Unexpected features of stretched Si-H...Mo beta-agostic interactions

Area of Science:

• Organometallic Chemistry
• Silicon Chemistry
• Molybdenum Complexes

Background:

• Imido complexes of transition metals are versatile precursors in inorganic synthesis.
• The reactivity of imido ligands with silicon compounds is an area of ongoing research.
• Understanding the factors influencing Si-H bond activation is crucial for catalytic applications.

Purpose of the Study:

• To investigate the coupling reactions between silanes and a specific molybdenum imido complex, (Ar'N)2Mo(PMe3)3.
• To characterize the resulting products and determine the factors governing their formation.
• To analyze the relationship between molecular structure and spectroscopic properties, particularly the Si-H coupling constant.

Main Methods:

• Synthesis of molybdenum imido complexes.
• Reaction of complexes with various silanes (e.g., chlorosilanes).
• Characterization of products using NMR spectroscopy (e.g., 1H, 29Si, 95Mo NMR) and X-ray crystallography.

Main Results:

• Formation of either silanimine dimers, (ArN-SiHCl)2, or Si-H agostic silylamido complexes depending on reaction conditions.
• Observed lack of expected correlation between silicon substituents, degree of Si-H addition, and Si-H coupling constant values.
• Structural diversity in the resulting silylamido complexes, including agostic interactions.

Conclusions:

• The coupling of silanes with (Ar'N)2Mo(PMe3)3 leads to complex product distributions.
• The electronic and steric properties of silanes do not predictably influence the outcome or the observed Si-H coupling constants.
• These findings challenge common assumptions about Si-H bond activation and reactivity in organometallic imido complexes.