Lanthanoid complexes hydrogenation

In the first of these techniques the lanthanoid complex (33) (5-8 mol%) is used as the organometallic activator in cumene hydroperoxide or tert-butyl hydrogen peroxide-mediated oxidation of chalcone (epoxide yield 99 % 99 % ee) or the ketone (34) (Scheme 20)[1001. 

Actinide and lanthanoid complexes have been employed for hydrogenation reactions, for which they often generate dramatic rate increases and high numbers of turnovers42. Many of these complexes exhibit good selectivity for preferential reduction of the less hindered alkene in situations where more than one is present in a substrate (Scheme l)43. 

In the presence of [Cp2Mo2(CO)4], 3 > [Ni2(COD)2( JL-ri2-RC R)],223 = and [Ni4(RNC)4( X3-V-RC=CR)3], alkynes are converted to ds-alkenes. The alkenes once formed no longer bind to the complex and hydrogenation does not proceed further to give alkanes or even isomerized alkenes. Cocondensation of lanthanoid metal atoms with internal alkynes generates lanthanoid complexes of alkynes, which are potential catalysts for hydrogenation. [ Sm(l-hexyne) n] or [ Er(3-hexyne) n] catalyzes hydrogenation of hex-3-yne to ds-hex-3-ene (97% cis) at room temperature and atmospheric pressure of H2. ... 

Figure 2.16 View of the molecular structure of [Eu(HL )3(CH30H)2]-CH30H-2H20. The non-coordinated methanol molecule and hydrogen atoms were omitted for clarity [40]. (Reprinted from Polyhedron, 28, S. Tanase, M. Viciano-Chumillas, J.M.M. Smits, R. de Gelder and J. Reedijk, Cop-per(II) and lanthanoid(III) complexes of a new fS-diketonate ligand with an appended non-coordinating phenol group, 457 60, 2009, with permission from Elsevier.)...

Shibasaki has recently described a process for epoxidation of electron-deficient alkenes catalyzed by chiral lanthanoid-BINOL complexes (5-8 mol %) using ferf-butyl hydrogen peroxide [or cumene hydroperoxide (CMHP)] [56]. Epoxides were obtained in excellent yields and enantioselectivities as shown in Scheme 21. 

The hexafluorophosphate ion has proved to be very useful for studies with complexes, since the [PF6] anion has a very weak coordinating ability.1 Lan-thanoid hexafluorophosphates can be obtained in very concentrated aqueous solutions by reaction of a freshly prepared solutions of hexafluorophosphoric acid and a hydrated lanthanoid basic carbonate.2 The resulting solution, after filtration, is evaporated to near dryness. Attempts to isolate the hydrated salts are unsuccessful because of decomposition accompanied by hydrogen fluoride evolution. Nevertheless, the complexes containing diphenylphosphinic amide are isolable and are quite stable.3... 

Organolanthanoide hydrides (1 11,1 8,215,221), cyclopentadienyl-ytterbium(ll) complexes (190) as well as the cocondensation products of lanthanoides with acetylenic derivatives (137,216,222) catalyze the hydrogenation of olefins and acetylenes. 

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