Studies into the synthesis of primary phosphines for the preparation of macrocycles by template methods

• Main Author: Reixach, Elisenda
• Published: Cardiff University 2006
• Subjects: 546
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.583752

This thesis is focused in the synthesis of phosphine-based macrocycles by template methods. Furthermore, it explores some alternative methods for the synthesis of known and unknown polydentate primary phosphine compounds necessary for the preparation of new macrocycles. Following this new procedure the novel tripodal primary phosphine cis, cis-1,3,5-triphosphinomethylcyclohexane (2.15) has been prepared in good yields as well as the reported bis(2-phosphinoethyl)amine (PNP, 3.4). Mono-alkylation of 3.4 allowed the preparation of the asymmetric 2-(allylphosphino)-N-(2-phosphinoethyl)ethanamine ligand (3.16) in low yields. Whilst ligands 2.15 and 3.16 failed to form well-defined facially coordinated molybdenum(O) and chromium(O) complexes respectively, 3.4 formed octahedral complexes with Cr(0) and Fe(II) metals, {/ac-Cr(CO)₃(PNP)}, 3.8 and {n5-C₅H₄(SiMe₃)}Fe(PNP) PF6, 3.10. Different attempts have been made to cyclise the facially coordinated chromium complex 3.8, however all of them have failed. The synthesis of 3.8 and 3.10 has been confirmed by X-ray diffraction. The synthesis of a new Mn(I) 9-membered tribenzanulated I1 triphosphamacrocycle complex Mn(CO)₃{(C₆H₄F)PC₆H₄PHC₆H₄PHC₆H₄} OTf, 4.10 has been successfully synthesised by sequential introduction of 1,2-diphosphinobenzene and tris(2-fluorophenyl)phosphine on a manganese(I) complex and subsequent addition of /-BuOK. Alkylation of the two secondary phosphorus of 4.10 with Mel allowed the isolation of the more stable manganese complex II Mn(CO)₃{(C₆H₄F)PC₆H₄P(CH₃)C₆H₄P(CH₃)C₆H₄} OTf/I 4.12. The liberation of the phosphine trioxide macrocycle, {(C₆H₄F)J>(0)C₆H₄P(0)(CH₃)C₆H₄(0)(CH₃)C₆H₄} 4.14 from the metal has been achieved using 4-methylmorpholine N-oxide in excess. In addition, the X-ray crystal structures of the non-cyclised precursor intermediate Mn(CO)₃{(C₆H₄F)₃P}{C₆H₄(PH₂)₂-o} OTf 4.9 and the half cyclised intermediate (I Mn(CO)₃{(C₆H₄F)₂PC₆H₄PHC₆H₄PH₂} OTf 4.11 as well as the final macrocycle 4.12 have also been established.