Half-sandwich compound
Half sandwich compounds are organometallic complexes that feature a cyclic polyhapto ligand bound to an MLn center, where L is a unidentate ligand. Thousands of such complexes are known. Well known examples include Cyclobutadieneiron tricarbonyl and (C5H5)TiCl3. Commercially useful examples include (C5H5)Co(CO)2, which is used in the synthesis of substituted pyridines, and methylcyclopentadienyl manganese tricarbonyl, an antiknock agent in petrol.
MMT is a commercially useful antiknock compound.
CpCo(CO)2 is a catalyst for the synthesis of pyridines.
(C4H4)Fe(CO)3.
CpFe(CO)2I is an example of an unsymmetrical piano stool complex.
The diruthenium of cymene is readily cleaved by ligands to give monoRu half-sandwich derivatives.
cycloheptatrienemolybdenum tricarbonyl.
Half sandwich complexes containing cyclopentadienyl ligands are common. Well studied examples include (η5-C5H5)V(CO)4, (η5-C5H5)Cr(CO)3H, (η5-C5H5)Mn(CO)3, (η5-C5H5)Cr(CO)3H, [(η5-CH3C5H4)Fe(CO)3]+, (η5-C5H5)V(CO)4I, (η5-C5H5)Co(CO)2.
In organometallic chemistry, (η6-C6H6) piano stool compounds are half-sandwich compounds with (η6-C6H6)ML3 structure (M = Cr, Mo, W, Mn(I), Re(I) and L = typically CO). (η6-C6H6) piano stool complexes are stable 18-electron coordination compounds with a variety of chemical and material applications. Early studies on (η6-C6H6)Cr(CO)3 were carried out by G. Natta, R. Ercoli, F. Calderazzo,E. O. Fischer and K. Ofele, and the crystal structure was determined by P. Corradini and G. Allegra in 1959. The x-ray data indicate that the plane of the benzene ring is nearly parallel to the plane defined by the oxygen atoms of the carbonyl ligands, and so the structure resembles a benzene seat mounted on three carbonyl legs tethered by the metal atom.
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