The syntheses of two cyclic diorganosilicon enamines =CH2) [R = Ph (2a), Me (2b)] are described. These compounds react with 8-oxyquinoline leading to bis(oxinato)silicon complexes RPhSi(oxinate)2 [R = Ph (5a), Me (5b)]. Their X-ray structures reveal hexacoordination of the Si atom with the monodentate substituents in cis-positions and N atoms as well as O atoms in trans-positions.In crystalline dimethylbis(oxinato)silicon, Me2Si(oxinate)2 (7), the silicon atom is only bicapped tetrahedrally coordinated, while for dichlorobis(oxinato)silicon, Cl2Si(oxinate)2 (8), there is an octahedral coordination of the Si atom with chlorine atoms in trans-positions. This conclusion is based on the results of spectroscopic analysis (IR, 29Si CP/MAS NMR) as well as quantum chemical calculations. The first example of a silicon-bis-oxinate with the N→Si dative bonds in a trans-arrangement has been detected in the hexacoordinate silicon tris-chelate (oxinate)2Si(PhN-CH2CH2-NPh) (11). Its configuration was proven by X-ray structure analysis. Thus, for hexacoordinate bis(oxinato)silicon compounds three new architectures were found which complement the previously established building pattern of the N,N’-cis-O,O’-trans-bis(oxinato)silicon complexes.The mer-tris(oxinato)siliconium cation (9+) (its configuration being proven by 1H and 13C NMR spectroscopy) features at least three coordination patterns with (O,O;N,N)-cis,cis-, -cis,trans- as well as -trans,cis-arrangements of two oxinate ligands.

O-Functionalised salen ligands were employed as bridging ligands in the synthesis of homo- and heterometallic salen complexes with early and late transition metals (H(2)salen: N,N'-bis(salicylidene)ethylenediamine, systematic name: 2,2'-{ethane-1,2-diylbis(nitrilomethylidine)}diphenol). A new type of O-functionalised salen ligand was synthesised, which contains alkyl groups to enhance the solubility in organic solvents as well as carboxyl groups to allow introduction of an early transition metal. Two new salen ligands derived from O-functionalised diamines were synthesised from 3,5-di-tert-butylsalicylaldehyde (bsal) and 3,4-diaminobenzoic acid (4cpn) or (R)-2,3-diaminopropionic acid (cen). By using the aryl diamines, a conjugated backbone is obtained, and the alkyl diamines can be used to introduce a chiral centre. The salen ligand derived from 3,4-diaminobenzoic acid was accessible only via a zinc(II)-mediated template reaction. Monometallic salen complexes could be obtained by template synthesis with nickel(II) and copper(II). The analogous chromium(III), manganese(III) and molybdenum(IV) salen complexes were synthesised directly from the salen ligands. The crystal structures of the molybdenum(IV) salen complex and a decomposition product thereof gave insight into the stability of this compound. Starting from (R)-2,3-diaminopropionic acid the corresponding nickel(II), chromium(III), manganese(III) and molybdenum(IV) salen complexes were obtained. Reactions of the conjugated nickel(II) salen complex with metallocene derivatives resulted in the formation of soluble di- and trinuclear heterobimetallic complexes, depending on the stoichiometry used. The compounds were characterised by NMR, IR and EPR spectroscopy, mass spectrometry and, for selected complexes, by X-ray crystallography. For selected mono- and bimetallic salen complexes the catalytic activity in the epoxidation of styrene was tested under different reaction conditions and with different oxidising agents. The highest values (up to 24%) for the conversion of styrene to styrene oxide were obtained with manganese(III) salen complexes.

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Starting from silicon tetrahalides SiCl 4 and SiBr 4 , respectively, and the bidentate 2-iminomethylphenol-type ligand HO-C 6 H 3 -2-[C(C 6 H 5 )ϭN(CH 2 -C 6 H 5 )]-5-OCH 3 , three novel complexes with hypercoordinate silicon atom were synthesized. Their coordination spheres consist of two halogen atoms (F, Cl, Br) and two six membered ring systems created by chelating bidentate ligands of 2-iminomethylphenolate type. Demonstrated by crystal structure analysis, the dichloro-and difluorosilicon complexes {O-C 6 H 3 -2-[C(C 6 H 5 )ϭN(CH 2 -C 6 H 5 )]-5-OCH 3 }SiX 2 (X ϭ Cl, F) reveal alltrans-configuration in solid state. The difluorosilicon complex

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