Metallophilic attraction

The latest contributions of physicists and the theoretical chemists to the explanation of this phenomenon stem from the results of ab initio and density functional theory calculations., which refute the previous s-d hybridization proposed by the extended Htickel theory. They suggest that the metallophilic attraction can be considered a correlation effect strengthened by the relativistic effect, which is important in the case of gold. ... 

A particular case is that of d -d secondary interactions, first identified in gold compounds and described as aurophilic attraction [78-80], later generalized as metallophilic attraction [81]. This leads to supramolecular self-assembly in many gold compounds, especially when associated with three-center Au- -C Au bonds, and can be also found in other d metal compounds, such as silver, gold, and thallium complexes. Such supermolecules are illustrated by the quasi-cyclic pen-tamers Au5(Mes)5 and Cus(Mes)5, 33, and the tetramer Ag4(Mes)4, 34 [82]. 

Catalano et al. reported the synthesis and characterization of a new series of Pd°-based metallocrypates that bind Tl1 ion in the absence of attractive ligand interactions through metal-lophilic connections. The cationic species have been characterized by a variety of methods and have considerable stability. From the solid-state structural data it is apparent that interaction of the metal atoms with one another is the dominant bonding interaction within the metallocryptate cavity. The characterization of complexes supports the concept of metallophilic behavior as a fundamental component of bonding in closed-shell systems. These materials may ultimately serve as prototypical systems for detection of closed-shell ions 946... 

Probably the most useful method for preparing polymeric materials through unsupported metallophilic interactions is an acid-base reaction. In these, basic gold(I) precursors react with metallic Lewis acids, forming supramolecular networks via acid-base stacking. The stability of these systems can be related to the ionic interactions nevertheless, the dispersion forces and relativistic effects can also be invoked to explain the formation of these systems, and in some occasions, these effects are even more important than the electrostatic attractions in determining the structural motifs. 

As described above, among the several closed-shell metal ions that form luminescent supramolecular entities with gold, thallium(I) forms the most numerous examples. While aurophilic attractions can be considered the upper extreme of the metallophilic interactions (with values up to 46 kJ mol-1), intermetallic contacts involving T1(I) centers appear as the weakest ones (even <20 kJ mol-1),46 which is explained by the enhancement of the Au---Au interactions and the weakening of the Van der Waals attractions between the s2 metal atoms produced by the relativistic effects.47 Nevertheless, the complexes in which this interaction appears are surprisingly stable, with additional electrostatic, packing forces, or the ligand architecture, responsible for this fact. 

A new series of metallocryptates that bind T1(I) ion in the absence of attractive ligand interactions through metallophilic connections has been synthesised by Catalano et al Vppt of4436 Hz and /ptxe of 5560 Hz have been measured for [Pt2Tl(2,9-bis(diphenylphosphino)-1,10-phenathroline)3](NO3) compound the corresponding J values found for [Pt2Tl(6,6 -bis(diphenylphosphino)-2,2 - bi-pyridine)3](N03) were 4436 and 6100 Hz, respectively. 

Closed-Shell Interactions. - Numerous studies appeared during the period on closed-shell interactions, notably on the metallophilic attraction221 between d10 cations, such as Ag(I) or Au(I). Look for the symbol dl0-d10 in Table 2. The attractions between compounds of the elements in Main Groups 15 and 16 were also performed.222 The largest contribution was found to be the dispersion one but also the ionic contributions (virtual excitations of type A- A, B- >A were found to contribute.223... 

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