Ligands bridges

This book is a highly readable introduction to the reactions of coordinated ligands. Bridging the gap between the traditional fields, this text presents the basic concepts of ligand reactivity as well as many synthetic applications of these reactions. 

The interaction of a complex anion SbY5Z with excessive Lewis acid SbX5 leads to the formation of a ligand-bridged (conjugated 1)) anion (see part 4.2.2) according to... 

Finally, we consider the alternative mechanism for electron transfer reactions -the inner-sphere process in which a bridge is formed between the two metal centers. The J-electron configurations of the metal ions involved have a number of profound consequences for this reaction, both for the mechanism itself and for our investigation of the reaction. The key step involves the formation of a complex in which a ligand bridges the two metal centers involved in the redox process. For this to be a low energy process, at least one of the metal centers must be labile. 

Another prefix used for complexes is p (mu), which indicates that the ligand bridges two metal atoms. 

Fig. 6.1b) in which twelve inner ligands bridge the edges of the Me octahedron, and six outer ligands occupy apical positions, predominate. These units are found in reduced zirconium, niobium, tantalum, and rare-earth halides, and niobium, tantalum, molybdenum and tungsten oxides [la, 6, 10]. 

Kiindig EP, Dupre C, Bourdin B, Cunningham A Jr, Pons D (1994) New C2-chiral bidentate ligands bridging the gap between donor phosphine and acceptor carbonyl ligands. Helv Chim Acta 77 421 28... 

The niobium phosphate complex ( Pr0)4Nb[02P(0 Bu)2] 2 was produced by the reaction of Nb(0 Pr)5 with H0P(0)(0 Bu)2 in pentane [71]. Although crystals of sufficient quality for an X-ray crystallographic analysis were not obtained, spectroscopic evidence suggests that the phosphate ligands bridge the two Nb centers. 

Scheme 1.57 Test reaction with bis(thiazolines) ligands bridged by a dibenzo[a,c]-cycloheptadiene backbone.

Another illustration of the structural changes that may result as a consequence of alkyl substitution at the 3-position of the pyrazolyl group is provided by the structures of the dimeric copper(I) complexes [Tp]Cu 2 (36), [TpMe2]Cu 2 (36), [TpPh2]Cu 2 (37), and [TpBut]Cu 2 (37), which differ in the manner in which the tris(pyrazo-lyDhydroborato ligand bridges the two copper centers (Fig. 16). 

Secondly, the molecular structure of [TpPr 2]Zn 2(/u,-7)1,7)2-C03), as determined by x-ray diffraction (151,153), reveals that the carbonate ligand is coordinated in an asymmetric manner, with unidentate coordination to one zinc center and bidentate coordination to the other zinc center, i.e., fi-ri1,ri2-C03 (Scheme 24). Such coordination is noticeably distinct from that of [TpBut Me]Zn 2(/x.-r)1,7 1-C03), in which the carbonate ligand bridges in a symmetric unidentate mode. 

When a bidentate ligand bridges two metalloporphyrins, a linear polymeric chain is formed. This arrangement has been dubbed shish... 

Diphosphinoamines (X2P-NR-PX2) are examples of a more unusual potentially chelating diphosphine. The dimer Co2(F2PN(CH3)PF2)3(CO)2 has three of these ligands bridging symmetrically between the two tetrahedral Co centers, which also carry a terminal CO group this molecule can undergo reduction with LiEt3BH in THF to form a stable mixed valence (d9—d10) radical anion.163... 

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