THE ISOMORPHOUS STRUCTURES OF AMMONIUM TRANS-DIIODOBIS(ETHANEDIAL-DIOXIMATO-(1-)-N,N')COBALTATE(III) AND AMMONIUM TRANS-DIIODOBIS(ETHANEDIAL-DIOXIMATO-(1-)-N,N')RHODATE(III) - EXTENDED METALOXIMATE CHAINS WITH A NOVEL =I-M-I=I-M-I= ZIGZAGGED STRUCTURE

The ammonium salts of the complex anions trans-diiodobis(ethanedial-dioximato)-cobaltate(III), [CoI2(GH)2]-, and trans-diiodobis(ethanedial-dioximato)rhodate(III). [RhI2(GH)2]- (GH- = ethanedial dioximate or glyoximate), have been synthesized and their structures determined from single crystal X-ray diffraction data at room temperature. The crystals of the two salts are monoclinic, space group C2/c. NH4[CoI2(GH)2] (I) crystallizes as dark-brown prisms with a greenish reflectance; its crystal data are: C4Hl0CoI2N5O4, Mr = 504.90; α = 8.910(6), b = 11.700(9), c = 11.691(6) Å; β = 93.55(5); V = 1216.4 Å3;Z= 4; Dc = 2.78 Mg m3 NH4[RhI2(GH)2] (II) crystallizes as yellow-brown blocks with crystal data: C4H10I2N5O4Rh, Mr = 548.88; α = 9.038(4). b = 11.949(5), c = 11.770(3) Å; β = 95.54(3); V = 1265.16 Å3; Z = 4; Dc = 2.87 Mg m3. The two structures were refined to a final Rw = 0.045 for 1209 observed independent reflections and 95 parameters for I, and to a final Rw = 0.040 for 1922 observed independent reflections and 87 parameters for II. The coordination geometry around Co or Rh in the anionic complexes is a distorted (4 + 2) octahedron of four equatorial chelating N atoms and two apical iodides. The H atoms of the hydroxyl groups are involved, as usual, in intramolecular O-H-O bridges with uniform 0…0 separations of 2.582 Å for I, and 2.713 Å for II. The rectilinear I-Co-I or I-Rh-I triads form “infinite” zigzag chains extending parallel to the αb plane, with a weak I…I contact of 3.988 Å for I, and 4.010 Å for II. © 1990, Walter de Gruyter. All rights reserved.