Ferrocene ligands derived from

A new class of easily accessible 1,2-disubstituted phosphinamidite-thioether ligands derived from Ugi s amine and based on a ferrocene motif has been... 

The catalytic efficiencies of some 1,3- and 1,4-amino alcohols remain high. Except for one ligand derived from hydroxyproline, most others are based on ferrocene. A similar ligand is a Cr(CO)j complex. /3-Hydroxy ethers and /3-amino thiols are also attracting a great deal of attention. 

The chiral (aminoferrocenyl)phosphine ligands derived from ferrocene (2-(T(dimethylamino)ethyl)-l-(diphe-nylphosphino)-ferrocene and [ j -cyclopentadienyl][77 -4-( r/(9-dimethylamino)-3-(diphenylphosphino)—4,5,6,7-... 

The review begins with a selective summary of the history of organome-taUic and reductive rare-earth chemistry as an introduction to bimetallic lanthanide complexes bridged by ligands derived from arenes and to complexes of ferrocene-based diamide ligands, a major subtheme in the chapter. Detailed discussions then follow on complexes derived from fused rings and their reactivity with phosphorus and on complexes derived from biphenyl and stilbene as substrates, with emphasis on ferrocene-based diamide complexes. 

Josiphos Chiral diphosphine ligand derived from ferrocene... 

Ferrocene has an even more interesting structure. A central iron is ir-bonded to two cyclopentadienyl ligands in what is aptly described as a sandwich. It, too, obeys the 18-electron rule. Each cyclopentadienyl ligand contributes five electrons for a total of ten and iron, with an electron configuration of [Arj Sd6 contributes eight. Alternatively, ferrocene can be viewed as being derived from Fe2+ (six valence electrons) and two aromatic cyclopentadienide rings (six electrons each). 

Bincoletto C, Terariol ILS, Oliveira CR, Dreher S, Fausto DM, Soufen MA, Nascimento FD, Caires ACF (2005) Chiral cyclopalladated complexes derived from N, N-dimethyl-1-phenethylamine with bridging bis(diphenylphosphine)ferrocene ligand as inhibitors of the cathepsin B activity and as antitumoral agents. Bioorg Med Chem 13 3047-3055... 

Chiral bis(oxazolines) 51 with an oxalylic acid backbone were used for the Ru-catalyzed enantioselective epoxidation of tran5-stilbene yielding franx-l,2-diphenyloxirane in up to 69% ee [24]. The asymmetric addition of diethylzinc to several aldehydes has been examined with ferrocene-based oxazoline ligand 52 [25], resulting in optical yields from 78-93% ec. The imide 53 derived from Kemp s triacid containing a chiral oxazoline moiety was used for the asymmetric protonation of prochiral enolates [26]. Starting from racemic cyclopentanone- and cyclohexanone derivatives, the enantioenriched isomers were obtained in 77-98 % ee. 

Many of the ferrocene ligand families described above are derived from a resolved chiral precursor (i.e. 289). Efforts to (76) prepare planar chiral ferrocenes also employ other strategies that rely on a directed metalation (see Orthometalation). Sulfoxide (338), acetal (339), and oxazolines of type (321)... 

A chiral C2-symmetric bridged ferrocene was constructed from a synthetic ligand containing two cyclopentadiene units (Fig. 4-12d). The key step in the synthesis of the ligand is a diastereoselective Diels — Alder reaction of anthracene with bis[(S)-l-ethoxycarbonylethyl]fumarate. When oxidized to the ferrocinium salt, the ferrocene derivative has Lewis acid properties and catalyzes Diels — Alder reactions with some enantioselectivity [85]. 

Mixed aza-thiamacrocyclic derivatives of ferrocene 71 and 72 have also been prepared and the X-ray crystal structures of 72 and its copper complex reported [90]. Electrochemical studies revealed that the redox couples of 71 and 72 were perturbed to more positive potentials by 60 and 40 mV, respectively, on coordination with Cu ", even though the X-ray structure of the complex with 72 showed square planar coordination of the Cu " by the four sulfur atoms rather than by nitrogen. The cyclam ligand 73 derived from ferrocene has also been prepared and shown to recognise Ni and cations electrochemically [90]. 

A relatively recent report has described the heterobimetallic diolate complex Ti (OPr )2-((OCPh2C5H4)2Fe) derived from a substituted ferrocene ligand.644... 

The overall bonding in ferrocene can now be summarized. The occupied orbitals of the cyclopentadienyl ligands—the zero-node and one-node group orbitals—are stabilized by their interactions with iron. In addition, six electrons occupy molecular orbitals that are largely derived from iron d orbitals (as one would expect for d6 iron(II)), but these occupied orbitals, displayed in Figure 5-10, have significant ligand character too. The molecular orbital picture in this... 

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