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New ternary Se Ru Cu octahedral-based complexes, namely, CuX-capped SeRu5 clusters [SeRu5(CO)14(μ3-CuX)]2− (2a–2c; X = Cl, Br, I), bis-CuX-capped SeRu5 clusters [SeRu5(CO)14(μ3-CuX)2]2− (3a, 3b; X = Cl, Br), Cu4X2-bridged di-SeRu5 clusters [{SeRu5(CO)14}2(μ6-Cu4X2)]2− (4a, 4b; X = Cl, Br), and bis-CuX-incorporated Se2Ru4 clusters [Se2Ru4(CO)10(μ-CuX)2]2− (5a–5c; X = Cl, Br, I), were prepared from the reaction of the binary cluster [SeRu5(CO)14]2− (1) with CuX under appropriate conditions. Their solid-state packing formed cluster-based 1D-supramolecular chains, which were stabilized by C H⋯X/Y (X = halides; Y = O) H-bonding between CuX/COs of cluster anions and the CH moieties of the [PPh4]+ or [PPN]+ cations. In addition, electrochemical studies showed that the successive anodic shifts were found for 1–4b, tuned by the incoming CuBr fragments introduced into the parent SeRu5 cluster, supported by their decreasing HOMO levels and increasing ionization energies. Solid-state diffuse reflectance spectra showed these Se Ru Cu complexes exhibited semiconducting behaviors with the low and tunable energy gaps of 0.82–1.08 eV. Significantly, the solid-state absorptions of 2b and 4b were red-shifted compared with the corresponding Te analogues, which was explained by the larger numbers of the density of states (DOS) close to the HOMO for the selenide cases.

Main-group element-bridged transition metal carbonyl complexes represent an important field in contemporary chemistry. This review will focus on the recent development of groups 6–8 carbonyl chalcogenide clusters, in particular on the anionic clusters which have been proven to exhibit versatile reactivity. This paper presents a review and discussion, from our group and others, of the rational synthetic methodologies, structural features, cluster-growth and transformations, and novel reactivities of these anionic clusters, as well as their special electrochemical, magnetic, and semiconducting properties. The description of the clusters in this review is arranged group-by-group based on the formation of both metal–chalcogen and metal–metal bonds. The literature survey is current through January 2011, and the review covers the chemistry of anionic groups 6–8 carbonyl chalcogenide clusters in this area of research and should significantly contribute to future research.

When trigonal-bipyramidal clusters, [PPN][E(2)Mn(3)(CO)(9)] (E = S, Se), were treated with Cr(CO)(6) and PPNCl in a molar ratio of 1:1:2 or 1:2:2 in 4 M KOH/MeCN/MeOH solutions, mono-Cr(CO)(5)-incorporated HE(2)Mn(3)-complexes [PPN](2)[HE(2)Mn(3)Cr(CO)(14)] (E = S, [PPN](2)[1a]; Se, [PPN](2)[1b]), respectively, were formed. X-ray crystallographic analysis showed that 1a and 1b were isostructural and each displayed an E(2)Mn(3) square-pyramidal core with one of the two basal E atoms externally coordinated with one Cr(CO)(5) group and one Mn-Mn bond bridged by one hydrogen atom. However, when the TMBA(+) salts for [E(2)Mn(3)(CO)(9)](-) were mixed with Cr(CO)(6) in a molar ratio of 1:1 in 4 M KOH/MeOH solutions and refluxed at 60 °C, mono-Cr(CO)(3)-incorporated E(2)Mn(3)Cr octahedral clusters [TMBA](3)[E(2)Mn(3)Cr(CO)(12)] (E = S, [TMBA](3)[2a]; Se, [TMBA](3)[2b]), respectively, were obtained. Clusters 2a and 2b were isostructural, and each consisted of an octahedral E(2)Mn(3)Cr core, in which each Mn-Mn or Mn-Cr bond of the Mn(3)Cr plane was semibridged by one carbonyl ligand. Clusters 1a and 1b (with [TMBA] salts) underwent metal core closure to form octahedral clusters 2a and 2b upon treatment with KOH/MeOH at 60 °C. In addition, 1a and 1b were found to undergo cluster expansion to form di-Cr(CO)(5)-incorporated HE(2)Mn(3)-clusters [HE(2)Mn(3)Cr(2)(CO)(19)](2-) (E = S, 3a; Se, 3b), respectively, upon the addition of 1 or 2 equiv of Cr(CO)(6) heated in refluxing CH(2)Cl(2). Clusters 3a and 3b were structurally related to clusters 1a and 1b, but with the other bare E atom (E = S, 3a; Se, 3b) further externally coordinated with one Cr(CO)(5) group. The nature, cluster transformation, and electrochemical properties of the mixed manganese-chromium carbonyl sulfides and selenides were systematically discussed in terms of the chalcogen elements, the introduced chromium carbonyl group, and the metal skeleton with the aid of molecular calculations at the BP86 level of the density functional theory.

