Osmium complexes range

OsCle- is a useful starting material for the synthesis of a range of osmium complexes (Figure 1.4). 

A similar range of reactions has also been reported for the ruthenium carbonyl-triphenylphosphine systems (148). In these systems, a high percentage of the products were dinuclear, reflecting the weaker bonding in the ruthenium system, and as for some of the osmium complexes discussed above, some contain orthometallated phenylphos-phine groups (see Fig. 29, structures I, IV, X). 

A considerable range of iron carbonyl clusters is now known to contain antimony or bismuth, and later developments have seen this extended to ruthenium and osmium complexes. Whitmire (711) has described the reaction between NaBi03 and methanolic [Fe(CO)5], which affords the anionic triiron cluster [BiFe3(CO)10] (108), which contains a tetrahedral BiFe3 core. Cluster 108 is an example of a closo tetrahedral cluster with three first-row... 

Novel picolinate derivatives have been synthesised that show hydrolysis rates intermediate between the slow values for the complexes with /V,/V-chelating ligands, and the rapidly-hydrolysing complexes with 0,0- or N,0- amino acidlike chelating ligands. For these organometallic osmium complexes, the hydrolysis rates fall into the range of the active ruthenium-arene relatives (Fig.l) [66]. 

Another promising technique based on Raman spectroscopy is SERS. In this technique the molecules to be studied are adsorbed on gold or silver colloidal particles, leading to an impressive amplification of the signal (typically by a factor of 100-1000). This technique was recently employed by Leong and coworkers to localize the osmium complex 55 (Scheme 11.10) adsorbed on gold nanoparticles [152]. This time the amplified t/(CO) peaks of the complex have an intensity sufficient to allow study at concentrations in the micromolar range. 

These neutral Ru(II)- and Os(II)-complexes are well soluble in a broad range of solvents as well as in the pure monomers. Osmium complexes of the type [Os(p-cymene)Cl2(PR3)] C2 do not initiate the thermal polymerization of norbornene (NBE). However, they can be activated by UV irradiation (200W Hg-lamp, 5 min). With the sterically demanding phosphine ligands PCys and P/Pr3 active photocatalysts are obtained, whereas for the complexes with less bulky phosphines (PPh3, P/1BU3) no or a very slow polymerization is observed. 

Subsequent research on osmium-modified polymers has shown how the redox potential can be controlled by altering bipyridine ligands of the immobilized osmium complexes. The ability to reliably modulate redox potential has significantly broadened the range of enzymes with which osmium redox polymer are compatible and allows for mediation of oxidative enzymatic reactions as well as reductive enzymatic reactions. 

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