Transition-metal sandwich complexes

For transition metal sandwich complexes the possibility of a non-degenerate ground level, in C v symmetry, arises for several dx configurations, namely... 

In conclusion though, it may reasonably be maintained that the ligand field model has contributed significantly to the advances in knowledge concerning transition metal sandwich complexes over the last ten years, and that it offers a valid and convenient framework for further experimental and theoretical progress. 

A tricyclic aromatic system closely related to borole, 9-boratafluorene, might be expected to form ( -coordinated transition metal sandwich complexes, but so far only the lithium complex has been characterized.19 Monohapto aluminum adducts of neutral 9-borafluorene, in which A1 is bound only to the boron atom, have been prepared.20... 

Almlof, J., K. Faegri, Jr., B. E. R. Schilling, and H. P. Luthi (1984). An investigation of correlation effects in transition-metal sandwich complexes. Har-tree-Fock studies on a series of metallocenes. Chem. Phys. Lett. 106, 266-70. 

Table 1. 1/2 values detennined for the transition-metal sandwich complexes (V relative to the SCE). 

To date, a great number of experimental and theoretical investigations have been carried out to elucidate the structures and chemical reactivities of transition metal sandwich complexes (11). The parallel interest in investigations of actinide sandwich complexes has revived again recently (4,12). We have found relativistic density functional theory (DFT) to be a superb tool for the elucidation of the... 

A thoroughly unexpected postwar breakthrough was the synthesis of the first aromatic type of transition metal sandwich complex known as dicyclo-pentadienyliron (II) or ferrocene. Realization of this intriguing structure has stimulated the synthesis of many similar types. 

Other experimental studies in the same years showed that this strange behaviour of the H NMR coupling constants was not exclusive of early-transition metal sandwich complexes. In 1987, Chaudret and co-workers [27] reported a similar behaviour for Cp RuH3(PRj) (R = Cy, Pr) complexes. The H-H coupling constant was also temperature-dependent, and reached a value as... 

P.J. Chirik (2010) Organometallics, vol. 29, p. 1500 - Group 4 transition metal sandwich complexes StiU fresh after almost 60 years . 

The NVE is often equal to 18 for transition-metal organometallics and for many inorganic complexes. This 18-electron rule should be better viewed as a strong tendency than a rule, but it is followed by a majority of complexes (despite many exceptions, vide infra). The 18-electron electronic structure often brings a good stability for complexes. For instance, this is the case for the metal carbonyl complexes, possibly the largest family. Transition-metal sandwich complexes are more stable in the 18-electron count than in others. The 18-electron electronic structure is also found most of the time in complexes containing a mixture of carbonyls, hydrocarbons, carbenes, hydrides, etc. - ... 

This first classic method can also be used sequentially in order to introduce two different cyclopentadienyl ligands in a transition-metal sandwich complex, especially if one of the Cp derivatives is Cp ... 

Why do first-row transition-metal-sandwich complexes exist in various oxidation states and not the second- and third-row ones ... 

The hydrostannation of a diyne followed by transmetallation using a borane leads to the phenylboratabenzene anion, isoelectronic to biphenyl (the prefix borata means that a benzene CH group is replaced by the isoelectronic BH group). It is equivalent to the cyclopentadienyl anion and gives transition-metal sandwich complexes that are equivalent to metallocenes with a variety of metals (V, Cr, Fe, Co, Ru, Os). - ... 

Table 3.3 Redox potentials of transition-metal sandwich complexes obtained by cyclic voltammetry in different ionic liquids...

Torriero AAJ, Sunarso J, Forsyth M, Pozo-Gonzalo C (2013) Assessment of permethylated transition-metal sandwich complexes as internal reference redox systems in ionic liquids. PCCP 15(7) 2547-2553... 

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