Structure and bonding: The synthesis and characterization of heteronuclear clusters

[摘要] The reaction of $m NaAsOsb2, TeOsb2$, and $m SeOsb2$ with methanolic solutions of KOH and $m Fe(CO)sb5$ produces the isoelectronic clusters ($m HAs{Fe(CO)sb4}sb3bracksp{2-}, lbrack Te{Fe(CO)sb4}sb3bracksp{2-}$, and $m lbrack Se{Fe(CO)sb4}sb3bracksp{2-}$. The selenium cluster, however, is unstable and rapidly loses CO to form the closo cluster $lbrackm SeFesb3(CO)sb9bracksp{2-}. lbrack Te{Fe(CO)sb4}sb3bracksp{2-}$ can also be transformed into the related closo cluster ($m TeFesb3(CO)sb9bracksp{2-}$ by either pyrolysis or photolysis. In contrast, pyrolysis or photolysis of $mlbrack HAs{Fe(CO)sb4}sb3bracksp{2-}$ yields the higher nuclearity species $m lbrack Assb2Fesb5(CO)sb{17}bracksp{2-}$. The stepwise protonation of $mlbrack EFesb3(CO)sb9bracksp{2-}$ (E = Se, Te) allows for the preparation of either $m lbrack HEFesb3(CO)sb9bracksp-$ or $m Hsb2EFesb3(CO)sb9$ in good yield. Low temperature $msp1H$ NMR studies of the protonation process suggest that the basic sites on the cluster are the iron-iron bonds rather than the main-group element. Spectral and structural characterization of these related clusters allows for the effect of cluster charge on structure to be probed. Reaction of $mlbrack TeFesb3(CO)sb9bracksp{2-}$ with solid CuCl produces the unusual Lewis acid-base adduct $mlbrack TeFesb3(CO)sb9(CuCl)bracksp{2-}$. This cluster can also be viewed as the initial step in the copper oxidation of the metal cluster, which produces the well known cluster $m Fesb3(CO)sb9Tesb2$. The reaction of elemental tellurium with $m Nasb2Fe(CO)sb4$ yields the unstable cluster $mlbrack Fesb2(CO)sb6(Tesb2)sb2bracksp{2-}$. Reaction of this unstable cluster with alkylating agents such as iodomethane and diiodomethane produces $m Fesb2(CO)sb6(TeMe)sb2$ and $m Fesb2(CO)sb6(Tesb2CHsb2)$ respectively, along with elemental tellurium. Oxidation of $mlbrack Fesb2(CO)sb6(Tesb2)sb2bracksp{2-}$ with $mlbrack Cu(MeCN)sb4brack BFsb4$ gives the known cluster $m Fesb2(CO)sb6Tesb2$ and tellurium metal. The reaction of $m TeClsb4$ with iron carbonylate anions produces a variety of products: $m Fesb2(CO)sb6Tesb2, Fesb3(CO)sb9Tesb2$, or $mlbrack TeFesb3(CO)sb9bracksp{2-}$, depending on the conditions employed. The reactive cluster $m Fesb2(CO)sb6Tesb2$ was structurally characterized as a 2:1 adduct with $mlbrack Etsb4Nbrack Cl$. The reaction of the dinuclear group VI anions $mlbrack Msb2(CO)sb{10}bracksp{2-}$ (M = Cr, Mo, W) with $m Phsb2BiCl$ produces the metallated organobismuth clusters $mlbrack Phsb2Bi{M(CO)sb5}sb2bracksp-$. The analogous reaction with $mlbrack Fesb2(CO)sb8bracksp{2-}$ generates $mlbrack Phsb2Bi{Fe(CO)sb4}sb2bracksp-$. The reaction of the previously synthesized cluster $mlbrack Phsb2BiFe(CO)sb4bracksp-$ with $m Fesb2(CO)sb9$ or $m Cr(CO)sb5THF$ produces $mlbrack Phsb2Bi{Fe(CO)sb4}sb2bracksp-$ or the heterometallic $mlbrack Phsb2Bi{Fe(CO)sb4}{Cr(CO)sb5}bracksp-$ respectively. Comparison of the structural parameters seen in these clusters and other related organobismuth species provides insight into the nature of the bonding at bismuth in compounds of this type. Additionally, in contrast to previous reports, the reactivity of $mlbrack Phsb2BiFe(CO)sb4bracksp-$ observed in these studies suggests that the bismuth atom is the site of nucleophillic attack.

[发布机构] Rice University