Structural researches on the chelating behaviour of the biguanide ligand. The crystal structures of Co(C2H6N5)3 � 2H2O and Cu(C2H7N5)2CO3�4H20

Abstract

SummaryCrystals of the title compounds are both monoclinic, with unit cell dimensions: a = 9.293(5), b = i0.122(5), c = 16.737(7) •,/3 = 103.44(3) ° , Z = 4, space group P21/c for the cobalt derivative; a = 13.185(7), b = 17.546(8), c = 6.871(3) ~/3 = 107.01(4) ° Z --4, space group P21/n for the copper derivative. The structures were solved from diffractometer data by the heavy-atom technique for the first compound and by direct methods for the second compound. Refinement by block diagonal least-squares gave R = 5.9% for 3511 independent reflections and R = 8.8% for 2885 independent reflections for the cobalt and copper compound respectively. In both compounds the biguanide moiety behaves as a bidentate chelating ligand in a symmetrical tautomeric form, but it is deprotonated in the octahedral cobalt compound and neutral in the square planar copper compound.

The assignment and validation of metal oxidation states in the Cambridge Structural Database

“…Some caution should be exercised, however, since the BVS parameters for [Cu(3)(CF 3 ) 4 ] ®t for both Cu(3) and Cu(1). The ligand templates may fail to give the correct result if the original chemical and crystal connectivity were not matched, so that the charges are not carried over into the new connectivity: BGCUCB (Coghi et al, 1978), GEHDIG (Lei et al, 1988) and GEHDIG10 (Huang et al, 1990) suffer from this sort of error which is an unfortunate artefact of the recalculation procedure (x3).…”

Electronic structure and reactivity of guanylthiourea: A quantum chemical study

“…GTU has wide industrial applications,15 and also used as starting material for synthesis of supramolecular cages 16. Depending upon the pH of the medium and the nature of the metal ions, GTU is known to form varieties of complexes with transition metals in different coordination modes such as N,S17–19 and N,N 20–22. Neutral and anionic forms of GTU isomers which coordinate with metal ions have been studied to understand arrays of hydrogen‐bonding sites in crystal engineering.…”

Pharmacophoric Features of Biguanide Derivatives: An Electronic and Structural Analysis

“…21 Some of the metal complexes of biguanide include [Mn(big) 3 ] 4+ , B(big) 2 Cl, [TcO(big) 2 ] 3+ , [ReO(big) 2 ] 3+ , Co(big) 3 ‚2H 2 O, [Cu(big) 2 ] 2+ , etc. [22][23][24][25] The crystal structures of neutral biguanide, 26 biguanide‚ HCl, 27 biguanide‚2HCl, 28 and several metal complexes with biguanide derivatives are available. [21][22][23][24][25] The X-ray crystal structure of biguanide shows that structure 7 (Scheme 1) should be the most preferred structure, 26 without hydrogen on the bridging nitrogen (N4).…”

“…[22][23][24][25] The crystal structures of neutral biguanide, 26 biguanide‚ HCl, 27 biguanide‚2HCl, 28 and several metal complexes with biguanide derivatives are available. [21][22][23][24][25] The X-ray crystal structure of biguanide shows that structure 7 (Scheme 1) should be the most preferred structure, 26 without hydrogen on the bridging nitrogen (N4). The crystal structure of the HCl salt of biguanide (8) also does not show hydrogen on the bridging nitrogen (N4).…”

“…The anionic biguanides form complexes with transition metals . Some of the metal complexes of biguanide include [Mn(big) 3 ] 4+ , B(big) 2 Cl, [TcO(big) 2 ] 3+ , [ReO(big) 2 ] 3+ , Co(big) 3 ·2H 2 O, [Cu(big) 2 ] 2+ , etc. − The crystal structures of neutral biguanide, biguanide·HCl, biguanide·2HCl, and several metal complexes with biguanide derivatives are available. − The X-ray crystal structure of biguanide shows that structure 7 (Scheme ) should be the most preferred structure, without hydrogen on the bridging nitrogen (N4). The crystal structure of the HCl salt of biguanide ( 8 ) also does not show hydrogen on the bridging nitrogen (N4) …”