Development and application of redox-active cyclometallating ligands based on W(II) alkyne complexes

The assembly of dinulear complexes with ultimative smallest ditopic ligands based on side-on complexes of methyl substituted alkynes is presented. In fact, the coordination of Ru(II) and Ir(III) by a...

Terminal and Internal Alkyne Complexes and Azide-Alkyne Cycloaddition Chemistry of Copper(I) Supported by a Fluorinated Bis(pyrazolyl)borate

Copper plays an important role in alkyne coordination chemistry and transformations. This report describes the isolation and full characterization of a thermally stable, copper(I) acetylene complex using a highly fluorinated bis(pyrazolyl)borate ligand support. Details of the related copper(I) complex of HCºCSiMe3 are also reported. They are three-coordinate copper complexes featuring η2-bound alkynes. Raman data show significant red-shifts in CºC stretch of [H2B(3,5-(CF3)2Pz)2]Cu(HCºCH) and [H2B(3,5-(CF3)2Pz)2]Cu(HCºCSiMe3) relative to those of the corresponding alkynes. Computational analysis using DFT indicates that the Cu(I) alkyne interaction in these molecules is primarily of the electrostatic character. The π-backbonding is the larger component of the orbital contribution to the interaction. The dinuclear complexes such as Cu2(μ-[3,5-(CF3)2Pz])2(HCºCH)2 display similar Cu-alkyne bonding features. The mononuclear [H2B(3,5-(CF3)2Pz)2]Cu(NCMe) complex catalyzes [3+2] cycloadditions between tolyl azide and a variety of alkynes including acetylene. It is comparatively less effective than the related trinuclear copper catalyst {μ-[3,5-(CF3)2Pz]Cu}3 involving bridging pyrazolates.

Vinylidene, allenylidene, cyclic oxycarbene, and η2-alkyne complexes from reactions of (η5-C5Me5)OsCl(PPh3)2 with alkynes and alkynols

Reactions of Cp*OsCl(PPh3)2 (Cp* = pentamethylcyclopentadienyl) with alkynes and alkynols are described. Treatment of Cp*OsCl(PPh3)2 with phenylacetylene and trimethylsilylacetylene gave the vinylidene complexes Cp*OsCl(=C=CHPh)(PPh3) and Cp*OsCl(=C=CH2)(PPh3), respectively. Treatment of Cp*OsCl(PPh3)2 with the internal alkyne dimethyl acetylenedicarboxylate produced the η2-alkyne complex Cp*OsCl(η2-MeO2C≡CCO2Me)(PPh3). Treatment of Cp*OsCl(PPh3)2 with the propargylic alcohol HC≡CC(OH)Ph2 gave the osmium allenylidene complex Cp*OsCl(=C = C=CPh2)(PPh3). The outcomes of the reactions of Cp*OsCl(PPh3)2 with ω-alkynols HC≡C(CH2)nOH are dependent on the length of the -(CH2)n- linker. The reaction with 3-butyn-1-ol produced the cyclic oxycarbene complex Cp*OsCl{=C(CH2)3O}(PPh3) exclusively. The reactions with 4-pentyn-1-ol produced a mixture of the hydroxyalkyl vinylidene complex Cp*OsCl{=C=CH(CH2)3OH}(PPh3) and the cyclic oxycarbene complex Cp*OsCl{=C(CH2)4O}(PPh3) in about 10:1 molar ratio. The reaction with 5-hexyn-1-ol gave exclusively the hydroxyalkyl vinylidene complex Cp*OsCl{=C=CH(CH2)4OH}(PPh3).

Acetylene and terminal alkyne complexes of copper(i) supported by fluorinated pyrazolates: syntheses, structures, and transformations

A variety of isolable, 2 : 1 and 1 : 1 copper(i)–alkyne complexes of containing pyrazolate ligand supports are presented as well as the copper pyrazolate mediated acetylenic C–H and alkyne CC bond functionalizations.

Fluorination as tool to improve bioanalytical sensitivity and COX-2-selective antitumor activity of cobalt alkyne complexes

Fluorination of the lead Co-ASS yielded antitumor active cobalt alkyne complexes that exhibited both improved COX-2 selectivity and better bioanalytical sensitivity.