Ruthenium Phosphine/Diimine Complexes:  Syntheses, Characterization, Reactivity with Carbon Monoxide, and Catalytic Hydrogenation of Ketones

Abstract

The cis-[RuCl2(PPh3)2(N−N)] (N−N = bipy (1), Me-bipy (2), phen (3), and bathophen (4)) complexes were used to synthesize five new electron-rich phosphine-containing complexes cis-[RuCl2(dcype)(N−N)] (N−N = bipy (1a), Me-bipy (2a), phen (3a), and bathophen (4a)) and cis-[RuCl2(PEt3)2(bipy)] (1c) by phosphine exchange. These complexes were obtained and characterized by NMR (31P{1H}, 1H), cyclic voltammetry, and elemental analysis. Electrochemical studies of these complexes reveal a single reduction process (RuIII/RuII). These complexes are more easily oxidized than their analogues cis-[RuCl2(dppb)(N−N)]. The reactivity of complexes cis-[RuCl2(dcype)(N−N)] with carbon monoxide was tested, and dissociation of one chloride was observed, leading to the formation of four new cationic species with general formula [RuCl(CO)(dcype)(N−N)](PF6) (bipy (1b), Me-bipy (2b), phen (3b), and bathophen (4b)). The complexes described here and elsewhere with general formulas cis-[RuCl2(P−P)(N−N)], [RuCl(CO)(dcype)(N−N)](PF6), and cis-[RuCl2(P)2(N−N)] were used as precatalysts in the transfer hydrogenation of functionalized aryl-ketones, and most of them were active. X-ray structures of cis-[RuCl2(PEt3)2(bipy)] (1c) and [RuCl(CO)(dcype)(bipy)](PF6) (1b) will be presented.

Experimental and theoretical study of the kinetics of dissociation in cis-[RuCl2(P-P)(N-N)] type complexes

“…The bond distances and angles listed in Table 2 are in the range expected for ruthenium diphosphine complexes. 7,[12][13][14][29][30][31][32] Similar behavior was observed for the complexes containing 4-methylpyridine and 4-phenylpyridine, as previously reported. 7,29,30 In all three complexes, the dissociated chloride was always the one trans to a phosphorus atom in the precursor cis-[RuCl 2 (P-P) (bipy)], as expected, given the stronger trans effect of the phosphorus atom and in accordance with the X-ray structures.…”

Neutral and cationic ruthenium carbonyl complexes [Ru(CO)(2,2′-dipyridylamine)(PR3)Cl2] and [Ru(CO)(N–N)(PPh3)2(H)]Cl: synthesis, structural characterization and transfer-hydrogenation

“…In the 1 H NMR spectra, the integrals indicated a dpa: PR 3 ratio of 1:1. HMBC 1 H- 31 P experiments showed that in both complexes the PR 3 ligand is in the trans position relative to a nitrogen atom of the 2,2 0 -dipyridylamine ligand, due to the presence of coupling of one o-H with the PR 3 ligand as described elsewhere [23]. These observations are in agreement with the structures found in the solid state by X-ray crystallography and found for analogous complexes as published previously [24].…”

“…The bond lengths RuCl1 = 2.4066(8), Ru-Cl2 = 2.4181 (7), Ru-C1 = 1.834 (3), C1-O1 = 1.143 (4) and Ru-P = 2.3670 (7) are within the ranges observed in other complexes [24][25][26][27][28][29][30][31][32][33][34]. The bond length Ru-Cl2 = 2.4181 (7) is longer than RuCl1 = 2.4066 (8), this difference is probably due to the hydrogen bond involving Cl2 and CH 3 OH, as can be seen in Fig.…”

Synthesis and characterization of ruthenium(II) complexes based on diphenyl-2-pyridylphosphine and their applications in transfer hydrogenation of ketones

“…The phenyl substituted dialkyl ketone 4-phenyl-2-butanone gets readily reduced. Reetz and Li have recently reported the use of p-cymene containing precursor [{(g 6 -C 10 H 14 )RuCl (l-Cl)} 2 ] in presence of BINOL-derived diphosphonites for extremely effective asymmetric hydrogen-transfer hydrogenation (from 2-propanol) of ketones, it is notable that these systems do not require ancillary diamine ligands [71]. In addition, Deng's and Noyori's group have earlier used the same precursor in presence of a chiral diamine for hydrogenation of ketones in either aqueous media using sodium formate or basic 2-propanol [72,73].…”