Aluminium Diphosphamethanides: Hidden Frustrated Lewis Pairs

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry

Background:

• Diphosphamethanide ligands offer unique coordination modes.
• Aluminum complexes with bulky ligands are of interest for catalysis and synthesis.

Purpose of the Study:

• To synthesize and characterize novel aluminum diphosphomethanide complexes.
• To investigate the reactivity of these complexes, particularly with small molecules.
• To explore the potential of these complexes as precursors for other organometallic compounds.

Main Methods:

• Synthesis of aluminum complexes [Al(tBu)2 {κ(2) P,P'-Mes*PCHPMes*}] (3) and [Al(C6 F5 )2 {κ(2) P,P'-Mes*PCHPMes*}] (4).
• Characterization of the synthesized compounds and the silylated analogue Mes*PCHP(SiMe3 )Mes* (5).
• Reaction studies of complex 3 with molecular dihydrogen and complex 5 with [(C6 F5 )2 AlCl]2.

Main Results:

• Successful synthesis and characterization of aluminum diphosphomethanide complexes 3 and 4, and silylated phosphine 5.
• Complex 4 was efficiently synthesized using silylated phosphine 5 as a precursor.
• Complex 3 reacted with dihydrogen, yielding an acyclic diphosphine and a dialkyl aluminum hydride, classifying it as a hidden frustrated Lewis pair.

Conclusions:

• Aluminum diphosphomethanide complexes with four-membered PCPAl cores were synthesized.
• Silylated phosphine 5 is a useful precursor for aluminum complex 4.
• Complex 3 demonstrates hidden frustrated Lewis pair characteristics, highlighting its potential in chemical transformations.