Molybdenum (VI) Imido Complexes Derived from Chelating Phenols: Synthesis, Characterization and ɛ-Caprolactone ROP Capability

Catalysts

Yahya Al-Khafaji²  Timothy J. Prior²  Mark R. J. Elsegood¹  Carl Redshaw² 

[1] Chemistry Department, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK; E-Mail:;Department of Chemistry, University of Hull, Hull HU6 7RX, UK; E-Mails:

关键词: molybdenum (VI);    imido;    phenolate;    chelate;    crystal structures;    ε-caprolactone;    ring opening polymerization;   

DOI  :  10.3390/catal5041928

来源: mdpi

【 摘 要 】

Reaction of the bulky bi-phenols 2,2′-RCH[4,6-(t-Bu)2C6H2OH]₂ (R = Me L^1MeH₂, Ph L^1PhH₂) with the bis(imido) molybdenum(VI) tert-butoxides [Mo(NR¹)(NR²)(Ot-Bu)₂] (R¹ = R² = 2,6-C₆H₃-i-Pr₂; R¹ = t-Bu, R² = C₆F₅) afforded, following the successive removal of tert-butanol, the complexes [Mo(NC₆H₃i-Pr₂-2,6)₂L^1Me] (1), [Mo(NC₆H₃i-Pr₂-2,6)₂L^1Ph] (2) and [Mo(Nt-Bu)(μ-NC₆F₅)(L^1Me)]₂ (3). Similar use of the tri-phenol 2,6-bis(3,5-di-tert -butyl-2-hydroxybenzyl)-4-methylphenol (L²H₃) with [Mo(NC₆H₃i-Pr₂-2,6)₂(Ot-Bu)₂] afforded the oxo-bridged product [Mo(NC₆H₃i-Pr₂-2,6)(NCMe)(μ-O)L²H]₂ (4), whilst use of the tetra-phenols α,α,α′,α′-tetrakis(3,5-di-tert-butyl-2-hydroxyphenyl)-p- or -m-xylene L^3pH₄/L^3mH₄ led to {[Mo(NC₆H₃i-Pr₂-2,6)₂]₂(μ-L^3p)} (5) or {[Mo(NC₆H₃i-Pr₂-2,6)₂]₂(μ-L^3m)} (6), respectively. Similar use of [Mo(NC₆F₅)₂(Ot-Bu)₂] with L^3pH₄ afforded, after work-up, the complex {[Mo(NC₆F₅)(Ot-Bu)₂]₂(μ-L^3p)}·6MeCN (7·6MeCN). Molecular structures of 1, 2·CH₂Cl₂, 3, 4·6MeCN, 6·2C₆H₁₄, and 7·6MeCN are reported and these complexes have been screened for their ability to ring open polymerize (ROP) ε-caprolactone; for comparative studies the precursor complex [Mo(NC₆H₃i-Pr₂-2,6)₂Cl₂(DME)] (DME = 1,2-dimethoxyethane) has also been screened. Results revealed that good activity is only achievable at temperatures of ≥100 °C over periods of 1 h or more. Polymer polydispersities were narrow, but observed molecular weights (M_n) were much lower than calculated values.

【 授权许可】

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