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Paper
Dalton Trans., 2010, 39, 1222 - 1234, DOI: 10.1039/b909708b
Syntheses and molecular structures of some tricobalt carbonyl clusters containing 2,4,6-trimethyl-1,3,5-trithiane
Michael I. Bruce, Natasha N. Zaitseva, Brian W. Skelton, Allan H. White, Mark A. Fox and Paul J. Low
Reactions of CCo3 carbonyl clusters Co3(
3-CR)(CO)9 with 2,4,6-trimethyl-1,3,5-trithiane (SMe3) have given Co3(3-CR)(3-SMe3)(CO)6 [R = H ( 1), C
CSiMe3 ( 2)]. A small amount of the coupled-alkyne product Me3SiC2[Co2(CO)6]C2[Co2(-SMe3)(CO)4]CCSiMe3 ( 3) was isolated from the latter reaction. The reaction of Co3(3-CCCSiMe3)(3-SMe3)(CO)6 ( 2) with AuCl(PPh3) in the presence of NaOMe gave Co3{3-CCCAu(PPh3)}(3-SMe3)(CO)6 ( 4), which in turn reacts with Co3(3-CBr)(CO)9 in the presence of catalytic amounts of Pd(PPh3)4 and CuI to give {(OC)9Co3}(-CCCC){Co3(3-SMe3)(CO)6} ( 5). Further substitution of 5 with SMe3 gave symmetrical {Co3(3-SMe3)(CO)6}2(-CCCC) ( 6), also obtained from a reaction between {Co3(CO)9}2(-CCCC) and two equivalents of SMe3. Similar substitution of Co3{3-C(CC)2[Ru(dppe)Cp*]}(CO)9 with SMe3 gave Co3{3-C(CC)2[Ru(dppe)Cp*]}(3-SMe3)(CO)6 ( 7). In all of these compounds, the SMe3 ligand caps the basal face of the CCo3 cluster on the opposite side to the 3-CR group. The three S donors occupy axial sites, with all CO groups being in equatorial sites. Reactions of Co3(3-CBr)(CO)9 with SMe3 gave only Co3(3-CX)(3-SMe3)(CO)6 [X = C(O)NMe2 ( 8), CO2H ( 9)]. The redox properties and electronic structure of the C4-bridged bis-cluster 6 have been investigated through a combination of cyclic voltammetry, IR spectroelectrochemistry and DFT calculations, with comparisons made with suitable model systems. Single-crystal X-ray diffraction structure determinations of 1, 2, 3, 4 and 8 are reported.
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