Outer-shell s 0 /p 0 orbital mixing with d 10 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 Au 4 Cu 2 {[Au 4 (μ-C 2 ,N 3 -EtIm) 4 Cu 2 (μ-3,5-(CF 3 ) 2 Pz) 2 ], (4a)}, Au 2 Cu {[Au 2 (μ-C 2 ,N 3 -BzIm) 2 Cu(μ-3,5-(CF 3 ) 2 Pz)], (1) and [Au 2 (μ-C 2 , N 3 -MeIm) 2 Cu(μ-3,5-(CF 3 ) 2 Pz)], (3a)}, AuCu 2 {[Au(μ-C 2 ,N 3 -MeIm)Cu 2 (μ-3,5-(CF 3 ) 2 Pz) 2 ], (3b) and [Au(μ-C 2 ,N 3 -EtIm)Cu 2 (μ-3,5-(CF 3 ) 2 Pz) 2 ], (4b)} and stacked Au 3 /Cu 3 {[Au(μ-C 2 ,N 3 -BzIm)] 3 [Cu(μ-3,5-(CF 3 ) 2 Pz)] 3 , (2)} form upon reacting Au 3 {[Au(μ-C 2 ,N 3 -(N-R)Im)] 3 ((N-R)Im = imidazolate; R = benzyl/methyl/ethyl = BzIm/MeIm/EtIm)} with Cu 3 {[Cu(μ-3,5-(CF 3 ) 2 Pz)] 3 (3,5-(CF 3 ) 2 Pz = 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 d 10 -d 10 polar-covalent bond with ligandunassisted Cu(I)-Au(I) distances of 2.8750(8) Å each-the shortest such an intermolecular distance ever reported between any two d 10 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 v Cu-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 (Φ PL = 0.90-0.97 vs. 0-0.83 for Au 3 and Cu 3 precursors), which bodes well for potential future utilization in inorganic and/or organic LED applications. Here, we show that outer 4s/p (Cu I ) and 6s/p (Au I ) orbitals can admix with the respective valence 3d and 5d orbitals to sensitize a bona fide polar-covalent metal-metal bond between two d 10 centers manifest by two rather short, 2.8750(8) Å, Cu(I)-Au(I) bonds without any ligand-bite-size assistance. The reduced symmetry in this family of complexes is also shown to impart higher extinction coefficients and phosphorescence quantum yields than those attained by the parent homometallic precursor complexes.Heterometallic complexes are remarkable molecules owing to their unique catalytic and optoelectronic properties (2, 3). Heterometallic species involving coinage metals have received immense attention owing to their fascinating structural a...

Flavins and related molecules catalyze organic Baeyer−Villiger reactions. Combined experimental and DFT studies indicate that these molecules also catalyze the insertion of oxygen into metal−carbon bonds through a Baeyer−Villiger-like transition state.S elective oxy functionalization reactions are among the most important classes of chemical transformations for both biological and nonbiological processes. In contrast to the broad progress on oxygen transfer reactions for olefins, 1 significant barriers remain for the development of catalysts for the selective partial oxidation of saturated hydrocarbons. 2 Transition-metal-mediated partial oxidation of alkanes involves two key steps: C−H bond cleavage and C−O bond formation. In the Pt-based Shilov reaction and related systems, 3 C−H activation occurs at Pt II , and C−O bond formation likely involves a nucleophilic addition to an electrophilic hydrocarbyl coordinated to Pt IV . The required formal two-electron redox sequence between Pt II and Pt IV has limited further development of this process, since scalable reactions with practical oxidants have not been developed. 3,4 A potential alternative to the Shilov pathway for partial oxidation of alkanes is shown in Scheme 1. 5 In this pathway, a metal alkoxide complex activates a C−H bond for 1,2-addition across the M−OR bond to form a metal hydrocarbyl complex and a free alcohol. Insertion of an oxygen atom into the M−R bond reforms the initial alkoxide complex.The 1,2-addition of C−H bonds across metal−heteroatom bonds is known. In 2004, we reported intramolecular C−H activation by a parent Ru II amido complex 6 followed by intermolecular C−H activation of benzene by Ru II hydroxide and anilido complexes. 7 Similar reactions of Ir III , 8 Rh I , 9 and other Ru II complexes 10 have also been observed and extensively modeled. 11 Although limited in number, examples of insertion of an oxygen atom into M−C bonds are also known. Insertion of an oxo ligand into a Re−Ph bond of a cationic Re VII complex has been observed. 12 A similar mechanism has been proposed for several Pd complexes. 13 Hillhouse and co-workers have studied the transfer of oxygen from N 2 O into the Ni−alkyl and Ni−aryl bonds of Ni II metallacycles. 14 Methylrhenium trioxide (MTO) reacts with oxidants to produce methanol. 15 Goddard, Periana, and co-workers 16 proposed a reaction pathway similar to the organic Baeyer− Villiger (BV) reaction that proceeds by coordination of the oxidant (YO) and subsequent methyl migration and loss of Y (Scheme 2 for YO = HOO − ). Related reactions of arylrhenium trioxides have been studied. 17 However, theoretical studies have indicated that the activation barrier for this pathway can be high, especially for late-transition-metal complexes. 18 Thus, the implementation of a combined C−H activation/oxygen insertion strategy for catalytic hydrocarbon oxidation depends on uncovering methods for lowering the activation barrier for oxygen insertion into metal−hydrocarbyl bonds. This work led us to consider...

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 d 10 metal centers. Mixing of (n + 1

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π-stacking in ground-state dimers/trimers/tetramers of N-butoxyphenyl(naphthalene)diimide (BNDI) exceeds 50 kcal ⋅ mol−1 in strength, drastically surpassing that for the *3[pyrene]2 excimer (∼30 kcal ⋅ mol−1; formal bond order = 1) and similar to other weak-to-moderate classical covalent bonds. Cooperative π-stacking in triclinic (BNDI-T) and monoclinic (BNDI-M) polymorphs effects unusually large linear thermal expansion coefficients (αa, αb, αc, β) of (452, −16.8, −154, 273) × 10−6 ⋅ K−1 and (70.1, −44.7, 163, 177) × 10−6 ⋅ K−1, respectively. BNDI-T exhibits highly reversible thermochromism over a 300-K range, manifest by color changes from orange (ambient temperature) toward red (cryogenic temperatures) or yellow (375 K), with repeated thermal cycling sustained for over at least 2 y.