Tantalum -Alkylidyne Compounds Containing o-Phenyl- and o-(1-Naphthyl)phenoxides: Probing Molecular Structure and Dynami
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- 作者：Patrick N. Riley ; Matthew G. Thorn ; Jonathan S. Vilardo ; Mark A. Lockwood ; Phillip E. Fanwick ; and Ian P. Rothwell
- 刊名：Organometallics
- 出版年：1999
- 出版时间：August 2, 1999
- 年：1999
- 卷：18
- 期：16
- 页码：3016 - 3024
- 全文大小：170K
- 年卷期：v.18,no.16(August 2, 1999)
- ISSN：1520-6041
文摘
The new o-(1-naphthyl)phenols 2-(1-naphthyl)-4,6-di-tert-butylphenol, 2,6-bis(1-naphthyl)phenol, 2,6-bis(1-naphthyl)-3,5-dialkylphenol (alkyl = Ph, Me, But), and 2-(1-naphthyl)-3,5,6-triphenylphenol have been synthesized. The reaction of these phenols and their o-phenylcounterparts with the compound [Ta2(
-CSiMe3)2(CH2SiMe3)4] has been investigated. Thisreaction produces the monosubstitution products [(ArO)(Me3SiCH2)Ta(-CSiMe3)2Ta(CH2SiMe3)2] at rates which are strongly dependent on the nature of the phenol substituents.The NMR spectroscopic properties of the resulting derivatives can be used to probe thephenoxide structure. Nonchiral phenoxides yield singlets for the CH2SiMe3 methylene protonsand one set of -CSiMe3 resonances, whereas the presence of a chiral phenoxide generatesdiastereotopic CH2SiMe3 protons and nonequivalent -CSiMe3 groups. The solid-statestructure of the 2-(1-naphthyl)-3,5,6-triphenylphenoxide and 2,6-bis(1-naphthyl)phenoxidederivatives shows that the 1,3-dimetallacyclobutadiene core remains intact with Ta-Tadistances of 2.8943(6) and 2.8886(7) Å, respectively. The rate expression for substitution ofthe first alkyl group in [Ta2(-CSiMe3)2(CH2SiMe3)4] (11) by 2-phenyl-4,6-di-tert-butylphenol(5) in C6D6 solvent is first order in both [11] and [5] with a second-order rate constant of[1.40(7)] × 10-4 mol-1 L-1 s-1 at 30(1) 
C. Use of the deuterated phenol ArOD gave a rateconstant of [0.25(3)] × 10-4 mol-1 L-1 s-1, hence demonstrating the primary kinetic isotopeeffect kH/kD = 5.6(5). Competition reactions have yielded the relative rates of substitution of11 by various phenols.
-CSiMe3)2(CH2SiMe3)4] has been investigated. Thisreaction produces the monosubstitution products [(ArO)(Me3SiCH2)Ta(-CSiMe3)2Ta(CH2SiMe3)2] at rates which are strongly dependent on the nature of the phenol substituents.The NMR spectroscopic properties of the resulting derivatives can be used to probe thephenoxide structure. Nonchiral phenoxides yield singlets for the CH2SiMe3 methylene protonsand one set of -CSiMe3 resonances, whereas the presence of a chiral phenoxide generatesdiastereotopic CH2SiMe3 protons and nonequivalent -CSiMe3 groups. The solid-statestructure of the 2-(1-naphthyl)-3,5,6-triphenylphenoxide and 2,6-bis(1-naphthyl)phenoxidederivatives shows that the 1,3-dimetallacyclobutadiene core remains intact with Ta-Tadistances of 2.8943(6) and 2.8886(7) Å, respectively. The rate expression for substitution ofthe first alkyl group in [Ta2(-CSiMe3)2(CH2SiMe3)4] (11) by 2-phenyl-4,6-di-tert-butylphenol(5) in C6D6 solvent is first order in both [11] and [5] with a second-order rate constant of[1.40(7)] × 10-4 mol-1 L-1 s-1 at 30(1) C. Use of the deuterated phenol ArOD gave a rateconstant of [0.25(3)] × 10-4 mol-1 L-1 s-1, hence demonstrating the primary kinetic isotopeeffect kH/kD = 5.6(5). Competition reactions have yielded the relative rates of substitution of11 by various phenols.