Recently, we have developed several synthetic routes to a series of chalcogen-containing group 6 (emphasizing on chromium) carbonyl clusters, in which the interesting structural transformations, reactivity, and properties of the resultant clusters have also been investigated. This review will focus on the aspects of the research carried out in our laboratory. In this account, the practical synthetic methodologies and metal-metal exchange and cluster expansion reactions together with structural features of these Cr-containing complexes are systematically described and compared.

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.

A new series of Te-Ru-Cu carbonyl complexes was prepared by the reaction of K(2)TeO(3) with [Ru(3)(CO)(12)] in MeOH followed by treatment with PPh(4)X (X=Br, Cl) and [Cu(MeCN)(4)]BF(4) or CuX (X=Br, Cl) in MeCN. When the reaction mixture of K(2)TeO(3) and [Ru(3)(CO)(12)] was first treated with PPh(4)X followed by the addition of [Cu(MeCN)(4)]BF(4), doubly CuX-bridged Te(2)Ru(4)-based octahedral clusters [PPh(4)](2)[Te(2)Ru(4)(CO)(10)Cu(2)X(2)] (X=Br, [PPh(4)](2)[1]; X=Cl, [PPh(4)](2)[2]) were obtained. When the reaction mixture of K(2)TeO(3) and [Ru(3)(CO)(12)] was treated with PPh(4)X (X=Br, Cl) followed by the addition of CuX (X=Br, Cl), three different types of CuX-bridged Te-Ru carbonyl clusters were obtained. While the addition of PPh(4)Br or PPh(4)Cl followed by CuBr produced the doubly CuBr-bridged cluster 1, the addition of PPh(4)Cl followed by CuCl led to the formation of the Cu(4)Cl(2)-bridged bis-TeRu(5)-based octahedral cluster compound [PPh(4)](2)[{TeRu(5)(CO)(14)}(2)Cu(4)Cl(2)] ([PPh(4)](2)[3]). On the other hand, when the reaction mixture of K(2)TeO(3) and [Ru(3)(CO)(12)] was treated with PPh(4)Br followed by the addition of CuCl, the Cu(Br)CuCl-bridged Te(2)Ru(4)-based octahedral cluster chain polymer {[PPh(4)](2)(Te(2)Ru(4)(CO)(10)Cu(4)Br(2)Cl(2)).THF}(infinity) ({[PPh(4)](2)[4].THF}(infinity)) was produced. The chain polymer {[PPh(4)](2)[4].THF}(infinity) is the first ternary Te-Ru-Cu cluster and shows semiconducting behavior with a small energy gap of about 0.37 eV. It can be rationalized as resulting from aggregation of doubly CuX-bridged clusters 1 and 2 with two equivalents of CuCl or CuBr, respectively. The nature of clusters 1-4 and the formation and semiconducting properties of the polymer of 4 were further examined by molecular orbital calculations at the B3LYP level of density functional theory.

Two sandwich-type Cu3Cl- or Cu2{Te2Ru4(CO)10}-bridging di-TeRu5 clusters, [{TeRu5(CO)14}2Cu3Cl]2− (1) and [{TeRu5(CO)14}2Cu2{Te2Ru4(CO)10}]4− (2), were obtained from the reaction of [TeRu5(CO)14]2− with 1 equiv. of [Cu(MeCN)4][BF4] in CH2Cl2 or THF at 0 °C, respectively, depending on the solvents. The chloride-abstracted 1 was structurally characterized to have two TeRu5 cores that were linked by a Cu3Cl moiety with two Cu–Cu bonds. If the reaction was carried out in a molar ratio of 1 : 2 at 0 or 30 °C in CH2Cl2, the structural isomers [TeRu5(μ-CO)2(CO)12(CuMeCN)2] (3a) and [TeRu5(μ-CO)3(CO)11Cu2(MeCN)2] (3b) were produced, respectively, as the major product. Cluster 3a displayed a TeRu5 core with two adjacent Ru3 triangles each capped by a μ3-Cu(MeCN) fragment, while 3b contained a TeRu5 core with one triangle Ru3 plane capped by a Cu2(MeCN)2 fragment with two Cu atoms covalently bonded. Upon heating, the isomerization of 3a into 3b proceeded to undergo an unusual skeletal arrangement of Cu(MeCN) and migration of CO, with the TeRu5 core remaining intact. An electrochemical study revealed that 3a and 3b each exhibited only one oxidation while cluster 1 had two consecutive oxidations, suggesting significant electronic communication between the two TeRu5 metal cores in 1via the Cu3 moiety. This work describes the facile synthesis of a series of semiconducting Cux-bridging Te–Ru carbonyl clusters, in which the incorporation of the Cux fragments has significantly influenced their resulting structures, rearrangements, and electronic properties, which was further elucidated by DFT calculations.

