Crystallographic characterisation of Ti(IV) piperazine complexes and their exploitation for the ring opening polymerisation of rac-lactide.
In this paper a series of eight Ti(IV) piperazine based complexes have been prepared and fully characterised in the solid-state by X-ray crystallography and in solution via NMR spectroscopy. In the solid-state either Ti(2)(L)(O(i)Pr)(6) or Ti(2)(L)(2)(O(i)Pr)(4) were observed depending upon the nature of the starting ligand. For complexes with less sterically demanding ligands (1H(2) and 2H(2)) an equilibrium was observed: 2 Ti(2)(L)(O(i)Pr)(6) ⇔ Ti(2)(L)(2)(O(i)Pr)(4) + 2 Ti(O(i)Pr)(4). The thermodynamic properties (ΔG, ΔH and ΔS) have been investigated via variable temperature NMR spectroscopy. With more sterically demanding ligands (3-8H(2)) the Ti(2)(L)(O(i)Pr)(6) form was the most prevalent in the solid-state and in solution. These complexes have been tested for the production of polylactide under melt and solution conditions with high conversions being obtained.
Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
Stuart L
SL
Hancock
Mary F
MF
Mahon
Matthew D
MD
Jones
D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry; D018360:Crystallography, X-Ray / Q000379:methods; D004146:Dioxanes / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D000077489:Piperazine; D010879:Piperazines / Q000737:chemistry*; D011091:Polyesters / Q000138:chemical synthesis* / Q000737:chemistry*; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry; D012996:Solutions / Q000737:chemistry; D013816:Thermodynamics; D014025:Titanium / Q000737:chemistry*
D056831:Coordination Complexes; D004146:Dioxanes; D008024:Ligands; D009942:Organometallic Compounds; D010879:Piperazines; D011091:Polyesters; D011108:Polymers; D012996:Solutions; D000077489:Piperazine; C033616:poly(lactide); C091880:dilactide; D014025:Titanium