Cluster moieties can be so conditioned by metal exchange that they support one and the same reaction in the region of the organic ligands both in the forward and reverse direction. A spontaneous alkylidyne‐vinylidene transformation has been observed for the first time within the sequences of the type shown below. equation image
Durch Umsctzung von alkinvcrbriickten Dicobalt-Komplcxen mit Fe2(CO), bzw. Fe3(C0)12 wurden alkin-und vinylidenverbriickte Cluster des allgemeinen Typs FeCo2(C0)9(p3-L) zuganglich. Auf diese und die homologen RuCo&luster liekn sich die Reaktionstypen Metallaustausch und Alkin-Vinyliden-Umlagerung anwenden. Kombination beider Reaktionstypen in der geeigneten Reihenfolge lieferte insgesamt 16 neue Hetero-Dreikerncluster mit p3-Alkin-Liganden und 29 entsprechende Verbindungen mit p,-Vinyliden-Liganden. Es kamen interne Alkine R2Cz rnit R = Me, Et, Ph und terminale Alkine HC2R mit R = H, Me, I-Bu, Ph zum Einsatz; letztere waren auch die Vorlaufer der entsprechenden Vinyliden-Liganden C2HR. Die entstehenden Metallgeruste waren vom Die bereits sehr umfangreiche Chemie metallorganischer Alkinkomplexe erlebt in den letzten Jahren eine Renaissance. Die zunehmende Leistungsfahigkeit strukturanalytischer Methoden hat es moglich gemacht, die ungewohnlichen Reaktivitaten des Alkinliganden und die zahlreichen Umwandlungsmoglichkeiten der Komplexgeruste zu verfolgen. Fur Cluster rnit Alkinliganden bedeutet dies regioselektive Reaktionen'), Auf-und Abbausequenzen im anorganischen" wie im organi~chen~) Molekulteil sowie Geriist~mwandlungen~). Weitere Herausforderungen in der Cluster-Alkin-Chemie bestehen darin, Stereo-Diskriminierung durch Einfuhrung von Chiralitat anzustreben sowie die oft fur Komplexsynthesen zu reaktiven terminalen Alkine systematisch einzubringen. Beides ist nicht nur von theoretischem Intere~se~,~), sondern eroffnet auch neue Reaktionswege',').Wir haben durch Uberdachung von RUCO~(CO),~ unter sehr milden Bedingungen einen Zugang zur MehrzentrenAnbindung von Acetylen und terminalen Alkinen gefunden'), wodurch prochirale RuC~~(CO)~(p~-L)-Cluster (L = Alkin oder Vinyliden) erhaltlich wurden. Wir erwarteten, da13 mit den verschiedenen Metallaustausch-Methoden") daraus chirale RuCoM-Cluster entstehen sollten. Da entsprechende FeCo2(C0)9(p3-L)-C1uster bisher nur unbequem und unsystematisch zuganglich waren, suchten wir auch fur sie nach einer gezielten Synthese als Voraussetzung fur den anschlieBenden Metallaustausch. Die vorliegende Arbeit, von der Einzelheiten schon kurz mitgeteilt wurden'), be- By reaction of alkyne-bridged dicobalt complexes with FeACO), or Fe3(C0)12 alkyne-and vinylidene-bridged clusters of the general type FeCo2(COk(p3-L) were accessible. These and the homologous RuCo2 clusters could be subjected to the reaction types metal exchange and alkyne-vinylidene rearrangement. Combination of both reaction types in the appropriate sequence yielded altogether 16 new hetero trinuclear clusters with p3-alkyne ligands and 29 corresponding compounds with p3-vinylidene ligands. Internal alkynes RzCz with R = Me, Et, Ph and terminal alkynes HCzR with R = H, Me, t-Bu, Ph were used; the latter were also the precursors of the corresponding vinylidene ligands. The resulting metal frameworks were of the FeCoNi, FeCoMo, FeCoW, RuCoNi, RuCoMo, RuCoW, FeNi2, and FeCo2 types. The alkyne-vinylidene rearrangements on...
Table 2. Relative rate of conversion of n-hexyl bromide 2b into n-hexyl azide 3b with the polymer 1 (after 4 h in various solvents; determined by GC). ~~ ~~ Solvent Conversion [No] to I u e n e 23 chloroform 26 methanol 32 tetrahydrofuran 38 pentane 52 Solvent Conversion [%] diethyl ether 54 acetone 82 acetonitrile > 95 dimethylformamide > 95even the more sluggishly reacting hexyl bromide 2b are converted into their azides 3a and 3b, respectively, by reaction with 1 at 20°C Within 3 h in acetonitrile o r within 24 h in dichloromethane.Most remarkably, this method allowed us, for the first time, to convert dibromomethane 2k or, more slowly, dichloromethane into diazidomethane 3k, a n explosive com-Although dichloromethane is a convenient, lowboiling solvent for reactions of 1 with alkyl halides (usually complete within 4-24 h), the above results indicate caution when employing this solvent (conversion into 3k requires over two weeks). The relative rate of reactivity with the polymer 1 is R-I>R-Br>R-OTos>R-CI, which is in accord with a nucleophilic substitution process. Experimental ProcedurePolymer 1 : Amberlite IR-400 was washed with 20% sodium azide soiution, then with water, methanol, and chloroform or ether. The polymer was dried at room temperature in vacuum and found to contain 2.55 mmol of azide per gram. The friction parameter of 1 as measured on a Julius-Peter apparatus was 14.4 kg, indicative of high friction stability. Reaction of 1 with Ze: To 4.9 g of 1 (12.5 mmol of azide) was added 4 mL of CH2Cl2 and 0.265 g (1.06 mmol) of p-bromobenzyl bromide 2e. After 2 h of mixing, the polymer was filtered and washed with CHZCIZ. Evaporation of the combined solvent mixture gave purep-bromobenzyl azide 3e as an oil in 93% yield: 'H-NMR: 6=7.5 and 7.2 (AA'BB', 4 H ) ; 4.29 (s, 2H). m / z 212.74, 210.84.
255ChemInform Abstract Reaction of alkyne-bridged dicobalt complexes with Fe2(CO)9 or Fe3(CO)12 gives the alkyne-and vinylidene-bridged clusters (III) and (V). These and the homologous RuCo2 clusters (VI) and (VII) can be subjected to the reaction types metal exchange using (CpNiCO)2, Na(MCp(CO)3), or (CpM(CO)3)2 (M: Mo, W) and alkyne-vinylidene rearrangements of terminal alkyne clusters to produce corresponding heterotrinuclear clusters (VIII)-(XIV) with µ3-alkyne or µ3-vinylidene ligands. The alkyne-vinylidene rearrangements show diastereoselectivities between 0 and 100%. The molecular structure of the RuCoW cluster (XIIc) (R: -tBu; space group P21/c, Z=4), determined crystallographically, allows to interprete the diastereoselectivity as not resulting from steric effects.
Cluster moieties can be so conditioned by metal exchange that they support one and the same reaction in the region of the organic ligands both in the forward and reverse direction.
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