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RESEARCH PRODUCT

[Cr(bpym)(C2O4)2]− in designing heterometallic complexes. Crystal structures and magnetic properties of PPh4[Cr(bpym)(C2O4)2]·H2O and [Ag(bpym)][Cr(C2O4)2](H2O)2]·2H2O (bpym=2,2′-bipyrimidine)

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Abstract The preparation, crystal structure and magnetic properties of PPh 4 [Cr(bpym)(C 2 O 4 ) 2 ]·H 2 O ( 1 ) and [Ag(bpym)][Cr(C 2 O 4 ) 2 (H 2 O) 2 ]·2H 2 O ( 2 ) (C 2 O 4  2− =oxalate dianion, bpym=2,2′-bipyrimidine and PPh 4  + =tetraphenylphosphonium cation) are described. The structure of 1 is made up of discrete (2,2′-bipyrimidine)bis(oxalato)chromate(III) anions, teraphenylphosphonium cations and uncoordinated water molecules. The structure of 2 consists chains of univalent silver cations bridged by bis-chelating 2,2′-bypyrimidine, cis -diaquabis(oxalato)chromate(III) anions and crystallisation water molecules. The chromium atom in 1 and 2 has a slightly distorted octahedral geometry with two bidentate oxalate groups ( 1 and 2 ), and one bidentate bpym ligand ( 1 ) or two cis -coordinated water molecules ( 2 ). The CrO(ox) bonds are in the ranges 1.951(3)–1.981(3) A ( 1 ) and 1.9575(12)–1.9585(14) A ( 2 ), values which are shorter than the CrO(w) bonds in 2 [1.9999(16) A]. The CrN(bpym) bond lengths are 2.064(4) and 2.090(4) A for 1 . The silver atom in 2 is disordered with two different four-coordinated environments from two bpym groups. One of these environments can be defined as a flattened tetrahedron with AgN(bpym) distances of 2.331(2) A (x2) and 2.360(2) A (x2) and the second one is distorted with values of the AgN(bpym) bonds in the range 2.132(18) and 2.59(2) A. The silver–silver separation across bridging bpym is 6.1854(8) A. Magnetic susceptibility measurements of 1 and 2 in the temperature range 1.9–290 K reveal the occurrence of weak antiferromagnetic interactions together with zero-field splitting effects. The use of the [Cr(bpym)(C 2 O 4 ) 2 ] − unit of 1 as a ligand towards different univalent and divalent metal ions is discussed in the light of the available structural information.