Metal-Assisted Opening of Intact P4 Tetrahedra.

The reactivity of ruthenium and manganese complexes bearing intact white phosphorus in the coordination sphere was investigated towards the low-valent transition-metal species [Cp'''Co] (Cp'''=η5 -C5 H2 -1,2,4-tBu3 ) and [L0 M] (L0 =CH[CHN(2,6-Me2 C6 H3 )]2 ; M=Fe, Co). Remarkably, and irrespective of the metal species, the reaction proceeds by the selective cleavage of two P-P edges and the formation of a square-planar cyclo-P4 ligand. The reaction products [{CpRu(PPh3 )2 }{CoCp'''}(µ,η1:4 -P4 )][CF3 SO3 ] (5), [{CpBIG Mn(CO)2 }2 {CoCp'''}(µ,η1:1:4 -P4 )] (6) and [{CpBIG Mn(CO)2 }2 {ML0 }(µ,η1:1:4 -P4 )] (CpBIG =C5 (C6 H4 nBu)5 ; L0 =CH[CHN(2,6-Me2 C6 H3 )]2 ; M=Fe (7 a), Co (7 b)), respectively, were fully characterized by single-crystal X-ray diffraction and spectroscopic methods. The electronic structure of the cyclo-P4 ligand in the complexes 5-7 is best described as a π-delocalized P4 2- system, which is further stabilized by two and three metal moieties, respectively. DFT calculations envisaged a potential intermediate in the reaction to form 5, in which a quasi-butterfly-shaped P4 moiety bridges the two metals and behaves as an η3 -coordinated ligand towards the cobalt center.

Pentaarylcyclopentadienyl Iron, Cobalt, and Nickel Halides.

The preparation of new stable half-sandwich transition metal complexes, having a bulky cyclopentadienyl ligand C5(C6H4-4-Et)5 (Cp(Ar1)) or C5(C6H4-4-nBu)5 (Cp(Ar2)), is reported. The tetrahydrofuran (THF) adduct [Cp(Ar1)Fe(µ-Br)(THF)]2 (1a) was synthesized by reacting K[Cp(Ar1)] with [FeBr2(THF)2] in THF, and its molecular structure was determined by X-ray crystallography. Complex 1a easily loses its coordinated THF molecules under vacuum to form the solvent-free complex [Cp(Ar1)Fe(µ-Br)]2 (1b). The analogous complexes [Cp(Ar1)Co(µ-Br)]2 (2), [Cp(Ar1)Ni(µ-Br)]2 (3), and [Cp(Ar2)Ni(µ-Br)]2 (4) were synthesized from CoBr2 and [NiBr2(1,2-dimethoxyethane)]. The mononuclear, low-spin cobalt(III) and nickel(III) complexes [Cp(Ar2)MI2] (5, M = Co; 6, M = Ni) were prepared by reacting the radical Cp(Ar2) with NiI2 and CoI2. The complexes were characterized by NMR and UV-vis spectroscopies and by elemental analyses. Single-crystal X-ray structure analyses revealed that the dimeric complexes 1a, 1b, and 3 have a planar M2Br2 core, whereas 2 and 4 feature a puckered M2Br2 ring.