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The Pentynoate Ligand as a Building Block for Multimetallic Systems



The complexes [RuRCl(CO)(BTD)(PPh3)2] (R = CH=CHtBu, CH=CHC6H4Me-4, CH=CHC5H4FeC5H5; BTD = 2,1,3-benzothiadiazole) and [Ru{C(C≡CPh)=CHPh}(CO)(PPh3)2] reacted with pentynoic acid to yield the same complex, [RuCl(O2CCH2CH2C≡CH)(CO)(PPh3)2], through cleavage of the vinyl ligand. In contrast, the products [RuR(O2CCH2CH2C≡CH)(CO)(PPh3)2] were formed when NaO2CCH2CH2C≡CH was used. An osmium example, [Os(CH=CHC6H4Me-4)(O2CCH2CH2C≡CH)(CO)(PPh3)2], was also prepared from treatment of [Os(CH=CHC6H4Me-4)Cl(CO)(BTD)(PPh3)2] with NaO2CCH2CH2C≡CH. Coupling of the pendant alkyne in [RuCl(O2CCH2CH2C≡CH)(CO)(PPh3)2] to yield the homodimetallic complex [{RuCl(O2CCH2CH2C≡C)(CO)(PPh3)2}2] was achieved by using [PdCl2(PPh3)2], CuI and NEt3. The reactivity of the alkyne unit was further exploited by the metallation of the alkyne with ClAu(PR3) (R = Ph, Cy) and Co2(CO)8 to yield the multimetallic species [Ru(CH=CHC6H4Me-4)(O2CCH2CH2C≡CAuPR3)(CO)(PPh3)2] and [Ru(CH=CHC6H4Me-4)(O2CCH2CH2CC{Co2(CO)6}H)(CO)(PPh3)2]. The structures of the complexes [Ru(CH=CHC6H4Me-4)(O2CCH2CH2C≡CH)(CO)(PPh3)2] and [Ru(CH=CHtBu)(O2CCH2CH2C≡CH)(CO)(PPh3)2] were determined crystallographically.

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