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Synthesis, Structure, and Magnetic Properties of Low-Valent Triangulo Cobalt−Hydride Clusters [XCo3(μ-CO)3(PMe3)6]

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posted on 24.09.1997, 00:00 by Hans-Friedrich Klein, Michael Mager, Andreas Schmidt, Martina Hüber, Wolfgang Haase, Ulrich Flörke, Hans-Jürgen Haupt, Roman Boca
Syntheses and properties of low-valent clusters [X{Co(μ-CO)(PMe3)2}3], X = none (1), H (2), and H3 (3), are reported. All solids are isostructural as explicitly shown by single-crystal structure data. The molecular structures of C21H54Co3O3P6 (1) and C21H57Co3O3P6 (3) contain central Co3 units which form perfect equilateral triangles with Co−Co distances of 2.4055(5) and 2.432(1) Å, respectively. Both compounds crystallize in trigonal space group Rc, with Z = 6:  1, a = 10.678(1) Å, c = 52.298(11) Å; 3, a = 10.679(2) Å, c = 52.729(12) Å. Compounds 1 and 2 form a continuous range of solid solutions. Powder samples exhibit molecular paramagnetism of different extent:  At 298 K the effective magnetic moments for 13 are μeffB = 1.9, 3.1, and 2.7, respectively. The magnetic behavior could be rationalized in terms of the Curie−Weiss law for a one electron system (1) and two electron system (2). The two electron approximation has been discussed as well for 3 above 6.2 K. A description of the scope of exchange coupling is presented for 1.