Alkyne Coupling and Cyclization on Metal Cluster Complexes. Additions and Couplings of Dimethyl acetylenedicarboxylate to Ru6(mu 6-C)(CO)14(mu 3-eta 4-C4H4)

Reactions of the hexaruthenium cluster complex Ru6(mu 6-C)(CO)14(mu 3-eta 4-C4H4), 2 with dimethyl acetylenedicarboxylate (DMAD) at 25 degrees C yielded five new compounds: Ru6(mu 5-C)(CO)16(mu-eta 4-C4H4), 3; Ru6(mu 6-C)(CO)14[eta 6-1,2-C6H4(CO2Me)2], 4; Ru6(mu 5-C)(CO)14(mu-eta 4-C4H4)[mu 3-C2(CO2Me)2], 5; Ru6(mu 5-C)(CO) 14(mu-eta 4-C4H4)[mu 3-C2(CO2Me)2], 6 and Ru6(mu 6-C)(CO)14[mu 3-eta 6-1,2 -C6H4(CO2Me)2 ], 7. Compounds 4 and 7 are isomers that contain the six-membered arene, dimethyl phthalate, 1,2 -C6H4(CO2Me)2, as a ligand. Compound 3 was formed as a side product in low yield (6%) by the simple addition of CO to 2. The addition of CO to 2 causes the cluster to open to that of a spiked, square pyramid. Direct reaction of CO to 2 provided 3 in a good yield (72%). A DMAD ligand was added to the cluster of 2 as a simple triply-bridging ligand to form open Ru6 clusters in compounds 5 and 6. Addition of DMAD to 3 yielded the DMAD derivative Ru6(mu 5-C)(CO)15(mu-eta 4-C4H4)[mu-C2(CO2Me)2], 8 which contains a DMAD ligand bridging a basal edge of an opened spiked-square pyramidal Ru6 cluster. Compound 5 was thermally converted to the new complex Ru6(mu 5-C)(CO) 14[mu 4-eta 6-CHCHCHCC(CO2Me)C(CO2Me)](mu-H), 9 that contains a bridging CHCHCHCC(CO2Me)C(CO2Me) ligand formed by a coupling of the DMAD ligand to the bridging C4H4 ligand in 5 accompanied by a cleavage of one CH bond and formation of a bridging hydrido ligand. Decarbonylation of 3 with Me3NO yielded the NMe3 derivative Ru6(mu 5- C)(CO)15(mu-eta 4-C4H4)(NMe3), 10 in which the NMe3 ligand is coordinated to the spiked metal atom on the square-pyramidal Ru5 cluster. Treatment of 4 and 7 with CO at 25 degrees C induced elimination of the 1,2 -C6H4(CO2Me)2 ligand to yield free dimethyl phthalate, 11 and formation of the known parent car-bonyl complex Ru6(mu 6-C)(CO)17. All of the new cluster compounds were characterized by single-crystal X-ray diffraction analyses.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

Reactions of hexaruthenium cluster complex with dimethyl acetylenedicarboxylate yielded five new compounds with different ligand structures and forms. The cluster structure can change under different reaction conditions, resulting in the formation of different compounds. The new compounds were characterized in detail by single-crystal X-ray diffraction analyses.