Reactivity of a Triruthenium Acetylide Complex toward Alkynes and the Silica-Mediated Dehydration of Cluster-Bound Alkynols:  X-ray Crystal Structures of the Novel Butadienyl Species [Ru₃(CO)₈{μ₃-η⁸-C(Bu^t)CC(Ph)C(H)Ph}] and the Unusual Complex [Ru₃(CO)₅(μ-CO){μ₃-η⁵-CC(Bu^t)- OC(Ph)₂CCH}{μ₃-η⁶-CHC(CPh₂OH)COC(CPh₂)CH}]

Abstract

The lightly ligated complex [Ru 3 (CO) 8 (MeCN)(µ-H)(µ-C 2 Bu t )] (4), derived from [Ru 3 (CO) 9 -(µ-H)(µ-C 2 Bu t )](1), reacts with terminal alkynes and alkynols under very mild conditions to give high yields of products derived from addition of three molecules of alkyne/alkynol. More interestingly, complex 4 also reacts with diphenylacetylene to form the novel butadienylic species [Ru 3 (CO) 8 {µ 3 -η 8 -C(Bu t )dCC(Ph)dC(H)Ph}] (6), stabilized by an uncommon interaction between a phenyl substituent and a cluster metal atom. Its formation represents a key step in understanding the reaction mechanism leading to tri-and tetra-alkyne-substituted derivatives. The acetonitrile derivative of 6 reacts further with diphenylacetylene to afford the complex [Ru 3 (CO) 7 {µ 3 -η 8 -C(Bu t )dCC(Ph)dC(H)Ph}{µ 3 -η 4 -C(Ph)dC(Ph)}] (7), which, upon heating, isomerizes to give [Ru 3 (CO) 7 {µ 3 -η 8 -C(Bu t )dCC(Ph)dC(Ph)H}{µ 3 -η 4 -C(Ph)dC(Ph)}]-(2) in high yield. The analogous complex [Ru 3 (CO) 7 {µ 3 -η 8 -C(Bu t )dCC(Ph)dC(CPh 2 OH)H}-{µ 3 -η 4 -C(CPh 2 OH)dC (Ph)}] (8) is formed directly from 4 through reaction with 1,1,3triphenyl-2-propyn-1-ol. Finally, the tetra-alkyne-substituted metallacyclic complex [Ru 3 (CO) 6 -{µ 3 -η 6 -C(Bu t )CC(CPh 2 OH)CH 2 }{µ 3 -η 6 -CHC(CPh 2 OH)COC(CPh 2 OH)CH}] (5a), obtained from reaction of 1,1-diphenyl-2-propyn-1-ol with 4, undergoes facile dehydration in the presence of silica gel to yield the cluster complex [Ru 3 (CO) 5 (µ-CO){µ 3 -η 5 -CC(Bu t )OC(Ph) 2 CCH}{µ 3η 6 -CHC(CPh 2 OH)COC(CPh 2 )CH}] (9), a process that involves formation of an unusual heterocycle. In addition, complex 9 contains a terminal carbene unit, one of the first examples of such a ligand in a cluster complex. The structures of complexes 6, 8, and 9 have been determined crystallographically and are discussed in association with possible reaction mechanisms.

Reaction of Fe3(CO)12 with but-2-yn-1,4-diol, 1,4-dichloro-but-2-yne, propargyl-alcohol and propargyl-chloride.

“…In addition, methanol may react with the tri-iron allenyl complexes of type I undergoing splitting into H and CH 3 O fragments to form compounds homologues of complex Fe 2 -(CO) 6 {H 2 CCC(H)C(OMe)O} reported in this paper [3]. Last, but not least, we have found that dehydration of cluster-bound alkynols (M = Ru) [4] is favoured by silica gel and that interconversions between allenylidene (type I) and vinyl-acetylide complexes (type II) on triruthenium clusters occur under acidic conditions [5] and that alumina and silica gel promote the interconversion and carbon-carbon coupling reactions of allenylidenes bound to triruthenium clusters [6,7].…”

“…The reaction pathways leading to the complexes described in this work show, once again, that alkynols, alkyne-diols, and chloro-alkynes easily loose all the functional groups both under thermal and under basic conditions [1][2][3][4][5][6]14,16]. We propose, on the basis of strong indirect evidence, that, in KOH/CH 3 OH solution, Fe 3 (CO) 12 forms the [HFe 3 (CO) 11 ] À anion, which undergoes stepwise fragmentation to bi-and mono-nuclear iron fragments.…”

Carbon–carbon coupling on tetrahedral iridium clusters: X-ray molecular structures and multinuclear NMR studies of the two isomeric forms of [Ir4(CO)6(μ3-η2-HCCPh)(μ2-η4-C4H2Ph2)(μ-PPh2)2]

“…Nonetheless, based on our results and on work by Sappa et al [16] on the reactions of [HRu 3 (CO) 8 (MeCN)(l 3 -g 2 -C 2 t Bu)] with HC"C t Bu, a qualitative discussion on the formation of 3 and 4 is attempted below.…”

“…Systematic studies involving the modes of interaction of alkynes [1][2][3][4][5][6], activation of C-C [7,8] and C-H [9,10] bonds, cyclotrimerization [10], oligomerization [11][12][13][14] and coupling with other ligands such as acetylides and phosphinoalkynes [15][16][17], incorporation of CO [16] and insertion into M-P bonds [18,19] have been performed and several reaction pathways elucidated, especially those involving clusters of the iron triad [2,20,21]. In contrast, reports on the reactions of iridium clusters with alkynes are rare, most probably due to the lack of suitably reactive starting materials besides [Ir 4 (CO) 12 ] and [Ir 6 (CO) 16 ]. The only reports in the literature involving iridium clusters describe the reactions of 0022-328X/$ -see front matter Ó 2004 Elsevier B.V. All rights reserved.…”

X-ray molecular structures and multinuclear NMR studies of the tetranuclear iridium clusters [Ir4(CO)7(μ4-η3-PhCC(H)CCPh)(μ-PPh2)3] and [Ir4(CO)7(μ3-η2-HCCPh)(η1-CCPh)(μ-PPh2)3]

“…Indeed, the chemically activated cluster [HRu 3 (l 3 -g 2 -CC t Bu)(CO) 8 (MeCN)], for example, has been shown to react with alkynes at room temperature due to facile MeCN loss. This low energy path has allowed characterization of reaction intermediates and the understanding of subsequent processes on the way to C 4 chain formation [26]. Unfortunately, attempts to activate cluster 1 via reaction with 1 equiv.…”