Solvento complexes coordination chemistry

Lanthanide Complexes with Multidentate Ligands Lanthanide Oxide/Hydroxide Complexes Lanthanides Coordination Chemistry Solvento Complexes of the Lanthanide Ions Trivalent Chemistry Cyclopentadienyl. 

Davies, J. A. Hockensmith, M. Kukushkin, V. Y. Kukushkin, Y. N., Homoleptic Solvento-Complexes Starting Materials for Preparative Coordination Chemistry, in Synthetic Coordination Chemistry Principles and Practice World Scientific River Edge, NJ, 1996, p 95. 

Because of ligand-field factors, certain transition metal ions, notably Cr + and Co +, almost exclusively exhibit a coordination number of six in their complexes. The kinetically inert nature of Cr and Co complexes, dramatically different from that of the extremely labile lanthanide solvento ions, facilitates the isolation of isomeric species and was crucial in enabling Alfred Werner to formulate the fundamental tenets of coordination chemistry. For simple lanthanide ion complexes, their lability and the lack of a marked sensitivity of their visually observed colors to the nature of the coordination sphere renders Wernerian procedures inapplicable, such that the establishment of high and variable coordination numbers as a characteristic of lanthanide ions has depended largely on modem spectroscopic and crystallographic measurements. 

It might be expected that, since the Sc + ion has a considerably greater crystal radius than the corresponding tripositive ions of the 3d metals (compare Sc + at 0.885 A with Ti +, Cr +, and Fe + at 0.810, 0.755, and 0.785 A, respectively), coordination numbers greater than six might be conunon in scandium complexes. With the exception of the aqua ion (and nitrate complexes), this has not been realized, but studies of scandium chemistry are still relatively rare (partly on account of cost). Aqua complexes and simple hydrates have been discussed in Solvento Complexes of the Lanthanide Ions. 

The Y + ion is comparable in size with heavier lanthanides, and its coordination chemistry therefore resembles them. Aqua complexes and simple hydrates have been discussed in Solvento Complexes of the Lanthanide Ions. Fewer solution studies of solvated species with other donors have been made for these metals, but an examination of the Y + ion in Odonor solvents using X-ray absorption fine structure (XAFS) and laige angle X-ray scattering shows that the metal is eight coordinate in dimethylformamide and dimethylsut-foxide, but seven coordinate in N, iV -dimethylpropyleneurea (dmpu), as are other lanthanides. It should be noted that in the solid state, six-coordinate [Ln(dmpu)6]l3 (Ln = La, Pr, Nd, Gd, Tb, Er, Yb, Lu) are isolated. ... 

Aryls Alkyl Homogeneous Catalysis The Electronic Stmcture of the Lanthanides Variable Valency Solvento Complexes of the Lanthanide Ions Lanthanides Coordination Chemistry The Divalent State in Solid Rare Earth Metal Halides Lanthanides Comparison to 3d Metals Trivalent Chemistry Cyclopentadienyl Tetravalent Chemistry Organometallic Organic Synthesis. 

Widely used in preparative coordination chemistry, labile solvento-complexes are generated by a number of different approaches. Aspects of the... 

The examples described above illustrate the utility of solvento-complexes in preparative coordination chemistry. The balance of this chapter reviews methods for the synthesis of homoleptic solvento-complexes. 

Reduction reactions that involve titanium(lll) species are common in preparative organic chemistryl 9 but relatively rare in coordination chemistry. However, Floriani and coworkers " have described the reduction of vanadium complexes, [VO(salophen)] and [VO(acacen)], by the titanium(IIl) solvento-complex, [TiCl3(THF)3]. Reaction of these vanadyl complexes in THF results in formation of [VCl(salophen)(THF)] and [VCl(acacen)(THF)]. Both compounds have been structurally characterized and an X-ray diffraction study of [VCl(salophen)(THF)] indicated pseudooctahedral coordination for V(Ill). Further, the CP and THF ligands were found to be trans to each other in the axial positions, while the equatorial plane was defined by the salophen ligand. Figure 9.7.1fl The proposed mechanism 2 for these conversions is shown in Scheme 9.7. 

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