Syntheses, structures and comparative electrochemical study of π-acetylene complexes of cobalt

Macazaga, M.J.; Marcos, M.L.; Moreno, C.; Benito‐Lopez, Fernando; Gomez-González, J.; González‐Velasco, J.; Medina, Rosa

doi:10.1016/j.jorganchem.2005.07.065

Cited by 8 publications

(23 citation statements)

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“…28 The interatomic distance of Co(1)−Co (2), at 2.4631 (7) Å, falls within the normal range for a Co−Co single bond 27 and is similar to Co−Co lengths observed for other dicobalt systems that are bridged by alkyne ligands. 16,27,29,30 The C(11)−C(12) length, 1.338(5) Å, lies in the range 1.33−1.36 Å reported for the alkylenic C−C bond in related dicobalt complexes. 16,27,29,30 This C−C distance shows a lengthening of ca.…”

Section: ■ Results and Discussionmentioning

confidence: 93%

“…16,27,29,30 The C(11)−C(12) length, 1.338(5) Å, lies in the range 1.33−1.36 Å reported for the alkylenic C−C bond in related dicobalt complexes. 16,27,29,30 This C−C distance shows a lengthening of ca. 0.15 Å from the value of 1.192(4) Å found in (CH 3 ) 3 Si CCC 6 H 4 NNC 6 H 4 CCSi(CH 3 ) 3 , 26 and this reflects the loss of triple-bond character as a result of coordination of the acetylenic moieties to the Co 2 units.…”

Section: ■ Results and Discussionmentioning

confidence: 93%

“…The resonances of the free and coordinated acetylene units were easily observed, and the chemical shifts of their carbon atoms are in the range of analogous complexes (δ 80−105 ppm). 15,16,18,22,24 Azobenzene carbon resonances appear between δ 120 and 155 ppm. The chemical shift for the C 4 atom in 4, 6, 8, and 10 is found to be very sensitive to cobalt complexation on the adjacent alkyne and shows a significant downfield shift (from 126 to 142 or 149 ppm) when they become 5, 7, 9, and 11 ( Table 2).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The change in hybridization at C(11)−C (12) is also reflected in the angles C(12)−C(11)−C(1), 139.9(3)°, and C(11)−C(12)− Si (1) The Co−C distances in the "Co 2 C 2 " core of 9 range from 1.955(4) to 1.978(4) Å, and these distances do not show an asymmetry pattern as observed in [{Co 2 (CO) 6 (H C C)} 2 (C 6 H 4 )] 29 and in [Co 2 (CO) 4 (μ-dppm)] 2 (μ-η 2 -HC 2 (C C) 2 C 2 H). 16 The average P−C distance of the bridging dppm ligands, 1.826(4) Å, is normal. 31 The bond angle of N(1)#1−N(1)−C(4) is 114.4(4)°and indicates that the two nitrogen atoms exist at almost sp 2 hybridization.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…[Co 2 (CO) 4 (μ-dmpm){μ 2 -η 2 -C 2 -(CH 2 ) 7 -CH 3 }] 2 (16). A solution of 15 (100 mg, 0.114 mmol) and 0.011 mmol of dmpm in CH 2 Cl 2 (50 mL) was prepared.…”

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Synthesis and Properties of New Dimeric η²-Diyne Complexes of Cobalt Linked through an Azobenzene Ligand

