Tris phosphine ligand

Introducing a chiral center in the amide functionality renders all 32 potential isomers diastereomeric and thus discernable (in principle) by NMR spectroscopy. In practice, the lanthanide complexes formed (Eu, Gd and Tb) with macrocyclic monoamide tris(phosphinate) ligands bearing a chiral center on the amide group exist as only two non-interconverting diastereomers in a ratio of 2 1 and 4 1 for the a-phenylethyl and a-l-napthylethyl derivatives, respectively (DOTMP-MPMeA and DOTMP-MNaphMeA) [114]. The configuration at... 

II) occurs readily at room temperature even in nonpolar solvents. Various tripodal tris-phosphine ligands have also been shown to attach all three phosphorus atoms providing [Ir(COD)P3]+ compounds. ... 

The coupling of the enol triflate 703 with the vinylstannane 704[397] has been applied to the synthesis of glycinoeclepin[576]. The introduction of a (Z)-propenyl group in the / -lactam derivative 705 proceeds by use of tri-2-furylphosphine[577]. However, later a smooth reaction to give the propenyl-iactam in 82% yield was achieved simply by treating with Pd(OAc)2 in NMP or CH2CI2 for 3-5 min without addition of LiCI and the phosphine ligand[578]. 

A number of tertiary phosphine ligands have been synthesized that also contain an alkene linkage capable of coordinating to a metal. A good example of this kind of coordination is formed in the complex of (tri-o-vinyl-phenyl)phosphine (Figure 2.29) with each alkene acting as a two-electron donor, a noble gas configuration is achieved [67],... 

The trinuclear gold(I) complexes [(AuX)3( j,-triphos)] (triphos = bis(2-diphenylphos-phinoethyl)phenylphosphine X = Cl, Br, I, CgFs ), where X = Br and I , were reported to emit at room temperature with emission energies significantly red-shifted from that ofthe free phosphine ligand (2477 cm for Br with Agx 350 nm 4482 cm for I with Aex 385 nm) [41]. The chloro, pentafluorophenyl, and l,3,5-tris(trifluor-omethyl)phenyl derivatives do not emit, even at Aex <300 nm. The emission properties... 

More recently, Atwood et al. developed a platinum complex of a water-soluble, bidentate phosphine ligand, cA-(TPPTS)2PtCl2 [TPPTS = tris(sodium m -benzenesuI onatc)phosphi nc, as an effective hydration... 

Ligand self-assembly through coordinative bonding has been used to increase the bulkiness of a monodentate tris-3-pyridyl phosphine ligand employing the zinc porphyrin/pyridine interaction (Scheme 33) [95-97]. The corresponding rhodium catalyst allowed for regioselective hydroformylation of2-octene [95]. 

Dopamine /3-hydroxylase (D/3H) is a copper-containing glycoprotein that hydroxylates dopamine at the benzylic position to norepinephrine.84 During the attempted crystallization of the bis(hydroxide)-bridged dicopper(II) dimer, a side product was subsequently isolated (complex (63)), revealing intramolecular hydroxylation at a formally benzylic position of the tris(imidazo-lyl)phosphine ligand.85 The copper(II) center has an axially compressed TBP structure. 

This is a valuable lesson for chemists trying to determine a catalytic mechanism compounds readily isolable are probably not true intermediates. Instead, they can be seen as labile reservoirs to catalytic intermediates that usually do not accumulate in sufficient concentrations to be detected. It is important to bear in mind that this mechanism or any other catalytic process could be different dependent on the nature of the alkene, solvent, and phosphine ligands. 

Orpen, A.G., Pringle, P.G., Smith, M.B., and Worboys, K., Synthesis and properties of new tris(cyanoethyl)phosphine complexes of platmum(0,II), palladium, II), iridium(I) and rhodium(I). Conformational analysis of tris(cyanoethyl)phosphine ligands, /. Organomet. Chem., 550, 255, 1998. 

The beneficial effect of added phosphine on the chemo- and stereoselectivity of the Sn2 substitution of propargyl oxiranes is demonstrated in the reaction of substrate 27 with lithium dimethylcyanocuprate in diethyl ether (Scheme 2.9). In the absence of the phosphine ligand, reduction of the substrate prevailed and attempts to shift the product ratio in favor of 29 by addition of methyl iodide (which should alkylate the presumable intermediate 24 [8k]) had almost no effect. In contrast, the desired substitution product 29 was formed with good chemo- and anti-stereoselectivity when tri-n-butylphosphine was present in the reaction mixture [25, 31]. Interestingly, this effect is strongly solvent dependent, since a complex product mixture was formed when THF was used instead of diethyl ether. With sulfur-containing copper sources such as copper bromide-dimethyl sulfide complex or copper 2-thiophenecarboxylate, however, addition of the phosphine caused the opposite effect, i.e. exclusive formation of the reduced allene 28. Hence the course and outcome of the SN2 substitution show a rather complex dependence on the reaction partners and conditions, which needs to be further elucidated. 

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