Phosphorus ylides are not only classical reagents in organic chemistry, but also play an increasingly important role as novel components in organometallic compounds. These metallic “ylide complexes” are either synthesized from “preformed ylides” and coordination compounds by addition or substitution, on the building block principle, or they are formed, in sometimes complicated reactions, from phosphanes, metal complexes, and C1 substrates in the coordination sphere of the metals. The resulting metal-carbon bonds are greatly modified in their properties by the immediate presence of the phosphonium center and often belong to the most stable of M-C structural units. The metal can come from any group of the periodic table, including the lanthanoids and actinoids. Numerous preparative and structural studies are gradually enabling us to gain an overall picture of the scope of this area of research.

Phosphorus Ylides in the Coordination Sphere of Transition Metals: An Inventory

Phosphor-Ylide sind nicht nur wichtige Reagentien der Organischen Chemie, sondern spielen in rasch wachsendem Umfang auch eine bedeutende Rolle als neuartige Komponenten metallorganischer Verbindungen. Diese „Ylid-Komplexe” von Metallen sind entweder nach dem Baukastenprinzip aus „vorgefertigten” Yliden und Koordinationsverbindungen der Metalle durch Addition oder Substitution erhaltlich oder entstehen erst in teilweise verwickelten Reaktionen aus Phosphanen, Metallkomplexen und C1-Substraten in der Koordinationssphare der Metalle. Die Metall-Kohlenstoff-Bindungen der Ylid-Komplexe sind in ihren Eigenschaften durch die direkte Nachbarschaft der Phosphonium-Zentren stark modifiziert und gehoren haufig zu den stabilsten M-C-Struktureinheiten. Das Metall kann aus beliebigen Bereichen des Periodensystems stammen, einschlieslich der Lanthanoide und Actinoide. Aus praparativen und strukturellen Studien last sich allmahlich ein uberblick uber die Moglichkeiten dieses Forschungsgebietes gewinnen.

Phosphor-Ylide in der Koordinationssphäre von übergangsmetallen: Eine Bestandsaufnahme†

New Complexes of Methyldiphenylphosphonium Cyclopentadienylide, Representative of a Class of Ligands Heretofore Much Neglected

Coordination complexes of aryl- and alkylphosphonium cyclopentadienylides (cyclopentadienylidene ylides), C5R4PR′R′′R′′′ (R = H, alkyl, aryl; R′, R′′, R′′′ = alkyl, aryl)

Reactions of Alkylidene-Bridged Cobaltadithiolene Complexes with Lewis Bases. Formation of M−S Sulfur Ylide Structure

Several new transition metal complexes of the cyclopentadienyl ylides (CpPPh3, CpSMe2, and CpPy are reported. Reactions of CpSMe2 with MnCl2, FeCl2, CoCl2 and NiX2 (where X=d or Br) leads to complexes in which the ylide:metal halide stoichiometry is 1:1. These complexes are assigned sandwich structures. Reaction of Pd(NO3)2 with CpSme2 yields a very air-sensitive compound having a unique (CpSMe2)3 Pd(NO3)2 stoichiometry. With HgX2 the CpSMe2 HgX2 (where X=Cl, Br, I) derivatives are formed; bonding of the mercury is shown for the iodide derivative to be at C-3 of the cyclopentadienyl ring. Reaction of CpPPh3 with FeCl2 produces two derivatives which appear to have stoichiometrieg unique in iron metallocene chemistry: (CpPPh3)Fe2 Cl4 and (CpPPh3)Fe2Cl4.

Mark Mojesky

Papers

Metallocene complexes of cyclopentadienyl ylides