Transition metal complexes classification

Table 2-2 Oxidative addition reactions on transition metal complexes classification of the adding compounds...

Busch DH (2005) First Considerations Principles, Classification, and History. 249 in press Bussiere G, Beaulac R, Belisle H, Lescop C, Luneau D, Rey P, Reber C (2004) Excited States and Optical Spectroscopy of Nitronyl Nitroxides and Their Lanthanide and Transition Metal Complexes. 241 97-118 Cadierno V, see Majoral J-P (2002) 220 53-77 Camara M, see Chhabra SR (2005) 240 279-315 Caminade A-M, see Majoral J-P (2003) 223 111-159 CantriU SJ, see Arico F (2005) 249 in press... 

Fig. 1. Scheme for classification of materials prepared from a donor or donor cation, D+p, and acceptor or acceptor cation, A-q, (p, q = 0,1,. ..) with one or both components being a planar transition-metal complex... 

Figure 1 Classification of transition metal complexes of boron...

Transition metal complexes are often very good nucleophiles and qualify as being supersoft under Pear son s HSAB classification for example, reaction with soft methyl iodide can be as much as 3 X 105 times faster than the reaction with hard methyl tosylate. Because soft nucleophiles are those with large a values in the Edwards equation, that rates for the transition metal nucleophiles are effectively correlated with oxidation potentials is not surprising. In the last chapter in this section, Chapter 16, Pearson uses recently obtained values of pKa for transition metal complexes to test the full Edwards... 

The mechanisms describing C—H activation by organometaUic complexes v/ere traditionally divided into (I) oxidative addition (OA), (H) o-bond metathesis (SBM) and (HI) electrophilic activation (EA) (Fig. 25.1). The classification was genCTaUy identified with the nature of the metal center therefore, electron-rich low-valence metal complexes usually promote oxidative addition, early complexes undergo o-bond metathesis, and electron-deficient late transition metal complexes react through electrophilic activation. 

Classification of Excited States in Transition Metal Complexes... 

This section is subdivided into eleven parts which contain NMR information about Groups 1 and 2 and transition-metal complexes presented by Groups according to the Periodic Table. Within each Group, classification is by ligand type. 

Similarly cyclopentadienyl complexes have been treated as being formed by the radical CjHs. In other words, they are considered as acting as 4- or 5-electron ligands respectively when they bond to a transition metal. This classification is really a formality, and the complexes could just as well be thought of as being derived from the 6-electron aromatic anions 4114 and CsHs" respectively and a metal cation carrying a suitable positive charge (-1-2 or -1-1) to maintain electroneutrality. The total number of electrons in the complex, of course, remains the same. 

Relatively few complexes of the early transition metals with 1,1-dithiolato ligands have been prepared and characterized. This is consistent with their classification as "hard or "class a acceptors. Thus,... 

Phosphinidenes [1] are low-valent organophosphorus compounds that have attracted attention since the early 1980s when they were first discovered [2]. They are known in two classifications, one being the six-electron singly substituted phosphorus species (A) and the other in which the phosphorus atom carries an additional ri -stabifizing group, typically, but not necessarily, a transition metal group (B). Much has been learned about the reactivities of the complexed phos-... 

We see that for the (alkali metal + oxygen macrocycle) complexes, charge and relative size of the ion play an important part in determining the stability of the complex. However, for the (transition metal + aza- or thia-substituted macrocycle) complexes, the nature of the bonding seems to be the important effect. Sten Ahrland16 has used a classification scheme for metal ion acceptors that helps us understand this difference. He designates the metal ion as either hard or soft. The characteristics that determine the assignment are as follows. 

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