Synthetic, structural and bonding studies of main group-transition metal carbonyl clusters

[摘要] Structural studies on solvated adducts of bismuth (III) chloride have demonstrated the ability of the main group element to form multiple bonding contacts, giving ;;hypervalent;; complexes. Similar interactions are observed in almost all aspects of the chemistry of the heavy main group elements. The reaction of $m lbrack Bisb2Cosb4(CO)11bracksp{1{-}}$ with $m Mo(CO)sb3(etasp6$-$m Csb6Hsb5Me)$ in tetrahydrofuran yields an unidentified cluster product which, upon slow oxidation with molecular dioxygen or mild metal-organic oxidants yields the two large cluster species, $m lbrack Bisb4COsb9(CO)sb8(mu$-$m CO)sb8bracksp{2{-}}$ and $m lbrack Bisb8Cosb{14}(CO)sb{12}(mu$-$m CO)sb8bracksp{2{-}}.$ These cluster products contain arrays of metal atoms in the cluster framework which are reminiscent of close-packed solid-state intermetallics. Halogenation of the bismuth-iron cluster $m lbrack Bisb4Fesb4(CO)sb{13}bracksp{2{-}}$ has been performed using the phosphine halide reagent, MePCl$sb2.$ With the addition of one equivalent of the reagent, two compounds are produced in an approximately 3:1 ratio, respectively: $m lbrack Fesb2(CO)sb6(mu$-$m H)Bisb2{mu$-$m Fe(CO)sb4}bracksp-$ and $m lbrack Bisb3Clsb4(mu$-$m Cl)sb4{musb3$-$m Fe(CO)sb3}bracksp{3{-}}.$ Upon the addition of a second equivalent of reagent, the latter compound apparently decomposes; however the former is converted into the related dichloro-cluster, $m lbrack Fesb2CO)sb6(mu$-$m H)Bisb2(mu$-$m Cl)sb2bracksp-.$ Addition of yet more reagent results in the formation of the bismuth chloride-iron carbonyl adduct $m lbrack Bisb2Clsb4(mu$-$m Cl)sb2{ mu$-$m Fe(CO)sb4}bracksp{2{-}}$ at the expense of the dichloride cluster. This latter complex may also be produced quantitatively by reaction of $m lbrack Fe(CO)bracksp{2{-}}$ with two equivalents of BiCl$sb3$ in MeCN. The reaction of the tellurium-iron cluster $m Tesb2Fesb3(CO)sb9$ with SO$sb2$Cl$sb2$ yields a variety of products, depending on the reaction stoichiometry and the solvent employed in the synthesis. In CH$sb2$Cl$sb2$ at a ratio of 1:2, respectively, the large dimeric complex $m lbrack Fesb2(CO)sb6(mu$-$m Cl)(mu$-$m TeCl)sb2bracksb2lbrack Tesb2Clsb{10}brack$ is formed, which decomposes in solution to the Zintl-ion complex $m lbrack Fesb2(CO)sb6(mu$-$m TeClsb2)(etasp2$-$musb2$-$musb2$-Te$sb4 )brack.$ In MeCN at a ratio of 1:1, the previously reported tetrahedral cluster Te$sb2$Fe$sb2$(CO)$sb6$ is produced, which reacts with additional reagent to yield a complex thought to be $m lbrack Fesb2(CO)sb6(mu$-$m TeCl)sb2(mu$-$m Cl)brack$ from spectroscopic evidence. This cluster in turn decomposes in solution to $m lbrack Fesb2(CO)sb6(mu$-$m TeClsb2)(etasp2$-$musb2$-$musb2$-Te$sb4)brack$ like the first compound. Different products result if the solvent system is again changed to SO$sb2$/Me$sb2$CO at $-$30$spcirc$C. Although these unstable products have not been structurally characterized, a fair amount of other analytical and spectroscopic data have been obtained. The bromination of Te$sb2$Fe$sb3$(CO)$sb9$ with CBr$sb4$ has also been performed in MeCN, giving initially Te$sb2$Fe$sb2$(CO)$sb6;$ however, upon reaction with more CBr$sb4$ over a few weeks time at 0$spcirc$C, the novel cubane-like cluster $m lbrack Fesb3(CO)sb9Tesb4(musb3$-$m CTeBrsb4)brack$ results in low to moderate yields of 30-65% based on Te. Theoretical calculations by the extended Huckel method have been performed on some model systems, and have provided valuable insight into the underlying bonding arrangements giving rise to the sometimes-unexpected stability and structural features of these products.

[发布机构] Rice University