Abstract
AbstractThe reaction of [RhCl(PiPr3)2] (1) with 1,4‐C6H4(C≡CH)2 at 0°C leads almost quantitatively to the formation of the bis(alkyne) complex [(PiPr3)2ClRh‐(HC≡C6H4‐C≡CH)RhCl(PiPr3)2] (2). At elevated temperatures (THF, 60°C) it rearranges to give the isomeric bis(vinylidene) complex [(PiPr3)2ClRh‐(=C=CH‐C6H4‐CH=C=)RhCl(PiPr3)2] (3). A one‐pot synthesis of 3 is also described. Treatment of either 2 or 3 with pyridine affords the bis(alkynyl)dihydrido compound [(PiPr3)2(py)Cl(H)Rh(‐C≡C‐C6H4‐C≡C‐)Rh(H)Cl(py)(PiPr3)2] (4) in which both metal centers are octahedrally coordinated. Whereas the reaction of 2 with NaC5H5 produces the complex CsH5(PiPr3)Rh(HC≡C‐C6H4‐C≡CH)Rh(PiPr3)C5H5 (7), the bis(vinyl‐idene) isomer C5H5(PiPr3)Rh(=C=CH‐C6H4‐CH=C=)Rh(PiPr3)C5Hs (8) is obtained from 4 and NaC5H5. Electrophiles preferably attack the Rh=C bonds of 8 and thus on protonation with CF3CO2H the bis(vinyl) complex C5H5(PiPr3)(CF3CO2)‐Rh(Z,Z‐CH=CH‐C6H4‐CH=CH)Rh(O2CCF3)(PiPr3)C5Hs (Z‐9) is formed. In acetone solution, it rearranges to give the E isomer. Reaction of 8 with sulfur affords the bis(thioketene) complex C5H5(PiPr3)Rh(≡2‐C,S; η2‐C,S‐S=C=CH‐C6H4‐CH=C=S)‐Rh(PiPr3)C5H5 (12), for which only one diastereomer is observed. All attempts to prepare mononuclear rhodium compounds containing the diyne HC≡C‐C6H4‐G≡CH or the isomeric vinylidene: C=CH‐C6H4‐G≡CH as ligand failed.
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