Syntheses and molecular structures of some tricobalt carbonyl clusters containing 2,4,6-trimethyl-1,3,5-trithiane

摘要

Reactions of CCo3 carbonyl clusters Co-3(mu(3)-CR)(CO)(9) with 2,4,6-trimethyl-1,3,5-trithiane (S(Me)3) have given Co-3(mu(3)-CR)(mu(3)-S(Me)3)(CO)(6) [R = H (1), C CSiMe3 (2)]. A small amount of the coupled-alkyne product Me3SiC2[Co-2(CO)(6)]C-2[Co-2(mu-S-3(Me))(CO)(4)]C CSiMe3 (3) was isolated from the latter reaction. The reaction of Co-3(mu(3)-CC CSiMe3)(mu(3)-S(Me)3)(CO)(6) (2) with AuCl(PPh3) in the presence of NaOMe gave Co-3{mu(3)-CC CAu(PPh3)}(mu(3)-S(Me)3)(CO)(6) (4), which in turn reacts with Co-3(mu(3)-CBr)(CO)(9) in the presence of catalytic amounts of Pd(PPh3)(4) and CuI to give {(OC)(9)Co-3}(mu-C CC C){Co-3(mu(3)-S(Me)3)(CO)(6)} (5). Further substitution of 5 with S(Me)3 gave symmetrical {Co-3(mu(3)-S(Me)3)(CO)(6)}(2)(mu C CC C) (6), also obtained from a reaction between {Co-3(CO)(9)}(2)(mu-C CC C) and two equivalents of S(Me)3. Similar substitution of Co-3{mu(3)-C(C C)(2)[Ru(dppe)Cp*]}(CO)(9) with S(Me)3 gave Co-3{mu(3)-C(C C)(2)[Ru(dppe)Cp*]}(mu(3)-S(Me)3)(CO)(6) (7). In all of these compounds, the S(Me)3 ligand caps the basal face of the CCo3 cluster on the opposite side to the mu(3)-CR group. The three S donors occupy axial sites, with all CO groups being in equatorial sites. Reactions of Co-3(mu(3)-CBr)(CO)(9) with S(Me)3 gave only Co-3(mu(3)-CX)(mu(3)-S(Me)3)(CO)(6) [X = C(O)NMe2 (8), CO2H (9)]. The redox properties and electronic structure of the C-4-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.