Related Experiment Video
Updated: Feb 28, 2026

Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of ChalcogenidoplumbatesII or IV
Published on: December 29, 2016
Comparative Study of Aqueous Acid-Base Properties of Tungstocene and Molybdocene Complexes
Niklas Stix1, Miljan Z Ćorović1, Sophia S Schiller1
1Institute of Chemistry, Inorganic Chemistry, University of Graz, 8010 Graz, Austria.
None:
The aqueous chemistry of molybdenum and tungsten complexes is relevant due to their occurrence in metalloenzymes. However, water-stable and -soluble model complexes in biologically relevant higher oxidation states are rare. Metallocenes of the type [Cp2M-(OH2)]2+ (M = Mo, W) exhibit such properties despite the nonbiomimetic cyclopentadienyl (Cp) ligand. Therefore, the aqueous acid-base properties of these bis-aqua tungstocenes and molybdocenes were investigated, as their +IV oxidation states and coordinated H2O render them ideal candidates. The precursors [Cp2MoCl2] (1a), [Cp2Mo-(μ-OH)2MoCp2]-(pTsO)2 (1b), [Cp2Mo-(pTsO)2] (3) and their tungsten analogues [Cp2WCl2] (2a), [Cp2W-(μ-OH)2WCp2]-(pTsO)2 (2b), and [Cp2W-(pTsO)2] (4) were studied via aqueous potentiometric titrations. Molybdocene acted as a triprotic acid, with deprotonation occurring from both mono- and dimeric species, while tungstocene reacted as a diprotic acid exclusively in its monomeric form. Tungsten complexes exhibit higher acidity with 1-1.5 lower pK a values than molybdenum, which is of general interest for the understanding of tungstoenzymes. The substitution of chlorides by tosylates allowed the isolation of 3 and 4, which proved to be less suitable precursors for aqueous chemistry, as they were more difficult to hydrolyze, leading to partial degradation upon hydrolysis. This indicates that simply the presence of a Cp2M motif is not sufficient for the formation of the aqueous species.
More Related Videos
07:49Characterizing Lewis Pairs Using Titration Coupled with In Situ Infrared Spectroscopy
Published on: February 20, 2020
11:04Ion Mobility-Mass Spectrometry Techniques for Determining the Structure and Mechanisms of Metal Ion Recognition and Redox Activity of Metal Binding Oligopeptides
Published on: September 7, 2019
Related Concept Videos
Complexometric Titration: Ligands
Titration of Polyprotic Base with a Strong Acid
Acid Strength and Molecular Structure
In the absence of any leveling effect, the acid strength of binary compounds of hydrogen with nonmetals (A) increases as the H-A bond strength decreases down a group in the periodic table. For group 17, the order of increasing acidity is HF < HCl < HBr < HI. Likewise, for group 16, the order of increasing acid strength is H2O < H2S < H2Se < H2Te. Across a row in the periodic table, the acid strength of binary hydrogen compounds increases with increasing...
Extraction: Advanced Methods
Complexation Equilibria: Factors Influencing Stability of Complexes
Formation of Complex Ions