(V) metallacyclopentadiene at the temperature of 90 C38 and in a cyclopentadiene Sc(III) complex that undergoes C  -C ' bond cleavage to generate the scandacyclopropene at 80 o C39 . In this work, thermal cycloreversion of metallacyclopentadienes is unprecedentedly attained at ambient temperature through the disruption of C  -C ' bonds.CONCLUSIONWe demonstrate in this research an initial approach to attain T-type photochromism through the formation of thermally sensitive copper(I) metallacyclopentadiene.…”

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confidence: 99%

Achieving T-Type Photochromism through Generating Copper(I) Metallacyclopentadiene Biradical

Zhang

Wang

et al. 2022

CCS Chem

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Photochromism due to organometallic ring-closure through CC linkage has not been attained ever before. In this work, we report an initial approach to achieve T-type photochromism by creating metallacyclopentadiene biradical under light irradiation. A class of CuPt 2 phenylacetylide compounds were prepared with distinguished photochromic recyclability and durability, which involve the formation of thermally sensitive copper(I)-butadienyl five-membered ring through copper(I)participated ring-closure. Upon UV light irradiation, metallacyclopentadiene with copper(I) center chelated by 1,3-butadiene-1,4-diyl biradical is generated through photochemical C-C linkage of two face-to-face oriented ethynyl units in close proximity, which gives rise to a drastic change in UV-Vis absorption spectrum. When UV light irradiation is ceased, decoloration occurs through thermal cycloreversion, which endows photochromic CuPt 2 complexes with self-recovery characteristics.Electron paramagnetic resonance (EPR) spectral study confirms a biradical feature of the ring-closed isomer. The thermal decoloration half-lives at ambient temperature are regulated from seconds to hours by increasing F substituents in phenylethynyl ligands.

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Early-transition-metal-mediated [2+2+2] cycloadditions: formation and fragmentation of a reactive metallacyclopentadiene and its direct conversion to .eta.6-arene and .eta.2-pyridine complexes of tantalum

Cited by 91 publications

References 1 publication

Cationic Rhodium(I)/Modified‐BINAP Catalyzed [2+2+2] Cycloaddition of Alkynes with Nitriles

Cationic Rhodium(I)/Modified‐BINAP Catalyzed [2+2+2] Cycloaddition of Alkynes with Nitriles

Synthesis and Characterization of Heterobimetallic Tantalum–Rhodium and Tantalum–Iridium Complexes Connected by a Tantalacyclopentadiene Fragment

Achieving T-Type Photochromism through Generating Copper(I) Metallacyclopentadiene Biradical

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