Group IV Complexes with Sterically Congested N-Aryl-adamantylcarbamidate Ligands

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Catalysis

Background:

• The synthesis and characterization of novel metal complexes are crucial for advancing catalytic applications.
• Bulky ligands can significantly influence the coordination environment and reactivity of metal centers.

Purpose of the Study:

• To synthesize and characterize novel amidate complexes of group IV metals (Ti, Zr, Hf) using a sterically demanding adamantane carboxamide ligand.
• To investigate the structural features and coordination behavior of these complexes.
• To evaluate their potential as catalysts in hydrofunctionalization reactions.

Main Methods:

• Metalation of N-(2,6-dibenzhydryl-4-tolyl)adamantane-1-carboxamide with M(NMe2)4 (M = Ti, Zr, Hf).
• Isolation and characterization of amidate complexes using spectroscopic and crystallographic techniques.
• Evaluation of catalytic activity in hydrofunctionalization of alkynes with amines and phosphane oxides.

Main Results:

• Synthesis of a monomeric titanium amidate complex (2) with a distorted tetrahedral geometry, stabilized by the bulky ligand.
• Formation of dimeric zirconium (3) and hafnium (4) amidate complexes with distorted octahedral geometries due to small amidate bite angles.
• Titanium complex 2 showed limited catalytic activity in hydrofunctionalization, with carboxamide 1 being the dominant product under reaction conditions.

Conclusions:

• The steric bulk of the adamantylamidato ligand dictates the coordination number and geometry of the group IV metal centers.
• The resulting complexes exhibit distinct structural characteristics influencing their catalytic performance.
• Further studies are needed to optimize these complexes for efficient catalytic hydrofunctionalization.