New Lithium Phosphonium Diylides: A Methylene and a Cyclopentadienyl Moiety as Ylidic Coordination Sites

• Published in: Organometallics Vol. 31; no. 11; pp. 4259 - 4266
• Main Authors: Lichtenberg, Crispin, Hillesheim, Nina S, Elfferding, Michael, Oelkers, Benjamin, Sundermeyer, Jörg
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 11.06.2012; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Chemistry, Organic; Physical Sciences; Science & Technology; COPPER(I) COMPLEXES; RAY CRYSTAL-STRUCTURES; OLIGOMERIC CHAIN-STRUCTURES; MOLECULAR-STRUCTURES; STRUCTURAL-CHARACTERIZATION; DINUCLEAR GOLD(I); METHYLDIPHENYLPHOSPHONIUM CYCLOPENTADIENYLIDE; OXIDATIVE ADDITION; WITTIG REACTIONS; SOLID-STATE
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om201182y

A set of lithium phosphonium diylides Li[CH2-PR2-CpX] (9–12; CpX = C5Me4, C5H3 tBu, R = Ph, Me) is presented. Two of the lithium complexes were characterized by means of single-crystal X-ray analysis, revealing a dimeric head-to-tail arrangement in the solid state. The coordination behavior of 9–12 in the liquid phase is solvent dependent. These lithium phosphonium diylides exist as contact ion pairs in benzene and as solvent-separated ion pairs in THF solutions. Phosphonium salts [H3C-PR2-CpXH)]+I– (1–4) are starting materials for the syntheses of the title compounds and exist as mixtures of isomers due to [1,5]-prototropic rearrangements. The dynamic behavior in solution has been investigated. Two different routes allow access to title compounds 9–12. Reactions of 1–4 with 2 equiv of nBuLi give 9–12 in a one-pot synthesis. In an alternative two-step route, dehydrodehalogenation of 1–4 with KH gives the corresponding phosphonium ylides 5–8. Two of these phosphonium ylides were characterized by single-crystal X-ray analysis. In one case two different conformers were obtained.