Synthesis of Tris(arylphosphite)-ligated Cobalt(0) Complexes [Co2(CO)6{P(OAr)3}2], and their Reactivity towards Phenylacetylene and Diphenylacetylene

Isabelle Jourdain, ,Michael Knorr,Carsten Strohmann,Lukas Brieger

doi:10.21926/acr.2004009

Abstract

The dinuclear complexes [Co2(CO)6{P(OAr)3}2] (1a, Ar = Ph; 1b, Ar = o-Tol) were prepared and reacted with PhC≡CH and PhC≡CPh to yield dimetallatetrahedranes [{(ArO)3P}(OC)2Co-Co(μ-RC≡CPh)(CO)2{P(OAr)3}] (3a, Ar = Ph, R = H; 3b, Ar = o-Tol, R = H; 3c, Ar = Ph, R = Ph; 3d, Ar = o-Tol, R = Ph). The main reaction of diphenylacetylene was accompanied by a side reaction, leading to the dissociation of a P(OAr)3 ligand for the formation of mono(phosphite) complexes [{(ArO)3P}(OC)2Co-Co(μ-PhC≡CPh)(CO)3] (2b, R = Ph; 2d, R = o-Tol). The crystal structures of 1b, 3a, and 3d were determined along with that of the mono(phosphite) complex [{(PhO)3P}(OC)2Co-Co(μ-PhC≡CPh)(CO)3] 2b.

Highlights

The organometallic reaction of dicobalt octacarbonyl with alkynes to yield dicobaltatetrahedranes [Co2(CO)6(μ-RC CR′)] [1, 2] has been extensively studied ever since its first discovery in the fifties [3]
The Pauson-Khand reaction is, the most common transformation, in which [Co2(CO)8] is reacted with an alkyne, alkene, and carbon monoxide to form an α,βcyclopentenone [9,10,11,12,13,14,15,16]. This [2+2+1] cycloaddition is often used in synthetic organic chemistry
More stabilization may be achieved by the replacement of one or more carbonyls by monodentate P-donors such as PR3 and P(OR)3

Summary

Introduction

The organometallic reaction of dicobalt octacarbonyl with alkynes to yield dicobaltatetrahedranes [Co2(CO)6(μ-RC CR′)] [1, 2] has been extensively studied ever since its first discovery in the fifties [3]. The Pauson-Khand reaction is, the most common transformation, in which [Co2(CO)8] is reacted with an alkyne, alkene, and carbon monoxide to form an α,βcyclopentenone [9,10,11,12,13,14,15,16]. This [2+2+1] cycloaddition is often used in synthetic organic chemistry. The structural characterization of [Co2(CO)n-x{P(OAr)3}x] complexes is limited, comprising of the structures of [Co2(CO)6{P(OPh)3}2] and [Co2(CO)6{P(O-2,4-t-Bu2C6H3)3}2] alone [28, 29] These compounds were probed for hydroformylation studies. The resultant Co(0) complexes were characterized in solution by IR and multinuclear NMR spectroscopy as well as four single-crystal X-ray diffraction studies

General procedure

Crystallographic Studies

Results and Discussion

Conclusions

Figure S1