3-Hydroxy-2-methyl-4-pyrone complexes, with

NMR spectra were measured. As RuCl(H20)(csb)2/02/Me2CHCH0/CH2Cl2/4°C it asymmetrically epoxidised styrene and substituted styrenes with e.e. of up to 30% [798]. Complexes with (csb =lR,2R(-)l,2-diaminocyclohexane with 3-acetyl-4-hydroxy-6-methyl-2-pyrone and salicylaldehyde, 5-chloro-5-methoxy, 5-methoxy and 5-nitrosalicyladehyde) asymmetrically epoxidised styrene as RuCKH O) (csb )2/PhIO/CH3CN [799]. 

Somewhat surprisingly, maltol (2-methyl-3-hydroxy-4-pyrone), an aromatic analogue to a-hydroxy carboxylic acids, shows little inclination toward formation of dimeric complexes. Rather, the chemistry is more in parallel with that of oxalate, and an x-ray structure of the bismaltolato complex [25] shows a cis octahedral coordination similar to that found for the oxalate complex. Under mildly acidic to moderately basic solution, the major complexes are mono- and bisligand derivatives. The corresponding vanadium chemical shifts are -509 and -496 ppm, respectively [25,26], The closely related amines, 2-methyl-3-hydroxy-4-pyridinone and its N-... 

Synthesis with sacrificial electrodes is employed as a direct method in several other preparations of organometallic compounds and complexes. 3-Hydroxy-2-methyl-4-pyrone derivatives of Sn 1 (and of Zn, Cu, In and Cd as well) were prepared using the metal as an anode. The low oxidation state Sn(II) compound is obtained by direct electrolysis134. 

Two other types of unusual indium(II)-oxygen ligand complexes are known. The polar-ographic reduction of In(acac)3, In(tropolonate)3 or In(pyronate)3 (pyronate = 3-hydroxy-2-methyl-4-pyronate anion) in non-aqueous solution shows a one-electron reduction in each case, corresponding to the formation of a (formally) In complex. Similar behaviour was observed with In(oxine)3, and in some cases a second one-electron reduction was also observed, implying the formation of In species, although in no case was the site of the reduction identified, so that the product may be either [In (acac)3] or [In (acac)2(acac )] (c/. sulfur ligands. Section 25.2.3.4). 

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