Scandium Cluster and Metallocene Chemistry

Demir, Selvan (2010) Scandium Cluster and Metallocene Chemistry. PhD thesis, Universität zu Köln.

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Abstract

This thesis focuses on the synthesis and characterization of scandium compounds. One goal was to investigate the solution reactivity of {CSc6}I12Sc, which resulted in the isolation of a molecular scandium nitride, [(C5H5)2ScNSc(C5H5)(THF)]2, and a scandium propoxide complex, [(C5H5)2Sc(µ-OPr)]2. Besides this, priority was given to the synthesis and characterization of the first scandium dinitrogen complex, [(C5Me4H)2Sc]2(µ-η2:η2-N2), along with its precursor compounds: (C5Me4H)2ScCl(THF), (C5Me4H)2Sc(η3-C3H5) and [(C5Me4H)2Sc]2[(µ-Ph)BPh3]. The reduction of the latter complex with KC8 under N2 gave the elusive [(C5Me4H)2Sc]2(µ-η2:η2-N2). Structure determination supported by DFT calculations revealed a coplanar arrangement of a bridging side-on bound dinitrogen unit and two scandium atoms. In one reaction, the dinitrogen complex co-crystallized with an oxide impurity as {[(C5Me4H)2Sc]2(µ-η2:η2-N2)[(C5Me4H)2Sc]2(µ-O)}. Additionally, the borohydride complexes (C5Me4R)2M(BH4)(THF)x (M = Sc, Y; R = H, Me; x = 0, 1) were prepared. Yttrium borohydride complexes were investigated with respect to their dinitrogen activation capability, but were found to be inactive. Ligand based reactivity of (C5Me4R)2Sc(η3-C3H5) (R = H, Me) occured with 9-BBN (9-borabicyclo[3.3.1]nonane) to form the corresponding (C5Me4R)2Sc(µ-H)2BC8H14 complexes, from which oxygen exposure (R = H) yielded (C5Me4H)2Sc(µ-O)BC8H14. Subsequent investigations focused on the reaction of [(C5Me4H)2Sc]2[(µ-Ph)BPh3] with KC5Me4H and gave (5-C5Me4H)2Sc(1-C5Me4H), which was structurally characterized and is the first example of an 1-coordination mode for a (C5Me4H)- ligand bound to a rare-earth metal. This complex undergoes Sigma Bond Metathesis (SBM) reactivity towards diphenyldichalcogenides, PhEEPh (E = S, Se, Te), to produce [(C5Me4H)2ScSPh]2 and (C5Me4H)2ScEPh (E = Se, Te) complexes. The analogous products could be isolated and were fully characterized through the ligand based reactivity of (C5Me4H)2Sc(η3-C3H5) and PhEEPh reagents. These reactions also worked in the presence of THF to yield the solvated complexes (C5Me4H)2ScEPh(THF) (E = S, Se, Te). The reaction of (C5Me4H)2Sc(η3-C3H5) with pySSpy produced the analogous (C5Me4H)2ScSpy complex. In addition, the formation of a scandium selenium cluster complex [(C5Me4H)Sc]3[SePh]6 was identified and reactivity studies with PhTeTePh additionally resulted in the isolation of a scandium tellurium cluster compound, {[(C5Me5)Sc]4(μ3-Te)4}. The functionalization of N2O via insertion into the metal carbon bond of allyl compounds, (C5Me4R)2M(η3-C3H5) (M = Sc, Y, La, Sm; R = H, Me) formed [(C5Me4R)2M(µ-1:2-ON=NC3H5)]2 complexes. The insertion of iPrN=C=NiPr into the Sc-C bond of (C5Me4H)2Sc(3-C3H5) gave (C5Me4H)2Sc[(iPr)NC(CH2CH=CH2)N(iPr)-κ2N,N']. Finally, although the desired products were not isolated from an attempted reaction of (C5Me4H)2Sc(3-C3H5) with diphenylhydrazine, a scandium hydroxo cluster complex (C5Me4H)5Sc5(µ5-O)(µ3-OH)4(µ2-OH)4∙[(C6H5)NH]2 was isolated.

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