Progress in the Compilation of an Oxovanada‐Silsesquioxane Portfolio and Catalytic Activity of Organometallic Representatives in Ethylene Polymerisation

Abstract

Employing various incompletely condensed silsesquioxanes as ligand precursors in reactions with simple oxovanadates a variety of oxovanadium silsequioxanes could be synthesized, that might be regarded as models for oxovanadium units on silica surfaces. These include a tetranuclear vanadium(IV) compound as well as two complexes where O 2 V + units are coordinated to two siloxide functions as part of a silsesquioxane framework. Moreover, compounds containing Cp*V(O) 2+ moieties were prepared, whose activities as polymerization procatalysts has been examined: They turned out to be moderately active for the polymerization of ethylene. All compounds were fully characterised, in case of the tetranuclear vanadium(IV) complex this also includes the investigation of magnetic behaviour. Moreover, for two complexes also the molecular structures could be determined with sufficient quality via XRD.

On the role of thermal activation in selective photochemistry: mechanistic insight into the oxidation of propene on the V4O11−cluster

“…1,[7][8][9][10][11][12] In this context, extensive efforts in gas phase studies on the structure of small cluster ions have given a fundamental understanding of the structural motifs in these systems in view of their reactive nature. [13][14][15][16][17][18][19][20][21][22][23][24] Within the class of small vanadium oxide cluster ions, the V 4 O 11…”

Multinuclear Clusters of Manganese and Lithium with Silsesquioxane-Derived Ligands: Synthesis and Ligand Rearrangement by Dioxygen- and Base-Mediated Si–O Bond Cleavage

“…Ligands L1 and L2 are illustrated in Scheme . L2 is an unusual silsesquioxane template, with only three structural reports of coordination complexes to our knowledge. ,, The L1 ligand scaffold is much more common, representing the templating ligand for the manganese chemistry of Lorenz et al, as well as four other reports of complexes of first-row transition metals. ,,, We additionally present rearrangement chemistry of ligand L1 involving Si–O bond cleavage reactions mediated by dioxygen (O 2 ) and by hydroxide.…”

“…In another study from Riollet et al, the silsesquioxane ligand was studied as a model of a silica-surface-templated active heterogeneous catalytic species . Among other first-row d-block metal complexes of silsequioxanes, titanium, − iron, − vanadium, − and zinc ,− are most common, although there are examples with cobalt, − chromium, ,, and copper ,− and one with scandium . We report here the synthesis of multinuclear manganese complexes of POSS-derived ligands via the reaction of Mn­(N­(SiMe 3 ) 2 ) 2 and 1,3,5,7,9,11,14-heptaphenyl-2,4,6,8,10,12,13,15,16-nonaoxa-1,3,5,7,9,11,14-heptasilatricyclo­[7.3.3.15,11]­hexadecane-3,7,14-triol [Ph 7 Si 7 O 9 (OH) 3 , (L1)­H 3 ] and (2 S ,4 S ,6 S ,8 S )-2,4,6,8-tetraphenyl-1,3,5,7,2,4,6,8-tetraoxatetrasilocane-2,4,6,8-tetraol [Ph 4 Si 4 O 4 (OH) 4 , (L2)­H 4 ].…”

Synthesis and catalytic properties for olefin polymerization of new vanadium complexes containing silsesquioxane ligands with different denticity

“…Further investigations involved oxovanadium‐based pre‐catalysts which contained both silsesquioxane and cyclopentadienyl ligands in conjunction with polymethylaluminoxane and EtAlCl 2 . These compounds were found to be moderately active in the polymerization of ethylene . Besides the above mentioned systems, some more examples of vanadium‐containing silsesquioxanes were synthesized and characterized; however, their catalytic activity was not examined to our knowledge …”

“…These compounds were found to be moderately active in the polymerization of ethylene. 17 Besides the above mentioned systems, some more examples of vanadium-containing silsesquioxanes were synthesized and characterized; however, their catalytic activity was not examined to our knowledge. 18 -28 Having considered (i) the high potential of vanadium-based catalysts in the polymerization of olefins, (ii) possible structural modifications, and hence the electronic and steric properties of silsesquioxanes which are used as ligands, and (iii) the lack of information available on catalysts other than those based on oxavanada-silsesquioxane, which turned out to be not very efficient in the polymerization of olefins, we decided to synthesize and study the catalytic properties of new vanadium-silsesquioxane complexes obtained in the reaction of VCl 4 with not fully condensed silsesquioxanes containing from one to four silanol groups.…”