Tailoring the selectivity in 2-butene conversion over supported d super(0) group 4, 5 and 6 metal hydrides: from dimerization to metathesis

2-Butenes are transformed in a continuous flow reactor over metal hydrides of zirconium, tantalum and tungsten supported on silica-alumina. Exceptionally high selectivity to dimeric products is obtained over supported zirconium hydride catalysts. Supported tantalum hydride gives high selectivity to dimeric products along with small amounts of metathesis products. Conversely, supported tungsten hydride leads only to metathesis products. The unprecedented selective production of mono-branched and di-branched octenes originates from the bi-functionality of the active sites, allowing isomerization of 2-butenes to 1-butene followed by fast insertion of 1-butene into the metal sec-butyl fragment.