Reactions of a Dihydrogen Complex with Terminal Alkynes: Formation of Osmium−Carbyne and −Carbene Derivatives with the Hydridotris(pyrazolyl)borate Ligand

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• 作者：Ruth Castro-Rodrigo ; Miguel A. Esteruelas ; Ana M. Ló ; pez ; Enrique On&#771 ; ate
• 刊名：Organometallics
• 出版年：2008
• 出版时间：July 28, 2008
• 年：2008
• 卷：27
• 期：14
• 页码：3547-3555
• 全文大小：300K
• 年卷期：v.27,no.14(July 28, 2008)
• ISSN：1520-6041

文摘

The dihydrogen complex [OsTp(η²-H₂)(κ¹-OCMe₂)(PⁱPr₃)]BF₄ (1; Tp = hydridotris(pyrazolyl)borate) reacts with tert-butylacetylene to give the hydride-carbyne derivative [OsHTp(CCH₂^tBu)(PⁱPr₃)]BF₄ (2). Similarly, the treatment of 1 with (trimethylsilyl)acetylene in the presence of methanol leads to [OsHTp(CCH₃)(PⁱPr₃)]BF₄ (3). In chloroform at 60 °C, complexes 2 and 3 evolve into the corresponding chloro derivatives [OsClTp(CR)(PⁱPr₃)]BF₄ (R = CH₂^tBu (4), CH₃ (5)), whereas in acetonitrile the carbenes [OsTp(CHR)(NCCH₃)(PⁱPr₃)]BF₄ (R = CH₂^tBu (6), CH₃ (7)) are formed. Complex 1 also reacts with phenylacetylene. The reaction initially gives [OsHTp(CCH₂Ph)(PⁱPr₃)]BF₄ (8). Subsequently, the insertion of a second molecule of alkyne into the Os−H bond of 8 and the migration of the resulting alkenyl group from the metal center to the carbyne carbon atom take place, to afford the carbene [OsTp{C(CH₂Ph)C(Ph)CH₂}(PⁱPr₃)]BF₄ (9). The metal center of 9 is saturated by means of a strong agostic interaction (r_bp = 0.4(1)) between the osmium atom and one of the ortho-CH bonds of the phenyl substituent of the alkenyl unit of the alkenylcarbene ligand. Treatment of 1 with methylpropiolate leads to the carbene [onstruct="bar">OsTp{CHCH₂C(O)OMe}(PⁱPr₃)]BF₄ (10) in a one-pot synthesis. Complexes 2, 4, 9, and 10 have been characterized by X-ray diffraction analysis.