title: Journey from Mo-Mo quadruple bonds to quintuple bonds.
abstract: Heating K(4)Mo(2)Cl(8) and 2 equiv of Li[RC(NDipp)(2)] (R = H, Ph; Dipp = 2,6-i-Pr(2)C(6)H(3)) in tetrahydrofuran (THF) at 60 degrees C gives two paddlewheel type quadruply bonded dimolybdenum complexes, Mo(2)(mu-Cl)[Cl(2)Li(OEt(2))][mu-eta(2)-RC(N-2,6-i-Pr(2)C(6)H(3))(2)](2) (R = H (1), Ph (2)). The Mo-Mo bond lengths of 1 and 2 are 2.0875(4) and 2.0756(8) A, respectively, indicating typical Mo-Mo quadruple bonds. Reduction of 1 and 2 by two electrons results in the isolation of their corresponding Mo-Mo quintuple bonded complexes, Mo(2)[mu-eta(2)-RC(N-2,6-i-Pr(2)C(6)H(3))(2)](2) (R = H (3), Ph (4)), and the Mo-Mo bond lengths dramatically decrease to 2.0187(9) A (3) and 2.0157(4) A (4), a consequence of the formation of the second delta bond and representing the shortest metal-metal bonds beyond the first row elements. The Mo-Mo quintuple bonding characters are corroborated by DFT calculations at the level of BP86/def2-TZVP and BP86/def2-TZVPP.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan, ROC. yictsai@mx.nthu.edu.tw
authors.forename: Yi-Chou
authors.initials: YC
authors.lastname: Tsai
authors.forename: Hong-Zhang
authors.initials: HZ
authors.lastname: Chen
authors.forename: Chie-Chieh
authors.initials: CC
authors.lastname: Chang
authors.forename: Jen-Shiang K
authors.initials: JS
authors.lastname: Yu
authors.forename: Gene-Hsiang
authors.initials: GH
authors.lastname: Lee
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.forename: Ting-Shen
authors.initials: TS
authors.lastname: Kuo
mesh_terms: D018360:Crystallography, X-Ray; D008982:Molybdenum / Q000737:chemistry*; D013696:Temperature
chemical_list: D008982:Molybdenum