No abstract

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.

The rational design of triplet-state sensitizers for the photodynamic therapy of cancers [1][2][3] and other diseases [4] remains an obdurate challenge. A prominent strategy [5][6][7] is the modification of existing photosensitizers with bromine (Z = 35) or iodine (Z = 53); the resulting heavy-atom effects potentiate the generation of therapeutic 1 D g O 2 . The (phosphane)gold(I) fragment is s-isolobal with the proton. Terminal substitution of aromatic organic molecules with gold (Z = 79) has clear desirability for developing phototherapy mediators. What is missing are mild means of carbon-gold bond formation in the presence of sensitive functional groups. We describe here a selective protocol that installs gold(I)-carbon bonds along the peripheries of organic molecules. Reducible, polar moieties are tolerated, including nitro groups, aldehydes, ketones, and esters. The organometallic compounds described here withstand air and water indefinitely. The ability to modify organic fluorophores with gold raises immediate opportunities in metallopharmaceuticals design. [8][9][10] Finally, the new protocol affords organogold(I) compounds more rapidly and in higher yield than by traditional methods [11] of arylating gold. In the palladium-catalyzed Suzuki-Miyaura cross-coupling, [12,13] carbon-carbon bond formation is believed to follow transmetalation from boron to palladium. The reaction often requires an auxiliary base, which is thought to quaternize boron and promote transmetalation.[14] Related precedents include observations by the groups of Schmidbaur [15] and Fackler [16] of phenyl-group transfer from BPh 4 À to gold(I) in aqueous and non-aqueous media.[*] Dr.

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.