Moreno¹,

Arnanz²,

Medina³

et al. 2015

Organometallics

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The reaction between 4,4′-diiodoazobenzene (0) with excess trimethylsilylacetylene or dec-1-yne in the presence of catalytic amounts of PdCl 2 (PPh 3 ) 2 and CuI, Sonogashira coupling conditions, gave rise to the formation of 4,4′-bis(trimethylsilylethynyl)azobenzene (1) and 4,4′-bis(dec-1-ynyl)azobenzene (2), in good yield, in addition to icosa-9,11-diyne (3) as byproduct in the last case. The analogous reactions from 0 and the alkynyl-cobalt complexes Co 2 (CO) 4 (μ-L-L)(μ 2 -η 2 -SiMe 3 C 2 )](CCH) (L-L = dppm, dmpm) afforded 12−14.Complexes 4−7 and 15 have been obtained by direct reaction between Co 2 (CO) 8 and the organic ligands 1−3. In order to increase the stabilization of Co−Co bonds, diphenylphosphinomethane-substituted alkyne-carbonyl complexes 8−11 were prepared by substitution reaction of carbonyl ligands in the presence of Me 3 NO at the Co 2 (CO) 6 units from 4−7. All products were characterized by analytical and spectroscopic data (IR, 1 H, 13 C, and 31 P NMR, and MS). Crystals of 9 suitable for single-crystal X-ray diffraction were grown, and the molecular structure of this compound is discussed. In this paper we report a comparative electrochemical study of these complexes by means of cyclic and square-wave voltammetry techniques, the trans−cis photoisomerization study of azobenzene compounds, and the thermotropic liquid-crystalline behavior. ■ INTRODUCTIONAzobenzene and its derivatives constitute a family of dye molecules known since the middle of the last century. 1 These chromophores are very versatile molecules that have received much attention in both fundamental and applied research areas. 2 Basically, they are characterized by intense color, high thermal stability (up to 350°C), and a trans to cis reversible isomerization of the NN double bond upon UV light irradiation, whereas the reverse isomerization can take place by visible light irradiation or by heating, the trans-form being generally more stable than the cis-form. 3 Photoinduced isomerization involves dramatic structural rearrangements: the distance between the para carbon atoms in the molecule decreases from about 9.0 Å in the trans-form to 5.5 Å in the cisform. Furthermore, the change in the configuration leads to a significant increase in the dipole moment. The trans-form has no dipole moment, while the dipole moment of the nonplanar cis compound is 3.0 D. 4 Azobenzene and nearly all its monosubstituted derivatives show a strong band in the UV region attributed to the π−π* transition at ca. 290 nm in the cis-form (depending on the solvent) and at ca. 320 nm in the trans-form and a much weaker band in the visible region (around 450 nm), due to the n−π* transition. 5 On conversion to the cis-isomer, the π−π* band shifts to shorter wavelengths, and the intensity of the n−π* absorption increases. Usually, four mechanisms for the trans−cis reaction are considered: rotation, inversion, concerted inversion, and inversion-assisted rotation. The actual mechanism depends on the exact surroundings of the azo group. 3,6 Since the tw...

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Section: ■ Results and Discussionmentioning

confidence: 93%

Section: ■ Results and Discussionmentioning

confidence: 93%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

“…[Co 2 (CO) 4 (μ-dmpm){μ 2 -η 2 -C 2 -(CH 2 ) 7 -CH 3 }] 2 (16). A solution of 15 (100 mg, 0.114 mmol) and 0.011 mmol of dmpm in CH 2 Cl 2 (50 mL) was prepared.…”

mentioning

confidence: 99%

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Synthesis and Properties of New Dimeric η²-Diyne Complexes of Cobalt Linked through an Azobenzene Ligand

Moreno¹,

Arnanz²,

Medina³

et al. 2015

Organometallics

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Electronic Interactions Between and Through Covalently-Bonded Polymetallic Complexes

Low

Brown

2010

J Clust Sci

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Supramolecular assemblies of multi-nuclear transition metal complexes: Synthesis and redox properties

Tanaka

Tsurugi

Mashima

2014

Coordination Chemistry Reviews

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The synthetic features of supramolecular assemblies comprised of multi-nuclear transition metal complexes were reviewed by classification of the reaction patterns: (1) substitution reaction by bridging ligands, (2) substitution reaction by monodentate ligands, and (3) coupling reaction of functional groups attached to peripheral ligands. Architectural control for assembling multinuclear units is difficult because of the complicated ligand substitution reactions of metal clusters; but controlled ligand substitution of multi-metallic complexes recently became a targeted subject of coordination chemistry by introducing suitable bridging and monodentate ligands to keep multimetallic entities intact, leading to the formation of 1D, 2D, and 3D supramolecules of multimetallic units. Another synthetic protocol is aimed at transition metal-catalyzed coupling reactions of peripheral ligands that provide selective oligomerization of multi-metallic complexes. These supramolecules are of particular interest because of their unique redox properties centered at multi-metallic units, and their redox behaviors are described.

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Syntheses, structures and comparative electrochemical study of π-acetylene complexes of cobalt

Cited by 8 publications

References 50 publications

Synthesis and Properties of New Dimeric η²-Diyne Complexes of Cobalt Linked through an Azobenzene Ligand

Synthesis and Properties of New Dimeric η²-Diyne Complexes of Cobalt Linked through an Azobenzene Ligand

Electronic Interactions Between and Through Covalently-Bonded Polymetallic Complexes

Supramolecular assemblies of multi-nuclear transition metal complexes: Synthesis and redox properties

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Syntheses, structures and comparative electrochemical study of π-acetylene complexes of cobalt

Cited by 8 publications

References 50 publications

Synthesis and Properties of New Dimeric η2-Diyne Complexes of Cobalt Linked through an Azobenzene Ligand

Synthesis and Properties of New Dimeric η2-Diyne Complexes of Cobalt Linked through an Azobenzene Ligand

Electronic Interactions Between and Through Covalently-Bonded Polymetallic Complexes

Supramolecular assemblies of multi-nuclear transition metal complexes: Synthesis and redox properties

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Product

Resources

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Synthesis and Properties of New Dimeric η²-Diyne Complexes of Cobalt Linked through an Azobenzene Ligand

Synthesis and Properties of New Dimeric η²-Diyne Complexes of Cobalt Linked through an Azobenzene Ligand