Electrophilic Half-Sandwich (Carbene)metal (Metal = Fe, Ru, Os) Complexes: Recent Developments in Synthesis and Applications

Abstract

This review covers synthetic and structural aspects of electrophilic half-sandwich (carbene)metal complexes of Group-8 metals as well as the use of these complexes in transforma-

Syntheses, Properties, and X-ray Crystal Structures of Piano-Stool Iron Complexes Bearing an N-Heterocyclic Carbene Ligand

“…Selected bond lengths and bond angles are reported in Table . The Fe−C bond distances are similar in 2a (1.980(5) Å) and 2b (1.977(4) Å), and they compare well with that of other heterocyclic iron carbene complexes, such as (1.969(5) Å). 8a,b The Fe−C bond distances in Fischer-carbene complexes are typically in the range 1.82−1.97 Å . In both complexes, the orientation of the carbene ligand is twisted with respect to the Cp ligand [Cp(c)−Fe−C(17) 126.2° ( 2a ), 128.7 °( 2b )], probably as a result of steric factors 7b.…”

“…These ligands, bulkier and more basic than the ubiquitous phosphines, are promising candidates as alternative ligands for organometallic chemistry; their use for stabilization of reactive intermediates has become significant . As a part of ongoing research on iron−carbene complexes, we sought to develop a convenient route to complexes containing an NHC ligand for their intrinsic interest in stabilizing reactive moieties.…”

Nucleophilic substitution on a Ru-coordinated Cp ring by a carborane anion

“…Cyclopentadienyl ruthenium(II) complexes have been mainly considered as useful model compounds and have only recently been successfully employed as catalysts in a series of C-C bond forming reactions. 1,2 In this context, the results obtained by Rigo's group in the decomposition of a variety of a-diazo carbonyl compounds catalyzed by [RuCl(Cp)(PPh 3 ) 2 ] appear rather interesting. This commercially available complex, in fact, is an excellent catalyst for their stereoselective transformation into symmetrical and unsymmetrical cis-enediones, which are useful starting materials in the synthesis, for example, of heterocyclic compounds and flavouring agents for food.…”

The chemistry of the carbon–transition metal double and triple bond: annual survey covering the year 2002

“…A review of polymerization catalysts features a section on metathesis [51]. Additional aspects of carbene complex chemistry have been reviewed in 2002, including: (1) high oxidation state multiple carbon-metal bonds [52]; (2) titanium alkylidenation reagents [53]; (3) use of Fischer carbene complexes for heterocycle synthesis [54]; (4) reaction of phosphaalkenes toward carbene complexes [55]; (5) the physical organic chemistry of Fischer carbene complexes [56]; (6) tungsten-pentacarbonyl-catalyzed construction of carbocyclic frameworks [57]; (7) metal-calixarene carbene complexes [58]; (8) ruthenium and osmium porphyrin carbene complexes [59]; (9) half sandwich group VIII metal carbene complexes [60]; (10) iridium-containing cumulenes [61]; and (11) reactions of palladium-carbene and carbyne complexes [62]. Although not specifically focusing on metal-carbene complexes, some review articles place a heavy emphasis on this subject.…”