Divalent transition metal(II) complexes of two heterocyclic ligands with pendant pyridinyl groups: Synthesis, characterization and electrochemistry

Influence of the Number of Metallophilic Interactions and Structures on the Optical Properties of Heterometallic Au/Ag Complexes with Mixed-Donor Macrocyclic Ligands

“…The crystal structure of complex 2 is similar to the those previously described by us for the crown thiother derivatives [{Au­(C 6 F 5 ) 2 }­Ag­([9]­aneS 3 ) 2 ] 2 and both isomers of [{Au­(C 6 Cl 5 ) 2 }­Ag­([9]­aneS 3 )] 2 , with a linear Ag–Au–Au–Ag arrangement of metals formed thanks to a couple of Au···Ag interactions and an aurophilic contact of 2.7459(5) and 3.2633(4) Å, respectively (Figure ). These distances are intermediate between those found in the related complexes cited above [Au–Ag: 3.0763(4), 2.7501(2), and 2.6772(3) Å; Au–Au: 3.3702(3), 3.4136(1), and 3.0397(3) Å].…”

“…Moreover, the Ag–N quinoline lengths [2.261(5) and 2.274(5) Å in 3 ·THF; 2.423(4) and 2.434(5) Å in 4 ] are also shorter than the Ag–N macrocycle ones [2.482(6) and 2.512(5) Å in 3 ·THF; 2.591(5) and 2.605(5) Å in 4 ]. This fact is related to the existence of back-donating π-bond between the metal and the quinoline moiety, as has previously been observed by Wei et al in other complexes containing methylpyridine instead of methylquinoline as coordinating groups …”

“…The central core of this crystal structure is a tetranuclear [Au 2 Ag 2 (C 6 F 5 ) 4 ] unit that is connected to peripheral [Au­(C 6 F 5 ) 2 ] − and [Ag­( L 3 )] + fragments through unsupported aurophilic contacts and bridging Ag–S bonds, respectively. The Au–Au distance [2.8835(4) Å] is considerably shorter than that in 2 [3.2633(4) Å] or that in the related Au/Ag complexes with thio-crown ethers previously described by us [3.0397(3)–3.4136(1) Å]. , In fact, it is closer to the Au–Au distances usually found among tetranuclear [Au 2 Ag 2 (C 6 X 5 ) 4 ] units, which vary from 2.7853(14) to 3.1959(3) Å. ,− Both the Au–Ag [2.7084(6) and 2.7385(6) Å] and Ag–C ipso [2.548(8) Å] interactions within the [Au 2 Ag 2 (C 6 X 5 ) 4 ] core in 5 ·2THF are stronger than that in 2 [2.750(6) Å] but compare well with those described for complexes displaying such tetranuclear units [2.6607(15)–2.9478(7) and 2.422(4)–2.707(18) Å, respectively]. ,− Also, the argentophilic interaction of 3.0238(11) Å displays a normal distance for such tetranuclear [Au 2 Ag 2 ] core [2.8799(7)–3.2291(6) Å]. ,− As in the structures of 2 and 3 ·THF, the Ag­(I) centers of the [Ag­( L 3 )] + cations show a distorted square-pyramidal geometry with the nitrogen of the aromatic ring at the vertex (τ = 0.11) . The Ag–S distances are dissimilar, with two shorter [2.474(2) and 2.529(2) Å] and two longer [2.802(2) and 2.928(2) Å] distances, but there is no relationship between these values and the behavior of the sulfur atoms as terminal or bridging.…”

“…Each gold atom binds two pentafluorophenyl rings with typical Au–C bond distances, and displays its usual linear environment, which is slightly distorted, probably by the presence of a Ag···C ipso interaction of 2.750(6) Å. This contact is weaker than those found in some of the related crown thioether complexes [2.461(3)–2.695(6) Å], , with the only exception of [{Au­(C 6 Cl 5 ) 2 }­Ag­([14]­aneS 4 )], where the Ag···C ipso distance is 2.900(6) Å . Furthermore, the Ag···C ipso contact in 2 is longer than that in other complexes containing the tetranuclear [Au 2 Ag 2 ] ring in which the [Au­(C 6 X 5 ) 2 ] − units interacts with the silver­(I) centers through both Au···Ag and Ag···C ipso contacts [Ag···C distances vary from 2.422(4) in [Au 2 Ag 2 (C 6 Cl 2 F 3 ) 4 (THF) 2 ] n to 2.707(18) Å in [Au 2 Ag 2 (4-C 6 F 4 I) 4 (THF) 2 ] n .…”

“…For example, the crown thioethers 1,4,7-trithiacyclononane, 1,5,8,11-tetrathiacyclotetradecane and 1,4,7,10,13,16,19,22-octathiacyclotetracosane react with the polymeric compounds [{Au­(C 6 X 5 ) 2 }­Tl] n and [Au 2 Ag 2 (C 6 F 5 ) 4 (OEt 2 ) 2 ] n (X = Cl, F), leading to the formation of discrete or polymeric structures in which the nature of the macrocyclic ligand rules the dimensionality/nuclearity of the complexes obtained. Furthermore, macrocyclic ligands armed with pyridinyl groups (σ-donor and π-acceptor) as substituents that show strong binding ability with transition metal ions and are able to stabilize low oxidation states of some metal ions have the potential capability to coordinate to more than one metal center.…”