Keywords: Asymmetric catalysis / Cyanohydrins / Titanium / AldehydesTitanium complexes 1 derived from chiral salen ligands are highly active precatalysts for the asymmetric addition of trimethylsilyl cyanide to aldehydes and ketones. Based on spectroscopic studies and the identification of adducts between complexes 1 and carbonyl compounds or trimethylsilyl Scheme 1 [a]

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In order to explain the different catalytic activity in hydrogenation of two new intermetallic Ni/Ga clusters, [Ga 7 ](NiCp*) 6 (1A) and [NiGa 6 ](NiCp*) 6 (1B) (Cp* = C 5 Me 5 ), investigations of structure-function relationship have been performed based on Raman and infrared (IR) spectroscopy and theoretical (density functional theory [DFT] and normal coordinate) calculations. Full interpretation of the Raman, far-IR, and mid-IR spectra of these dark colored solids has been proposed. Based on the overview of metal-Cp* complexes, all the 14 characteristic Cp* À skeletal fundamental modes have been identified. By comparison of the Ni Cp* stretching and tilting external modes (350-380 cm À1), their force constants, and bond lengths, cluster 1B exhibited slightly stronger metal-ligand bonding. Vibrations of Ga 7 and NiGa 6 cluster cores showed that the stretching wavenumbers and force constants of Ni Ga (100-350 cm À1 ) and Ga Ga (60-250 cm À1 ) bonds are higher for cluster 1B, in agreement with the shorter averaged experimental and calculated bond lengths of Ga Ga bonds (2.873 and 2823 Å for clusters 1A and 1B, respectively). Cluster hydrogenation experiments with H 2 and D 2 showed strong Ni H and N D stretching features (at 1750 and 1260 cm À1 , respectively), and at the same time, characteristic bands of self-hydrogenated Cp*H and remained nondegraded clusters have been detected. The extent of H D exchange in cluster deuteration was obtained about 1.5 times more effective with cluster 1B than cluster 1A. The stronger hydrogen or deuterium uptake by cluster 1B and the more intensive self-hydrogenation of Cp* clearly support the higher hydrogenation activity of cluster 1B compared with that of 1A.

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The reaction of Cp2MCI 2 complexes (M = Ti and Zr) with 2 equiv, of. (OC)3Mn(r ll,qs-CsH4)Fe(CO)2(~5-CsH4COONa) results in the formation of thc pcntanuclear complexes [(OC)3Mn(nI,qS-CsH4)Fe(CO)~(qt,qs-CsH4CO2)I2M(qs-CsHs)2, which are characterizecl by IR and IH NMR spectroscopy and cyclic voltammetry.Key words: Group IV metal, polynuclear complex, synthesis; IR spectra; electrochemistry.The synthesis and study of polynuclear complexes including diverse metals and bridged organic ligands are of special interest because of their unique conducting and catalytic properties. 1 We have previously obtained homo-and heterometallic, bi-and trinuclear transition metal complexes with bridged cyclopentadienyl ligands 2,3 linked in different ways.In this work, the pentanuclear complexes containing metal atoms of IV, VII, and VIII Groups and bridged ligands --OC(=O)CsH 4 and rll,rlS-CsH4 were synthesized: [(OC)3Mn(nt,nS-CsH4) Fe(CO)2(nl,n 5-CsH4CO2)I2M(rlS-CsH~)2, where M = Ti (I), Zr (2).In the previous work, 4 we have shown that in the "staircase" type complexes, individual metal-containing groups mutually affect adjacent fragments resulting in the rearrangement of the electron density in the molecule. This was indicated by the frequencies of the stretching modes of the carbonyl groups in the IR spectra_ It was of interest to reveal whether the regularities that were elucidated previously can be valid for the pentanuclear complexes obtained. In addition, the redistribution of the electron density should have an effect on the redox properties of these complexes; therefore, it seemed to be interesting to carry out an electrochemical study of their redox properties. The starting compound was the acid (OC)3Mn(n t,ns-C~H4) Fe(CO)2('qs-CsH4COOH) that was previously synthesized s by the metaUation of the binuclear complex (OC)3Mn(rl[,nS-CsH4)Fe(CO)2Cp (3) under the action of BunLi followed by the treatment with CO 2.Complexes 1 and 2 were obtained by the reaction of Cp2MC12 (M = Ti, Zr) with the sodium salt (OC)3Mn(~II,nS-CsH4) Fe(CO)2(nS-CsH4COONa) (2 equiv.). They are brown and yellow powders, respectively, soluble in CH2C12, Et20 , and benzene and insoluble in hexane.