A case study on the conversion of Li/Cl phosphinidenoid into phosphinidene complexes

Area of Science:

• Organometallic Chemistry
• Main Group Chemistry
• Tungsten Chemistry

Background:

• Dichlorophosphane tungsten complexes serve as precursors for novel reactive intermediates.
• Understanding the reactivity of low-coordinate phosphorus species is crucial in inorganic chemistry.

Purpose of the Study:

• To synthesize and characterize novel phosphinidenoid and phosphinidene tungsten complexes.
• To investigate the reactivity and transformation pathways of these transient species.
• To elucidate reaction mechanisms using experimental and computational methods.

Main Methods:

• Synthesis of N,N-disubstituted dichlorophosphane tungsten complexes.
• Generation and characterization of transient phosphinidenoid complexes via low-temperature 31P{1H} NMR spectroscopy.
• Trapping reactions with various substrates (alcohols, amines, alkenes, alkynes).
• Density Functional Theory (DFT) calculations to explore reaction pathways.

Main Results:

• Formation of thermally labile Li/Cl phosphinidenoid W(CO)5 complexes (2a,b) from dichlorophosphane precursors (1a,b).
• Confirmation of transient complex 2a via NMR spectroscopy and evidence for 2a,b from E-H insertion reactions (E=O, N) yielding complexes 3a,b and 4a.
• Conversion of nucleophilic phosphinidenoid complexes 2a,b into electrophilic terminal phosphinidene complexes 5a,b.
• Characterization of trapping products, including 1H-phosphirene (6) and phosphirane complexes (7, 8), from reactions with tolane and alkenes.
• DFT calculations supported proposed reaction pathways and ruled out direct reaction of 2a,b with alkenes.

Conclusions:

• Successfully synthesized and characterized novel phosphinidenoid and phosphinidene tungsten complexes.
• Demonstrated the transformation of nucleophilic phosphinidenoid species into electrophilic phosphinidenes.
• Provided mechanistic insights into the formation and reactivity of these transient organometallic compounds.