Salen-type compounds of calcium and strontium

Area of Science:

• Inorganic Chemistry
• Coordination Chemistry
• Organometallic Chemistry

Background:

• Salen ligands are versatile chelating agents widely used in coordination chemistry.
• Heavy alkaline-earth metals like calcium and strontium offer unique coordination environments.
• Exploring their complexes can lead to novel structural motifs and reactivity.

Purpose of the Study:

• To synthesize and characterize new salen complexes of calcium and strontium.
• To investigate the coordination behavior of heavy alkaline-earth metals with bulky Schiff-base ligands.
• To explore the structural diversity and potential for unusual cluster formation.

Main Methods:

• Reaction of metal precursors with various salen-type ligands (salen(t-Bu)H(2), salpen(t-Bu)H(2), salophen(t-Bu)H(2)) in ethanol.
• Isolation and purification of synthesized compounds.
• Structural characterization using single-crystal X-ray diffraction for key compounds.

Main Results:

• Six new calcium and strontium compounds were successfully prepared.
• An unusual tetrametallic strontium cluster, [(OC(6)H(2)(t-Bu)(2)CHN(CH(2))(2)NH(2))Sr(mu(3)-salean(t-Bu)H(2))Sr(mu(3)-OH)](2), was unexpectedly synthesized.
• Structural data confirmed the coordination modes and molecular architectures of four compounds (1, 5, 6, and 7).

Conclusions:

• The study demonstrates the successful synthesis of novel calcium and strontium salen complexes.
• The formation of a tetrametallic cluster highlights the potential for complex aggregation with these metals and ligands.
• This work expands the known coordination chemistry of heavy alkaline-earth metals.