�Green Tires� are reinforced with silica(1).  They afford low rolling resistance and consequently, improved fuel economy.   Sulfur silanes are used to provide effective coupling between the rubber and silica filler (2).  Recently, sulfur silanes derived from the mono-hydrosilylation product of 1,2,4-trivinylcyclohexane (TVCH) with triethoxysilane  have been shown to give both low rolling resistance and improved wear resistance to silica-filled automotive tires (3).  The trialkoxysilyl group allows bonding to the silica surface while still leaving the two remaining vinyl groups available for functionalization with sulfur and eventual crosslinking into the rubber matrix.  Owing to the 1,2,4- vinyl substitution on the cyclohexane ring, it is believed to be advantageous to have selective monohydrosilylation at the 4-position. Unfortunately, the selectivity of conventional precious metal-based catalysts towards mono-hydrosilylation is normally less than desirable.  For example, even when a sub-stoichiometric amount of a trialkoxysilane is used in the platinum catalyzed hydrosilylation of 1,2,4-trivinylcyclohexane (silane:vinyl ratio of 0.8:1) a mixture containing only about 50 weight percent of the desired mono-hydrosilylated product and about 30 weight percent of the bis-hydrosilylated derivative is produced.  Furthermore, the monohydrosilylation occurs randomly at all three possible positions and not regioselectively at the desirable 4-position.  In contrast, aryl-substituted bis(imino)pyridine iron dinitrogen complexes exhibit 70 � 98 percent regioselectivity at the 4-position in the hydrosilylation of 1,2,4-trivinylcyclohexane with trialkoxysilanes and other tertiary silanes (4).REFSR. Rauline, EP 0 501227A1 (February 12, 1992)S. Wolff, Rubber Chem. Technol., 69 (1996) 325R. W. Cruse, et al., US 7,696,269 (April 13, 2010)C. C. H. Atienza, et al, ACS Catalysis, 2 (2012) 2169

Highly regioselective bis(imino)pyridine iron catalysts for the hydrosilylation of 1,2,4-trivinylcyclohexane

246th National Meeting (2013)

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