Cyaphido Complexes of the Rare-Earth Metals and Their Tetramerization

Area of Science:

• Organometallic Chemistry
• Rare-Earth Chemistry
• Coordination Chemistry

Background:

• Rare-earth (RE) metallocene complexes are versatile coordination compounds.
• The cyaphide (CP-) ligand presents unique bonding and reactivity challenges in organometallic chemistry.
• Understanding RE ion influence on ligand speciation is crucial for designing novel complexes.

Purpose of the Study:

• To synthesize and characterize crystalline rare-earth metallocene complexes featuring the cyaphide ligand.
• To investigate the role of RE ionic radius in determining the solution-phase speciation and solid-state structures.
• To explore the formation of novel cyaphide-containing motifs and their potential for materials science.

Main Methods:

• Salt metathesis reactions using [RE(Cp^ttt)2Cl] and [Mg(DippNacNac)(CP)]2.
• Characterization via multielement NMR and IR spectroscopy.
• Single-crystal X-ray diffraction for structural elucidation.
• Computational studies to probe reaction mechanisms.

Main Results:

• Successful synthesis of monomeric [RE(Cp^ttt)2(CP)] (RE = Y, Sm, Lu) and tetrameric [{RE(Cp^ttt)2}4(μ4-C4P4)] (RE = La-Nd) complexes.
• Demonstrated the first examples of terminal κ1-cyaphide ions coordinated to rare-earth elements.
• Identified an unprecedented [P═C═C-P═P-C═C═P]4- motif in the tetrameric species.
• Observed that smaller RE ionic radii favor monomeric species, while larger radii lead to tetramerization.

Conclusions:

• The ionic radius of rare-earth elements critically influences the speciation of cyaphide metallocene complexes.
• The study reports novel terminal cyaphide complexes and a unique tetrameric cyaphide cluster.
• Computational insights suggest potential for controlled polymerization of cyaphide compounds into targeted oligomers or extended solids.