The synthesis, co-ordination chemistry and catalytic applications of phosphine ligands containing long-chain perfluoro-alkyl groups

• Main Author: Paige, Danny R.
• Published: University of Leicester 1998
• Subjects: 546
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.696459

A review is presented of the use of catalytic liquid-liquid biphase systems containing a perfluorinated phase, commonly referred to as 'fluorous biphase systems' or F.B.S. catalysis. The phosphines PPh(3-x)(C2H4C6F13), PPh(3-x)(C6H4-p-C6F13)x and PPh(3-x)(C6H4-m-C6F13), where x = 1, 2 and 3, have been synthesised and fully characterised by 1H, 19F and 31P NMR spectroscopy, mass spectroscopy and elemental analysis, with a view to assessing their potential for use in F.B.S. catalysis. The crystal structures of O=P(C6H4-m-C6F13) and Cl-P(C6H4-o-C6F13)2 are also reported. The synthetic route to P(C2H4C6F13)3 represents an improvement on the literature preparation. These phosphines have been reacted with a variety of transition metals to form complexes of the type cis- and trans-[MCl2L2] (M = Pt, Pd), trans-[MCl(CO)L2] (M = Rh, Ir), [RhCp*Cl2L] and [RhClL3]. These complexes have all been isolated and fully characterised, except for the complexes [RhClL3], which have not been isolated, but whose solution chemistry is described. The crystal structures of the complexes cis-[PtCl2(PPh2C2H4C6F13)2] and trans-[RhCl(CO)(P{C2H4C6F13}3)2] are also reported. All of the complexes described above have been extensively investigated using a variety of analytical techniques including 31P, 19F and 1H NMR spectroscopy, mass spectroscopy and IR spectroscopy. The results from an EXAFS spectroscopic study on some of these complexes is included as an appendix to this work. The electronic and steric influence of the perfluorinated chains on the reactivity and behaviour of both the free phosphines and the metal complexes has been evaluated from the nature of the products isolated, from a comparison of their spectroscopic and structural data with those for related metal-phosphine complexes and, for the complexes trans-[IrCl(CO)L2], from a kinetic study on the rate of O2 addition. Preliminary catalytic hydrogenation and hydroformylation studies have been carried out using the complexes [RhClL3] and [RhH(CO)L3] respectively, where L = phosphine. These catalytic species were gathered in situ and the study involved the use of F.B.S. catalysis. The effect of the variation of the phosphine type, the solvents and the reaction conditions, has been examined in terms of reaction rate, product selectivity and product/catalyst separation. The potential of F.B.S. catalysis using phosphine ligands has been assessed.