Ruthenium complexes with Group 14 ligands

This is the second of the common oxidation states for iron and is familiar for ruthenium, particularly with Group 15-donor ligands (Ru probably forms more nitrosyl complexes than any other metal). Osmium(II) also produces a considerable number of complexes but is usually more strongly reducing than Ru". 

Ruthenium complexes containing this ligand are able to reduce a variety of double bonds with e.e. above 95%. In order to achieve high enantioselectivity, the reactant must show a strong preference for a specific orientation when complexed with the catalyst. This ordinarily requires the presence of a functional group that can coordinate with the metal. The ruthenium-BINAP catalyst has been used successfully with unsaturated amides,23 allylic and homoallylic alcohols,24 and unsaturated carboxylic acids.25... 

Compounds 81 and 83-86 were linked to P-CD, the ruthenium p-complexes prepared in situ and reductions carried out with the standard substrate 63 (Fig. 26). Comparing the results of ruthenium complexes with ligands 87-91 reveals that any substituent adjacent to the tosyl group leads to modest to good ee values but reduces the reactivity of the catalyst considerably, see 87-89 (Fig. 26), improvement of the 5delds between 33% and 53% was only achieved at elevated temperatures (50°C). In contrast, ruthenium complexes with ligands... 

The reaction between acetylenes and ruthenium carbonyls produces a series of n complexes with cyclic ligands which, as in the iron system, have either the metal or a CO group incorporated into the ring. Accordingly, 3-hexyne 536) and hexafluoro-2-butyne 90) react with Ru3(CO)i2 to give the (substituted cyclopentadienone)tricarbonylruthenium complexes with structures presumably comparable to those of the iron complexes (93-95). Although diphenylacetylene will not react directly with Ru3(CO)i2 to produce this type of complex 536), it can be prepared 90) by treating Ru3(CO)i2 with tetracyclone in benzene under reflux. 

There are a limited number of group VHI-X metal-based catalytic systems active and selective in asymmetric hydrosilylation of 0=0 bond. These few systems include Fe(OAc)2/DUPHOS active in hydrosilylation of aryl methyl ketones with (EtO)2MeSiH or PMHS (301,302), ruthenium complexes bearing oxazolinylferrocenephosphine ligand (303), or chiral bis(paracyclophane)-substituted (NHC) ligands in hydrosilylation of aryl alkyl ketones with H2SiPh2 (304) and iridium(I)/DIPOF system active in hydrosilylation of acetophenone with diphenylsilane. 

Ruthenium and Osmium Complexes with Group 13 Ligands... 

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