Transfer of Amido Groups from Isolated Rhodium(I) Amides to Alkenes and Vinylarenes

Abstract

The reaction of monomeric and dimeric rhodium(I) amido complexes with unactivated olefins to generate imines is reported. Transamination of {(PEt(3))(2)RhN(SiMePh(2))(2)} (1a) or its -N(SiMe(3))(2) analogue 1b with p-toluidine gave the dimeric [(PEt(3))(2)Rh(mu-NHAr)](2) (Ar = p-tolyl) (2a) in 80% isolated yield. Reaction of 2a with PEt(3) generated the monomeric (PEt(3))(3)Rh(NHAr) (Ar = p-tolyl) (3a). PEt(3)-ligated arylamides 2a and 3a reacted with styrene to transfer the amido group to the olefin and to form the ketimine Ph(Me)C=N(p-tol) (4a) in 48-95% yields. The dinuclear amido hydride (PEt(3))(4)Rh(2)(mu-NHAr)(mu-H) (Ar = p-tolyl) (5a) was formed from reaction of 2a in 95% yield, and a mixture of this dimeric species and the (PEt(3))(n)RhH complexes with n = 3 and 4 was formed from reaction of 3a in a combined 75% yield. Propene reacted with 2a to give Me(2)C=N(p-tol) (4b) and 5a in 90 and 57% yields. Propene also reacted with 3a to give 4b and 5a in 65 and 94% yields. Analogues of 2a and 3a with varied electronic properties also reacted with styrene to form the corresponding imines, and moderately faster rates were observed for reactions of electron-rich arylamides. Kinetic studies of the reaction of 3a with styrene were most consistent with formation of the imine by migratory insertion of olefin into the rhodium-amide bond to generate an aminoalkyl intermediate that undergoes beta-hydrogen elimination to generate a rhodium hydride and an enamine that tautomerizes to the imine.

Intervalent Bis(μ‐aziridinato)MIIMI Complexes (M=Rh, Ir): Delocalized Metallo‐Radicals or Delocalized Aminyl Radicals?

“…Orbital and spin density plots were generated with Molden. [36] Structural analysis of 2, 3, [3]PF 6 , [4]PF 6 , [7]BF 4 and [9]A C H T U N G T R E N N U N G (PF 6 ) 2 ·CH 2 Cl 2 : X-ray data were collected by using a Bruker Smart Apex CCD diffractometer, with graphite-monochromated Mo Ka radiation (l = 0.71073 ) using w scans (0.38). Data were corrected for absorption using a multiscan method applied with SADABS program.…”

“…[4] A survey of the literature on this topic made us aware of the absence of data about the redox behavior of dinuclear Rh I and Ir I amido derivatives. Dinuclear amido complexes of these metals are well-known, [5] and some of them have been reported as useful precursors for the synthesis of imido complexes, [6] for the transfer of the amido group to olefins, [7] and in catalyzed CÀC bond formation reactions. [8] Further, studies of the oxidative addition reactions of halocarbons allowed the synthesis of Ir I /Ir III derivatives [9] and the detection of S N 2 profiles in the activation of chloro compounds.…”

“…-(H 2 NC 6 H 4 -Me)}]BF 4 ( [7]BF 4 ) whose structure is drawn in Figure 9 (for selected bond lengths and angles, see the Supporting Information).…”

Migratory Insertion of Alkenes into Metal–Oxygen and Metal–Nitrogen Bonds

“…[102][103][104][105] More recently, Hartwig and co-workers reported the transfer of an amido group to alkenes and vinylarenes from an isolated rhodium amido complex. [106] A series of triethylphosphine-ligated rhodium amido complexes react with vinylarenes at 60 8C to from the corresponding N-aryl imine and a dimeric hydridorhodium amide complex (Scheme 23).…”

Mechanistic Studies on the Catalytic Oxidative Amination of Alkenes by Rhodium(I) Complexes with Hemilabile Phosphines

“…On the other hand, the intermolecular transfer of amido ligands from rhodium(I) amides to unactivated olefins have been recently reported. 22,23 On the basis of these results, we propose that the oxidative amination catalysed by rhodium complexes containing P,O-functionalized phosphine ligands proceeds through the catalytic cycle shown in figure 10. The first step of the proposed mechanism is the replacement of the piperidine ligand by styrene in 9 to give a key styrene-amido intermediate.…”