A facile synthesis of the novel selenium-capped trimolybdenum and tritungsten ring carbonyl clusters [Se 2 M 3 (CO) 10 ] 2− (M = Mo, 1 ; W, 4 ) have been achieved. The selenium-capped trimolybdenum cluster compound [Et 4 N] 2 [Se 2 Mo 3 (CO) 10 ] ([Et 4 N] 2 [ 1 ]) can be obtained from the reaction of the trichromium cluster compound [Et 4 N] 2 [Se 2 Cr 3 (CO) 10 ] with 4 equiv. of Mo(CO) 6 in refluxing acetone. On the other hand, when [Et 4 N] 2 [Se 2 Cr 3 (CO) 10 ] reacted with 4 equiv. of W(CO) 6 in refluxing acetone, the planar cluster compound [Et 4 N] 2 [Se 2 W 4 (CO) 18 ] ([Et 4 N] 2 [ 3 ]) was isolated, which could further transform to the tritungsten cluster compound [Et 4 N] 2 [Se 2 W 3 (CO) 10 ] ([Et 4 N] 2 [ 4 ]) in good yield. Alternatively, clusters 1 and 4 could be formed from the reactions of the monosubstituted products [Et 4 N] 2 [Se 2 Cr 2 M(CO) 10 ] (M = Mo; W, [Et 4 N] 2 [ 2 ]) with 3 equiv. of M(CO) 6 in acetone, respectively. Complexes 1 – 4 are fully characterized by IR, 77 Se NMR spectroscopy, and single-crystal X-ray analysis. Clusters 1 , 2 , and 4 are isostructural and each display a trigonal bipyramidal structure with a homometallic M 3 ring (M = Mo, 1 ; W, 4 ) or a heterometallic Cr 2 W ring that is further capped above and below by μ 3 -Se atoms. Further, the intermediate planar complex 3 exhibits a Se 2 W 2 square with each Se atom externally coordinated to one W(CO) 5 group. This paper describes a systematic route to a series of selenium-capped trimetallic carbonyl clusters and the formation and the structural features of the resultant clusters are discussed.

The unprecedented ternary Te-Fe-Cu chain polymers [{Et4N}{TeFe3(CO)9Cu}]infinity and [{TeFe3(CO)9Cu2}(mu-4,4'-dipyridyl)1.5]infinity were prepared from the self-assembly of [Et4N]2[TeFe3(CO)9] with [Cu(MeCN)4][BF4] in THF or in the presence of 4,4'-dipyridyl in THF. These two chain polymers, which can also be constructed from the precursor complex TeFe3(CO)9Cu2(MeCN)2, show semiconducting behaviors with low band gaps of 0.59 and 0.41 eV, respectively. In addition, their conductivity and the effect of the bridging ligand are further elucidated by theoretical calculations.

Recently, we have developed several synthetic routes to a series of chalcogen-containing group 6 (emphasizing on chromium) carbonyl clusters, in which the interesting structural transformations, reactivity, and properties of the resultant clusters have also been investigated. This review will focus on the aspects of the research carried out in our laboratory. In this account, the practical synthetic methodologies and metal-metal exchange and cluster expansion reactions together with structural features of these Cr-containing complexes are systematically described and compared.

The paramagnetic even-electron cluster, [Et(4)N](2)[Se(2)Cr(3)(CO)(10)], was found to react readily with Mn(CO)(5)Br in acetone to produce two unprecedented mixed chromium-manganese selenide carbonyl complexes, [Et(4)N][Me(2)CSe(2){Mn(CO)(4)}{Cr(CO)(5)}(2)] ([Et(4)N][1]) and [Et(4)N](2)[Se(2)Mn(3)(CO)(10){Cr(CO)(5)}(2)] ([Et(4)N](2)[2]). X-ray crystallographic analysis showed that anion 1 consisted of two Se-Cr(CO)(5) moieties, which were further bridged by one isopropylene group and one Mn(CO)(4) moiety. The dianionic cluster 2 was shown to display a Se(2)Mn(3) square-pyramidal core with each Se atom externally coordinated by one Cr(CO)(5) group. The formation of complex 1, presumably via C=O activation of acetone, was further facilitated by acidification of the reaction of [Et(4)N](2)[Se(2)Cr(3)(CO)(10)] with Mn(CO)(5)Br in acetone. Complex 1 readily transformed into 2 upon treatment with Mn(2)(CO)(10) in a KOH/MeOH/MeCN solution. Cluster 2 was a 51-electron species, which readily converted to the known 49-electron cluster [Se(2)Mn(3)(CO)(9)](2-) upon heating and bubbling with CO. Magnetic studies of the even-electron cluster, [Et(4)N](2)[Se(2)Cr(3)(CO)(10)], and the odd-electron species, [Et(4)N](2)[2] and [PPN](2)[Se(2)Mn(3)(CO)(9)], were determined by the SQUID measurement to have 2, 3, and 1 unpaired electrons, respectively. In addition, the nature and formation of complexes 1 and 2 are discussed, and the magnetic properties and electrochemistry of [Se(2)Cr(3)(CO)(10)](2-), 2, and [Se(2)Mn(3)(CO)(9)](2-) were further studied and elucidated by molecular orbital calculations at the PW91 level of density functional theory.

