Minghuey Shieh

Mixed-Valence Tetra- and Hexanuclear Manganese Complexes from the Flexibility of Pyridine-Containing β-Diketone Ligands

The reactions of [Mn3O(O2CCCl3)6(H2O)3] with 1-phenyl-3-(2-pyridyl)propane-1,3-dione (HL(1)) and 1-(2-pyridly)-3-(p-tolyl)propane-1,3-dione (HL(2)) in CH2Cl2 afford the mixed-valence Mn(II)2Mn(III)2 tetranuclear complexes [Mn4O(O2CCCl3)6(L(1))2] (1) and [Mn4O(O2CCCl3)6L2(2)] (2), respectively. Similar reactions employing [Mn3O(O2CPh)6(H2O)(py)2] with HL(1) and HL(2) give the Mn(II)3Mn(III)3 hexanuclear complexes [Mn6O2(O2CPh)8(L(1))3] (3) and [Mn6O2(O2CPh)8L3(2)] (4), respectively. Complexes 1.2CH2Cl2, 2.2CH2Cl2.H2O, 3.1.5CH2Cl2.Et2O.H2O, and 4.2CH2Cl2 crystallize in the triclinic space group P1, monoclinic space group P2(1)/c, monoclinic space group P2 1/ n, and monoclinic space group P2(1)/n, respectively. Complexes 1 and 2 consist of a trapped-valence tetranuclear core of [Mn(II)2Mn(III)2(mu4-O)](8+), and complexes 3 and 4 represent a new structural type, possessing a [Mn(II)3Mn(III)3(mu4-O)2](11+) core. The magnetic data indicate that complexes 3 and 4 have a ground-state spin value of S = 7/2 with significant magnetoanisotropy as gauged by the D values of -0.51 cm (-1) and -0.46 cm (-1), respectively, and frequency-dependent out-of-phase signals in alternating current magnetic susceptibility studies indicate their superparamagnetic behavior. In contrast, complexes 1 and 2 are low-spin molecules with an S = 1 ground state. Single-molecule magnetism behavior confirmed for 3 the presence of sweep-rate and temperature-dependent hysteresis loops in single-crystal M versus H studies at temperatures down to 40 mK.

[(TeMe2)Mn(CO)4(μ5-Te)(μ4-Te)Mn4(CO)12]-: A pentacoordinate bridging tellurido ligand in a square-pyramidal geometry

The first Te-Mn-CO clusters were obtained by the thermal reaction of K2 TeO3 with [Mn2 (CO)10 ] in MeOH. The basicity of the μ4 -Te ligand in the octahedral cluster anion [(μ4 -Te)2 Mn4 (CO)12 ]2- is demonstrated by its binding to the fragment [(TeMe2 )Mn(CO)4 ]+ in an axial fashion to afford the novel cluster 1.

Recent Developments of Tellurium- and Selenium-Containing Iron Carbonyl Clusters

In recent years, quite a number of tellurium-or selenium-containing iron carbonyl clusters have been synthesized and structurally characterized, and some interesting structural transformations and reactivity of these clusters have been systematically investigated as well. The syntheses and reactivity of these clusters are reviewed and compared.

Tellurium-Bridged Manganese Carbonyl Clusters: Synthesis and Structural Transformations of [Te4Mn3(CO)10]−, [Te2Mn3(CO)9]2−, [Te2Mn3(CO)9]−, and [Te2Mn4(CO)12]2−

The reactions of appropriate ratios of K2TeO3 and [Mn2(CO)10)] in superheated methanol solutions lead to a series of novel cluster anions [Te4Mn3(CO)10] (1), [Te2Mn3(CO)9]2- (2), [Te2Mn3(CO)9]- (3), and [Te2Mn4(CO)12]2- (4). When cluster 1 is treated with [Mn2(CO)10]/KOH in methanol, paramagnetic cluster 2 is formed in moderate yield. Cluster 2 is oxidized by [Cu(MeCN)4]BF4 to give the closo-cluster [Te2Mn3(CO)9]- (3), while treatment of 2 with [Mn2(CO)10]/KOH affords the closo-cluster 4. IR spectroscopy showed that cluster 1 reacted with [Mn2(CO)10] to give cluster 4 via cluster 2. Clusters 1-4 were structurally characterized by spectroscopic methods or/and X-ray analyses. The core structure of 1 can be described as two [Mn(CO)3] groups doubly bridged by two Te2 fragments in a mu2-eta2 fashion. Both [Mn(CO)3] groups are further coordinated to one [Mn(CO)4] moiety. Cluster 2 is a 49 e- species with a square-pyramidal core geometry. While cluster 3 displays a trigonal-bipyramidal metal core, cluster 4 possesses an octahedral core geometry.

