Ligand substitution reactivity

Scheme 1. Ligand substitution reactivity of RuCl2(CN(Me)CH2CH2NMe)4.

Efforts continue to elucidate the excited-state dynamics and ligand substitutional reactivities of d6 transition metal complexes.201-203 Fluorescence from incompletely relaxed ligand field singlet states has been detected for some haloamminerhodium(III) complexes.204... 

In addition to clusterification, ligand substitution also occurs for Fe(CO)5, and in fact for most metal carbonyls. This has proved useful as a mechanistic probe of the reactive species formed during cavitation. Sonica-tion of Fe(CO)5 in the presence of phosphines or phosphites produces Fe(CO)5 L (n = 1,2, and 3). The ratio of these products is independent of length of sonication the multiply substituted products increase with increasing initial [L] Fe(CO)4L is not sonochemically converted to Fe(CO)3L2 on the timescale of its production from Fe(CO)5. These observations are consistent with the same primary sonochemical event... 

Kinetic studies of aquation of dinuclear [ traras-PtCl(NH3)2 2 (p-NH2(CH2)6NH2)]2+ established rate constants for the loss of the first and second chloride ligands (7.9 x 10-5 and 10.6 x 10-4s-1), and for the reverse anations (1.2 and 1.5M-1s-1). Reactivities here are very similar to those in analogous mononuclear systems [Pt(amine)3Cl]+ (204). A kinetic and equilibrium study of axial ligand substitution reactions... 

Chemisorption Adsorbate Orientation Competitive Chemisorption Adsorbate Exchange Adsorbate Reactivity Electrocatalvsis Synthesis Mode of Coordination Ligand Substitution Ligand Exchange Ligand Reactivity Homoqeneous Catalysis... 

Major emphasis is placed on the reactions of metal complexes in solution undergoing either inner-sphere ligand substitution or electron transfer to and from the metal center. Such studies relate to the important selective role of metal catalysts in many areas of enzymatic, commercial, and modem synthetic chemistry. Clearly, this field has now matured to the point where basic theoretical considerations, although incomplete, can provide a logical framework for understanding the chemical reactivity of such systems and stimulate the investigation of (1) new and unique reaction pathways, (2) modified reagents, and (3) unorthodox matrices. 

When the initial vinylcarbene complex is substituted with a second me-thoxycarbonyl group (complex 169), a different reactivity pattern is observed. Addition of methyldiphenylphosphine or dimethylphenylphosphine to 169 results in formation of the expected vinylketene complex 170. However, the analogous reaction with triphenylphosphine yielded a complex mixture at room temperature, and upon heating the simple ligand-substituted product 171 is formed. When 169 is reacted with carbon monoxide, the pyrone complex 172 is formed. Finally, reaction of the vinylketene... 

Non-heteroatom-substituted carbene complexes of almost all transition metals are known. Depending on the oxidation state of the metal, the overall charge of the complex, and the properties of the additional ligands, the reactivity of alkyl or aryl carbene complexes can vary greatly. Some examples of compounds with strikingly different chemical properties are shown in Figure 3.1. 

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