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Monomeric Ti(IV) homopiperazine complexes and their exploitation for the ring opening polymerisation of rac-lactide.

Hancock SL, Mahon MF, Jones MD - Chem Cent J (2013)

Bottom Line: Lewis acidic metal centres are currently one of the most popular choices for the initiator for the polymerisation.However, when the ortho substituent is an H-atom then the trans-isomer is formed in the solid-state and solely in solution.This shows the potential applicability of Ti(IV) to initiate the polymerisations.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK. mj205@bath.ac.uk.

ABSTRACT

Background: The area of biodegradable/sustainable polymers is one of increasing importance in the 21st Century due to their positive environmental characteristics. Lewis acidic metal centres are currently one of the most popular choices for the initiator for the polymerisation. Thus, in this paper we report the synthesis and characterisation of a series of monometallic homopiperazine Ti(IV) complexes where we have systematically varied the sterics of the phenol moieties.

Results: When the ortho substituent of the ligand is either a Me, tBu or amyl then the β-cis isomer is isolated exclusively in the solid-state. Nevertheless, in solution multiple isomers are clearly observed from analysis of the NMR spectra. However, when the ortho substituent is an H-atom then the trans-isomer is formed in the solid-state and solely in solution. The complexes have been screened for the polymerisation of rac-lactide in solution and under the industrially preferred melt conditions. Narrow molecular weight material (PDI 1.07 - 1.23) is formed under melt conditions with controlled molecular weights.

Conclusions: Six new Ti(IV) complexes are presented which are highly active for the polymerisation. In all cases atactic polymer is prepared with predictable molecular weight control. This shows the potential applicability of Ti(IV) to initiate the polymerisations.

No MeSH data available.


Related in: MedlinePlus

Synthesis of titanium monometallic complexes supported by homopiperazine salan ligands.
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C1: Synthesis of titanium monometallic complexes supported by homopiperazine salan ligands.

Mentions: Literature preparation methods were utilised to prepare the homopiperazine salan ligands, (1-6)H2[3,45]. The complexes were prepared by a 1:1 reaction of the salan with Ti(OiPr)4 at 80°C, this was carried out under a flow of Ar to facilitate the removal of isopropanol to drive the reaction to the formation of the 1:1 complex. The additional heating (80°C) allowed the homopiperazine ring backbone to adopt the thermodynamically unfavourable boat type configuration and furthermore coordinate both phenols and nitrogen centres to a single titanium metal centre, Scheme 1. These complexes were characterised by elemental analysis, 1H, 13C{1H} NMR spectroscopy and where possible single crystal X-ray diffraction.


Monomeric Ti(IV) homopiperazine complexes and their exploitation for the ring opening polymerisation of rac-lactide.

Hancock SL, Mahon MF, Jones MD - Chem Cent J (2013)

Synthesis of titanium monometallic complexes supported by homopiperazine salan ligands.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750606&req=5

C1: Synthesis of titanium monometallic complexes supported by homopiperazine salan ligands.
Mentions: Literature preparation methods were utilised to prepare the homopiperazine salan ligands, (1-6)H2[3,45]. The complexes were prepared by a 1:1 reaction of the salan with Ti(OiPr)4 at 80°C, this was carried out under a flow of Ar to facilitate the removal of isopropanol to drive the reaction to the formation of the 1:1 complex. The additional heating (80°C) allowed the homopiperazine ring backbone to adopt the thermodynamically unfavourable boat type configuration and furthermore coordinate both phenols and nitrogen centres to a single titanium metal centre, Scheme 1. These complexes were characterised by elemental analysis, 1H, 13C{1H} NMR spectroscopy and where possible single crystal X-ray diffraction.

Bottom Line: Lewis acidic metal centres are currently one of the most popular choices for the initiator for the polymerisation.However, when the ortho substituent is an H-atom then the trans-isomer is formed in the solid-state and solely in solution.This shows the potential applicability of Ti(IV) to initiate the polymerisations.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK. mj205@bath.ac.uk.

ABSTRACT

Background: The area of biodegradable/sustainable polymers is one of increasing importance in the 21st Century due to their positive environmental characteristics. Lewis acidic metal centres are currently one of the most popular choices for the initiator for the polymerisation. Thus, in this paper we report the synthesis and characterisation of a series of monometallic homopiperazine Ti(IV) complexes where we have systematically varied the sterics of the phenol moieties.

Results: When the ortho substituent of the ligand is either a Me, tBu or amyl then the β-cis isomer is isolated exclusively in the solid-state. Nevertheless, in solution multiple isomers are clearly observed from analysis of the NMR spectra. However, when the ortho substituent is an H-atom then the trans-isomer is formed in the solid-state and solely in solution. The complexes have been screened for the polymerisation of rac-lactide in solution and under the industrially preferred melt conditions. Narrow molecular weight material (PDI 1.07 - 1.23) is formed under melt conditions with controlled molecular weights.

Conclusions: Six new Ti(IV) complexes are presented which are highly active for the polymerisation. In all cases atactic polymer is prepared with predictable molecular weight control. This shows the potential applicability of Ti(IV) to initiate the polymerisations.

No MeSH data available.


Related in: MedlinePlus