Phosphorus Analogues of [Ni(bpy)2]: Synthesis and Application in Carbon-Halogen Bond Activation.

The neutral, homoleptic pyridylphosphininenickel(0) complex [Ni(2-Py-4,6-Ph2-PC5H2)2] (1) has been obtained by reaction of the formal Ni(0) source [(IPr)Ni(H2C═CHSiMe3)2] with 2 equiv of 2-(2'-pyridyl)-4,6-diphenylphosphinine (L). Compound 1 can be oxidized both electrochemically and through the use of ferrocenium salts, to afford the corresponding Ni(I) complexes [1]BF4, [1(THF)]PF6, and [12](BArF4)2. The structures of these salts reveal an interesting dependence on the nature of the anion. While [1]BF4 and [1(THF)]PF6 show trigonal-bipyramidal coordination of Ni in the solid state, [12](BArF4)2 exists as a dinuclear Ni(I) complex and possesses a bridging phosphinine moiety in a rare µ2 mode. Reactions of 1 with halobenzenes highlight the noninnocent behavior of the aromatic phosphinine ligand, leading to the formation of oxidized Ni complexes but not to classical oxidative addition products. The reaction of 1 with bromobenzene affords the λ5 phosphinine 2 and the bipyramidal Ni(I) complex [1]Br, whereas a more unconventional oxidation product 3 is formed from the reaction of 1 and iodobenzene.

Heparin-associated thrombocytopenia: successful therapy with the heparinoid Org 10172 in a patient showing cross-reaction to LMW heparins.

A patient suffering from heparin-associated thrombocytopenia (HAT), recurrent arteriothromboses, and acute renal failure after treatment with standard heparin is described. He failed to improve when therapy was continued with low-molecular-weight (LMW) heparin (Fragmin, Kabi Pfrimmer, Erlangen, FRG). By means of the in vitro heparin-induced platelet activation (HIPA) assay it was shown that standard heparin and the LMW heparins Fragmin and Fraxiparin (Sanofi Labaz, Munich, FRG), as well as the enoxaparine Clexane (Nattermann, Cologne, FRG), all induced platelet activation with the patient's serum. In contrast, the LMW heparinoid Org 10172 (Organon, Oss, The Netherlands) did not cause platelet activation. When the patient was subsequently treated by parenteral administration of Org 10172 as anticoagulant over a period of several weeks the number of platelets rapidly increased and the patient almost completely recovered. This case shows that strong in vivo and in vitro cross-reactivity between standard heparin and LMW heparins may occur, but can be avoided by the use of a novel heparinoid, Org 10172. The HIPA assay provides a simple and sensitive laboratory method for the choice of an innocuous heparin or heparinoid for continued parenteral anticoagulation.