Organometallics coordination compounds

Among titanium compounds, many sit on the border of being organometallic/coordination compounds. One which is of interest in relation to the enhancing effects of F (see Section 9.5.5.2) is the titanium fluoride complex (52), which is highly active for the hydrosilylation of imines (Scheme 33).143... 

An enormous variety of r-bonded systems, whether they be neutral or ionic, cyclic or linear, odd or even in the number of carbon atoms, serve as ligands that coordinate to transition metals. Figure 14.3.1 shows some representatives of the innumerable organometallic coordination compounds stabilized by metal-TT bonding. 

Molecular mechanics calculations have been used to describe low- 471-473] and high-order metal-metal bonds[473,474]. These will be discussed here although many relevant examples are classical rather than organometallic coordination compounds. The force constant for Rh-Rh single bonds has been determined from the vibrational frequency of the metal-metal bond and the strain-free value was fitted using a conventional force field for the ligand systems and a series of experimentally determined structures (Fig. 14.6). The Rh-Rh bond distances cover a range of ca. 0.25 A, and the experimentally observed trends are reasonably well reproduced by the calculations (Table 14.2). 

Homogeneous catalysts capable of producing polyethylene [12] and isotaclic polypropylene [13] employ metallocenes. These are organometallic coordination compounds comprising two cyclopentadienyl rings bonded to a metal atom, as in 9-22. 

Metallocenes - Organometallic coordination compounds in which one atom of a transition metal such as iron, ruthenium or osmium is bonded to and only to the face of two cyclopen-tadienyl ligands which lie in parallel planes. [5]... 

Metallocenes are organometallic coordination compounds composed of a metal center that s bonded to the face of planar closed loop hydrocarbons, such as cyclopentadienyl ligands. These are more commonly known as sandwich molecules because the metal is sandwiched between the two planar molecules. They have the general formula (C5Hg)2M. 

The efficiency of a catalytic system based on an organometallic coordination compound depends on the number of metal-atom orbitals that can be involved in bonding. Therefore derivatives of the reare earths, especially the lanthanides with their partially filled d- and f-orbitals, should provide interesting new opportunities for catalyzing a great variety of organic reactions. 

Frequently, decomposition of organometallic coordination compounds takes place... 

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