cis-(R'2PC2H4PR'2)PdH(SnR3) Complexes: Trapped Intermediates in the Palladium-Catalyzed Hydrostannation of Alkynes

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• 作者：Roman Trebbe ; Frank Schager ; Richard Goddard ; and Klaus-Richard P&ouml ; rschke
• 刊名：Organometallics
• 出版年：2000
• 出版时间：February 21, 2000
• 年：2000
• 卷：19
• 期：4
• 页码：521 - 526
• 全文大小：169K
• 年卷期：v.19,no.4(February 21, 2000)
• ISSN：1520-6041

文摘

The complexes (R'₂PC₂H₄PR'₂)Pd(C₂H₄) (R' = ⁱPr, ^tBu) react with R₃SnH (R = Me, ⁿBu) bydisplacement of the ethene ligand and oxidative addition of the Sn-H bond to generate thechelating phosphane stabilized cis Pd^II hydrido stannyl complexes (R'₂PC₂H₄PR'₂)PdH(SnR₃)(R' = ⁱPr (1), ^tBu (2)). Complex 1a (R' = ⁱPr, R = Me), containing the smallest substituents,is only transiently formed but has been detected at -80 C by NMR spectroscopy. It reactsfurther with Me₃SnH, even at -120 C, by eliminating hydrogen to give (dⁱppe)Pd(SnMe₃)₂(3). In contrast, the isolated (dⁱppe)PdH(SnⁿBu₃) (1b) is briefly stable at ambient temperature,whereas the sterically encumbered species (d^tbpe)PdH(SnR₃) (R = Me (2a), ⁿBu (2b)) arestable well above 100 C. The molecular structure of 2a has been determined by X-raycrystallography. Complex 2a reacts with 2 equiv of C₂R' '₂ (R' ' = CO₂Me) to give (d^tbpe)Pd(C₂R' '₂) (4) and predominantly the corresponding (E)-vinylstannane (E)-(R' ')(H)C=C(SnMe₃)(R' ') (E-5). Since 2a also catalyzes the hydrostannation of the alkyne, the cis Pd^II hydridostannyl complexes 1a,b and 2a,b represent trapped intermediates in the Pd-catalyzedhydrostannation of alkynes. The existence of the complexes also sheds light on the mechanismof the Pd-catalyzed degradation of R₃SnH into Sn₂R₆ and H₂.