Synthesis, Electronic Structure, and Reactivity of Strained Nickel-, Palladium-, and Platinum-Bridged [1]Ferrocenophanes
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- 作者：Inmaculada Matas ; George R. Whittell ; Benjamin M. Partridge ; Jason P. Holland ; Mairi F. Haddow ; Jennifer C. Green ; Ian Manners
- 刊名：Journal of the American Chemical Society
- 出版年：2010
- 出版时间：September 29, 2010
- 年：2010
- 卷：132
- 期：38
- 页码：13279-13289
- 全文大小：431K
- 年卷期：v.132,no.38(September 29, 2010)
- ISSN：1520-5126
文摘
The group 10 bis(phosphine)metalla[1]ferrocenophanes, [{Fe(ηp>5 p>-C5H4)2}M(Pn-Bu3)2] [M = Ni (4a), Pd (4b), and Pt (4c)], have been prepared by the reaction of Li2[Fe(ηp>5 p>-C5H4)2]·tmeda (5, tmeda = N,N,N′,N′-tetramethylethylenediamine) with trans-[MCl2(Pn-Bu3)2] [M = Ni (trans-6a) and Pd (trans-6b)] and cis-[PtCl2(Pn-Bu3)2] (cis-6c), respectively. Single crystal X-ray diffraction revealed highly tilted, strained structures as characterized by α angles of 28.4° (4a), 24.5° (4b), and 25.2° (4c) and a distorted square planar environment for the group 10 metal center. UV/visible spectroscopy and cyclic voltammetry indicated that all three compounds had smaller HOMO−LUMO gaps and were more electron-rich in nature than ferrocene and other comparable [1]ferrocenophanes. DFT calculations suggested that these differences were principally due to the electron-releasing nature of the M(Pn-Bu3)2 metal−ligand fragments. Attempts to induce thermal or anionic ring-opening polymerization of 4a−c were unsuccessful and were complicated by, for example, competing ligand dissociation processes or unfavorable chain propagation. In contrast, these species all reacted rapidly with acids effecting clean extrusion of the bis(phosphine)metal fragment. Carbon monoxide inserted cleanly into one of the palladium−carbon bonds of 4b to afford the ring-expanded, acylated product [{Fe(ηp>5 p>-C5H4)(ηp>5 p>-C5H4)(CO)}Pd(Pn-Bu3)2] (10). The nickel analogue 4a, however, afforded [Ni(CO)2(Pn-Bu3)2] whereas the platinum-bridged complex 4c was inert. Remarkably, all compounds 4a−c were readily oxidized by elemental sulfur to afford the [5,5′]bicyclopentadienylidene (pentafulvalene) complexes [{ηp>4 p>:ηp>0 p>-C5H4(C5H4)}M(Pn-Bu3)2] [M = Ni (11a)] and [(ηp>2 p>-C10H8)M(Pn-Bu3)2] [M = Pd (11b) and Pt (11c)] by a formal 4-electron oxidation of the carbocyclic ligands. Compounds 11b and 11c represent the first examples of [5,5′]bicyclopentadienylidene as a neutral ηp>2 p>-ligand. The relative energies of ηp>2 p>-coordination with respect to that of ηp>4 p>:ηp>0 p> bonding were investigated for 11a−c by DFT calculations.