Phenoxy functionalised complexes

Figure 4.14 Synthesis of a phenoxy functionalised NHC and its titanium(IV) carbene complex.

Shen and coworkers used Kawaguchi s phenoxy functionalised carbene ligand for the preparation of nickel(II) [62] and iron (II) [63] carbene complexes. Using the same deprotonation method — NaN(SiMe3)2— they attempted the synthesis of a mono-carbene nickel(II) complex that resulted in the formation of the homoleptic complex instead [62] (see Figure 4.16). Use of the correct stoichiometries significantly increased the yield. 

The homoleptic iron(II) phenoxy functionalised carbene complex was used in the ROP of e-caprolactone [64]. The polymerisation proceeds via a coordination-insertion mechanism [65-67] and the final product has the functionalised imidazolium unit as end group. Performance was riddled by poor control over number-average molecular weight and decreasing molecular weight with decreasing feedstock levels. This was attributed to inter-and/or intramolecular transesteriflcation processes [65,66],... 

Figure 4.16 Synthesis of a homoleptic nickel(Il) carbene complex with a phenoxy functionalised NHC ligand.

Figure 4.20 Synthesis of phenoxy functionalised benzimidazolium salts and theirpalladium(ll) complexes.

Agboola BO, Ozoemena Kl, Nyokong T et al (2010) Tuning the physico-electrochemical properties of novel cobalt (II) octa[(3,5-biscaiboxylate)-phenoxy] phthalocyanine complex using phenylamine-functionalised SWCNTs. Carbon 48 763-773... 

Attachment of the catalyst to a polymeric support can also be facilitated using a bis-carbene as the ligand [253]. The bisimidazoUum salt featuring a hydroxyalkyl sidechain on each of the two imidazolium units was reacted with palladium (II) acetate to form the neutral catalyst complex (see Figure 4.82). Immobilisation was then achieved by reacting the functionalised catalyst with 4-(bromomethyl)phenoxy-methyl polystyrene, known as Wang resin, as the polymeric support. 

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