Abstract
AbstractA new tungsten alkylidene complex, W(NAr)(CHCMe2Ph)(OHIPT‐NMe2)(pyrrolide) {Ar=2,6‐(i‐Pr)2C6H3; HIPT‐NMe2=2,6‐[2,4,6‐(i‐Pr)3C6H2]2‐4‐NMe2‐C6H2}, has been synthesized and shown to be highly selective for Z homocoupling metathesis of selected terminal olefins in pentane, as is W(NAr)(CH2CH2CH2)(OHIPT)(pyrrolide) (5). Both 5 and W(NAr)(CHCMe2Ph)(OHIPT‐NMe2)(pyrrolide) (6) are adsorbed onto calcined alumina. Control experiments and metathesis homocoupling of four substrates lead to the conclusions that 5 is largely adsorbed in a reaction that liberates HIPTOH, while 6 is adsorbed largely through an interaction between the dimethylamino group and an acidic site on the surface. There is no evidence that any adsorbed catalyst can give rise to Z selectivity of a magnitude equal to that found in a homogeneous reaction involving 5 or 6.
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