Molecular Calcium Phosphides and Mixed Phosphide Hydrides.

Area of Science:

• Organometallic Chemistry
• Calcium Chemistry
• Coordination Chemistry

Background:

• The synthesis of low-valent main group element compounds is crucial for understanding fundamental bonding and reactivity.
• Calcium compounds, particularly those with bulky ligands, offer unique coordination environments and reactivity profiles.
• Phosphido ligands are versatile building blocks in organometallic chemistry, enabling diverse synthetic transformations.

Purpose of the Study:

• To synthesize novel diorganophosphido- and bis(trimethylsilyl)phosphidocalcium derivatives.
• To investigate the structural diversity and bridging modes of these calcium phosphide compounds.
• To explore the reactivity and potential catalytic applications of these new calcium complexes.

Main Methods:

• Synthesis of calcium phosphide derivatives from a bis(dihydroilido)calcium hydride precursor.
• Reaction with diphenylphosphine (Ph2PH) to form bridging phosphido complexes.
• Transmetalation reactions with mercury phosphides (Hg(PR2)2) to introduce different phosphido ligands.
• Reactions with unsaturated substrates and organometallic reagents to probe reactivity.

Main Results:

• [(BDI)Ca-μ-PPh2]2 was synthesized, displaying differentiated phosphide bridging modes.
• Selective replacement of one hydride in [(BDI)Ca-μ-H]2 was achieved via transmetalation with Hg(PR2)2 (R = t-Bu, SiMe3).
• Heating [(BDI)Ca-μ-H]2 with P(SiMe3)3 yielded the labile [(BDI)Ca-μ-P(SiMe3)2]2, also with differentiated bridging modes.

Conclusions:

• Novel calcium phosphide derivatives with unique structural features have been successfully synthesized.
• The synthesized compounds exhibit interesting phosphide bridging modes, offering insights into calcium-phosphine interactions.
• While showing some reactivity, the catalytic enhancement for phosphine additions is marginal compared to existing precatalysts.