When [TeRu(5)(CO)(14)](2-) () was treated with 1 equiv. of CuX (X = Cl, Br, I) in THF, mono-CuX-TeRu(5) clusters [TeRu(5)(CO)(14)CuX](2-) (X = Cl, ; Br, ; I, ) were obtained. Clusters consist of an octahedral TeRu(5) core, in which one triangular Ru(3) plane is capped by a mu(3)-CuX fragment. For CuX (X = Cl, Br), the reaction of complex with 2 equiv. of CuX in THF at room temperature formed Cu(4)X(2)-linked di-TeRu(5) clusters [{TeRu(5)(CO)(14)}(2)Cu(4)X(2)](2-) (X = Cl, ; Br, ), while the same reaction in MeCN at -35 degrees C produced bis-CuX-TeRu(5) complexes [TeRu(5)(CO)(14)(CuX)(2)](2-) (X = Cl, ; Br, ). X-Ray analysis showed that displays a TeRu(5) core with two adjacent Ru(3) triangles each capped by a mu(3)-CuBr ligand while has two TeRu(5) cores that are linked by a mu(6)-Cu(4)Br(2) moiety. Clusters and underwent coupling reactions in THF to yield clusters and , and easily transformed to bis-CuX-Te(2)Ru(4) clusters [Te(2)Ru(4)(CO)(10)(CuX)(2)](2-) (X = Cl, ; X = Br, ) in MeCN. On the other hand, the reaction of with 2 equiv. of CuI in THF directly produced the bis-CuI-Te(2)Ru(4) cluster [Te(2)Ru(4)(CO)(10)(CuI)(2)](2-) (). The nature, stability, stepwise cluster transformation, and electrochemistry of these CuX-incorporated TeRu(5)- and Te(2)Ru(4)-based complexes are discussed systematically. In particular, the effects of CuX and the metal cores (TeRu(5)vs. Te(2)Ru(4)) on the resultant Te-Ru-Cu clusters are further elucidated by molecular orbital calculations at the B3LYP level of the density functional theory.

When the μ3-sulfido triiron cluster [SFe3(CO)9]2− was treated with BrCH2C(O)OCH3 in MeCN, the ester-functionalized complex [SFe3(CO)9(CH2C(O)OCH3)]− (1) was obtained. Cluster 1 displays a SFe3 tetrahedral core with one of the Fe atoms bonded to an ester ligand CH2C(O)OCH3. In contrast, when [SFe3(CO)9]2− was treated with dihaloalkanes X(CH2)nX′ (X = Cl, X′ = Br, n = 3; X = X′ = I, n = 4) in MeCN, the sulfur-alkylated complexes [X(CH2)nSFe3(CO)9]− (X = Cl, n = 3, 2; X = I, n = 4, 3) were formed, respectively. Clusters 2 and 3 each exhibits a SFe3 tetrahedral core with the sulfur atom attached to the halide-functionalized alkyl group. Furthermore, the Hg-bridged di-SFe3 complex [{SFe3(CO)9}2(μ4-Hg)]2− (4) was isolated from the reaction of [SFe3(CO)9]2− with 2 equiv. of Hg(OAc)2 in acetone. However, when [SFe3(CO)9]2− was treated with HgI2 under similar conditions, the HgI-bridged cluster [SFe3(CO)9(μ-HgI)]− (5) was produced. In addition, complex 4 could be transformed into complex 3 upon treatment with I(CH2)4I in MeCN. Conversely, complex 3 could be reconverted into 4 in the presence of Hg(OAc)2 in an acetone solution. Clusters 1–5 were fully characterized by spectroscopic methods and single-crystal X-ray analysis. In particular, the nature and selective formation as well as electrochemistry of complexes 1–5, which resulted from the different reactive sites (Fevs. S atom) of [SFe3(CO)9]2−, were also examined and compared systematically by molecular orbital calculations at the B3LYP level of the density functional theory.