Silver-Phosphine Complexes of the Highly Methylated Carborane Monoanion [closo-1-H-CB11Me11]-

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• 作者：Adam J. Clarke ; Michael J. Ingleson ; Gabriele Kociok-Kö ; hn ; Mary F. Mahon ; Nathan J. Patmore ; Jonathan P. Rourke ; Giuseppe D. Ruggiero ; and Andrew S. Weller
• 刊名：Journal of the American Chemical Society
• 出版年：2004
• 出版时间：February 11, 2004
• 年：2004
• 卷：126
• 期：5
• 页码：1503 - 1517
• 全文大小：397K
• 年卷期：v.126,no.5(February 11, 2004)
• ISSN：1520-5126

文摘

The synthesis of the silver(I) salt of the highly methylated carborane anion [closo-1-H-CB₁₁Me₁₁]^- is described, Ag[closo-1-H-CB₁₁Me₁₁] 1, which in the solid state shows close intermolecular Ag···H₃Ccontacts. Addition of various monodentate phosphines to 1 results in the formation of the complexes (R₃P)Ag[closo-1-H-CB₁₁Me₁₁] [R = Ph, 2; cyclohexyl (C₆H₁₁), 3; (3,5-Me₂-C₆H₃), 4]. All these complexes showclose intermolecular Ag···H₃C contacts in the solid state that are considerably shorter than the sum of thevan der Waals radius of methyl (2.00 Å) and the ionic radius of silver(I) (1.29 Å). For 2 and 3 there areother close intermolecular Ag···H₃C contacts in the solid state, arising from proximate carborane anions inthe crystal lattice. Addition of methyl groups to the periphery of the phosphine ligand (complex 4) switchesoff the majority of these interactions, leaving essentially a single cage interacting with the cationic silver-phosphine fragment through three CH₃ groups. In solution (CD₂Cl₂) Ag···H₃C contacts remain, as evidencedby both the downfield chemical shift change and the significant line-broadening observed for the cagemethyl signals. These studies also show that the metal fragment is fluxional over the surface of the cage.The Ag···H₃C interactions in solution may be switched off by addition of a stronger Lewis base than [closo-1-H-CB₁₁Me₁₁]^-. Thus, addition of [NBu₄][closo-1-H-CB₁₁H₅Br₆] to 2 affords (Ph₃P)Ag[closo-1-H-CB₁₁H₅Br₆], while adding Et₂O or PPh₃ affords the well-separated ion-pairs [(Ph₃P)(L)Ag][closo-1-H-CB₁₁Me₁₁] (L= OEt₂ 5, PPh₃ 6,) both of which have been crystallographically characterized. DFT calculations on 2 (atthe B3LYP/DZVP level) show small energy differences between the possible coordination isomers of thiscompound, with the favored geometry being one in which the {(Ph₃P)Ag}⁺ fragment interacts with threeof the {BCH₃} vertices on the lower surface of the cage, similar to the experimentally observed structureof 4.