Evidence for π bonding in the boron-thiolate compounds (2,4,6-Me3C6H2)2B(SPh) and (2,4,6-Pri 3C6H2)B(SPh)2

Rudolf Wehmschulte, Karin Ruhlandt, Marilyn M. Olmstead, Mark A. Petrie, Philip P. Power

Research output: Contribution to journalArticle

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Abstract

The use of the bulky aryl substituent groups 2,4,6-Me3C6H2 and 2,4,6-Pri 3C6H2 has allowed the structural characterization of two monomeric boron-sulfur compounds (2,4,6-Me3C6H2)2B(SPh) 1 and (2,4,6-Pri 3C6H2)B(SPh)2 2. The crystal structures of 1 and 2 show a close alignment between the boron and sulfur p orbitals that is consistent with a π interaction. Furthermore, the B-S distances in 1 [1.790(6)] and 2 [1.801(6) Å] are slightly shorter than the sum of the covalent radii (with allowance made for ionic effects) of boron and sulfur. Variable-temperature 1H and 13C NMR data for 2 indicate an average barrier to rotation around the B-S bond of ca. 12 kcal mol-1. This value is significantly less than the 18.4 kcal mol-1 reported earlier for 1. The lower rotational barrier observed in 2 is consistent with the delocalization of the B-S π bond over the three atom BS2 π system which has a similar electronic arrangement to that of an allyl anion. Crystal data at 130 K: 1, triclinic, space group P1, a = 7.851(5), b = 11.685(6), c = 13.096(7) Å, α = 63.52(2), β = 73.93(2), γ = 74.54(2)°, Z = 2, R = 0.073; 2, monoclinic, space group P21/c, a = 18.373(3), b = 12.713(2), c = 10.844(2) Å, β = 99.96(1)°, Z = 4, R = 0.072.

Original languageEnglish (US)
Pages (from-to)2113-2117
Number of pages5
JournalJournal of the Chemical Society - Dalton Transactions
Issue number14
DOIs
StatePublished - 1994
Externally publishedYes

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Boron compounds
Boron
Sulfur
Sulfur Compounds
Anions
Crystal structure
Nuclear magnetic resonance
Atoms
Crystals
Temperature

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Evidence for π bonding in the boron-thiolate compounds (2,4,6-Me3C6H2)2B(SPh) and (2,4,6-Pri 3C6H2)B(SPh)2 . / Wehmschulte, Rudolf; Ruhlandt, Karin; Olmstead, Marilyn M.; Petrie, Mark A.; Power, Philip P.

In: Journal of the Chemical Society - Dalton Transactions, No. 14, 1994, p. 2113-2117.

Research output: Contribution to journalArticle

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title = "Evidence for π bonding in the boron-thiolate compounds (2,4,6-Me3C6H2)2B(SPh) and (2,4,6-Pri 3C6H2)B(SPh)2",
abstract = "The use of the bulky aryl substituent groups 2,4,6-Me3C6H2 and 2,4,6-Pri 3C6H2 has allowed the structural characterization of two monomeric boron-sulfur compounds (2,4,6-Me3C6H2)2B(SPh) 1 and (2,4,6-Pri 3C6H2)B(SPh)2 2. The crystal structures of 1 and 2 show a close alignment between the boron and sulfur p orbitals that is consistent with a π interaction. Furthermore, the B-S distances in 1 [1.790(6)] and 2 [1.801(6) {\AA}] are slightly shorter than the sum of the covalent radii (with allowance made for ionic effects) of boron and sulfur. Variable-temperature 1H and 13C NMR data for 2 indicate an average barrier to rotation around the B-S bond of ca. 12 kcal mol-1. This value is significantly less than the 18.4 kcal mol-1 reported earlier for 1. The lower rotational barrier observed in 2 is consistent with the delocalization of the B-S π bond over the three atom BS2 π system which has a similar electronic arrangement to that of an allyl anion. Crystal data at 130 K: 1, triclinic, space group P1, a = 7.851(5), b = 11.685(6), c = 13.096(7) {\AA}, α = 63.52(2), β = 73.93(2), γ = 74.54(2)°, Z = 2, R = 0.073; 2, monoclinic, space group P21/c, a = 18.373(3), b = 12.713(2), c = 10.844(2) {\AA}, β = 99.96(1)°, Z = 4, R = 0.072.",
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T1 - Evidence for π bonding in the boron-thiolate compounds (2,4,6-Me3C6H2)2B(SPh) and (2,4,6-Pri 3C6H2)B(SPh)2

AU - Wehmschulte, Rudolf

AU - Ruhlandt, Karin

AU - Olmstead, Marilyn M.

AU - Petrie, Mark A.

AU - Power, Philip P.

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N2 - The use of the bulky aryl substituent groups 2,4,6-Me3C6H2 and 2,4,6-Pri 3C6H2 has allowed the structural characterization of two monomeric boron-sulfur compounds (2,4,6-Me3C6H2)2B(SPh) 1 and (2,4,6-Pri 3C6H2)B(SPh)2 2. The crystal structures of 1 and 2 show a close alignment between the boron and sulfur p orbitals that is consistent with a π interaction. Furthermore, the B-S distances in 1 [1.790(6)] and 2 [1.801(6) Å] are slightly shorter than the sum of the covalent radii (with allowance made for ionic effects) of boron and sulfur. Variable-temperature 1H and 13C NMR data for 2 indicate an average barrier to rotation around the B-S bond of ca. 12 kcal mol-1. This value is significantly less than the 18.4 kcal mol-1 reported earlier for 1. The lower rotational barrier observed in 2 is consistent with the delocalization of the B-S π bond over the three atom BS2 π system which has a similar electronic arrangement to that of an allyl anion. Crystal data at 130 K: 1, triclinic, space group P1, a = 7.851(5), b = 11.685(6), c = 13.096(7) Å, α = 63.52(2), β = 73.93(2), γ = 74.54(2)°, Z = 2, R = 0.073; 2, monoclinic, space group P21/c, a = 18.373(3), b = 12.713(2), c = 10.844(2) Å, β = 99.96(1)°, Z = 4, R = 0.072.

AB - The use of the bulky aryl substituent groups 2,4,6-Me3C6H2 and 2,4,6-Pri 3C6H2 has allowed the structural characterization of two monomeric boron-sulfur compounds (2,4,6-Me3C6H2)2B(SPh) 1 and (2,4,6-Pri 3C6H2)B(SPh)2 2. The crystal structures of 1 and 2 show a close alignment between the boron and sulfur p orbitals that is consistent with a π interaction. Furthermore, the B-S distances in 1 [1.790(6)] and 2 [1.801(6) Å] are slightly shorter than the sum of the covalent radii (with allowance made for ionic effects) of boron and sulfur. Variable-temperature 1H and 13C NMR data for 2 indicate an average barrier to rotation around the B-S bond of ca. 12 kcal mol-1. This value is significantly less than the 18.4 kcal mol-1 reported earlier for 1. The lower rotational barrier observed in 2 is consistent with the delocalization of the B-S π bond over the three atom BS2 π system which has a similar electronic arrangement to that of an allyl anion. Crystal data at 130 K: 1, triclinic, space group P1, a = 7.851(5), b = 11.685(6), c = 13.096(7) Å, α = 63.52(2), β = 73.93(2), γ = 74.54(2)°, Z = 2, R = 0.073; 2, monoclinic, space group P21/c, a = 18.373(3), b = 12.713(2), c = 10.844(2) Å, β = 99.96(1)°, Z = 4, R = 0.072.

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