Efficient catalytic alkyne metathesis with a fluoroalkoxy-supported ditungsten(III) complex.

Henrike Ehrhorn,Dirk Bockfeld,Janin Schlösser,Matthias Tamm

doi:10.3762/bjoc.14.220

Abstract

The molybdenum and tungsten complexes M2(OR)6 (Mo2F6, M = Mo, R = C(CF3)2Me; W2F3, M = W, R = OC(CF3)Me2) were synthesized as bimetallic congeners of the highly active alkyne metathesis catalysts [MesC≡M{OC(CF3)nMe3−n}] (MoF6, M = Mo, n = 2; WF3, M = W, n = 1; Mes = 2,4,6-trimethylphenyl). The corresponding benzylidyne complex [PhC≡W{OC(CF3)Me2}] (WPhF3) was prepared by cleaving the W≡W bond in W2F3 with 1-phenyl-1-propyne. The catalytic alkyne metathesis activity of these metal complexes was determined in the self-metathesis, ring-closing alkyne metathesis and cross-metathesis of internal and terminal alkynes, revealing an almost equally high metathesis activity for the bimetallic tungsten complex W2F3 and the alkylidyne complex WPhF3. In contrast, Mo2F6 displayed no significant activity in alkyne metathesis.

Highlights

While the field of olefin metathesis has seen significant progress in the past decades [1,2,3,4,5], the synthetic potential of alkyne metathesis has been growing only recently [6,7,8,9,10,11]
The catalytic alkyne metathesis activity of these metal complexes was determined in the self-metathesis, ring-closing alkyne metathesis and cross-metathesis of internal and terminal alkynes, revealing an almost high metathesis activity for the bimetallic tungsten complex W2F3 and the alkylidyne complex WPhF3
We have reported the optimum level of fluorination in MoF6 and WF3 as the most catalytically active alkylidyne complexes [54]

Summary

Introduction

While the field of olefin metathesis has seen significant progress in the past decades [1,2,3,4,5], the synthetic potential of alkyne metathesis has been growing only recently [6,7,8,9,10,11]. The molybdenum and tungsten complexes M2(OR)6 (Mo2F6, M = Mo, R = C(CF3)2Me; W2F3, M = W, R = OC(CF3)Me2) were synthesized as bimetallic congeners of the highly active alkyne metathesis catalysts [MesC≡M{OC(CF3)nMe3−n}] (MoF6, M = Mo, n = 2; WF3, M = W, n = 1; Mes = 2,4,6-trimethylphenyl).

Results

Conclusion