Mono-oxo molybdenum(VI) and tungsten(VI) complexes bearing chelating aryloxides: synthesis, structure and ring opening polymerization of cyclic esters

Sun, Ziyue; Zhao, Yanxia; Prior, Timothy J.; Elsegood, Mark R.J.; Wang, Kuiyuan; Xing, Tian; Redshaw, Carl

Abstract

The mono-oxo aryloxide complexes [M(O)(L1)2] (M = Mo (1·hexane), W(2·2MeCN)) have been prepared from [Mo(O)(Cl)4] or [W(O)(Ot-Bu)4] and two equivalents of the di-phenol 2,2/-ethylidenebis(4,6-di-tert-butylphenol) L1H2, respectively. Use of in-situ generated [Mo(O)(Ot-Bu)4] with two equivalents of L1H2 also led to the isolation of 1·2MeCN. In the presence of adventitious oxygen, attempts to generate in-situ [Mo(O)(Ot-Bu)4] and reaction with one equivalent of L1H2 afforded the bi-metallic complex [Mo(O)(L1)(-O)Li(THF)(MeCN)]2·2MeCN (3·2MeCN). Use of the tetra-phenol α,α,α′,α′-tetrakis(3,5-di-tert-butyl-2-hydroxyphenyl)-p-xyleneH4 (L2H4) with [Mo(O)(Oi-Pr)4] led to the isolation of {[Mo(O)]L2}2 (4), whilst the analogous tungsten complex {[W(O)]L2}2 (5) was isolated from the reaction of L2H4 with [W(O)(Ot-Bu)4]. Similar reaction of p-tert-butylcalix[4]areneH4 (L3H4) with [Mo(O)(Oi-Pr)4] afforded ([Mo(O)L3(NCMe)]·3MeCN (6·3MeCN). Modification of known routes were employed to access the complexes [W(Cl)2L3]·3.5MeCN (7·3.5MeCN) and ([W(O)L3(NCMe)] (8), whilst use of [WO(Ot-Bu)4] with L3H4 unexpectedly afforded [W(Ot-Bu)2L3]·MeCN (9·MeCN). The molecular crystal structures for 1 – 9 are reported, and the ability of these complexes to act as catalysts for the ring opening polymerization (ROP) of epsilon-caprolactone (epsilon-CL), delta-valerolactone (delta-VL) and gamma-pentadecalactone (gamma-PDL) has been investigated. The molybdenum complexes 1 and 4 were the best performers for epsilon-Cl and delta-VL, but all complexes exhibited poor control and were also inactive toward the ROP of PDL.

Citation

Sun, Z., Zhao, Y., Prior, T. J., Elsegood, M. R., Wang, K., Xing, T., & Redshaw, C. (2019). Mono-oxo molybdenum(VI) and tungsten(VI) complexes bearing chelating aryloxides: synthesis, structure and ring opening polymerization of cyclic esters. Dalton Transactions : an international journal of inorganic chemistry, 48(4), 1454-1466. https://doi.org/10.1039/c8dt04566f

• Journal Article Type: Article
• Acceptance Date: Dec 23, 2018
• Online Publication Date: Dec 27, 2018
• Publication Date: Jan 22, 2019
• Deposit Date: Dec 29, 2018
• Publicly Available Date: Dec 28, 2019
• Journal: Dalton Transactions
• Print ISSN: 1477-9226
• Electronic ISSN: 1477-9234
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 48
• Issue: 4
• Pages: 1454-1466
• DOI: https://doi.org/10.1039/c8dt04566f
• Keywords: Inorganic Chemistry
• Public URL: https://hull-repository.worktribe.com/output/1199373
• Publisher URL: https://pubs.rsc.org/en/Content/ArticleLanding/2018/DT/C8DT04566F
• Additional Information: : This document is Similarity Check deposited; : Supplementary Information; : Single-blind; : Received 17 November 2018; Accepted 23 December 2018; Accepted Manuscript published 27 December 2018