Study of the Nature of Closed-Shell Hg^II···M^I (M = Cu, Ag, Au) Interactions

Abstract

Heteronuclear complexes PPh 2 ) 2 ]X (M = Au, X = ClO 4 (1); M = Ag, X = BF 4 (2); M = Ag, X = CF 3 CO 2 (3); M = Cu, X = Br (4)) were prepared by the treatment of [Hg(o-C 6 H 4 PPh 2 ) 2 ] with one equivalent of the corresponding coinage metal salt. Their crystal structures, determined by X-ray diffraction methods, display Hg II ··· M I (M = Au, Ag, Cu) contacts. Ab initio calculations show similar interaction energies (ca. 40 kJ·mol −1 ) and similar origin (dispersive forces) for these Hg···Au, Hg···Ag, and Hg···Cu interactions. ■ INTRODUCTIONNowadays, relativistic effects have shown an enormous importance to understand the chemical and physical properties of the heaviest 6s transition and post-transition metallic elements. From them, the element whose physical and chemical properties are more influenced by these effects is gold. 1−3 Probably, the most important structural consequence of the relativistic effects in gold is the high tendency to form closedshell interactions between gold(I) centers. This type of interactions were first described by Schmidbaur in 1988, 4 and subsequently, theoretical studies quantified the strength of these interactions up to −57 kJ·mol −1 , a surprisingly strong value, from which a non-negligible 26% is due to relativistic effects. 5 These strong interactions made possible a high number of structural motifs, 2,6 and in addition, parallel to this, the complexes often displayed interesting optical properties. 7−9 In the case of other heavy atoms, although the contraction of the radius due to the relativistic effects is not so important as in gold, these effects also play an important role in their properties. 10−14 Also, more recent studies on the relativity of the lead−acid or mercury batteries attribute a non-negligible 80% or 30%, respectively, of the electromotoric forces to the relativistic effects. 15,16 On the other hand, a logical next step in these studies was the study of the relativity in heteronuclear systems in which different metals maintain noncovalent interactions between them and in which at least one of them is a heavy 6s element, preferably gold. The synthesis of these complexes has been possible, making use of different synthetic strategies (acid− base, transmetalation, etc.). In such a way, a good number of heterometallic gold(I) compounds were described in which gold maintains an interaction with different closed shell ions such as Ag I , Bi III , Tl I , or Cu I , among others. 17−23 Thus, for instance, with the, in principle, more favorable coinage congeners, the energy of Au I ···Ag I and Au I ···Cu I contacts has been theoretically estimated to be 22 and 17 kJ·mol −1 , respectively. Besides, both of them have in common a high electronic correlation contribution probably induced by the relativistic effects present in gold. 24 In addition, the importance of the dispersive-type forces is evident in the intermetallic acid−base interactions that take place between gold(I) and thallium(I) or bismuth(III), which are, in both cases, around 20% of the total inter...

Role of Dispersion in Metallophilic Hg···M Interactions (M = Cu, Ag, Au) within Coinage Metal Complexes of Bis(6-diphenylphosphinoacenaphth-5-yl)mercury

“…Very recently, López-de-Luzuriaga et al prepared a series of coinage metal complexes with a bis­(diphenyl-phosphinobenzene)­mercurial ligand. In the complex [( o -C 6 H 4 PPh 2 ) 2 Hg·CuBr] ( III ), the Hg···Cu interatomic distances of 2.8656(5) and 2.8619(5) Å are in the midrange . Concomitantly, we published a related bis­(6-diphenylphosphinoacenaphth-5-yl)­mercury ligand ( 1 ), which undergoes complex formation with the closed-shell metal ions M = Hg­(II), Ag­(I), and Au­(I) .…”

The Pincer Platform Beyond Classical Coordination Patterns

“…The authors analyzed the Hg–M interactions by means of ab initio calculations on suitable model compounds and concluded for all compounds similar metallophilic interactions originating from dispersive forces. [ 139 ] Note, the above mentioned dinuclear metal complexes, obviously, can also be described as Hg complexes with dianionic (bisphenylate) [X–M–X] (M = Au, Ag; Cu) pincer ligand. However, with respect to the synthesis strategy i.e.…”

Stimuli‐Responsive Dynamic Gold Complexes

“…The brightly luminescent gold–heterometal complexes [Au 2 M 2 (R) 4 (L) 2 ] n ( 6 , M = Ag or Cu, R = C 6 F 5 and L = N≡CMe, Scheme ) and {[Au(C 6 X 5 ) 2 ][Cu(N≡CR)(μ 2 ‐C 4 H 4 N 2 )]} n ( 7 , X = F, Cl; R = Me, Ph; Scheme ) also exhibit some redshifts in their emission maxima with decreasing temperature 18,19…”