Amine Attack on Coordinated Alkenes:  An Interconversion from Anti-Markovnikoff to Markovnikoff Products

Abstract

A sequence of alkene complexes of platinum, PtCl(2)(PPh(3))(alkene) (alkene = ethylene, propene, 1-butene, cis-2-butene, 1-hexene, 1-octene, and 1-decene), has been prepared. These complexes are characterized by NMR spectroscopy, including assignment of each proton, and X-ray crystal structures of the 1-propene and 1-hexene complexes. Each complex was reacted with diethylamine. For the 1-hexene, 1-octene, and 1-decene complexes, the amine displaces the alkene. For the smaller alkenes, the diethylamine nucleophilically attacks the coordinated alkene. For propene and 1-butene, the low-temperature addition leads to the anti-Markovnikoff nucleophilic attack, which slowly converts at room temperature to the Markovnikoff product. The transformation from anti-Markovnikoff to Markovnikoff addition occurs without diethylamine dissociation.

Palladium‐Catalyzed anti‐Markovnikov Oxidation of Terminal Alkenes

“…At the same time, Atwood and co-workers reported a stoichiometric amine addition to platinum(II)-coordinated alkyl olefins. [61] In this case, regiochemical distinction between the kinetic and thermodynamic products was observed also, however, the AM aminoplatination adduct was favored kinetically, presumably for steric reasons, and is isomerized to the Markovnikov adduct at elevated temperatures.…”

Platinum(II) complexes containing unsaturated ligands. Nucleophilic substitution versus nucleophilic attack to ligand: a stereochemistry driven outcome

“…Therefore, the stereo-isomerism of the precursor appears to be pivotal in addressing the chemo-selectivity of the process. About the results reported in the literature [5] for the systems cis-PtCl 2 (PPh 3 )(alkene)/NHEt 2 (see Introduction) the substitution of the alkene (favoured raising the temperature or for alkenes with more of 4 carbon atoms), may be due to a prior partial (even quite small) cis ? trans isomerisation of the precursors, although no evidence of trans-PtCl 2 (PPh 3 )(alkene) has been found.…”

“…(5). Notwithstanding the low temperature, traces of [SP4-4]-1 were observed, reasonably due to isomerisation of the precursor, catalysed by the addition of the amine [15].…”

“…The 13 C NMR spectrum recorded at room temperature shows a signal at 167.7 ppm due to the carbamoyl (CON) and resonances of the aromatic nuclei at 134. 5,130.5,130.4 and 127.9 ppm. Four signals at 48.5,47.7,43.5 and 38.7 ppm are due to the CH 2 of the four magnetically non equivalent ethyl groups, while three resonances observed at 15.0, 14.0, 13.8 are assigned to the four non-equivalent methyl carbon atoms, assuming the overlapping of two signals.trans-[PtCl 2 (CO)(PPh 3 )] [15] was prepared in situ by reacting trans-[PtCl(l-Cl)(PPh 3 )] 2 with CO in CH 2 -Cl 2 at low temperature (Eq.…”

“…Recently Atwood et al have re-examined the reactivity of a series of platinum(II) neutral alkene complexes cis-[PtCl 2 (C@C) (PPh 3 )], [5] reporting alkene substitution or nucleophilic attack to the unsaturated ligand in dependence of the alkene nature (alkenes with more than four carbon atoms being displaced by NHEt 2 ) and of the temperature (ligand substitution rather than nucleophilic attack being observed also for the smaller alkenes if the reaction mixture, initially at -75°C, is allowed to reach room temperature too rapidly). Ligand substitution reactions in platinum(II) chemistry are strongly influenced by the ''trans effect' ' [6], exploited for synthetic goals to foresee or justify (with some prudence) the outcome of a reaction [6] or the different behaviour of two geometric isomers [7].…”