CRYSTALLOCHEMISTRY OF NON-LINEAR PSEUDOHALIDES IN COPPER(II) COMPLEXES
Michal Dunaj - Jurco, Dusan Miklos, Ivan Potocnak
Department of Inorganic Chemistry, Slovak Technical
University Bratislava, 812 37 Bratislava, Slovak Republic
dunaj@cvt.stuba.sk
Keywords: crystallochemistry, non-linear pseudohalide,
copper(II) complexes, phenanthroline and bipyridine complexes
This contribution is a part of our study on synthesis, crystal chemistry and properties of copper compounds containing a constant cationic part ([Cu(phen)2]2+, [Cu(phen)]2+ or [Cu(bipy)2]2+, [Cu(bipy)]2+) and a variable anionic part with a slim (X-) and a bulky (Y-) pseudohalide anions coupled in an XY-pair (X-= CN-, NCO-, NCS- or N(CN)2-, combined with Y-= C(CN)3- or ONC(CN)2- = ndcm).
Both bulky ONC(CN)2- and C(CN)3- anions are known to have quite good coordination ability. Especially the nitrosodicyanomethanide anion is very interesting. It can be bonded to the central atom as end-O-bonded, end-N-bonded or after the nucleophilic addition reaction as an N,N'-chelate-bonded ligand. It can be also bonded in the outer coordination sphere as an anion. Compounds [Cu(bipy)(mcoe)(ndcm)] (I) [1] (mcoe = methyl(2-cyano-2-imidoxy ethaneimidate); [(ON)(NC)C-C(NH)(OCH3)]-) and [Cu(phen)2{ONC(CN)2}(H2O)][ONC(CN)2 (VI) are the first known examples where two nitrosodicyanomethanide anions are bonded in the same compound but in different modes:
i) only in the inner coordination sphere as end-O-bonded and as a part of the mcoe ligand,
ii) in the outer and inner coordination sphere as an uncoordinated anion and as end-O-bonded ligand.
In the [Cu(phen)2X]+ cation of the bis(phenanthroline) complexes the Cu(II) atom is five-coordinated, the slim anions enter the inner and the bulky anions the outer coordination sphere; [Cu(phen)2(CN)][C(CN)3].2H2O (II) [2], [Cu(phen)2(NCS)][C(CN)3] (III) [3]; [Cu(phen)2(N(CN)2)][C(CN)3] (IV) [4], [Cu(phen)2(NCS)][ONC(CN)2] (V) [5].
If the slim anion is missing, than in the [Cu(phen)2YS]+ cation (S= solvent) the Cu(II) atom is six-coordinated with two phenanthroline molecules, one bulky anion (ndcm) and one water molecule in the apices of a deformed tetragonal bipyramid; [Cu(phen)2{ONC(CN)2}(H2O)][ONC(CN)2] (VI) [6].
If the bulky anion is missing, a situation can encounter as in the above [Cu(phen)2X]+ cation in which the Cu(II) atom is five-coordinated by two phenanthroline molecules and one slim anion in a distorted trigonal bipyramidal arrangement with the anion in the equatorial plane; [Cu(phen)2(CN)]2(SCN)2(phen).5.5(H2O) (VII) [7] or as in the [Cu(phen)2X2] complex in which the Cu(II) atom is six-cordinated by two phenanthroline molecules and two slim anions in an elongated tetragonal bipyramidal arrangement with one anion in an equatorial and the second anion in an axial position; [Cu(phen)2(N(CN)2)2] (VIII) [8].
For the bis(bipyridine) complexes containing the [Cu(bipy2X]+ cation the crystal chemistry is analogous to that discussed for the bis(phenanthroline) complexes; [Cu(bipy)2(NCS)][C(CN)3] (IX) [9], [Cu(bipy)2(NCO)][C(CN)3] (X) [10].
In the compounds containing the [Cu(bipy)2Y]+ cation the Cu(II) atom is five-cordinated by two bipyridine molecules and one bulky anion forming a distorted trigonal bipyramid with the {CuN5} chromophore [Cu(bipy)2{C(CN)3}][C(CN)3] (XI) [11]. The solvent molecule does not enter the coordination sphere to take up a sixth coordination position as happened in the analogical above case of the phenanthroline complex (VI);
In the (mono)bipyridine complexes the nucleophilic addition reaction between the coordinated bulky nitrosodicyanomethanide anion and the solvent (methanol) molecule takes place and a new mcoe ligand is created. In the [Cu(bipy)(mcoe)X] complex the Cu(II) atom is five-coordinated, creating a distorted tetragonal-pyramidal {CuN5} chromophore; [Cu(bipy)(mcoe){N(CN)2}] (XII) [12]. Replacement of X= N(CN)2- in complex (XII) by Y= ndcm resulted in the compound [Cu(bipy)(mcoe)(ndcm)] (I) [1]. The same reaction between the above discussed particles was also described in the presence of Ni(II); [Ni(mcoe)2(H2O)2] (XIII) [13].
The details concerning stereochemistry including the modes of coordination polyhedra deformation and ORTEP drawings will be presented.