Organometallic complexes mononuclear

Organometallic Compounds. Mononuclear carbon monoxide complexes of palladium are relatively uncommon because of palladium s high labihty, tendency to be reduced, and competing migratory insertion reactions in the presence of a Pd—C bond (201). A variety of multinuclear compounds... 

An exhaustive treatment of the electrochemical behaviour of transition metal complexes is beyond the scope of this book, because the enormous number of ligands available, combined with the possibility to prepare mono- and/or polynuclear complexes using identical or mixed ligands, would render such a task almost impossible. Therefore, the discussion is limited to some aspects associated with the redox properties of (essentially) mononuclear metal complexes. In particular, we will concentrate representatively on the redox changes of first row transition metal complexes (excluding the metallocene complexes, as they have been already discussed in Chapter 4) that give stable, or relatively stable products. A systematic and useful examination of the redox activity of organometallic complexes of transition metals dated to 1984 has appeared.1... 

Organometallic Compounds. Osmium forms numerous mononuclear and polynuclear organometallic complexes, primarily in lower... 

Organometallic Compounds. Mononuclear carbon monoxide complexes of palladium are relatively uncommon because of palladium s high lability, tendency to be reduced, and competing migratory insertion reactions in the presence of a Pd—C bond (201). A variety of multinuclear compounds are known (202), including [Pd2Cl4(CO)2] [75991-68-3], [Pd3(P(C6H5)3)3(CO)3] [36642-60-1], and [Pd7(P(CH3)3)7(p3-CO)3(p2-CO)4] [83632-51-3]. 

Organom etallic Compounds. Organometallic complexes of platinum are usually more stable than palladium complexes. Carbon monoxide complexes of platinum are formed more readily than with palladium. Mononuclear and polynuclear complexes in oxidation states 0 to +2 exist such as... 

There are no well-documented mononuclear non-organometallic complexes of Re0 known as of this time. 

This report summarizes conventional methods for UV irradiation of air sensitive organometallic compounds at ambient or subambient temperatures. Of the irradiation sources available (l ) the medium pressure Hanovia 450 W arc lamp systems (2) are of moderate price, reliable, and versatile in our experience. Caution Powerful arc lamps can cause eye damage or blindness within seconds and UV protective goggles (available from most scientific supply houses) must be worn. Never look directly at the radiation source. For safety of other workers lamps should be enclosed in a vented box with baffles. If Pyrex transmits enough UV radiation for an efficient reaction, as for photochemical reactions of metal-metal bonded complexes (3), then conventional Schlenkware can be used for photolysis and no special glassware is needed. Since a 2 mm thick wall of Pyrex transmits only 10% of the UV light at 300 nm, UV transparent quartz reaction vessels are often needed for photoreactions of mononuclear organometallic complexes. 

In this chapter and in an upcoming review (Part II), the chemistry of mononuclear paramagnetic organometallic complexes of the second- and third-row groups 9(VIIIB) and lO(VlII) platinum metals (Rh, Ir, Pd, Pt) are summarized. In this chapter, the higher valent species (Rh(II), Ir(II), Rh(IV), Ir(IV), Pd(ni), Pt(III) and complexes with oxidized redox noninnocent ligands) are described. In the next chapter, the lower valent species (Rh(0), lr(0), Pd(I), Pt(I), and complexes with reduced redox noninnocent ligands will be discussed. 

A principal motivation in the study of dinuclear organometallic complexes is the hope that they can accomplish catalytic reactions that are not achievable by mononuclear complexes. There are a number of cases where metal-metal complexes are catalysts precursors. The most famous is... 

This bonding mechanism is quite general and has important consequences for understanding the properties of mononuclear or polynuclear organometallic complexes. In fact, it is quite obvious that bonding with ligands causes a substantial change in the nature of the metal atom. This is clearly shown by the simple case of... 

In organic and organometallic chemistry, asymmetric catalysts play an important role in enantioselective synthesis, and the majority of these are mononuclear organometallic compounds. It was for their work on asymmetric catalysis that W. S. Knowles, R. Noyori and K. B. Sharpless won the Nobel Prize for Chemistry in 2001, " and hence the study of chirality for this class of compounds is of the utmost importance. For this reason, following on from Chapter 2, which lays the necessary groundwork in organometallic and coordination chemistry, in Chapter 3 we will develop the study of the chemistry of chiral mononuclear organometallic complexes and asymmetric catalysis in brief. 

Despite the vast number of outstanding examples of enzymatic catalysis that rely on the collaboration of two or more vicinal metal centers hitherto disclosed, the design and development of efficient binuclear organometallic complexes able to enhance the performance of mononuclear catalyst by means of an intermetallic cooperative process remains widely unexplored [22-24]. In fact, the formation of bi- or polynuclear complexes has been often described as a catalyst deactivation pathway [25-30]. However, the availability of more electron density at the active site, extra coordination positions, and the possibility to develop more preorganized systems that allow for (enantio)selective reactions shows great promise for an improved catalytic performance [9]. 

The history of organometallic complexes suitable for cell imaging goes back to 2004 with the synthesis by Valliant and coworkers of the c-rheniirm tricarbonyl bispyridyl complex 4 (Scheme 11.3) [48,49]. Like most, if not all, of the rhenium mononuclear complexes used as luminescent agents for cell imaging, this complex contains a c-Re(CO)s unit and possesses the general formula of l /flc-[Re(CO)3(N N)L]. 

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