New Bonding Modes, Fluxional Behavior, and Reactivity in Dinuclear Complexes Bridged by Four-Electron Donor Unsaturated Hydrocarbons

Organometallic chemistry of extended periodic π-electron systems: hexahapto-chromium complexes of graphene and single-walled carbon nanotubes

“…47,48 In SWNT, HOPG and graphene chemistry the use of IR spectroscopy is sometimes limited by weak spectral features as a result of the dynamic dipole moments and IR assignments of even well documented complexes can be difficult. 49 In the case of metal complexes of polyaromatic arenes, haptotropic slippage 50 and fluxional behavior 51 of the ligands further complicates characterization using FT-IR spectroscopy. 43 Scanning tunneling microscopy provides more direct evidence of chemical functionalization, if well ordered samples from optimized reactions are available.…”

Stabilization of Carbenium Ions Derived from Ethynylestradiol by Different Adjacent Organometallic Moieties. Implication in the Inactivation of the Estrogen Receptor

“…Published procedures were employed for the synthesis of 17α-propynylestradiol, 1 and 3, [29] 4-6, [10] and model complex 3a. [30] Model complexes 1a, 2a, 4a, and 5a were synthesized by reaction of Co 2 (CO) 8 , Co 2 (CO) 6 (dppm), [31] or M 3 (CO) 10 (NCCH 3 ) 2, [32] (M ϭ Ru for 7a and Os for 8a) with propargyl alcohol. Their purity was checked by IR, MS, and NMR spectroscopy.…”

“…Hydration/dehydration equilibrium involving a [(propargyl)Co 2 (CO) 6 ]-like compound A large variety of propargyl cations coordinated to many different organometallic fragments have been investigated to date. [5][6][7][8] The major interest in these compounds is based on the possibility of employing them as electrophilic synthons. In this context, 17α-alkynylestradiol organometallic derivatives ( Figure 2) may be regarded as analogous to the propargylic alcohol complexes.…”

On the nature of the dative bond: Coordination to metals and beyond. The carbon case

“…Resumption of the state-of-the-art in this field is out of the scope this review [129], but the operating bonding modes in dicobalt carbonyl complexes of type II are briefly surveyed.…”

“…Complexes of type II derived from propargylic alcohols undergo ready protonation to give  3 -propargylic carbenium complexes of type III, where the -cationic charge is delocalized by overlap of a filled d orbital of the metal with the empty p z orbital of the generated carbenium center Dicobalt propargylium complexes are thus generally less stable than dimolybdenum or ditungsten analogues, but insights into their structure was first gained from X-ray diffraction analysis of a doubly stabilized carbocationic cluster 11 [133b]. Variable temperature NMR studies showed that cobalt complexes of type III exhibit a dynamic behaviour, where the CR 1 R 2 carbenium center migrates from one Co center to the other, through intramolecular Walden inversion as shown for chiral representatives [129,134].…”