Reaction of {LiC6H2−2,4,6‐Cyp3⋅Et2O}2(Cyp=cyclopentyl) (
π-stacking in ground-state dimers/trimers/tetramers of
- NSF-PAR ID:
- 10308270
- Publisher / Repository:
- Proceedings of the National Academy of Sciences
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 118
- Issue:
- 44
- ISSN:
- 0027-8424
- Page Range / eLocation ID:
- Article No. e2106572118
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract 1 ) of the new dispersion energy donor (DED) ligand, 2,4,6‐triscyclopentylphenyl with SnCl2afforded a mixture of the distannene {Sn(C6H2−2,4,6‐Cyp3)2}2(2 ), and the cyclotristannane {Sn(C6H2−2,4,6‐Cyp3)2}3(3 ).2 is favored in solution at higher temperature (345 K or above) whereas3 is preferred near 298 K. Van't Hoff analysis revealed the3 to2 conversion has a ΔH =33.36 kcal mol−1and ΔS =0.102 kcal mol−1 K−1, which gives a ΔG 300 K=+2.86 kcal mol−1, showing that the conversion of3 to2 is an endergonic process. Computational studies show that DED stabilization in3 is −28.5 kcal mol−1per {Sn(C6H2−2,4,6‐Cyp3)2unit, which exceeds the DED energy in2 of −16.3 kcal mol−1per unit. The data clearly show that dispersion interactions are the main arbiter of the3 to2 equilibrium. Both2 and3 possess large dispersion stabilization energies which suppress monomer dissociation (supported by EDA results). -
Abstract Reaction of {LiC6H2−2,4,6‐Cyp3⋅Et2O}2(Cyp=cyclopentyl) (
1 ) of the new dispersion energy donor (DED) ligand, 2,4,6‐triscyclopentylphenyl with SnCl2afforded a mixture of the distannene {Sn(C6H2−2,4,6‐Cyp3)2}2(2 ), and the cyclotristannane {Sn(C6H2−2,4,6‐Cyp3)2}3(3 ).2 is favored in solution at higher temperature (345 K or above) whereas3 is preferred near 298 K. Van't Hoff analysis revealed the3 to2 conversion has a ΔH =33.36 kcal mol−1and ΔS =0.102 kcal mol−1 K−1, which gives a ΔG 300 K=+2.86 kcal mol−1, showing that the conversion of3 to2 is an endergonic process. Computational studies show that DED stabilization in3 is −28.5 kcal mol−1per {Sn(C6H2−2,4,6‐Cyp3)2unit, which exceeds the DED energy in2 of −16.3 kcal mol−1per unit. The data clearly show that dispersion interactions are the main arbiter of the3 to2 equilibrium. Both2 and3 possess large dispersion stabilization energies which suppress monomer dissociation (supported by EDA results). -
Abstract The structure of liquid lithium pyroborate, Li4B2O5(
J = Li/B = 2), has been measured over a wide temperature range by high‐energy X‐ray diffraction, and compared to that of its glass and borate liquids of other compositions. The results indicate a gradual increase in tetrahedral boron fraction from 3(1)% to 6(1)% during cooling fromT = 1271(15) to 721(8) K, consistent with the largerN 4 = 10(1)% found for the glass, and literature11B nuclear magnetic resonance measurements. van't Hoff analysis based on a simple boron isomerization reaction BØ3O2–⇌ BØO22–yields ΔH = 13(1) kJ mol–1and ΔS = 40(1) J mol–1 K–1for the boron coordination change from 4 to 3, which are, respectively, smaller and larger than found for singly charged isomers forJ ≤ 1. With these, we extend our model forN 4(J ,T ), nonbridging oxygen fractionf nbr(J ,T ), configurational heat capacity , and entropyS conf(J ,T ) contributions up toJ = 3. A maximum is revealed in atJ = 1, and shown semi‐quantitatively to lead to a corresponding maximum in fragility contribution, akin to that observed in the total fragilities by temperature‐modulated differential scanning calorimetry. Lithium is bound to 4.6(2) oxygen in the pyroborate liquid, with 2.7(1) bonds centered around 1.946(8) Å and 1.9(1) around 2.42(1) Å. In the glass,n LiO= 5.4(4), the increase being due to an increase in the number of short Li–O bonds. -
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