title: Trigonal-bipyramidal and square-pyramidal chromium-manganese chalcogenide clusters, [E2CrMn2(CO)n](2-) (E=S, Se, Te; n=9, 10): synthesis, electrochemistry, UV/Vis absorption, and computational studies.
abstract: The reactions of E powder (E=S, Se) with a mixture of Cr(CO)6 and Mn2(CO)10 in concentrated solutions of KOH/MeOH produced two new mixed Cr-Mn-carbonyl clusters, [E2CrMn2(CO)9](2-) (E=S, 1; Se, 2). Clusters 1 and 2 were isostructural with one another and each displayed a trigonal-bipyramidal structure, with the CrMn2 triangle axially capped by two μ3-E atoms. The analogous telluride cluster, [Te2CrMn2(CO)9](2-) (3), was obtained from the ring-closure of Te2Mn2 ring complex [Te2Mn2Cr2(CO)18](2-) (4). Upon bubbling with CO, clusters 2 and 3 were readily converted into square-pyramidal clusters, [E2CrMn2(CO)10](2-) (E=Se, 5; Te, 6), accompanied with the cleavage of one Cr-Mn bond. According to SQUID analysis, cluster 6 was paramagnetic, with S=1 at room temperature; however, the Se analogue (5) was spectroscopically proposed to be diamagnetic, as verified by TD-DFT calculations. Cluster 6 could be further carbonylated, with cleavage of the Mn-Mn bond to produce a new arachno-cluster, [Te2CrMn2(CO)11](2-) (7). The formation and structural isomers, as well as electrochemistry and UV/Vis absorption, of these clusters were also elucidated by DFT calculations.
authors.affiliation: Department of Chemistry, National Taiwan Normal University, Taipei 116, Taiwan, Republic of China. mshieh@ntnu.edu.tw
authors.forename: Minghuey
authors.initials: M
authors.lastname: Shieh
authors.forename: Chun-Hsien
authors.initials: CH
authors.lastname: Yu
authors.forename: Yen-Yi
authors.initials: YY
authors.lastname: Chu
authors.forename: Yu-Wen
authors.initials: YW
authors.lastname: Guo
authors.forename: Chung-Yi
authors.initials: CY
authors.lastname: Huang
authors.forename: Kai-Jieah
authors.initials: KJ
authors.lastname: Hsing
authors.forename: Pei-Chi
authors.initials: PC
authors.lastname: Chen
authors.forename: Chung-Feng
authors.initials: CF
authors.lastname: Lee
mesh_terms: D002248:Carbon Monoxide / Q000737:chemistry*; D018011:Chalcogens / Q000737:chemistry*; D002857:Chromium / Q000737:chemistry*; D055664:Electrochemical Techniques; D008345:Manganese / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet
chemical_list: D018011:Chalcogens; D002857:Chromium; D008345:Manganese; D002248:Carbon Monoxide