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Five new hetero-metallic nickel(II)–mercury(II) complexes, [(NiL 1 )HgCl 2 ] ( 1 ), [(NiL 1 ) 2 HgCl 2 ] ( 3 ), [(NiL 1 ) 2 Hg(N 3 ) 2 ] ( 4 ), [{(NiL 2 ) 2 Hg(N 3 )(μ 1,1 -N 3 )} 2 ] ( 5 ) and [{(NiL 2 ) 2 Hg(N 3 )(μ 1,1 -N 3 )HgCl 2 } 2 {Hg(N 3 )(μ 1,1 -N 3 )}] ( 6 ) have been synthesized by reacting metalloligands [NiL 1 ] or [NiL 2 ] (where H 2 L 1 is N,N′-bis(salicylidene)-1,2-ethylenediamine and H 2 L 2 is N,N′-bis(salicylidene)-1,3-propanediamine) with HgX 2 (X − = Cl − or N 3 − ) at different molar ratios. All five complexes have been characterised by X-ray single-crystal structural, elemental and spectroscopic analyses. In complex 1 , the Hg(II) ion is coordinated to two phenoxido oxygen atoms of one [NiL 1 ] moiety and two terminal chloride ions to form a NiHg dinuclear complex. In the trinuclear complexes 3 and 4 , the central Hg(II) ion is coordinated by two terminal [NiL 1 ] units through two phenoxido oxygens from each and two terminal chloride (in 3 ) or azide (in 4 ) ions. The centrosymmetric hexanuclear complex 5 consists of two trinuclear [(NiL 2 ) 2 Hg(N 3 )(μ 1,1 -N 3 )] units, where the phenoxido bridges connect two terminal Ni(II) atoms of the trinuclear units. In these trinuclear units, one azido ligand adopts a μ l,1 -briding mode between Hg and Ni whereas the other one is terminal. In the nonanuclear complex 6 , two tetranuclear [{(NiL 2 ) 2 Hg(N 3 )(μ 1,1 -N 3 )}HgCl 2 ] units are linked to a central Hg(II) positioned on a two fold axis, via chlorido, azido, and phenoxido bridges. The tetranuclear unit is formed by the addition of a HgCl 2 molecule to a trinuclear [(NiL 2 ) 2 Hg(N 3 )(μ 1,1 -N 3 )] unit, similar to that present in 5 . Complex 5 shows weak ferromagnetic interactions ( J = +2.1 cm −1 ) between the two octahedral Ni(II) ions through double phenoxido bridges with a Ni–O–Ni bond angle of 95.87(11)°. [ABSTRACT FROM AUTHOR]

Abstract: Two phenoxido bridged dinuclear Cu(II) complexes, [Cu2(L1)2(NCO)2] (1), and [Cu2(L2)2(NCO)2]·2CH3OH (2), have been synthesized using the tridentate reduced Schiff-base ligands 2-[(2-dimethylamino-ethylamino)-methyl]-phenol (HL1) and 2-[(2-diethylamino-ethylamino)-methyl]-phenol (HL2) respectively. Re-crystallization of compound 2 from dichloromethane produced desolvated complex [Cu2(L2)2(NCO)2] (3). The compounds 2 and 3 are pseudopolymorphs or solvomorphs which differ in the crystal system (orthorhombic, Pbca for 2 and monoclinic, P21/n for 3). The complexes have been characterized by X-ray structural analyses and spectroscopic methods. In all three complexes Cu(II) is penta-coordinated having the geometry intermediate between distorted square pyramid and trigonal bipyramid with Addison parameter (τ)=0.33, 0.48 and 0.53 for 1, 2 and 3 respectively. Using 3,5-di-tert-butylcatechol (3,5-DTBC) as the substrate, the catecholase activity of complexes 1 and 2 has been studied in methanol solution; compound 2 shows slightly higher catecholase activity (k cat =98.4h−1) than compound 1 (k cat =64.2h−1). [Copyright &y& Elsevier]

Abstract: Three new trinuclear hetero-metallic copper(II)–cadmium(II) complexes [(CuL)2Cd (NCS)2] (1A and 1B), [(CuL)2Cd(NCO)2] (2) have been synthesized using [CuL] as so-called “ligand complex” (where H2L= N,N′-bis(salicylidene)-1,3-propanediamine) and structurally characterized. Crystal structure analyses reveal that all three complexes have trinuclear entity in which two square planar [CuL] units are bonded to a cadmium ion through double phenoxido bridges. The Cd(II) is in a six-coordinate distorted octahedral environment being bonded additionally to two mutually cis nitrogen atoms of terminal thiocyanate (in 1A and 1B) and cyanate (in 2). Complexes 1A and 1B have the same molecular formula but crystallize in different monoclinic unit cells (P21/c for 1A and P21/n for 1B) and can be considered as polymorphs. On the other hand, complex 2 is crystallized only in one form and its conformation is similar to that observed in 1A. A theoretical investigation shows that 1A is slightly more (2.25kcal/mol) stable than 1B. However, in the crystal lattice, 1A establishes a C–H/π interaction while 1B interacts through a C–H···S hydrogen bond to form dimer and the more favorable dimerization energy in the later (ca. 3kcal/mol) compensates the difference in the relative energy of the polymorphs. Complex 2 crystallizes only in one form and conformation of the molecule is similar to 1A. Analyses of the noncovalent interactions of 2 show a weakening of the dimerization energy compared to 1A or 1B. Moreover, the H-bonding interaction that facilitates the formation of 1B is unlikely to be established in 2. Therefore this polymorph is not isolated. [Copyright &y& Elsevier]