“…It might be envisaged that the trinuclear complex 7 is formed via addition of a free radical fragment such as [Ru(CO) 2 (η-C 5 H 5 )] across the unsaturated metal-metal bond of the diruthenium complex 5, since a similar process involving addition of monometallic fragments across a ruthenium-ruthenium double bond has been effected in this laboratory, leading to the formation of a range of trinuclear µ 3 -alkyne complexes. 14 If this suggestion were correct, initial formation of 5 from 2i,j might be expected, with a build up of 7 at longer time. However, varying the time of photolysis affects only the yields of the products 5-7, which reach a maximum after 20 h, and does not significantly change their ratios, strongly suggesting that they are formed from 2i,j via distinct pathways.…”
8). The structures of the unusual complexes 6 and 7 have been determined by X-ray diffraction studies. Complexes 5, 6 and 7 are shown to be formed from 2i,j via independent pathways.
“…It might be envisaged that the trinuclear complex 7 is formed via addition of a free radical fragment such as [Ru(CO) 2 (η-C 5 H 5 )] across the unsaturated metal-metal bond of the diruthenium complex 5, since a similar process involving addition of monometallic fragments across a ruthenium-ruthenium double bond has been effected in this laboratory, leading to the formation of a range of trinuclear µ 3 -alkyne complexes. 14 If this suggestion were correct, initial formation of 5 from 2i,j might be expected, with a build up of 7 at longer time. However, varying the time of photolysis affects only the yields of the products 5-7, which reach a maximum after 20 h, and does not significantly change their ratios, strongly suggesting that they are formed from 2i,j via distinct pathways.…”
8). The structures of the unusual complexes 6 and 7 have been determined by X-ray diffraction studies. Complexes 5, 6 and 7 are shown to be formed from 2i,j via independent pathways.
“…The interatomic distances of Fe1−Fe2 (2.5119(8) Å), Fe1−Fe4 (2.4792(9) Å), Fe2−Fe3 (2.5025(8) Å), Fe2−Fe4 (2.5837(8) Å), and Fe3−Fe4 (2.4995(8) Å) indicate that these represent the five iron−iron bonds, whereas the value of Fe1···Fe3 (3.4385(8) Å) indicates that there is no interaction for these atoms . According to the structural features described, cluster 6 is recognized as an Fe 4 C 2 closo octahedron, consistent with Wade−Mingos theory. , 2 2 ORTEP drawing of (η 5 -C 5 H 4 Me) 4 Fe 4 (μ 3 -CO) 2 (HCCH) ( 6 ). The C 5 H 4 Me ligands are omitted for clarity.…”
Treatment of (η5-C5H4Me)4Fe4(μ3-CO)4 with LiAlH4, followed by air-oxidation in the
presence of NH4PF6, led to stepwise reduction of the four carbonyl ligands to afford [(η5-C5H4Me)4Fe4(μ3-CO)3(μ3-CH)](PF6), [(η5-C5H4Me)4Fe4(μ3-CO)2(μ3-CH)2](PF6)2, [(η5-C5H4Me)4Fe4(μ3-CO)(μ3-CH)(HCCH)](PF6), and [(η5-C5H4Me)4Fe4(HCCH)2](PF6). Two-electron reduction
of [(η5-C5H4Me)4Fe4(μ3-CO)2(μ3-CH)2](PF6)2 resulted in coupling of two methylidyne ligands
to form the acetylene-coordinated cluster (η5-C5H4Me)4Fe4(μ3-CO)2(HCCH), two-electron
oxidation of which regenerated [(η5-C5H4Me)4Fe4(μ3-CO)2(μ3-CH)2](PF6)2. Further treatment
of isolated (η5-C5H4Me)4Fe4(μ3-CO)2(HCCH) with LiAlH4 produced (η5-C5H4Me)4Fe4(HCCH)2.
All clusters were fully characterized by X-ray diffraction studies.
“…One of the established routes to higher nuclearity alkyne clusters is the reaction of preformed alkyne complexes with suitable metal fragments. Initially our objective in this work was to explore whether compounds of type 1 could be used as precursors to higher nuclearity alkyne clusters, since similar cluster-forming reactions are already known for related alkyne complexes such as Co 2 (CO) 6 (μ-R 1 C 2 R 2 ), Ni 2 (μ-C 2 Ph 2 )Cp 2 , and recently Ru 2 (μ-CO)(μ-C 2 R 2 )Cp 2 (R = Ph, CF 3 ). 3e,4f-h, …”
The reaction of the dimolybdenum alkyne complexes Mo 2 (CO) 4 (µ-R 1 CtCR 2 )Cp 2 (Cp ) η-C 5 H 5 ; R 1) H, R 2 ) H, Me, Ph, CO 2 Me; 1a-d) with Ru 3 (CO) 12 in refluxing toluene or heptane affords reasonable yields of the orange µ 3 -vinylidene clusters [Mo 2 Ru(µ 3 -CdCHR 2 )(CO) 7 Cp 2 ] (2a-d). The crystal structure of Mo 2 Ru(µ 3 -CdCHMe)(CO) 7 Cp 2 (2b) has been determined and shows that the metal triangle is capped by a vinylidene ligand which is formally σ-bound to the two molybdenum atoms and π-bound to the ruthenium. Low to moderate yields of the blue-turquoise hexanuclear bis(alkylidyne) clusters Mo 2 Ru 4 (µ 3 -CR 1 )(µ 3 -CR 2 )(CO) 12 Cp 2 (3a-d) are formed in addition to the vinylidene clusters, especially if the reaction is carried out in heptane. The synthesis of 3a is particularly noteworthy, as it represents the first example of the scission of ethyne into two methylidyne fragments on a metal cluster. The disubstituted alkyne complex 1e (R 1) R 2 ) Me) leads to the corresponding hexanuclear cluster 3e in either solvent, but complexes of bulkier disubstituted alkynes 1f and 1g (R 1 ) R 2) Et, CO 2 Me) do not give analogous products. The X-ray crystal structure of the cluster Mo 2 Ru 4 (µ 3 -CMe) 2 (CO) 12 Cp 2 ‚CH 2 Cl 2 (3e‚CH 2 Cl 2 ) reveals an octahedral metal core in which the two MoCp fragments occupy adjacent positions, with the two alkylidyne groups formed by scission of the alkyne ligand capping the two Mo 2 Ru faces. Unusually for octahedral clusters, complexes of type 3 have 84 cluster valence electrons.
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