A novel synthesis of calix[4]thiophenes and calix[4]furans

The addition of heteroaryllithium to various ketones followed by dehydration gave 1-(2-heteroaryl)cycloalkenes and (2-hetero- aryl)alkenes. When alkenes were treated with 10 mol% NIS, calix[4]thiophenes and calix[4]furans were obtained in good yields.

Construction of Copper Halide-Triiron Selenide Carbonyl Complexes: Synthetic, Electrochemical, and Theoretical Studies

A new family of CuX-, Cu(2)X(2)-, and Cu(4)X(2)-incorporated mono- or di-SeFe(3)-based carbonyl clusters were constructed and structurally characterized. When the selenium-capped triiron carbonyl cluster [Et(4)N](2)[SeFe(3)(CO)(9)] was treated with 1-3 equiv of CuX in tetrahydrofuran (THF) at low or room temperatures, CuX-incorporated SeFe(3) complexes [Et(4)N](2)[SeFe(3)(CO)(9)CuX] (X = Cl, [Et(4)N](2)[1a]; Br, [Et(4)N](2)[1b]; I, [Et(4)N](2)[1c]), Cu(2)X(2)-incorporated SeFe(3) clusters [Et(4)N](2)[SeFe(3)(CO)(9)Cu(2)X(2)] (X = Cl, [Et(4)N](2)[2a]; Br, [Et(4)N](2)[2b]), and Cu(4)X(2)-linked di-SeFe(3) clusters [Et(4)N](2)[{SeFe(3)(CO)(9)}(2)Cu(4)X(2)] (X = Cl, [Et(4)N](2)[3a]; Br, [PPh(4)](2)[3b]) were obtained, respectively, in good yields. SeFe(3)CuX complexes 1a and 1b were found to undergo cluster expansion to form SeFe(3)Cu(2)X(2) complexes 2a and 2b, respectively, upon the addition of 1 equiv of CuX (X = Cl, Br). Furthermore, complexes 2a and 2b can expand further to form Cu(4)X(2)-linked di-SeFe(3) clusters 3a and 3b, upon treatment with 1 equiv of CuX (X = Cl, Br). [Et(4)N](4)[{SeFe(3)(CO)(9)(CuCl)(2)}(2)] ([Et(4)N](4)[4a]) was produced when the reaction of [Et(4)N](2)[SeFe(3)(CO)(9)] with 2 equiv of CuCl was conducted in THF at 40 degrees C. The Cu(2)Cl(2)-linked di-SeFe(3)CuCl cluster 4a is a dimerization product derived from complex 2a. Further, it is found that complex 4a can convert to the Cu(4)Cl(2)-linked di-SeFe(3) cluster 3a upon treatment with CuCl. The nature, formation, stepwise cluster expansion, and electrochemical properties of these CuX-, Cu(2)X(2)-, and Cu(4)X(2)-incorporated mono- or di-SeFe(3)-based clusters are elucidated in detail by molecular calculations at the B3LYP level of the density functional theory in terms of the effects of selenium, iron, copper halides, and the size of the metal skeleton.

Copper halide-incorporated tellurium-iron carbonyl complexes: transformation, electrochemical properties, and theoretical calculations.

