Stable Agostic (C-H···M) closo-Irida- and closo-Rhodacarboranes with ,
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- 作者：Alexander V. Safronov ; Tatiana V. Zinevich ; Fedor M. Dolgushin ; Oleg L. Tok ; Evgenii V. Vorontsov ; and Igor T. Chizhevsky
- 刊名：Organometallics
- 出版年：2004
- 出版时间：October 11, 2004
- 年：2004
- 卷：23
- 期：21
- 页码：4970 - 4979
- 全文大小：200K
- 年卷期：v.23,no.21(October 11, 2004)
- ISSN：1520-6041
文摘
Agostic (C-H···M) complexes [closo-3,3-(
,
2-C8H13)-1,2-
-(ortho-xylylene)-3,1,2-IrC2B9H9](5) and [closo-3,3-(,2-C8H13)-1,2--(ortho-xylylene)-3,1,2-RhC2B9H9] (9), stable in the solidstate, have been prepared via the reaction of [M(4-COD)Cl]2 (M = Ir, Rh) with the K+ saltof the [nido-7,8--(ortho-xylylene)-7,8-C2B9H10]- anion and characterized by a combinationof analytical (in the case of 5) and multinuclear NMR data, including a single-crystal X-raydiffraction study of 5. The crystallographic study confirmed the agostic structure of 5 andrevealed that the orientation of the ,2-cyclooctenyl moiety relative to the carborane ligandis substantially influenced by the specific intramolecular C-H···
interaction between theagostic hydrogen and the -system of the cage aromatic substituent. In solution, 5 exhibitedboth "side-to-side" agostic hydrogen migration and reversible interconversion with [closo-3-(3-C8H13)-1,2--(ortho-xylylene)-3,1,2-IrC2B9H9] (8). The agostic rhodium complex (9), incontrast, converts irreversibly both in the solid state and in solution to its 3-cyclooctenylisomer [closo-3-(3-C8H13)-1,2--(ortho-xylylene)-3,1,2-RhC2B9H9] (11), which thus could beobtained as a pure solid. In solution, complex 11 is fluxional and shows an agostic C-H···Rhinteraction. The fluxional process involves the exchange between the endo hydrogen atoms,on one hand, and the exo and allyl hydrogens of the C8-ring, on the other hand, confirmedby 2D [1H-1H]-EXSY spectroscopy. Solution structures of the agostic complexes obtainedare discussed in detail on the basis of normal and low-temperature 1H and 13C/13C{1H} NMRspectroscopic data.
,2-C8H13)-1,2--(ortho-xylylene)-3,1,2-IrC2B9H9](5) and [closo-3,3-(,2-C8H13)-1,2--(ortho-xylylene)-3,1,2-RhC2B9H9] (9), stable in the solidstate, have been prepared via the reaction of [M(4-COD)Cl]2 (M = Ir, Rh) with the K+ saltof the [nido-7,8--(ortho-xylylene)-7,8-C2B9H10]- anion and characterized by a combinationof analytical (in the case of 5) and multinuclear NMR data, including a single-crystal X-raydiffraction study of 5. The crystallographic study confirmed the agostic structure of 5 andrevealed that the orientation of the ,2-cyclooctenyl moiety relative to the carborane ligandis substantially influenced by the specific intramolecular C-H··· interaction between theagostic hydrogen and the -system of the cage aromatic substituent. In solution, 5 exhibitedboth "side-to-side" agostic hydrogen migration and reversible interconversion with [closo-3-(3-C8H13)-1,2--(ortho-xylylene)-3,1,2-IrC2B9H9] (8). The agostic rhodium complex (9), incontrast, converts irreversibly both in the solid state and in solution to its 3-cyclooctenylisomer [closo-3-(3-C8H13)-1,2--(ortho-xylylene)-3,1,2-RhC2B9H9] (11), which thus could beobtained as a pure solid. In solution, complex 11 is fluxional and shows an agostic C-H···Rhinteraction. The fluxional process involves the exchange between the endo hydrogen atoms,on one hand, and the exo and allyl hydrogens of the C8-ring, on the other hand, confirmedby 2D [1H-1H]-EXSY spectroscopy. Solution structures of the agostic complexes obtainedare discussed in detail on the basis of normal and low-temperature 1H and 13C/13C{1H} NMRspectroscopic data.