Ligand asymmetry

Hgure 3. The structure of Miij0(0,CPh) (py)2(H20) illustrating the unique terminal ligand asymmetry Mn(3) is the Mn center possessing a terminal H O ligand. (Reproduced from ref. 8. Copyright 1987 American Qiemical Society.)... 

Use of achiral additives without chiral conformations 3.7.3 Metal Geometry-Induced Ligand Asymmetry... 

Palladium-catalysed asymmetrie allylations of various carbonyl compounds have been studied by Hiroi et al. using various types of chiral sulfonamides derived from a-amino acids. In particular, the chiral bidentate phosphinyl sulfonamide derived from (5)-proline and depicted in Scheme 1.63 was employed in the presence of palladium to eatalyse the allylation of methyl aminoacetate diphenyl ketimine with allyl aeetate, leading to the eorresponding (7 )-product with a moderate enantioseleetivity of 62% ee. This ligand was also applied to the allylation of a series of other nueleophiles, as shown in Seheme 1.63, providing the eorresponding allylated produets in moderate enantioseleetivities. 

The ability of cobalt(II), nickel(II), and copper(II) to exhibit a greater tendency than Zn(II) towards bidentate coordination is further illustrated by structural comparisons within a series of bridging carbonate complexes (188). For example, of the complexes [TpPr 2]M 2(/x-C03) (M = Mn, Fe, Co, Ni, Cu, Zn), only the zinc derivative does not exhibit bidentate coordination at both metal centers (151,153). Furthermore, the carbonate ligand in the complexes [TpPr 2]M 2(/x-C03) (M = Mn, Fe, Co, Ni, Cu) also exhibits varying degrees of asymmetry that closely parallel the series of nitrate complexes described earlier (Fig. 47 and Table IX). 

FABMS has shown that the bulky Pr PCEhCHhPPr forms the dimeric [ TcNCl2(P-P) 2]. The 3,PNMR spectrum indicates a chlorine bridged structure [57]. The reaction of MePhNNH2/dppe/[TcOCl4] in MeOH, however, yields a cationic complex formulated as the oxo-imido tra .v-[TcO(NH)(dppe)2]+. Few details are available, but the crystal structure determination showed marked asymmetry in the bonding of the two axial ligands [74]. A distinction between the [HN=Tc=OJ+ core and the tautomeric [N=Tc-OH]+ core should be possible... 

The range in Mo-C(Cp) distances reflects the electronic asymmetry about the molybdenum caused by the nature and spatial arrangement of the other ligands bonded to the metal. In other words, these variations are a manifestation of the trans-influence. 

Monodentate (monometallic monoconnective) phosphor-1,1-dithiolato ligands are rare. Bidentate (monometallic biconnective) form chelate rings and three sub-types can be distinguished according to the degree of asymmetry (Scheme 2). The most asymmetric type (anisobidentate) occurs when a covalent bond is associated with a secondary bond this takes place mostly in main-group metal complexes. The second type is rare and is the result of the association between a covalent and a dative coordinate bond. The symmetric bidentate bonding (isobidentate) is found mainly in transition metal complexes. 

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