Coordinative Behaviour of Tridentate NS2-Donor Ligands with Cadmium: Synthesis and Crystal Structures of New Complexes

Abstract

The reaction of cadmium salts with various amounts of the tridentate NS 2 -chelating ligands 1-(2-mercapto-acetophenone)-4-triphenylmethylthiosemicarbazone (H 2 L 1 ) and 1-(5-mercapto-3-methyl-1-phenylpyrazole-4-carboxaldehyde)-4-triphenyl-methylthiosemicarbazone (H 2 L 2 ) in the presence of bases like N-methylimidazole (N±MeIm), pyridine (py) or triethylamine (Et 3 N) provided a series of novel mono-, di-, tri-and heptanuclear cadmium complexes. They are of the general formulas [CdL 1 (N±MeIm)] 2 (1), [CdL 1 (py)] 2 (2), [CdL 2 (N±MeIm)] 2 (3), [CdL 2 (py) 3 ]0 .25 C 6 H 14´0 .5 py (4), [Et 3 NH] 2 [Cd 3 L 2 4 ]´7 MeOH (5), [Et 3 NH] 2 [Cd 3 L 1 4 ] (6) and [Et 3 NH] 2 [Cd 7 L 2 8 ]´14 MeOH (7). The compounds were characterized by elemental analysis, IR-and 1 H-NMR-spectroscopy. Single-crystal X-ray struc-ture analyses are reported for the complexes 2, 4, 5 and 7. While 2 has a dimeric structure where each cadmium ion is pentacoordinated in a N 2 S 3 -environment, 4 consists of a monomeric cadmium center with distorted octahedral N 4 S 2coordination. The complexes 5 and 7 exhibit new structural types for tri-and heptanuclear cadmium compounds. It is shown that sulfur bridging might proceed via arylthiolates, iminothiolates or even both functions of the ligand. Aggregation is influenced by various factors like solvents, counterions and ligand properties.Koordinationsverhalten tridentater NS 2 -Donor-Liganden mit Cadmium: Synthese und Kristallstrukturen neuer Komplexverbindungen Inhaltsu È bersicht. Die Reaktion von Cadmiumsalzen mit unterschiedlichen Mengen der dreifach chelatisierenden Liganden 1-(2-Mercapto-acetophenon)-4-triphenylmethylthiosemicarbazon (H 2 L 1 ) und 1-(5-Mercapto-3-methyl-1phenylpyrazole-4-carboxaldehyde)-4-triphenylmethylthiosemicarbazone (H 2 L 2 ) in Gegenwart verschiedener Basen wie N-Methylimidazol (N±MeIm), Pyridin (py) oder Triethylamin (Et 3 N) ergab eine Reihe neuer mono-, di-, triund heptanuklearer Cadmiumkomplexe mit folgenden Strukturformeln: [CdL 1 (N±MeIm)] 2 (1), [CdL 1 (py)] 2 (2), [CdL 2 (N±MeIm)] 2 (3), [CdL 2 (py) 3 ]´0.25 C 6 H 14´0 .5 py (4), [Et 3 NH] 2 [Cd 3 L 2 4 ]´7 MeOH (5), [Et 3 NH] 2 [Cd 3 L 1 4 ] (6) und [Et 3 NH] 2 [Cd 7 L 2 8 ]´14 MeOH (7). Die Verbindungen wurden durch Elementaranalysen, IR-und 1 H-NMR-Spektroskopie charakterisiert. Ro È ntgenstrukturanalysen wurden fu È r die Komplexe 2, 4, 5 und 7 durchgefu È hrt. Wa È hrend 2 eine dimere Struktur hat, in der jedes Cadmiumatom in einer N 2 S 3 -Umgebung fu È nffach koordiniert ist, ist 4 ein Monomer mit einer verzerrt oktaedrischen N 4 S 2 -Koordination. 5 und 7 stellen neue Strukturtypen fu È r tri-und heptanukleare Cadmiumkomplexe dar. Die Verbru È ckung durch die Schwefelatome geschieht einerseits nur u È ber die Aryl-oder Iminothiolate und andererseits u È ber beide Funktionen des Liganden. Der Umfang der Aggregation wird dabei durch verschiedene Faktoren wie Lo È sungsmittel, Gegenionen und Ligandeigenschaften beeinfluût.

Homo- and Heteronuclear Group 12 Metallothionein Type B Cluster Analogs: Synthesis, Structure, 1H NMR and ESI-MS

“…26,27 Other structurally characterized Zn 3 S 3 metallacycle complexes have an additional μ 3sulfido, 28 μ 2 -alkylthiolato, 29−31 or bridging ligand between the metal atoms. 32 Structurally characterized trinuclear cadmium thiolate clusters have tricyclo[3.1.1.0 3,6 ] 33 or bicyclo[3.1.1] 34,35 Cd 3 S 4 cores, and there are no trinuclear mercury thiolate clusters in the Cambridge Structural Database. 24,25 Furthermore, there are no structurally characterized group 12 complexes with a M 4 S 5 core.…”

“…The smaller structurally characterized thiolate-bridged group 12 complexes commonly have monocyclic M 2 S 2 and M 4 S 4 or tricyclo[3.3.1.1]­M 4 S 6 (adamantyl) cores. , The only structurally characterized trinuclear zinc clusters with single alkylthiolato bridges between zinc atoms , were prepared with deprotonated ligands L2H and L3H (Figure b) and had half-chair and twist boat metallacycle conformations, respectively. , Other structurally characterized Zn 3 S 3 metallacycle complexes have an additional μ 3 -sulfido, μ 2 -alkylthiolato, − or bridging ligand between the metal atoms . Structurally characterized trinuclear cadmium thiolate clusters have tricyclo­[3.1.1.0 , ] or bicyclo[3.1.1] , Cd 3 S 4 cores, and there are no trinuclear mercury thiolate clusters in the Cambridge Structural Database. , Furthermore, there are no structurally characterized group 12 complexes with a M 4 S 5 core. However, we recently isolated a Hg­(II) complex with a bicyclic [3.3.3]­Hg 5 S 6 core and structural parallels to the type A MT clusters using L4H (Figure c) as the ligand .…”