Synthesis, Characterisation, Properties and X‐ray Structures of Cu II Coordination Compounds with 5,5′‐Dimethylbipyridine and Various Anions: Control of Stoichiometry and Structure by the Counterions

The synthesis, crystal structures, and electronic and magnetic properties of eight new Cu II compounds containing the ligand 5,5‐dimethyl‐2,2,′‐bipyridine (dmbpy) with the general formula [Cu II (dmbpy) x (L) 2 ] (where L = BF 4 − , CF 3 SO 3 − , NO 3 − , Br − , NCS − , N 3 − , HCOO − , and x = 1−3) are reported. The geometries of the Cu II ions include a four‐coordinate square‐planar polymeric compound [Cu(dmbpy)(N 3 ) 2 ] n ( 7 ), the five‐coordinate compounds, [Cu(dmbpy) 2 (C 2 H 6 O)](CF 3 SO 3 ) 2 ( 2 ), [Cu(dmbpy) 2 (NO 3 )](NO 3 ) ( 3 ), [Cu(dmbpy) 2 (Br)]Br ( 5 ), [Cu(dmbpy)(NCS) 2 ] n ( 6 ) and [Cu(dmbpy) 2 (HCOO)](CF 3 SO 3 ) ( 8 ), which have geometries ranging from square pyramidal to trigonal bipyramidal, and the six‐coordinate compounds [Cu(dmbpy) 3 ](BF 4 ) 2 (C 2 H 6 O) ( 1 ) and [Cu(dmbpy)(NO 3 ) 2 ] ( 4 ), which adopt an octahedrally based geometry. Except for compounds 3 and 4 , with nitrate as the anion, a variation of the copper/ligand ratios in the synthesis has no influence on the stoichiometry. The compounds have been characterised in detail by infrared, ligand field and EPR spectroscopy; the data are consistent with the single‐crystal X‐ray structures. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)