Two-Step Hydrosilylation Promoted by the Yttrium−Iron Tandem Catalytic System: An Efficient and Selective Post-Polymerization Modification Approach for Accessing In-Chain Alkoxysilyl-Functionalized Polybutadiene

Hydrosilylation has emerged as a powerful post-polymerization functionalization strategy for introducing alkylsilyl and alkoxysilyl functionalities into polybutadienes (PBs); however, existing methods primarily rely on noble metal catalysts, and developing cost-effective and efficient alternatives remains a significant challenge. Herein, we report a yttrium/iron tandem catalytic system that enables efficient two-step hydrosilylation of polybutadienes, providing direct access to in-chain alkoxysilyl-functionalized materials using rare-earth metals. In the first step, the organoyttrium complexes promote highly anti-Markovnikov-selective hydrosilylation of PB with arylsilanes, affording silane-functionalized precursors with high regioselectivity. Systematic studies reveal that the hydrosilylation efficiency is strongly dependent on catalyst structure and loading, silane steric and electronic properties, and reaction conditions, reaching up to 20.5% under optimized parameters. In the second step, an α-diimine iron catalyst mediates the hydrosilylation of the pendant Si–H groups with diverse carbonyl compounds, furnishing alkoxysilyl-functionalized PBs with a broad substrate scope; for reactive aldehydes, quantitative conversion can be achieved. Notably, the two catalytic transformations are mutually compatible. They can be integrated into a one-pot, in situ process, either from preformed polymers or directly from butadiene via tandem polymerization–functionalization. This Y/Fe tandem strategy establishes a practical, scalable, and noble-metal-free platform for the synthesis of in-chain functionalized polydienes, offering promising opportunities for preparing silicon-compatible elastomeric materials.