Tetradentate chiral ligand

RuCl(PNNP)KPF ) and [RuCl(H,0)(PNNP)](PF ) (PNNP=tetradentate chiral ligands, e.g.iV,A -[bis(o-diphenylphosphino)-benzylidene]-(15, 25)-di-iminocyclohexane (Fig. 1.42) [928,929] andiV,iV -[bis(o-diphenylphosphino)-benzylidene]-2,2-di-imino-l, F-(S)-binaphthylene) [928], These complexes were made from the ligands and RuCljCPPhj) in CH Cl P NMR spectra were measured [929]. 

Ligand substitution in salicylaldiminate [NiA2] complexes has been studied in detail.1161 Substitution in chiral [NiA2] species by chiral salen-type tetradentate H2B ligands in acetone proceeds according to Equation (7) ... 

SCHEME 106. Titanium-catalyzed asymmetric oxidation of aryl alkyl sulfides using a chiral tetradentate trialkanolamine ligand... 

Platinum(II) and ruthenium(II) complexes with chiral modified diphosphines like 47 or tetradentate P2N2 ligands like 48 have been used for the asymmetric epoxidation of olefins with hydrogen peroxide with ee values of 18-23%, which increased up to 41% when cationic solvato derivatives such as P2Pt(CF3)(CH2Cl2)(BF4) are used . Similar chiral inductions were reported for Ru derivatives, although the nature of the active intermediate was still in question. ... 

Tetradentate Polyaminocarboxylate Complexes As the following examples indicate, stereospecific formation of metal complexes with chiral tetradentate polyaminocarboxylate ligands do not always lead to the same absolute structures as that of the corresponding complexes with achiral ligands.171... 

The trialkyl complexes see Alkyl Complexes) of (N-N)Pt are typically prepared by oxidative addition see Oxidative Addition), as shown in Scheme 58. The complex (N-N)Pt Mc2 with an imino-cyclohexane ligand, as shown in Scheme 11, undertakes protonation from different acids to give rise to A,A,C-tridentate and A,A,C,A-tetradentate chiral aminoalkyl species, respectively (Scheme 59). The chiral selectivity at the aminoalkyl carbon is opposite in... 

Another major contribution of polydentate ligands is the creation of a chiral pocket around the catalytic center providing, an appropriate chiral environment. The chiral pocket concept has been introduced by Trost for catalytic enantioselective allylic alkylation with the tetradentate aminophosphine ligand 33 [133]. The nucleophile fits into the chiral environment created by the chiral ligand and the allyl Pd intermediate. As a result, the enantiocontrol of the newly formed chiral center is very effective. In addition, the chiral control is likely to be efficient even at positions remote from the chiral ligand. That auxiliary has been widely... 

Asymmetric tetradentate chiral SB ligands having either two different salicylaldehyde derivatives or a combination of sal and acac units are prepared by the stepwise protocol, preparing first the chiral half unit intermediate which is reacted further to give the desired asymmetric... 

The piperidone precursor of 57 (see Chart 6) is a possible starting material for the synthesis of 2,6-substituted chiral, tetradentate bispidine ligands. The copper(II) complex of 57 is chiral [see Fig. 2(d) for a plot of the experimental structure] and has an interesting set of bond distances. Quite unexpectedly on the basis of the chelate ring sizes, the 2-pyridine substituent of the bispidine backbone is the axial donor (2.25 A), while N3 (2.08 A), N7 (2.05 A), the N7-pendant pyridine (2.01 A) and the chloride (2.28 A) are the in-plane donors (80). 

The ship-in-a-bottle technique is perhaps the most common method for encapsulation of transition metal complexes. In this way the tetradentate Schiff base ligand SALEN (bis-salicylidene) ethylenediamine can diffuse through the 12 MR windows of faujasite. Then, when complexed with a previously exchanged metal ion, nearly square planar coordination geometry is formed inside the a-cages [97-100], Mn complexes with a chiral ligand, prepared by the ship-in-a-bottle technique inside Y and EMT zeolites, have enantioselectively carried at the epoxidation of olefins [101,102]. 

A.S. Abu-Surrah, B. Rieger, R. Fawzi, M. Steiman, Synthesis of chiral and C2-S5nnmetric iron (II) and cobalt(II) complexes bearing a new tetradentate amine ligand system. J. OrganomeL Chem. 497, 73-79 (1995)... 

Figure 10 Chiragen ligands (a) [4,5]-pineno-2,2 -bipyridine, one of the chiral bnilding blocks of the Chiragen ligands and (b) an example of a tetradentate Chiragen ligand.

The tetradentate Chiragen ligands have made a significant contribution to the transfer of chirality in metallo-supramolecnlar synthesis. This is discussed below with a limited number of illustrative examples, and it has been substantially reviewed. ... 

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