Molekülverbindungen mit Mo‐O‐Bi‐Einheiten

Abstract

Professor Manfred Meisel zum 65. Geburtstag gewidmetDie bemerkenswerte katalytische Aktivität von n MoO 3 / Bi 2 O 3 -Phasen bei der allylischen Propenoxidation (SOHIOProzess) ist seit langem Gegenstand kontroverser Diskussionen.[1] Sie könnte mit dem Vorliegen von Mo-O-Bi-Strukturelementen auf der Katalysatoroberfläche zusammenhängen, wenn man davon ausgeht, dass diese ein besonderes Potenzial für H-Atom-Abstraktionen oder Radikaleinfangreaktionen entwickeln können. Über die strukturelle Charakterisierung von molekularen Verbindungen mit Mo-O-Bi-Gruppen ist bislang nicht berichtet worden, [2] doch die Annahme, dass solche Einheiten eventuell Schlüsselrollen in der heterogenen Katalyse spielen, [1] hat uns angeregt, ihre Etablierung in der Molekülchemie zu verfolgen. Nachdem in ersten Versuchen zur Synthese von Komplexen mit oxoverbrückten Molybdän-und Bismutzentren durch nahe liegende Metathesereaktionen immer nur unlösliche Feststoffe erhalten worden waren, wandten wir uns zunächst der ebenfalls noch unerschlossenen

Synthesis and Structural Characterization of Heterobimetallic Bismuth Complexes with Main Group and Transition Metals

“…In 6 the Hf−O bond length (1.957(3) Å) is longer than that in LAlMe(μ-O)HfMeCp 2 (1.919 Å) . The Bi−O bond length in compounds 3 − 6 (av 2.038 Å) is comparable to those observed in (BiTi 2 O(O i Pr) 9 (2.090 Å) and [(Cp* 2 MoO 3 )BiPh 3 ] (2.201 Å) but considerably shorter than that found in [{Bi(Hsal) 3 } 2 {Al(acac) 3 }] (2.765 Å) …”

Heterometallic Complexes with Re−Bi Metal Bonds

“…With the background of the oxidation of propene to acrolein, which can be catalyzed by mixed metal oxides n MoO 3 /Bi 2 O 3 , , we and others have developed routes to compounds with Mo−O−Bi units , and with Mo−Bi metal bonds. − We found that Mo−Bi bonds can be created by reactions of molybdocene dihydrides with bismuth alkoxides or siloxides. ,,, It was also shown that replacement of the bismuth alkoxides in such reactions by tin and antimony halides results in complexes with Mo−Sn and Mo−Sb bonds . We were interested in investigating whether also the molybdocene dihydride component can be exchanged by other transition metal hydrides in reactions with bismuth alkoxides and in how far the “hydride-alkoxide” route thus might represent a more general procedure to access transition metal−bismuth systems.…”

Iron–molybdenum-oxo complexes as initiators for olefin autoxidation with O2

“…In recent years, we have been interested in molecular heterobimetallic oxo compounds that can mimic certain structural units proposed to occur on the surfaces of corresponding heterogeneous catalysts composed of two metal oxide components. [16][17][18][19][20][21][22] The fact that MoO 3 /Fe 2 O 3 catalysts are employed for the oxidation of methanol to formaldehyde in the so-called FORMOX process has spurred us to investigate Fe-O-Mo compounds. While some purely inorganic polyoxometal aggregates [23][24][25][26][27][28][29][30] and coordination polymers [30][31][32][33][34][35][36][37] featuring Fe-O-Mo entities have been published, so far only five structurally characterised molecular coordination compounds have been reported, where molybdate units are bridging ligated iron ions.…”