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As the tenth year that follows the premature passing of the inorganic chemistry legend F. Albert (Al) Cotton comes to a close, we provide some soul food that we believe Al would have enjoyed as he looks down upon two generations of disciples, a grandchild and two great grandchildren, in his scientific family tree. This article also represents a new tradition by which the editors of Comments on Inorganic Chemistry wish to lead by example, whereby we start publishing original research content that nonetheless preserves the journal’s identity as a niche for “critical discussion of the current literature” of inorganic chemistry. Thus, we show novel demonstrations of a posteriori validation and a priori prediction of possible counterintuitive covalent M-M’ bonds—after and before synthesis, respectively—contrasted with non-covalent M···M interactions of the metallophilic type in bridge-dimeric systems of d10 metal centers. Mixing of (n + 1)s0/p0 orbitals with (n)d10 orbitals in the former heterobimetallics case—and lack thereof in the latter homobimetallics case—is hypothesized to be responsible for the presence or absence of covalency, respectively. However, we also demonstrate that the consequent d-s’ and/or d-p’ orbital mixing/hybridization can occur even in homobimetallic complexes that contain asymmetric bridging ligands (e.g., with -S^C- donor atoms that lead to orbital interactions between M-S and M-C fragments). Hence, the “control” metallophilic case for the hypothesized d10-d10 polar-covalent bonding herein is best manifest by M2(P^P)2 homobimetallics vis-à-vis M2(S^C)2 embodiments. Finally, we also offer a point/counterpoint commentary to the readers to contrast factors that argue for covalency vs metallophilicity and forewarn against exaggerating the extent of covalent bonding in such d10-d10 species. Thus, scrutinizing the various theoretical parameters has pointed to M-M’ and M-M partially bonded S^C-bridge dinuclear d10 complexes vis-à-vis the classic Cotton-type multiple metal-metal bond description in d0

Outer-shell s0/p0 orbital mixing with d10 orbitals and symmetry reduction upon cupriphication of cyclic trinuclear trigonal-planar gold(I) complexes are found to sensitize ground-state Cu(I)–Au(I) covalent bonds and near-unity phosphorescence quantum yields. Heterobimetallic Au4Cu2 {[Au4(μ-C2,N3-EtIm)4Cu2(µ-3,5-(CF3)2Pz)2], (4a)}, Au2Cu {[Au2(μ-C2,N3-BzIm)2Cu(µ-3,5-(CF3)2Pz)], (1) and [Au2(μ-C2,N3-MeIm)2Cu(µ-3,5-(CF3)2Pz)], (3a)}, AuCu2 {[Au(μ-C2,N3-MeIm)Cu2(µ-3,5-(CF3)2Pz)2], (3b) and [Au(μ-C2,N3-EtIm)Cu2(µ-3,5-(CF3)2Pz)2], (4b)} and stacked Au3/Cu3 {[Au(μ-C2,N3-BzIm)]3[Cu(µ-3,5-(CF3)2Pz)]3, (2)} form upon reacting Au3 {[Au(μ-C2,N3-(N-R)Im)]3 ((N-R)Im = imidazolate; R = benzyl/methyl/ethyl = BzIm/MeIm/EtIm)} with Cu3 {[Cu(μ-3,5-(CF3)2Pz)]3 (3,5-(CF3)2Pz = 3,5-bis(trifluoromethyl)pyrazolate)}. The crystal structures of 1 and 3a reveal stair-step infinite chains whereby adjacent dimer-of-trimer units are noncovalently packed via two Au(I)⋯Cu(I) metallophilic interactions, whereas 4a exhibits a hexanuclear cluster structure wherein two monomer-of-trimer units are linked by a genuine d10–d10 polar-covalent bond with ligand-unassisted Cu(I)–Au(I) distances of 2.8750(8) Å each—the shortest such an intermolecular distance ever reported between any two d10 centers so as to deem it a “metal–metal bond” vis-à-vis “metallophilic interaction.” Density-functional calculations estimate 35–43 kcal/mol binding energy, akin to typical M–M single-bond energies. Congruently, FTIR spectra of 4a show multiple far-IR bands within 65–200 cm−1, assignable to vCu-Au as validated by both the Harvey–Gray method of crystallographic-distance-to-force-constant correlation and dispersive density functional theory computations. Notably, the heterobimetallic complexes herein exhibit photophysical properties that are favorable to those for their homometallic congeners, due to threefold-to-twofold symmetry reduction, resulting in cuprophilic sensitization in extinction coefficient and solid-state photoluminescence quantum yields approaching unity (ΦPL = 0.90–0.97 vs. 0–0.83 for Au3 and Cu3 precursors), which bodes well for potential future utilization in inorganic and/or organic LED applications. [ABSTRACT FROM AUTHOR]

