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Paramagnetism of Tetranuclear Complexes between TCNX Ligands (TCNE, TCNQ, TCNB) and Four Pentaammineruthenium or Dicarbonyl(pentamethylcyclopentadienyl)manganese Fragments

, , , and . Inorganic Chemistry, 36 (15): 3248--3252 (1997)
DOI: 10.1021/IC960998S

Abstract

Tetranuclear (μ4-TCNX)Ru(NH3)54(A)8 and (m4-TCNX)Mn(CO)2(C5Me5)4 A = PF6 or CF3SO3; TCNX = TCNE (tetracyanoethene), TCNQ (7,7,8,8-tetracyano-p-quinodimethane), or TCNB (1,2,4,5-tetracyanobenzene) were studied by variable-temp. (2-300 K) SQUID susceptometry. Mono- and dinuclear (PhCN)Ru(NH3)5(PF6)2 (PhCN = benzonitrile) and (μ-L)Ru(NH3)52(PF6)4 (L = 1,4-dicyanobenzene (terephthalodinitrile) or pyrazine) were studied for comparison and were essentially diamagnetic. Despite the even electron count, both the Ru and Mn tetranuclear complexes are paramagnetic, albeit with different spin-spin exchange coupling patterns. The Mn systems were characterized by exchange-coupled S = 1 states at the individual metal centers, whereas the magnetic behavior of the tetranuclear Ru compds. results from an exchange-coupling interaction between two S = 1/2 sites, identified as RuIII/RuII mixed-valence pairs. on SciFinder(R)

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