The Synthesis and Conformation of Sterically Congested Seven-membered Rings Containing Tetracoordinate Germanium(IV):  Determination of the Δ<i>G</i>* For Ring Inversion<sup>1</sup>

Pastor, Stephen D.; Carinci, Adam J.; Khoury, Nancy; Rahni, David N.

doi:10.1021/ic010180t

Cited by 8 publications

(7 citation statements)

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“…A plausible transition state in such a process is illustrated in Scheme 1b. The observed barrier for this process (ΔG ‡ ≈ 12 kcal mol −1 ) is low, compared to the sum of the barriers for a Bailar twist (ΔG ‡ ≈ 9 kcal mol −1 in oxobis(catecholates) 3,21 ) and racemization of 2,2′-disubstituted biphenyls (e.g., ΔG ‡ ≈ 14 kcal mol −1 for racemization in titanium 18a and germanium 22 2,2′-biphenoxides). However, the two events are likely to be strongly coupled.…”

Section: Resultsmentioning

confidence: 91%

Mixed amidophenolate–catecholates of molybdenum(vi)

Shekar

Brown

2014

Dalton Trans.

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The dioxomolybdenum(vi) complex ((t)BuClipH2)MoO2 ((t)BuClipH4 = 4,4'-di-tert-butyl-N,N'-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-2,2'-diaminobiphenyl) reacts with 3,5-di-tert-butylcatechol to form oxo-free ((t)BuClip)Mo(3,5-(t)Bu2Cat). The bis(amidophenoxide)-monocatecholate complex is monomeric and exhibits a cis-β geometry in the solid state. Variable-temperature NMR data are consistent with two fluxional processes, one that interconverts several geometric isomers at low temperature, and a second that interchanges the ends of the (t)BuClip ligand at ambient temperatures. The high-temperature fluxional process can be explained by a single Bailar trigonal twist coupled with atropisomerization of the chiral diaminobiaryl backbone. Addition of excess catechol to ((t)BuClipH2)MoO2 results in formation of a dimolybdenum mono-oxo complex ((t)BuClip)Mo(μ-3,5-(t)Bu2Cat)2Mo(O)(3,5-(t)Bu2Cat). This complex, which contains a seven-coordinate bis(amidophenoxide)molybdenum center and a six-coordinate oxomolybdenum center, represents a structural hybrid between dimeric oxomolybdenumbis(catecholate) and molybdenum tris(catecholate) complexes. Both mono- and dimolybdenum complexes are best formulated as containing Mo(vi), but there is structural evidence for significant π donation from the amidophenolates. ((t)BuClip)Mo(3,5-(t)Bu2Cat) binds pyridine to form a mixture of isomeric seven-coordinate adducts. The Lewis acidity of the mixed amidophenoxide-catecholate appears to be lower than its tris(catecholate) or oxobis(amidophenoxide) analogues, which manifests itself principally in relatively slow binding of pyridine to the six-coordinate complex (k = 8 × 10(4) L mol(-1) s(-1) at 0 °C) rather than in the rate of dissociation of pyridine from the seven-coordinate adduct.

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Section: Resultsmentioning

confidence: 91%

Mixed amidophenolate–catecholates of molybdenum(vi)

Shekar

Brown

2014

Dalton Trans.

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“…19 The observed C 2 symmetry in the solidstate crystallographic data of 1 is consistent with the previous suggestion based upon VT NMR spectral data in a solution of rapid atropisomerism at an ambient temperature about the C C single bond connecting the two aryl groups in the seven-membered dibenzo[d, f ][1,3,2]dioxagermepin. 13 The magnitude of the dihedral angle connecting the aryl ring in the seven-membered germanium heterocycle 1 is similar in magnitude to the corresponding phosphorus system that has bulky substituents on the annulated aryl rings (47.4-52.0 • ). 3 13 by the reaction of the corresponding tert-octyl-substituted 1,1 -biphenyl-2,2 -diol with dimethylgermanium dichloride using triethylamine as a hydrogen chloride acceptor.…”

