A novel organometallic oxide cluster with multi-valley sites: synthesis and structure of [NBun4]2[{(η5-C 5Me5)Rh}2Mo6O20 (OMe)2] and its framework transformations

Direct Observation by Electrospray Ionization Mass Spectrometry of [Cp*RhMo3O8(OMe)5]−, a Key Intermediate in the Formation of the Double-Bookshelf-Type Oxide Cluster [(Cp*Rh)2Mo6O20(OMe)2]2−

“…The MS/MS measurements were carried out at room temperature. [1] and imido [2] complexes of the heavier Group 15 elements (Sb and Bi) have been reported in recent years, for the related phosphorus compounds (containing R 2 P À or RP 2À groups) only those of Sb have appeared in the literature.…”

“…[2] Furthermore, 3 is converted into the facesharing triple-cubane-type cluster [(Cp*Rh) [2,3] Understanding the mechanism of formation for these clusters may provide strategies for the synthesis of desired oxide cluster catalysts for hydrocarbon transformations.…”

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Organometallic oxide clusters with cubic and incomplete cubic frameworks are very useful as homogeneous and heterogeneous catalysts in the oxidation and metathesis of unsaturated hydrocarbons.[ [2, 3] Understanding the mechanism of formation for these clusters may provide strategies for the synthesis of desired oxide cluster catalysts for hydrocarbon transformations.We have investigated the formation mechanism of 3 by electrospray ionization mass spectrometry (ESI-MS), [4] which allows us to detect unstable species generated in solution. The 95 Mo NMR spectrum of 2 in MeOH showed one broad signal (d À 15, reference: Na 2 MoO 4 ) even at À 50 8C because of the rapid exchange of Mo centers between several species in equilibrium.

[6] As shown in Figure 1 a, the negativeion ESI mass spectrum of a cooled solution (À 788C in an acetone/dry ice bath) of 2 in MeOH in the range of m/z 1200 to 250 confirmed that 2 exists as an equilibrium mixture of di- ( À : m/z 926 [7] ).

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“…[(Cp*Rh) 2 (2) We have simultaneously monitored the intensity changes of three selected envelopesÐnamely, those at m/z 690 (Mo 3 ), 809 (3 im ), and 953 (3 OMe = )Ðduring the reaction of 1 with two equivalents of 2 in MeOH (À 78 8C) by rapid scanning [11] ( Figure 2). After mixing of the reagents, the envelope at m/z 690 decreased immediately in intensity (Figure 2 b, c, e), concomitant with the appearance and increase in intensities of the envelopes at m/z 809 and 953.…”

Strategic Isolation of a Polyoxocation Mimicking Vanadium(V) Oxide Layered-Structure by Stacking of [H2V2O8]4− Anions Bridged by (1,4,7-Triazacyclononane)Co(III) Complexes

“…To realize their oxide surface structures as model clusters, a synthetic chemistry of anionic oxide clusters of polyoxomolybdate, polyoxotungstate, or polyoxovanadate have been developed in the past decade. Some of the attempts to control oxide cluster structures have been achieved using organometallic capping ligand to prevent the formation of infinitely condensed oxide precipitates and the capping ligands restrict an unlimited condensation and facilitate a formation of an oligometric oxide core (Hayashi et al, 1988; Do et al, 1991; Proust et al, 1993; Takara et al, 1997; Artero et al, 2000, 2001; Villanneau et al, 2003; Boujday et al, 2007). …”