Noncovalent Interactions in Organometallic Chemistry: From Cohesion to Reactivity, a New Chapter

Abstract

Metrics & More Article Recommendations * sı Supporting Information CONSPECTUS: Noncovalent interactions (NCIs) have long interested a vast community of chemists who investigated their "canonical categories" derived from descriptive crystallography, e.g., H-bonds, π−π interactions, halogen/chalcogen/tetrel bonds, cation−π and C−H−π interactions, metallophilic interactions in the broad sense, etc. Recent developments in theoretical chemistry have enabled the treatment of noncovalent interactions under new auspices: dispersion-force-inclusive density functionals have emerged, which are reliable for modeling small to large molecular systems. It is possible to perform the full analysis of the contributions of London, Debye, and Keesom forces, i.e., the main components of van der Waals forces, by the DFT-D and ab initio methods at a reasonable computational cost. Our research has been focusing for now 15 years on the role of NCIs in the cohesion of organometallic complexes. NCIs are not only effective in Werner's secondary coordination sphere but also in the metal's primary one. The stabilization of electron-unsaturated transition metal complexes by hemichelation, metal−metal donor−acceptor complexes, and self-aggregation of cationic Rh(I) chromophores have indeed outlined the significance of the London dispersion force as an attractive force operating throughout the whole molecule or molecular assembly. The recent outburst of interest in C−H bond functionalization led us to address the broader question of reaction and catalyst engineering: although one can now satisfactorily analyze bonding and molecular cohesion in transition-metalbased organometallic systems, can modern theoretical methods guide reactivity exploration and the engineering of novel catalytic systems? We addressed this question by investigating the ambiphilic metal−ligand activation/concerted metalation−deprotonation mechanism involved in transition-metal-catalyzed directed C−H bond functionalization. This endeavor was initiated having in scope the construction of a rationale for the transposition of 4−5d metal chemistry to earth-abundant 3d metals. In this base-assisted mechanism of C−H bond metalation, agostic interactions are necessary but not sufficient because C−H bond breaking actually relies on the attractive NCI coding of a proton-transfer step and the minimization of metal−H repulsion. This Account introduces the recent shift of our research toward the construction of an NCI-inclusive paradigm of chemical reactivity engineering based on experimental efforts propped up by state-of-the-art theoretical tools.

Beyond Steric Crowding: Dispersion Energy Donor Effects in Large Hydrocarbon Ligands

“…For the most part, these species are stabilized by large ligands which limit access to the reactive metal centers and prevent their association and further reaction. A variety of non-H···H dispersion effects had been recognized in several types of transition complexes, ,− for example, in certain nonbridged binuclear species such as hemichelated complexes and in species with closed-shell d 10 –d 10 metal interactions, and were thought to play a role during cyclometalation reactions in organometallic complexes , or in catalytic cycles. In contrast, interest in C–H···H–C dispersion-based interactions (Figure ) in sterically crowded transition-metal–organic derivatives has been slower to develop.…”

Inorganic–organic {dz2-MIIS4}⋯π-hole stacking in reverse sandwich structures: the case of cocrystals of group 10 metal dithiocarbamates with electron-deficient arenes

“…In the past five years, the demand for square-planar d 8 -metal complexes as sterically accessible sites involved in diverse noncovalent interactions has increased dramatically. [1][2][3][4][5][6][7][8][9][10][11][12] Despite their positive charges, these centers can function as d z 2-orbital centered nucleophiles (hereinafter d z 2-nucleophiles) toward various σ-hole donors (for a recent review see ref. 13).…”

Halogen Bonding Involving Gold Nucleophiles in Different Oxidation States

“…According to the recently refined IUPAC recommendations, “in XB, the electrophilic region of a halogen atom (σ-hole) attractively interacts with any nucleophilic region (or regions in cases of bi- , or polyfurcated XB); the electrophilic region is not necessarily electropositive, but it should be less electronegative than the partner”. This type of noncovalent interactions − has found applications in various fields of chemical science, such as supramolecular chemistry, − crystal engineering, , drug design, − stabilization of explosives, noncovalent catalysis, − and polymer chemistry . Predominantly, XB acceptors span electronegative nonmetal elements featuring lone pair(s) [abbreviated as LP(s)] as basicity functions. ,− …”