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Please use this identifier to cite or link to this item: http://ir.ncue.edu.tw/ir/handle/987654321/14772

Title: A Planar Tetracoordinate Carbon and Unusual Bonding in an Organodimetallic Propynylidene Complex Arising from Double C-H Activation of an Allene Ligand
Authors: Huang, Jui-Hsien;Luci, Jeffrey J.;Lee, Ting-Yu;Swenson, Dale C.;Jensen, Jan H.;Messerle, Louis
Contributors: 化學系
Date: 2003
Issue Date: 2012-12-10T01:39:32Z
Publisher: American Chemical Society
Abstract: Reduction of the organoditantalum allene complex (η-C5Me4R)2Ta2(μ-X)X3(μ-η1,η3-C3H4) (R = Me (Cp*), Et; X = Cl, Br) with sodium amalgam leads to the propynylidene complex (η-C5Me4R)2Ta2(μ-H)2X2(μ-HCCCH) by a formal double 1,3-C−H activation of the allene ligand. The solid-state molecular structure contains a planar HCCCH ligand bridging, in parallel coordination mode, the two tantalum atoms, with the HCCCH and Ta atoms coplanar. Key structural features are a Ta−Ta distance of 2.8817(7) Å, propynylidene C−C−C angle of 153.7(13)°, C−C distance of 1.370(8) Å, Ta−C(central) distance of 2.194(9) Å, and Ta−C(terminal) distance of 1.970(9) Å. Molecular orbital calculations on the complex at the RHF/SBK(d) and B3LYP/LanL2dz levels of theory demonstrate that the propynylidene ligand is best viewed formally as an allenediylidene(4−) ligand bonded to two d0 tantalum atoms via two TaC(terminal) double bonds and an unusual three-center, two-electron bridge bond involving both tantalum atoms and a lone pair on the planar, tetracoordinate central carbon. There is no net Ta−Ta bonding based on the orbital analysis.
Relation: J. Am. Chem. Soc., 125(7): 1688-1689
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