Kinetics and Mechanism of the Stereochemical Isomerization of an Arene−Ruthenium Complex of the Atropisomeric Ligand 1,1‘-Biphenyl-2,2‘-diamine

Abstract

(η6-Benzene)(δ/λ-1,1‘-biphenyl-2,2‘-diamine)chlorometal(II) hexafluorophosphate (1; metal = ruthenium, osmium) have been synthesized. The rigid nature of the seven-membered chelate ring formed by the 1,1‘-biphenyl-2,2‘-diamine (dabp) ligand renders the complexes chiral. The resulting C 1 molecular symmetry of 1(M=Ru) that we have observed in the solid state by single-crystal X-ray crystallography is preserved in solution on the NMR time scale. The four N−H protons of 1(M=Ru,Os) are chemically inequivalent in the 1H NMR spectrum at 20 °C. Spin-perturbation NMR experiments in acetone solutions reveal pairwise exchange of the resonances that correspond to the N−H protons on the spin-relaxation time scale. The three mechanisms that would account for such an exchange (atropisomerization of the dabp ligand, inversion of stereochemistry at the metal center, and simultaneous inversion of the stereochemistry at the metal and the ligand) are distinguishable, provided a proper assignment of the four N−H protons can be made in the NMR spectra. Having made that assignment, we conclude from 2D EXSY NMR spectroscopy that the mechanism of exchange is inversion of stereochemistry at the dabp ligand center. This observation contrasts with previous reports that conformational isomers of dabp can be resolved.

Catalytic sugar-assisted transfer hydrogenation with Ru(II), Rh(III) and Ir(III) halfsandwich complexes

“…benzylidene-2,3-dideoxy-3-tosylamido-␣-D-glucopyranoside ligand (5, Chart 1), (S)-2,2 -diamino-1,1 -binaphthalene (6, Chart 1) and (R,R)-1,2,-diphenylethylenediamine (7, Chart 1) as ligands of Á 6 -arene-ruthenium(II), pentamethyl-Á 5 -cyclopentadienylrhodium(III) and pentamethyl-Á 5 -cyclopentadienyliridium(III) (8-25, Chart 1) were prepared by common methods [15][16][17][18][19][20][21] , and were recently published [22]. Such compounds with chelating nitrogen ligands are effectively used in catalysis, e. g. in water oxidation [23], intramolecular hydroamination of alkynes [24], Diels-Alder reactions [25], asymmetric Michael addition reactions [26], asymmetric hydrogenation [27,28], and transfer hydrogenation [29][30][31], reactions of ketones and imines.…”

“…The formerly unknown precursor complexes with methyl 2,3-diamino-4,6-O-benzylidene-2,3-dideoxy-␣-D-hexopyranosides (compounds 1-4, Chart 1), methyl 2-amino-4,6-OChart 1. Diaminomonosaccharides 1-4, methyl 2-amino-4,6-O-benzylidene-2,3-dideoxy-3-tosylamido-␣-D-glucopyranoside (5) and corresponding diamino derivatives (S)-2,2 -diamino-1,1 -binaphthalene (6) and (R,R)-1,2-diphenylethylenediamine (7) and their halfsandwich complexes of iridium(III), -rhodium(III) and ruthenium(II) (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25) for transfer hydrogenation ([T-4-R] and [T-4-S] denote the absolute configuration of the metal center in a pseudo-tetrahedral environment following the CIP rules).…”

Self-Adaptable Tropos Catalysts

“…Tropoinversion in the octahedral Ru complex 4 ( Figure 3 ) ( t 1/2 ≈ 20 min at 25 °C) was found to involve decoordination and solvent-assisted rotation around the biphenyl single bond and subsequent recoordination of phosphine to the Ru center, 29 whereas tropoinversion in 3 ( t 1/2 ≈ 100 ms; Figure 3 ) as well as in the analogous Os complex did not involve isomerization at the metal center and thus not cleavage of a nitrogen–metal bond. 30 …”

Dual chirality control of palladium(ii) complexes bearing tropos biphenyl diamine ligands

“…1). In this paper, we report dual control of N-center chirality 6 and axial chirality 7 in Pd complexes with the tropos diamines bearing the biphenyl backbone like BIPHEP ligands (Eq. 1).…”

“…Of the 51634 reflections that were collected, 4678 were unique (R int 5 0.0628). R 5 0.0745, Rw 5 0.1860, goodness of fit 5 1.179, shift/error 5 0.003, the Flack parameter 5 0.06(7). CCDC 277176.…”