A Planar Tetracoordinate Carbon and Unusual Bonding in an Organodimetallic Propynylidene Complex Arising from Double C-H Activation of an Allene Ligand
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- 作者：Jui-Hsien Huang ; Jeffrey J. Luci ; Ting-Yu Lee ; Dale C. Swenson ; Jan H. Jensen ; and Louis Messerle
- 刊名：Journal of the American Chemical Society
- 出版年：2003
- 出版时间：February 19, 2003
- 年：2003
- 卷：125
- 期：7
- 页码：1688 - 1689
- 全文大小：132K
- 年卷期：v.125,no.7(February 19, 2003)
- ISSN：1520-5126
文摘
Reduction of the organoditantalum allene complex (
-C5Me4R)2Ta2(
-X)X3(-1,3-C3H4) (R = Me (Cp*), Et; X = Cl, Br) with sodium amalgam leads to the propynylidene complex (-C5Me4R)2Ta2(-H)2X2(-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 Ta=C(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.
-C5Me4R)2Ta2(-X)X3(-1,3-C3H4) (R = Me (Cp*), Et; X = Cl, Br) with sodium amalgam leads to the propynylidene complex (-C5Me4R)2Ta2(-H)2X2(-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 Ta=C(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.