Homogeneous platinum(II)-catalysed hydrogen exchange in the alkylbenzenes: relationship to simple alkane exchange

Abstract

Deuteriation in the side-chain of the long-chain alkylbenzenes using a homogeneous platinum(I1) catalyst occurs predominantly at the ccand terminal carbon positions, isotope incorporation progressively decreasing from n-butyl-to n-nonyl-benzenes; in the side-chain of 1,l-dimethylpropylbenzene exchange is exclusively a t the y-position. THE deuteriation of methane and ethane has been reported,l employing a homogeneous platinum(I1) catalyst previously discovered for aromatic compounds.2 The work has been

H/D exchange under mild conditions in arenes and unactivated alkanes with C6D6 and D2O using rigid, electron-rich iridium PCP pincer complexes

“…1) is pyramidalized (the sum of the angles about C1 is 335.2(8) ), and the central 6 membered ring containing this a-carbon has also adopted a "boat"-like conformation. The sp 3 hybridization of the a-carbon is also indicated by the central Ir1-C1 bond length of 2.184(5)Å which is similar to other sp 3 hybridized Ir-C bonds we have observed with these NR 2 substituted ligand frameworks 44,45 and lengthened signicantly from the values of z1.93 A seen in PC carbene P complexes of this ligand. 44 Given the lack of crystallographic data concerning the iridium hydrides in Ir-H 4 , we turned to criteria developed by Halpern and co-workers 55 to shed some light on what form dominates the speciation of Ir-H 4 in solution.…”

“…A brown powder (0.301 g, 0.410 mmol) was isolated in 80% yield. Elemental analysis calcd (%): C, 52.37; H, 7.00; N, 3…”

“…Metal-catalyzed hydrogen isotope exchange (HIE) is a key fundamental process for preparing isotopically labeled organic compounds necessary for studying reaction mechanisms and biological metabolic processes. 1 Since the seminal work on homogeneous HIE by Garnett and Hodges 2,3 as well as Shilov and co-workers, 4,5 advances in analytical biology and chemistry have created an ever growing demand for deuterium 6 and tritium 7 labeled molecules. 8 Consequently, an important body of research devoted to studying the homogeneously catalyzed exchange of hydrogen and deuterium atoms (H/D exchange) has developed over the last 25 years.…”

“…32 Following these reports, PNP (III) and PCP (IV) complexes synthesized by Grubbs 33 and Wendt, 34 respectively, were also tested as HIE mediators. The iridium dihydride species III was able to selectively deuterate aromatic compounds and silanes, while the cyclohexyl-based PCP complex IV was found to successfully deuterate arenes and to a limited extent C sp 3 -H sites, albeit at elevated temperatures of 150 C.…”

Iridium‐Catalyzed H/D Exchange at Vinyl Groups without Olefin Isomerization

“…[3] H/D exchange of aromatic hydrogen atoms is well known and has been conducted with a variety of catalysts, including acid, base, and metal complexes. [4] H/D exchange of nonactivated, aliphatic CÀH bonds has also been conducted with transition-metal catalysts, [5] including [Cp*Ir(PMe 3 )], [6,7] [Cp*Ir(carbene)], [8] and [(Tp Me2 )Ir] complexes. [9] H/D exchanges catalyzed by the recently developed systems afford a high degree of isotope incorporation, and some have been conducted with D 2 O as the deuterium source.…”