Section: Resultsmentioning

confidence: 88%

“…13 The magnitude of the dihedral angle connecting the aryl ring in the seven-membered germanium heterocycle 1 is similar in magnitude to the corresponding phosphorus system that has bulky substituents on the annulated aryl rings (47.4-52.0 • ). 3 13 by the reaction of the corresponding tert-octyl-substituted 1,1 -biphenyl-2,2 -diol with dimethylgermanium dichloride using triethylamine as a hydrogen chloride acceptor. (1) 5910 (4) 7189(2) 107 (2) …”

Section: Resultsmentioning

confidence: 88%

The Conformation of Sterically Congested Seven-Membered Rings Containing Tetracoordinate Germanium(IV): A First X-Ray Crystallographic Structure Determination

Pastor

Rahni

Khoury

et al. 2006

Phosphorus, Sulfur, and Silicon and the Related Elements

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“…The value of ∆G for ring inversion, atropisomerism about the C-C bond, was determined to be 13.8 kcal mol Ϫ1 . 48 The complex H 3 GeONMe 2 was prepared and the gas phase electron diffraction structure determined. The strength of the Ge-N β-interaction was found to be greater than the equivalent interaction of the corresponding silicon or tin complexes.…”

Section: Complexes With Group 16 Ligandsmentioning

confidence: 99%

5 Carbon, silicon, germanium, tin and lead

Parr

2002

Annu. Rep. Prog. Chem., Sect. A: Inorg. Chem.

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A number of review articles have appeared that are relevant to this area, covering the effect of substituent groups upon the reactivity of silicon-carbon double bonds, 1 the low coordination number complexes of germanium, tin and lead, 2 a classification of the crystallographic and structural data of known germanium coordination compounds, 3 and of dimeric tin compounds. 4 New carbon compoundsThe oxide of carbon C 3 O 2 has been crystallized from the melt (Ϫ112.5 ЊC) and its structure determined. The molecule has a near linear configuration, with a maximum deviation of only 1.71Њ at the central carbon atom. The bond lengths were found to be shorter than was previously believed based upon gas phase electron diffraction data (O term -C 1.1479, 1.1442 Å, C-C central 1.256, 1.2475 Å). 5 The oxidation of the carbon sulfur anions [C 6 S 8 ] 2Ϫ and [C 3 S 5 ] 2Ϫ gives in both cases dimers with long sulfur-sulfur bonds and acute [C-S-S-C] torsion angles. In [C 6 S 10 ] 2Ϫ the unusual bonding patterns are attributed to strong attractive inter-ring interactions, whereas in [C 12 S 16 ] 2Ϫ π-delocalisation of the charge dominates. In solution, [C 12 S 16 ] 2Ϫ reversibly dissociates into two [C 6 S 8 ] Ϫ ions. 6 Complexes with M(14)-carbon bondsA range of functionalised aryl-and heteroaryl-chlorosilanes have been prepared by the electrochemical reduction of halothiophenes, halofurans, halopyridines and substituted aryl halides in the presence of organodi-and tri-chlorosilanes, using single cell methods and sacrificial electrodes of magnesium or aluminium. Amongst these, compounds such as 1 which comprise donor and acceptor units at different ends are precursors to silicon materials with non-linear optical properties. 7

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The Synthesis and Conformation of Sterically Congested Seven-membered Rings Containing Tetracoordinate Germanium(IV): Determination of the ΔG* For Ring Inversion¹

Cited by 8 publications

References 27 publications

Mixed amidophenolate–catecholates of molybdenum(vi)

Mixed amidophenolate–catecholates of molybdenum(vi)

The Conformation of Sterically Congested Seven-Membered Rings Containing Tetracoordinate Germanium(IV): A First X-Ray Crystallographic Structure Determination

5 Carbon, silicon, germanium, tin and lead

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The Synthesis and Conformation of Sterically Congested Seven-membered Rings Containing Tetracoordinate Germanium(IV): Determination of the ΔG* For Ring Inversion1

Cited by 8 publications

References 27 publications

Mixed amidophenolate–catecholates of molybdenum(vi)

Mixed amidophenolate–catecholates of molybdenum(vi)

The Conformation of Sterically Congested Seven-Membered Rings Containing Tetracoordinate Germanium(IV): A First X-Ray Crystallographic Structure Determination

5 Carbon, silicon, germanium, tin and lead

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The Synthesis and Conformation of Sterically Congested Seven-membered Rings Containing Tetracoordinate Germanium(IV): Determination of the ΔG* For Ring Inversion¹