The Role of [η²‐Bis(tert‐butylsulfonyl)acetylene](carbonyl)(η⁵‐cyclopentadienyl)cobalt(I) as an Intermediate in the Alkyne Dimerisation

Abstract

Dicarbonyl(η5‐cyclopentadienyl)cobalt(I) (1) reacts with the electron‐poor alkyne bis(tert‐butylsulfonyl)acetylene to give the corresponding cyclobutadiene complex 6, whereas the reaction of [CpCo(CO)2] with dimethyl acetylenedicarboxylate yields the cyclopentadienone complex 7 under the same conditions. The cyclobutadiene complex 6 could not be obtained by the treatment of [η2‐bis(tert‐butylsulfonyl)acetylene](carbonyl)(η5‐cyclopentadienyl)cobalt(I) [3(H)] with an excess of bis(tert‐butylsulfonyl)acetylene. The same holds for the treatment of 3(H) with dimethyl acetylenedicarboxylate and bis(catecholatoboryl)acetylene. With these results we assume that the monoalkyne complex 3(H) is not an intermediate in the alkyne oligomerisation of electron‐poor alkynes, as was shown for electron‐rich ones. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

(η4-Tetraarylcyclobutadiene)(η5-formylcyclopentadienyl)cobalt(I) complexes: Facilities to finetune the electron-donating capability in dipolar organometallics

“…Both of the complexes 1c and 1e display very similar Co-C distances, which are slightly shorter for the cobalt-cyclobutadiene (CBD) unit (198.4(3)-199.0(3) pm for 1c and 197.7(8)-200.4(7) pm for 1e) than for the cobalt-cyclopentadienyl coordination (205.4(4)-207.6(4) pm for 1c and 205.6(8)-207.9(8) pm for 1e) ( Table 1). The structural data of the sandwich core of 1c and 1e are quite comparable to other molecular structures of (g 4 -cyclobutadiene)(g 5 -cyclopentadienyl)cobalt(I) complexes reported in the literature [9][10][11][12][13][14][15]. The difference in Co-C bond lengths suggests a stronger cobalt bonding to the CBD ligand than to the C 5 -ring ligand, which is in agreement with theoretical calculations (see below) [14,15].…”

“…The structural data of the sandwich core of 1c and 1e are quite comparable to other molecular structures of (g 4 -cyclobutadiene)(g 5 -cyclopentadienyl)cobalt(I) complexes reported in the literature [9][10][11][12][13][14][15]. The difference in Co-C bond lengths suggests a stronger cobalt bonding to the CBD ligand than to the C 5 -ring ligand, which is in agreement with theoretical calculations (see below) [14,15]. On the contrary, the distance between the Co atom and the centroid of the five-membered ring is slightly reduced (167.3 pm for 1c and 168.3 pm for 1e) compared to the distance between the Co atom and the centroid of the C 4 -ring (169.3 and 169.4 pm for 1c and 1e, respectively).…”

Insights into the Molecular Structure and Reactivity of α,ω‐Dialkoxy‐Substituted Ethyne and Butadiyne

“…[18] In the two "push-pull" systems 11 and 13 we find the shortest bond length between C3 and C4 and the longest bond length between C1 and C2. This is remarkable since the tert-butyl groups in 11 and the phenyl group in 13 are bent out of the plane of the cyclobutadiene ring which hampers a good conjugation between the p lone pair of the ether oxygen atoms or the sulfide center, respectively, with the cyclobutadiene ring.…”

“…Comparison of the relevant bond lengths and angles (with standard deviation) of 11, 13 [17] and 14. [18] All distances are given in Å, the angle between the Cp and the Cbd plane is given in°. The numbering refers to that given in Scheme 5.…”

Acetylenedithiolate as directional bridging ligand in cobalt(i) alkyne platinumdithiolato bimetallic complexes

“…Alkyne complexes of Co(I) are prone to C-C-coupling reactions of coordinated alkynes. 23,24 This applies particularly to the [(h 5 -C 5 H 5 )Co] moiety, 25 but it has also been observed at [(PMe 3 ) 3 Co]. 26, 27 In order to suppress this reactivity we have chosen 1,1,1-tris(diphenylphosphinomethyl)ethane (triphos) as ancillary ligand.…”