A novel type of double butterfly, two mu-CO-containing dianions {[(mu-CO)Fe2(CO)6]2[mu-SCH2(CH2OCH2)nCH2S-mu]}2- (m1, n = 2, 3), has been synthesized from dithiol HSCH2(CH2OCH2)nCH2SH (n = 2, 3), Fe3(CO)12, and Et3N in THF at room temperature. While dianions m1 react in situ with CS2 followed by treatment with dihalide 1,4-(BrCH2)2C6H4 or 1,4-I(CH2)4I to give macrocyclic clusters [mu-SCH2(CH2OCH2)nCH2S-mu](mu-CS2ZCS2-mu)[Fe2(CO)6]2 (1a, n = 2, Z = 1,4-(CH2)2C6H4; 1b, n = 3, Z = (CH2)4), reactions of dianions m1 with (mu-S2)Fe2(CO)6 followed by treatment with dihalide 1,4-I(CH2)4I afford macrocyclic clusters [mu-SCH2(CH2OCH2)nCH2S-mu]{[Fe2(CO)6]2(mu4-S)}2[mu-S(CH2)4S-mu] (2a, n = 2; 2b, n = 3). The crystal structures of 1a and 2b are described.

Reaction of 1,4-diazabutanediyl-bridged bis(phenols) [(HOC 6 H 2 -4,6-t Bu 2 ) 2 NR(CH 2 ) 2 NR] (R=H, 1; Me, 2) with the appropriate metal precursors MX 4 (M=Ti, Zr, Hf; X=Cl, O i Pr) gave a series of group 4 metal dichloro and di(isopropoxy) complexes [M{2,2 0 -(OC 6 H 2 -4,6-t Bu 2 ) 2 NR(CH 2 ) 2 NR}X 2 ] (R=H, X= Cl, M=Ti, 3; R=Me, X=O i Pr, M=Ti, 4; R=Me, X=Cl, M=Ti, 5; Zr, 6; Hf, 7). While for complexes 3, 4, 6, and 7 single isomers were observed, titanium complex 5 formed as a mixture of cis-R (5a) and cis-β (5b) isomers. Variable-temperature NMR spectroscopy shows that titanium complexes 3 and 5b are unstable and favor a cis-R ligand configuration at elevated temperatures, whereas 4 and 5a are configurationally stable. Complexes 6 and 7 show rigid C 2 -symmetric structures in solution up to 100°C. Upon activation with methylaluminoxane, 3-7 show good (M=Ti) to excellent (M=Zr, Hf) activity in the polymerization of 1-hexene, giving low molecular weight atactic polymers. Styrene is polymerized with modest activity.

The [Et3NH]+ salts of novel anions (μ-RE)(μ-S-)[Fe2(CO)6]2(μ4-S) (RE = t-BuS, p-MeC6H4Se) have been prepared by reaction of [(μ-RE)(μ-CO)Fe2(CO)6][Et3NH] with (μ-S2)Fe2(CO)6. While these salts react in situ with MeI to yield the double clusters [(μ-RE)Fe2(CO)6](μ4-S)[(μ-MeS)Fe2(CO)6], their reactions with SO2Cl2 in the presence of excess [(μ-RE)(μ-CO)Fe2(CO)6][Et3NH] afford the triple clusters [(μ-RE)Fe2(CO)6]2[(μ4-S)(Fe2(CO)6)2(μ4-S)].

The gold-catalyzed endo-cycloisomerization of allenes bearing nucleophilic substituents in the α- or β-position opens up a versatile access to various five- and six-membered heterocycles. Key features of these transformations are the high reactivity of the allene in the presence of Lewis-acidic, carbophilic gold(I) or gold(III) catalysts, and the chirality transfer from the allenic axis of chirality to the new stereogenic center in the cyclization product. Recent contributions of our group include the optimization of chirality transfer by using σ-donor ligands to gold, and applications in the total synthesis of natural products, e.g., of the β-carboline alkaloids (-)-isocyclocapitelline and (-)-isochrysotricine.

A new type of double-butterfly [[Fe(2)(mu-CO)(CO)(6)](2)(mu-SZS-mu)](2-) (3), a dianion that has two mu-CO ligands, has been synthesized from dithiol HSZSH (Z=(CH(2))(4), CH(2)(CH(2)OCH(2))(1-3)CH(2)), [Fe(3)(CO)(12)], and Et(3)N in a molar ratio of 1:2:2 at room temperature. Interestingly, the in situ reactions of dianions 3 with various electrophiles affords a series of novel linear and macrocyclic butterfly Fe/E (E=S, Se) cluster complexes. For instance, while reactions of 3 with PhC(O)Cl and Ph(2)PCl give linear clusters [[Fe(2)(mu-PhCO)(CO)(6)](2)(mu-SZS-mu)] (4 a,b: Z=CH(2)(CH(2)OCH(2))(2,3)CH(2)) and [[Fe(2)(mu-Ph(2)P)(CO)(6)](2)(mu-SZS-mu)] (5 a,b: Z=CH(2)(CH(2)OCH(2))(2,3)CH(2)), reactions with CS(2) followed by treatment with monohalides RX or dihalides X-Y-X give both linear clusters [[Fe(2)(mu-RCS(2))(CO)(6)](2)(mu-SZS-mu)] (6 a-e: Z=CH(2)(CH(2)OCH(2))(1,2)CH(2); R=Me, PhCH(2), FeCp(CO)(2)) and macrocyclic clusters [[Fe(2)(CO)(6)](2)(mu-SZS-mu)(mu-CS(2)YCS(2)-mu)] (7 a-e: Z=(CH(2))(4), CH(2)(CH(2)OCH(2))(1-3)CH(2); Y=(CH(2))(2-4), 1,3,5-Me(CH(2))(2)C(6)H(3), 1,4-(CH(2))(2)C(6)H(4)). In addition, reactions of dianions 3 with [Fe(2)(mu-S(2))(CO)(6)] followed by treatment with RX or X-Y-X give linear clusters [[[Fe(2)(CO)(6)](2)(mu-RS)(mu(4)-S)](2)(mu-SZS-mu)] (8 a-c: Z=CH(2)(CH(2)OCH(2))(1,2)CH(2); R=Me, PhCH(2)) and macrocyclic clusters [[[Fe(2)(CO)(6)](2)(mu(4)-S)](2)(mu-SYS-mu)(mu-SZS-mu)] (9 a,b: Z=CH(2)(CH(2)OCH(2))(2,3)CH(2); Y=(CH(2))(4)), and reactions with SeCl(2) afford macrocycles [[Fe(2)(CO)(6)](2)(mu(4)-Se)(mu-SZS-mu)] (10 d: Z=CH(2)(CH(2)OCH(2))(3)CH(2)) and [[[Fe(2)(CO)(6)](2)(mu(4)-Se)](2)(mu-SZS-mu)(2)] (11 a-d: Z=(CH(2))(4), CH(2)(CH(2)OCH(2))(1-3)CH(2)). Production pathways have been suggested; these involve initial nucleophilic attacks by the Fe-centered dianions 3 at the corresponding electrophiles. All the products are new and have been characterized by combustion analysis and spectroscopy, and by X-ray diffraction techniques for 6 c, 7 d, 9 b, 10 d, and 11 c in particular. X-ray diffraction analyses revealed that the double-butterfly cluster core Fe(4)S(2)Se in 10 d is severely distorted in comparison to that in 11 c. In view of the Z chains in 10 a-c being shorter than the chain in 10 d, the double cluster core Fe(4)S(2)Se in 10 a-c would be expected to be even more severely distorted, a possible reason for why 10 a-c could not be formed.