Heterometallic Cr−Mn Complexes Containing Cyanide and Oxalate Bridges

Three heterometallic Cr−Mn compounds, {Mn(μ-ox)0.5(H2O) [Cr(phen)(CN)4]}n·nH2O·2nCH3OH, (1), {Mn(μ-ox)0.5(H2O)[Cr(bpy)(CN)4]}n·2nH2O·nCH3OH, (2), and {Mn(μ-ox)0.5(bpy)[Cr(bpy)(CN)4]}n, (3) (ox = oxalate), containing
cyanide and oxalate bridges based on building blocks [Cr(L)(CN)4]- (L = phen and 2,2‘-bipyridine) have been
prepared. A new approach was first employed to synthesize ox-bridged compounds via facile oxidation-hydrolysis
reactions of diaminomaleonitrile. X-ray crystallography revealed that the structures of 1 and 2 are similar, where
cyano-bridged corrugated ladderlike chains are further connected through bis-bidentate oxalato bridges to unique
two-dimensional layered structures. Of note is that the introduction of 2,2‘-bipyridine led to an interesting cluster-based chainlike compound (3) with cyano-bridged squares [Mn2Cr2] extended by ox bridges. Magnetic studies
show antiferromagnetic (AF) interaction between cyano-bridged CrIII−MnII and ox-bridged MnII−MnII ions, with the
result that 1 and 2 exhibit AF ordering with spin-flop behaviors below 18 and 19 K, respectively.