“…The dihedral angle θ between the C(1)−C(2)−C(6) plane and the rest of the oxo−dienyl unit is 14°; this angle θ is smaller than that reported for 8 (θ = 19°) and 9 (θ = 23°). In conclusion, the X-ray data show that the ketonic character of CO in 5 is less pronounced relative to the analogous iridium complexes 8 and 9 ; , therefore, the X-ray data are in accord with 13 C NMR values obtained in solution for complex 5 . 6 …”
Section: Resultssupporting
confidence: 78%
“…Finally, we have found that oxidation of the p - and o -benzoquinone iridium complexes by iodine provides the free ligand along with the starting material recycled in the form of [Cp*Ir(μ-I)I] 2 . These results are significant since it shows that functionalization of this type of sensitive ligand promoted by a Cp*Ir fragment is possible and may occur in a fashion similar to that described recently by us for the regioselective nucleophilic phenol reactions (Scheme ). , …”
Section: Resultssupporting
confidence: 65%
“…Suitable crystals of 4 were obtained by recrystallization from a CH 3 CN/Et 2 O solution. Although several X-ray structures of η 4 -duroquinone complexes were reported in the literature, ,, those of simple η 4 - p -benzoquinone are rare . Complex 4 crystallizes with two molecules of water in the orthorhombic space group Pbca .…”
Section: Resultsmentioning
confidence: 99%
“…Sternberg, Markby, and Wender reported in 1958 the first duroquinone complex [Fe(CO) 3 (η 4 -duroquinone)] (duroquinone = 2,3,5,6-tetramethyl-1,4-benzoquinone) − For instance, Liebeskind and co-workers reported a high-yield synthetic procedure for the preparation of substituted η 4 -benzoquinone and η 4 -naphthaquinone metal complexes. − Unlike η 4 -duroquinone complexes, the π-complexation of the sensitive benzoquinone ligand has attracted less attention; this is due in part to the absence of a simple synthetic procedure for such π-complexes. …”
Section: Introductionmentioning
confidence: 99%
“…Sternberg, Markby, and Wender reported in 1958 the first duroquinone complex [Fe(CO) 3 (η 4 -duroquinone)] (duroquinone ) 2,3,5,6-tetramethyl-1,4-benzoquinone). 1 Since then, the coordination chemistry of η 4 -duroquinone and substituted η 4 -benzoquinone have received intense investigation.…”
Treatment of hydroquinone with
[Cp*Ir(solvent)3][BF4]2
(1) in acidic medium afforded the
stable π-bonded complex
[Cp*Ir(η6-hydroquinone)][BF4]2
(2) in 93% yield. Complex 2
can
be easily deprotonated by a base to give the related
[Cp*Ir(η5-semiquinone)][BF4]
(3) and
[Cp*Ir(η4-p-benzoquinone)]
(4) compounds, identified by spectroscopic methods.
Further,
the X-ray molecular structure of p-benzoquinone iridium
complex 4 is reported; such
compounds are rare in the literature. Complex 4 reacts
with an excess of HBF4·Et2O
to
give the starting material 2 quantitatively.
Interestingly, the chemical transformations from
2 to 4 and vice versa occur with facile
reversible changes of the oxidation state from
Ir(III)
to Ir (I). On the other hand, the oxo−dienyl iridium complex
[Cp*Ir(η5-2,6-dimethoxy-C6H3O)][BF4] (5), identified by spectroscopic methods
and X-ray analysis, reacts with NaOMe in
methanol to give unexpectedly but reproducibly the substituted
o-benzoquinone iridium
compound
[Cp*Ir{η4-(3-methoxy)-o-benzoquinone}]
(6). The solution behavior and the
reactivity of 6, as well as a rationale explaining its
formation, is advanced.
“…The dihedral angle θ between the C(1)−C(2)−C(6) plane and the rest of the oxo−dienyl unit is 14°; this angle θ is smaller than that reported for 8 (θ = 19°) and 9 (θ = 23°). In conclusion, the X-ray data show that the ketonic character of CO in 5 is less pronounced relative to the analogous iridium complexes 8 and 9 ; , therefore, the X-ray data are in accord with 13 C NMR values obtained in solution for complex 5 . 6 …”
Section: Resultssupporting
confidence: 78%
“…Finally, we have found that oxidation of the p - and o -benzoquinone iridium complexes by iodine provides the free ligand along with the starting material recycled in the form of [Cp*Ir(μ-I)I] 2 . These results are significant since it shows that functionalization of this type of sensitive ligand promoted by a Cp*Ir fragment is possible and may occur in a fashion similar to that described recently by us for the regioselective nucleophilic phenol reactions (Scheme ). , …”
Section: Resultssupporting
confidence: 65%
“…Suitable crystals of 4 were obtained by recrystallization from a CH 3 CN/Et 2 O solution. Although several X-ray structures of η 4 -duroquinone complexes were reported in the literature, ,, those of simple η 4 - p -benzoquinone are rare . Complex 4 crystallizes with two molecules of water in the orthorhombic space group Pbca .…”
Section: Resultsmentioning
confidence: 99%
“…Sternberg, Markby, and Wender reported in 1958 the first duroquinone complex [Fe(CO) 3 (η 4 -duroquinone)] (duroquinone = 2,3,5,6-tetramethyl-1,4-benzoquinone) − For instance, Liebeskind and co-workers reported a high-yield synthetic procedure for the preparation of substituted η 4 -benzoquinone and η 4 -naphthaquinone metal complexes. − Unlike η 4 -duroquinone complexes, the π-complexation of the sensitive benzoquinone ligand has attracted less attention; this is due in part to the absence of a simple synthetic procedure for such π-complexes. …”
Section: Introductionmentioning
confidence: 99%
“…Sternberg, Markby, and Wender reported in 1958 the first duroquinone complex [Fe(CO) 3 (η 4 -duroquinone)] (duroquinone ) 2,3,5,6-tetramethyl-1,4-benzoquinone). 1 Since then, the coordination chemistry of η 4 -duroquinone and substituted η 4 -benzoquinone have received intense investigation.…”
Treatment of hydroquinone with
[Cp*Ir(solvent)3][BF4]2
(1) in acidic medium afforded the
stable π-bonded complex
[Cp*Ir(η6-hydroquinone)][BF4]2
(2) in 93% yield. Complex 2
can
be easily deprotonated by a base to give the related
[Cp*Ir(η5-semiquinone)][BF4]
(3) and
[Cp*Ir(η4-p-benzoquinone)]
(4) compounds, identified by spectroscopic methods.
Further,
the X-ray molecular structure of p-benzoquinone iridium
complex 4 is reported; such
compounds are rare in the literature. Complex 4 reacts
with an excess of HBF4·Et2O
to
give the starting material 2 quantitatively.
Interestingly, the chemical transformations from
2 to 4 and vice versa occur with facile
reversible changes of the oxidation state from
Ir(III)
to Ir (I). On the other hand, the oxo−dienyl iridium complex
[Cp*Ir(η5-2,6-dimethoxy-C6H3O)][BF4] (5), identified by spectroscopic methods
and X-ray analysis, reacts with NaOMe in
methanol to give unexpectedly but reproducibly the substituted
o-benzoquinone iridium
compound
[Cp*Ir{η4-(3-methoxy)-o-benzoquinone}]
(6). The solution behavior and the
reactivity of 6, as well as a rationale explaining its
formation, is advanced.
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