TANIAPHOS

Entry Ligand (R, R ) Sub- p(H2) TONa) strate [bar] TOFa) [h-1] ee [°/o] Comments Refer- ence ) 

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The catalytic behaviour of MandyPhos (1) and TaniaPhos (2) ligands (see structures in Scheme 23.1) in chiral hydrogenations was explored in former publications by applying in situ catalytic procedures (1). 

Pre-Catalyst Systems Using TaniaPhos/MandyPhos Ligands... 

The coordination chemistry of MandyPhos and TaniaPhos with rhodium and palladinm has been explained by Knochel (1, Knochel). The chemistry of ligands snch as Duphos or BINAP with all relevant established ratheninm(II) precnrsors is known and was derived from their bidentating coordination behaviour ... 

TaniaPhos In comparison to MandyPhos (1) the structural properties of TaniaPhos (2) gave reason to other synthetic behaviour in those reactions. In spite of... 

Precursors synthesis The observed reaction of TaniaPhos (2) with [Ru(benzene)Cl2]2 or [Ru(p-cymene)Cl2]2 confirmed that defined and stable metal-complexes could also be synthesized with this ligand. 

These precnrsois were then reacted with MandyPhos and TaniaPhos. 

TaniaPhos with (9) or (5) Reacting TaniaPhos with (9) in THF at r.t. resulted in amine coordination (Scheme 23.6) ... 

TaniaPhos active catalyst discussion As shown by Salzer (2) such complexes with half sandwich stracture result in the catalyst cycle into a hydride species where the pentadienyl moiety can be hydrogenolyticaUy liberated (2, 6). This was verified in the case of BINAP complexes (2, diss. Podewils, Geyser). In accordance to this fact and other mechanistic aspects from Noyori s work (3, 5) it is likely that the pre-catalyst species undergoes the same reaction pathway and that the reactive part of the pre-catalyst, the pentadienyl moiety, will be liberated under hydrogenolytic conditions as shown below in Scheme 23.9 ... 

It was not possible to isolate defined complexes with clear bidentate coordination for the ligands MandyPhos and TaniaPhos using established ruthenium precursors such as [Ru(COD)Cl2]x, [Ru(benzene)Cl2]2, [Ru(p-cymene)Cl2]2,... 

For ruthenium, special precursors are required to synthesize defined bidentate diphosphine complexes. With Taniaphos for instance, it is possible to synthesize such complexes starting from unusual rathenium(ll) species. The complexes were characterized by NMR and single crystal analysis. 

Riant et al. applied the catalytic system [CuF(Ph3P)3]2MeOH (0.1-1 mol%) and PhSiH3 (140 mol %) in the combination with Ph-TANIAPHOS as ligand to the syn-selective reductive coupling of aldehydes and methyl... 

A series of non-f, -symmetrical ferrocene-based 1,5-diphosphane ligands (TaniaPhos) has been developed by Knochel.88,88a,88b The ligands have been effectively used in Rh- or Ru-catalyzed asymmetric hydrogenations. The ligand 39, which has an MeO group at the chiral carbon center, has shown excellent applications in the hydrogenation of several olefin and ketone substrates.89 Weissensteiner and Spindler have reported a series of structurally different... 

The recent introduction of the TaniaPhos ligands (34) provides another excellent catalyst system for the reduction of dehydroamino acid derivatives and enol... 

Fig. 25.12 Structure of taniaphos derivatives and substrates listed in Table 25.5.

Table 25.5 Selected results for Rh-catalyzed hydrogenations using taniaphos (Ar = Ph, pH2 1 bar) (for structures, see Fig. 25.12).

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