A DFT analysis of the reaction of bpyNiEt2 with ArN3 was performed for para-tolyl-azide (Ar = pTol), 3,5-dimethyl-phenyl-azide (Ar = mXy) and ortho-tolyl-azide (Ar = oTol), and mesityl-azide (MesN3). Of particular interest were the different products obtained for the latter (ethylene, butane, azomesitylene, mesityl-ethylamine, etc.) versus the other reagents, i.e., (bpyNi(N(Ar)Et)(Et)). Calculated thermodynamics and kinetics for metal-free reactions did not differentiate MesN3 from the other aryl azides. Once (2)bpyNiEt• was generated via bond homolysis, formation of ethylene by ß-H elimination was facile, as was formation of nickel-imidyl (NR-•) intermediates by reaction of ArN3 with bpyNiEtx (x = 0-2). On the basis of computed energetics, three reactions of bpyNiEt2 were proposed to compete: Ni-C bond homolysis, reductive elimination of butane, and nucleophilic attack (NA) by ArN3. Inspection of their temperature dependence suggested that NA and Ni-Et bond homolysis dominated at lower and higher temperatures, respectively. Calculated Ni-N and Ni-C bond dissociation free energies (BDFEs) suggested the role of radical pathways in discriminating bpyNiEt2/ArN3 reactions, and implied that the concentration of radicals such as aminyl (ArN•(Et)), (2)bpyNiEt•, and Et• will be greatest for MesN3. [ABSTRACT FROM AUTHOR]

The reactivity of a series of oxidants with [(tbpy)Pt(Ph)(L)]+ and [(tbpy)2Rh(Me)(OTf)]+ [tbpy = 4,4′-di- tert-butyl-2,2′-bipyridine, L = thf or triflate (OTf)] complexes was investigated. The PtII and RhIII complexes [(tbpy)Pt(Ph)(ONMe3)][BAr′4], [(tbpy)Pt(Ph)(OPy)][BAr′4], [(tbpy)2Rh(Me)(ONMe3)][BAr′4][OTf], and [(tbpy)2Rh(Me)(OPy)][BAr′4][OTF] (Ar′ = 3,5-(CF3)2C6H3, OPy = pyridine N-oxide) have been isolated and characterized by 1H, 13C, and 19F NMR spectroscopy as well as elemental analysis. In addition, single-crystal X-ray diffraction studies of the complexes [(tbpy)Pt(Ph)(OPy)][BAr′4], [(tbpy)2Rh(Cl)2][BAr′4], [(tbpy)2Rh(Me)2][BAr′4], [(tbpy)2Rh(Me)( I)][BAr′4], and [(tbpy)2Rh(Me)(OPy)][BAr′4][OTf] are reported. DFT calculations computationally model the conversions of Pt-Ph and Rh-Me species to the corresponding Pt-OPh and Rh-OMe complexes, providing insight into activation barriers for the oxygen-atom insertion into PtII-R and RhIII-R bonds. [ABSTRACT FROM AUTHOR]