Rhodium‐catalyzed transfer hydrogenation with aminophosphines and analysis of electrical characteristics of rhodium(I) complex/n‐Si heterojunctions

Abstract

A series of novel neutral mononuclear rhodium(I) complexes of the P-NH ligands have been prepared starting from [Rh(cod) Cl] 2 complex. Structural elucidation of the complexes was carried out by elemental analysis, IR and multinuclear NMR spectroscopic data. The complexes were applied to the transfer hydrogenation of acetophenone derivatives to 1-phenylethanol derivatives in the presence of 2-propanol as the hydrogen source. Catalytic studies showed that all complexes are also excellent catalyst precursors for transfer hydrogenation of aryl alkyl ketones in 0.1 M iso-PrOH solution. In particular, [Rh(cod)(PPh 2 NH-C 6 H 4 -4-CH(CH 3 ) 2 )Cl] acts as an excellent catalyst, giving the corresponding alcohols in excellent conversion up to 99% (turnover frequency ≤ 588 h À1 ). Furthermore, rhodium(I) complexes have been used in the formation of organic-inorganic heterojunction by forming their thin films on n-Si and evaporating Au on the films. It has been seen that the structures have rectifying properties. Their electrical properties have been analyzed with the help of currentvoltage measurements. Finally, it has been shown that the complexes can be used in the fabrication of temperature and light sensors.

The Golden Age of Transfer Hydrogenation

“…The catalytic performance of 136b containing an i -Pr group at the para -position was superior to those of 136a and 136c . With the use of 136b , complete conversions were observed, and the TOF values were as high as 588 h –1 . The phosphane ligand 137 featuring a hydrophilic pyrazine was a good promoter in rhodium-mediated ATH of acetophenone in terms of both activity and enantioselectivity .…”

“…Given the considerably growing applications of functional P- and P–N-based ligands in catalysis, some rhodium complexes with these ligands were shown to be active in the TH of unsaturated compounds (Scheme ). Aydemir’s group , synthesized a series of rhodium complexes of aminophosphine containing the cyclohexyl moiety. Complex 135a containing a furan unit exhibited good catalytic performances in the TH of acetophenone derivatives with 2-PrOH and NaOH, and 233–576 h –1 TOF values were measured with 4-fluoro-, 4-chloro-, 4-bromo-, 2-methoxy-, and 4-methoxy-acetophenones as starting materials.…”

“…With the use of 136b, complete conversions were observed, and the TOF values were as high as 588 h −1 . 493 The phosphane ligand 137 featuring a hydrophilic pyrazine was a good promoter in rhodium-mediated ATH of acetophenone in terms of both activity and enantioselectivity. 494 TH of polar bonds including CO and CN bonds was catalyzed by an iminophosphorane-based [P 2 N 2 ] rhodium complex 138, although the reaction rate was relatively low.…”

Transfer Hydrogenation from 2-propanol to Acetophenone Catalyzed by [RuCl2(η6-arene)P] (P = monophosphine) and [Rh(PP)2]X (PP = diphosphine, X = Cl−, BF4−) Complexes

“…Regarding the reduction of ketones, Rh-phosphine complexes have been successfully employed as catalytic precursors mainly in the presence of molecular hydrogen [66]. Activation of 2-propanol by Rh-phosphine complexes and the achievement of TH under these conditions has been reported for few complexes such as those containing amino-phosphines [67][68][69][70]. Recently, the TH from 2propanol to acetophenone in the presence of mononuclear Rh complexes bearing phosphine ligands has been also described ( A detailed mechanistic proposal on the catalytic activity of these complexes in TH has never been reported.…”