When the tellurium-capped tri-iron carbonyl cluster [Et(4)N](2)[TeFe(3)(CO)(9)] was treated with 1 equiv of CuX in THF at 0 degrees C, CuX-incorporated clusters [Et(4)N](2)[TeFe(3)(CO)(9)CuX] (X = Cl, [Et(4)N](2)[1a]; Br, [Et(4)N](2)[1b]; I, [Et(4)N](2)[1c]) were formed, respectively. X-ray analysis showed that 1a-1c each exhibited a TeFe(3) core with one Fe-Fe bond bridged by one CuX fragment. When the reactions were carried out at a molar ratio of 1:2 (X = Cl, Br) or 1:3 (X = I) in tetrahydrofuran (THF) or MeCN at 0 degrees C, Cu(2)X(2)-incorporated clusters [Et(4)N](2)[TeFe(3)(CO)(9)Cu(2)X(2)] (X = Cl, [Et(4)N](2)[2a]; Br, [Et(4)N](2)[2b]; I, [Et(4)N](2)[2c]) were obtained, respectively. Cluster 2a was structurally characterized by X-ray analysis to display a TeFe(3) core, in which one TeFe(2) plane was asymmetrically bridged and capped by one mu(3)-CuCl and another mu(4)-CuCl with two Cu atoms bonded. Complexes 1a-1c underwent skeleton expansion to form Cu(3)X-incorporated di-TeFe(3) clusters [{TeFe(3)(CO)(9)}(2)Cu(3)X](2-) (X = Cl, 3a; Br, 3b; I, 3c), respectively, upon treatment with 1 equiv of [Cu(MeCN)(4)][BF(4)] at 0 degrees C. X-ray analysis showed that 3b and 3c each consisted of two TeFe(3) clusters that were linked by a Cu(3)X moiety. However, a similar reaction for 1a and 1b with 1 equiv of [Cu(MeCN)(4)][BF(4)] at room temperature produced Cu(4)X(2)-linked di-TeFe(3) clusters [{TeFe(3)(CO)(9)}(2)Cu(4)X(2)](2-) (X = Cl, 4a; Br, 4b). Cluster 4a was shown by X-ray analysis to have two TeFe(3) cores linked by a Cu(4)Cl(2) moiety. Clusters 4a and 4b were also produced directly from the reaction of [Et(4)N](2)[TeFe(3)(CO)(9)] with 4 equiv of CuX (X = Cl, Br) in THF. Furthermore, the nature, the formation, the cluster transformation, and the electrochemistry of the CuX-incorporated mono- or di-TeFe(3) clusters are explained in terms of the effects of tellurium, copper halide, and the size of the metal skeleton, all of which are elucidated by molecular calculations at the B3LYP level of density functional theory.

Chalcogen-Containing Manganese Carbonyl Clusters: Synthesis and Structural Transformations

Recently, we have developed several synthetic routes to the new classes of chalcogen-containing manganese carbonyl clusters, and the interesting structural transformations and reactivity of the resultant clusters have been investigated as well. In this short review, the syntheses and bonding modes of the sulfur, selenium, and tellurium-containing manganese carbonyl complexes reported by our laboratory will be presented, and the cluster growth and transformation will be systematically compared and discussed.

Selective Insertion of Oxygen and Selenium into an Electron-Precise Paramagnetic Selenium-Manganese Carbonyl Cluster [Se6Mn6(CO)18]4-

The facile synthesis of a novel electron-precise paramagnetic hexamanganese carbonyl selenide cluster [Se(6)Mn(6)(CO)(18)](4-) (1) was discovered, which demonstrates contrasting reactivity toward O(2) and Se(8) under markedly mild conditions to afford the O- and Se-inserted clusters [Se(6)Mn(6)(CO)(18)(O)](4-) (2) and [Se(10)Mn(6)(CO)(18)](4-) (3), respectively. Clusters 1-3 represent the first examples of electron-precise paramagnetic main-group transition metal carbonyl clusters, and their formation and bonding properties are further elucidated by theoretical calculations.

Carbonylchromium Derivatives of Bismuth: New Syntheses and Relevance to CO Activation

We have discovered a series of novel pentacarbonylchromium derivatives of bismuth from the reactions of NaBiO(3) with [Cr(CO)(6)] in KOH/MeOH solutions. When the reaction was carried out at room temperature, the highly charged [Bi[Cr(CO)(5)](4)](3-) (1) was obtained, whose structure was shown by X-ray analysis to possess a central bismuth atom tetrahedrally coordinated to four [Cr(CO)(5)] groups. As the reaction was heated at 80 degrees C, the methyl-substituted complex [MeBi[Cr(CO)(5)](3)](2-)(2) was obtained, presumably via the CbondO activation of MeOH. Further reactions of 1 with CH(2)Cl(2) or CHtbondCCH(2)Br form the halo-substituted complexes [XBi[Cr(CO)(5)](3)](2-)(X=Cl, 3; Br, 4), respectively. On the other hand, the reactions of 1 with RI (R=Me, Et) led to the formation of the alkyl-substituted complexes [RBi[Cr(CO)(5)](3)](2-)(R=Me, 2; Et). The formation of complexes 1-4 is discussed, presumably via the intermediate bismuthinidene [Bi[Cr(CO)(5)](3)](-) or the trianion [Bi[Cr(CO)(5)](3)](3-).