Transition Metal Complexes with cyclo-Triphosphorus (η3-P3) and tetrahedro-Tetraphosphorus (η1-P4) Ligands

Salts of 3d, 4d, and 5d metals in the presence of the ligands 1,1,1,-tris(diphenylphosphinomethyl)ethane (triphos) or tris (2-diphenylphosphinoethyl) amine (np₃) react with white phosphorus P₄ (or yellow As₄) to produce several mononuclear sandwich and dinuclear triple-decker sandwich complexes, which contain the unprecedented cyclo-triphosphorus (or cyclo-triarsenic) unit acting as a trihapto-ligand. In these complexes the metal atoms are bonded to the there phosphorus atoms of the phosphane ligand and to the three atoms of the cyclo-P₃ or cyclo-As₃ unit. The complexes are diamagnetic or have μ_eff-values corresponding to one or two unpaired electrons. The cyclo-P₃ ligand is coordinatively unsaturated as proved by the fact that the mononuclear sandwich compounds may form Lewis-base adducts with electron-acceptor fragments. Reaction of the complexes (np)₃M (M = Ni, Pd) with white P₄ leads to formation of diamagnetic compounds [(np₃)M(η¹-P₄)], in which the metal atom is bonded to the three phosphorus atoms of the np₃-ligand and in addition to one P atom of the intact P₄ molecule, which behaves as a monohapto-ligand. This article contains a review of the syntheses and structures of these complexes as well as a unified, albeit qualitative, approach to their bonding and properties.     

Komplexkatalyse. XXXII. Synthese und Charakterisierung von η3-Allyl-, η3-Crotyl-und η1,η2-Cyclooct-4(Z)-en-1-yl-nickel(II)-bis(brenzcate-chinato)-borat und ihre Eignung als Katalysatoren für die stereospezifische Butadienpolymerisation

Complex Catalysis. XXXII. Synthesis and Characterization of η³-Allyl-, η³-Crotyl-, and η¹,η²-Cyclooct-4(Z)-en-1-yl-nickel(II)-bis(brenzcatechinato)borate and their Suitability as Catalysts for the Stereospecific Butadiene Polymerization By reaction of [(η³-C₃H₅)₂Ni], [(η³-C₄H₇)₂Ni], and [Ni(cycloocta-1,5-diene)₂] with one equivalent bis(brenzcatechinato)boric acid HB(O₂C₆H₄)₂ in ether the complexes given in the title could be synthesized in good yields. The allyl complex [η³-C₃H₅NiB(O₂C₆H₄)₂] reacts with cycloocta-1,5-diene (COD) to give a cationic complex [η³-C₃H₅Ni(COD)]B(O₂C₆H₄)₂ and catalyses the 1,4-trans-polymerization of butadiene with an activity of ca. 150 ml C₄H₆/mol Ni · h and a selectivity of 78% under standard conditions at room temperature.     

One-Bond 13C, 13C-Spin Coupling in η4-, η3- and η2-Olefin Transition Metal Complexes

One-bond ¹³C, ¹³C-spin-coupling constants have been measured, with natural isotope abundance, in η⁴-diene, η³-allyl and η²-ene transition-metal carbonyl complexes. Typical values of ¹J(C,C) are given for Fe-, Ru- and Os-complexes with the three types of olefinic ligands. The effects of substituents and the structural significance of the C,C-coupling constants are discussed.