Carbon-gold bond formation propels a growing number of homogeneous catalyses, but the C-Au bond formation itself is comparatively underinvestigated. Reported here are C-Au bond-forming reactions that result from [3 + 2] cycloaddition of (triphenylphosphine)gold(I) azide to terminal alkynes. The reaction proceeds with the preformed azide complex or, in situ, by reaction of the corresponding gold(I) alkynyl with trimethylsilyl azide in the presence of protic solvents. This metal-mediated cycloaddition is analogous to the Huisgen dipolar addition of azides and alkynes and provides access to new classes of gold-bearing compounds and materials.

Phosphine)-and (N-heterocyclic carbene)gold(I) derivatives of naphthalene and pyrene are reported, containing one or two gold atoms per hydrocarbon. The new complexes are prepared by arylation of gold(I) substrates by arylboronic acids or aryl pinacolboronate esters in the presence of cesium carbonate. Isolated yields range from 52% to 98%. The boron precursors themselves derive from the parent hydrocarbon, where boron is installed in an iridium-catalyzed reaction, or from the aromatic bromides, which are borylated with palladium catalysis. Most of the new gold(I) complexes are air-and moisture-stable colorless solids; they are characterized by multinuclear NMR and optical spectroscopy, combustion analysis, and high-resolution mass spectrometry. X-ray diffraction crystal structures are reported for seven. Gold binding red-shifts optical absorption profiles, which are characteristic of the aromatic skeleton. All compounds show triplet-state luminescence, and dual singlet and triplet emission occurs in some instances. Phosphorescence persists for milliseconds at 77 K and for hundreds of microseconds at room temperature. The compounds' photophysical characteristics, along with time-dependent density-functional theory calculations, suggest emission from ππ* states of the aromatic core. Triplet-state geometry optimization finds minimal geometric rearrangement upon one-electron promotion from the (singlet) ground state.

The copper(I)-catalyzed Huisgen [3 þ 2] cycloaddition is a general reaction encompassing wide ranges of organoazide and primarily terminal alkyne reacting partners. Strained internal alkynes can also undergo cycloaddition with azides. We report here that tetrakis(acetonitrile)copper(I) hexafluorophosphate catalyzes the [3 þ 2] cycloaddition of (phosphine)-and (N-heterocyclic carbene)gold(I) alkynyls with benzyl azide. Isolated yields of up to 96% result. The reaction protocol broadly tolerates functionalities on the alkynyl reagent. Gold(I) triazolate products form with complete 1,4-regioselectivity. Some 15 new gold(I) triazolates are reported along with crystal structures of nine. Triazolate complexes bearing polycyclic aromatic substituents show dual singlet-and triplet-state luminescence from excited states localized on the aromatic fragment. Time-resolved emission experiments find long lifetimes consistent with triplet emission parentage. Absorption and emission transitions are analyzed with time-dependent density-functional theory calculations.

Tetraarylazadipyrromethenes, and especially their boron chelates, are a growing class of chromophores that are photoactive toward red light. The coordination chemistry of these ligands remains to be explored. Reported here are four-coordinate zinc(II) and mercury(II) complexes of tetraarylazadipyrromethene ligands. The new complexes contain two azadipyrromethenes bound per d(10) metal center and are characterized by (1)H NMR, optical absorption spectroscopy, X-ray diffraction crystallography, and elemental analysis. Solid-state structures show that these bis-chelate complexes distort significantly from idealized D2d symmetry. AM1 geometry optimizations indicate relaxation energies in the range of 6.8-15.2 kcal mol(-1); interligand pi-stacking provides an added energetic impetus for distortion. The absorption spectra show a marked increase in the absorption intensity in the red region and, in the case of the zinc(II) complexes, the development of a second distinct absorption band in this region, which is red-shifted by ca. 40-50 nm relative to the free ligand. Semiempirical INDO/S computations indicate that these low-energy optical absorptions derive from allowed excitations among ligand-based orbitals that derive from the highest occupied molecular orbital and lowest unoccupied molecular orbital of the free azadipyrromethene.

Boron azadipyrromethenes are red-light-absorbing dyes with chromophoric capabilities deriving from a conjugated, chelating framework. Reported here are tricoordinate copper(I), silver(I), and gold(I) complexes of a tetraphenylazadipyrromethene ligand. The new complexes are characterized by optical absorption and emission spectroscopy, multinuclear NMR, mass spectrometry, elemental analysis, and X-ray diffraction crystallography. Time-dependent density functional theory calculations indicate that the principal absorption features in azadipyrromethene complexes result from optically allowed intraligand transitions that undergo configuration interaction.

A series of phosphane‐ and (N‐heterocyclic carbene)gold(I) complexes were prepared by deprotonation of terminal alkyne precursors and reaction with the corresponding gold(I) chlorides. Some ten new compounds are reported; these are characterized by multinuclear NMR, optical spectroscopy, and elemental analysis. Crystallographic characterization is reported for five complexes. Organogold species bearing conjugated aryl substituents on the alkynyl ligand are luminescent. Density‐functional theory calculations on a model complex suggest that emission and the first several absorption transitions result from excited states dominated by the arylacetylide ligand. Excited‐state geometry optimization finds that the lowest‐energy triplet state bears linear, two‐coordinate gold(I) with a miniscule lengthening of the alkynyl carbon–carbon bond. An unusual triplet excited state having a bent geometry at gold lies at higher energy in arylacetylide complexes. For the model terminal acetylideMe3PAuC≡CH, the calculations find this bent state to be the lowest‐energy triplet.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Aryl-group transfer from arylboronic acids to gold has emerged as a functionally tolerant alternative to classical lithiation-and magnesiation-based synthesis of arylgold(I) species. Here, the scope of the reaction is explored with attention to the sterics of the boronic acid starting material and the supporting ligand on gold. Dicyclohexylbiaryl phosphines are selected as supporting ligands on gold(I) because of their substantial bulk. Aryl-group transfer is compatible with steric buildup on either reaction partner. The structural preference of gold(I) for linear, two-coordinate geometries circumvents potential steric clashes. The new organometallics likely gain added stability through dative interactions with the flanking phosphine biaryl arm and, in three cases, through π-interactions with the aryl ligand σ-bonded to gold. The new compounds are characterized by multinuclear NMR and optical spectroscopy, X-ray diffraction crystallography, and combustion analysis. All compounds absorb ultraviolet light at wavelengths λ < 325 nm. Time-dependent density-functional theory calculations find that multiple singlet-singlet transitions account for the absorption profile, which has both intraligand and (ligand-metal)-to-ligand charge-transfer character.

1,6-Bis(ferrocenyl)-1,3,5-hexatriyne (Fc(C⋮C)3Fc) was prepared from the reaction between 3-(dibromomethylidene)-1,5-bis(ferrocenyl)penta-1,4-diyne and BuLi via an alkynyl migration in a vinylidene carbenoid mechanism. Both the title compound and its precusors were thoroughly characterized, and the electronic couplings between two ferrocenyl units were assessed with voltammetric techniques.