Ligands bonds with metals

The availability of organic ligands in the surface complexes obtained by the reaction of organometallic compounds with supports allows us to consider two possibilities of the initiation process (1) the monomer insertion into the organic ligand-metal bond (bensyl, allyl, etc.) (9a) ... 

It is not yet known whether the breaking of the ligand-metal bond is concerted with electron transfer or occurs as a separated step. The dichotomy and relationships between these two pathways has not yet received the same detailed analyses and answers that it has in the organic field (Chapter 3). 

NMR studies of Ag1 with CyDTA indicated a high degree of ionic character for the ligand-metal bond since no coupling to 1H, 13C or 15N was observed and the spectra were similar to that found for the free ligand.426-428 Table 57 gives some chemical shift data. 

A large variety of ligands form bonds with transition metals via one or more pnictide atoms. These range from simple ER3 (E = P, As, Sb, Bi R = alkyl, aryl, alkoxy, aryloxy, halogen and their combinations/permutations) molecules to ligands of elaborate architecture such as the macrocycles described in Section 14.2.1.7. 

Reduction of HNCC is seldom a simple process in which there is substitution of a carbon monoxide ligand, or of a metal-metal bond, with an electron pair. A rare example of this type is (102)... 

Kandioller W, Hartinger CG, Nazarov AA, Bartel C, Skocic M, Jakupec MA, Arion VB, Keppler BK (2009) Maltol-derived ruthenium-cymene complexes with tumor inhibiting properties the impact of ligand-metal bond stability on anticancer activity in vitro. Chem-EurJ 15 12283-12291... 

The UPS valence band spectra of multilayer and monolayer samples of phthalimide (pirn) and methyl-phthalimide (mpim) on copper have been compared with the calculated DOVS for corresponding systems. Very good agreement is found between theory and experiment for all the systems included in this study. This made it possible to interpret the features appearing in the UPS spectra in terms of specific molecular orbitals. Furthermore, by analyzing the MO s, the nature of the ligand-metal bonding is uncovered. 

To summarize this long section on metal effects, we can state metal clusters can mimic main-group clusters (late-metal clusters with acceptor ligands) metal clusters with four-connect or higher vertices can be described with localized bond models (early-metal clusters with donor ligands) and metal clusters can have reduced (Pt clusters) or no tangential bonding (Au clusters). The characteristically more... 

P-donor ligands usually form phosphorus-metal bonds with a main group or transition metal that are essentially covalent and in which the phosphorus is the lone pair donor. Despite the vast number of complexes prepared, often with elaborate architecture, the nature of the phosphorus-metal bond remains elusive and controversial, in particular, for transition metals. The simple statement of the bond as a neutral donor-acceptor complex has been elaborated by identifying the many contributing factors. We will discuss the steric factor and the electronic component of the P-M bond separately. The separation of the electronic component into a and n factors is a formal exercise, the reality being Synergic Bonding, wherein these electronic factors are mutually dependent. 

Stable early-late M-M metal-metal-bonded heterobimetallic complexes 1273 (M = Zr, Hf M = Fe, Ru) supported by tripodal amido ligands have been synthesized by the reaction of the zirconium and hafnium complexes MeSi(SiMe2NAr)3MCl 1272 with K[CpM (CO)2], as shown in Scheme 302.960,961 The molecular structure of the Zr-Fe complex (Ar =p-to y ) determined by X-ray diffraction establishes the presence of an unsupported metal-metal bond with a Zr-Fe bond distance of 2.605(2) A. The reaction of 1273 with isonitriles leads to insertion into the metal-metal bond and formation of metallaiminoacyl complexes 1274. 

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