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Group 5 imido complexes derived from diamido-pyridine ligands
S M Pugh1, A J Blake, L H Gade
1Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K.
Inorganic Chemistry
|July 24, 2001
Summary
New vanadium, niobium, and tantalum complexes were synthesized using pyridine-based ligands. These metal complexes exhibit fluxional behavior in solution, with dynamic exchange processes observed in six-coordinate species.
Area of Science:
- Organometallic Chemistry
- Coordination Chemistry
- Inorganic Synthesis
Background:
- Vanadium(V) imide complexes and their reactions with nitrogen-donor ligands are of interest.
- Heavier Group 5 metals (Nb, Ta) offer diverse coordination chemistry with imido and pyridine ligands.
- Understanding ligand exchange and dynamic processes in metal complexes is crucial for reactivity studies.
Purpose of the Study:
- To synthesize and characterize novel vanadium(IV) and Group 5 metal(V) complexes.
- To investigate the reactivity of vanadium(V) imide with a pyridine-based diamine ligand.
- To explore the coordination chemistry of niobium and tantalum imides with a dilithiated pyridine ligand and study their dynamic behavior.
Main Methods:
- Reaction of [V(NAr)Cl(3)(THF)] with H(2)N'(2)N(py) to form a vanadium(IV) complex.
- Reaction of [M(NR)Cl(3)(py)(2)] (M=Nb, Ta) with Li(2)[N(2)N(py)] to yield six-coordinate M(V) complexes.
- Characterization using X-ray crystallography, solution NMR spectroscopy to study fluxionality, and activation parameter determination.
Main Results:
- A vanadium(IV) species [V(NAr)(H(3)N'N' 'N(py))Cl(2)] (1) was obtained from the reaction with the diamino-pyridine derivative.
- Six-coordinate M(V) complexes [M(NR)Cl(N(2)N(py))(py)] (2-4) were synthesized for M=Nb, Ta.
- Compounds 2-4 exhibited fluxional behavior in solution, attributed to dynamic exchange via five-coordinate intermediates. Activation parameters were determined for complexes 2 and 3. Compound 5, [Nb(N(t)()Bu)Cl(N(2)N(py))], was obtained by sublimation of complex 2. X-ray crystal structures of 1, 2, 3, and 4 were determined.
Conclusions:
- The study successfully synthesized and structurally characterized novel vanadium and Group 5 metal complexes.
- The reactivity of vanadium imides and the coordination versatility of niobium and tantalum imides were demonstrated.
- Dynamic processes in solution were observed and quantified for the Group 5 metal complexes, providing insights into their fluxional nature.