A new subgroup of bis(pyrazolyl)methane ligands has been developed through the synthesis of the first N,N,N,Ntetradentate bis(pyrazolyl)methane compounds, namely, bis-(pyrazolyl)bipyridinylmethane [HC(Pz) 2 Bipy, L1] and bis(3,5methylpyrazolyl)bipyridinylmethane [HC(3,5-MePz) 2 Bipy, L2].From these ligands, a large variety of new mononuclear Fe II and Zn II complexes with counterions ranging from halides to carboxylates and sulfate were synthesised and characterised by [a]
Heteroscorpionate ligands of the bis(pyrazolyl)methane family have been applied in the stabilisation of terminal copper tosyl nitrenes. These species are highly active intermediates in the copper-catalysed direct C-H amination and nitrene transfer. Novel perfluoroalkyl-pyrazolyl- and pyridinyl-containing ligands were synthesized to coordinate to a reactive copper nitrene centre. Four distinct copper tosyl nitrenes were prepared at low temperatures by the reaction with SO tBuPhINTs and copper(I) acetonitrile complexes. Their stoichiometric reactivity has been elucidated regarding the imination of phosphines and the aziridination of styrenes. The formation and thermal decay of the copper nitrenes were investigated by UV/Vis spectroscopy of the highly coloured species. Additionally, the compounds were studied by cryo-UHR-ESI mass spectrometry and DFT calculations. In addition, a mild catalytic procedure has been developed where the copper nitrene precursors enable the C-H amination of cyclohexane and toluene and the aziridination of styrenes.
A series of dinuclear chelate complexes of the general composition [Rh2(kappa2-L)2(mu-CR2)2(mu-SbiPr3)] (R = Ph, p-Tol; L = CF3CO2-, acac-, acac-f3-) and [Rh2Cl(kappa2-L)(mu-CR2)2(mu-SbiPr3)] (R = Ph, p-Tol; L = acac-, acac-f3-) has been prepared by replacement of the chloro ligands in the precursors [Rh2Cl2(mu-CR2)2(mu-SbiPr3)] by anionic chelates. The lability of the SbiPr3 bridge in the rhodium dimers is illustrated by the reactions of [Rh2(kappa2-acac)2(mu-CR2)2(mu-SbiPr3)] (7, 8) with Lewis bases such as CO, CNtBu, and SbEt3 which lead to the formation of the substitution products [Rh2(kappa2-acac)2(mu-CR2)2(mu-L')] (13-16) in excellent yields. Treatment of 7 and 8 with sterically demanding tertiary phosphanes PR3 (R3 = iPr3, iPr2Ph, iPrPh2, Ph3) affords the mixed-valence Rh0-RhII complexes [(kappa2-acac)2Rh(mu-CPh2)2Rh(PR3)] (21-24) and [(kappa2-acac)2Rh(mu-C(p-Tol)2]2Rh(PiPr3)] (25) for which there is no precedence. The terminal PiPr3 ligand of 21 is easily displaced by alkynes, CNtBu, and CO to give, by preserving the [(kappa2-acac)2Rh(mu-CPh2)2Rh] molecular core, the related dinuclear compounds 26-31 in which the coordination number of the Rh0 center is 3, 4, or 5. The molecular structures of [Rh2Cl(kappa2-acac)(mu-CPh2)2(mu-SbiPr3)] (5), [Rh2(kappa2-acac)2(mu-CPh2)2(mu-CO)] (13), [(kappa2-acac)2Rh(mu-CPh2)2Rh(PiPr3)] (21), and [(kappa2-acac)2Rh(mu-CPh2)2Rh(CNtBu)2] (30) have been determined crystallographically.
It is well-known that transition-metal carbene complexes readily undergo C-C coupling reactions not only with alkenes (olefin metathesis) and alkynes (Dötz reaction) but also with CO and other C-nucleophiles. 1 During attempts to study the reactivity of the halfsandwich-type compounds [(η 5 -C 5 H 5 )Rh(dCPh 2 )(SbiPr 3 )] (1) and the corresponding triisopropylphosphine derivative 2 (Scheme 1), which were prepared from the squareplanar precursors trans-[RhCl(dCPh 2 )L 2 ] and NaC 5 H 5 , 2 we observed that the course of the reaction of 1 and 2 with CO and isocyanides depends critically on the ligand L of the starting material. While the stibane complex 1 on treatment with CO or CNtBu yields the mixed (carbene)(carbonyl) and (carbene)(isocyanide)rhodium compounds [(η 5 -C 5 H 5 )Rh(dCPh 2 )(CX)] (3a, X ) O; 3b, X ) NtBu), the phosphine derivative 2 affords the noncarbene-containing products [(η 5 -C 5 H 5 )Rh(PiPr 3 )(CX)] (4a,b) together with diphenylketene or the corresponding ketenimine. 2, 3 We have now found that PF 3 , despite the similarity of its σ-donor/π-acceptor capabilities with those of CO, reacts with 2 in a completely different way, leading to an unprecedented migratory insertion of the CPh 2 unit into an sp 2 C-H bond.Treatment of compound 2 with PF 3 in benzene at room temperature leads to a smooth change of color from blue to orange and finally to the isolation of the orange air-and moisture-sensitive solid 5 in moderate yield. 4 The most characteristic spectroscopic features of 5 are the signals for the CHPh 2 proton at δ 4.79 in the 1 H NMR and the two resonances for the phosphorus nuclei of the PF 3 and PiPr 3 ligands at δ 119.4 and 79.0 in the 31 P NMR spectrum. 5 Both 31 P NMR signals show strong Rh-P couplings of 446 and 221 Hz, respectively. The X-ray crystal structure analysis of 5 ( Figure 1) 6 X Abstract published in Advance ACS Abstracts, December 15, 1997. (1) (a) Dötz, K. H.; Fischer, H.; Hofmann, P.; Kreissl, F. R.; Schubert, U.; Weiss, K.(4) The preparation of 5 is as follows. A slow stream of PF3 was passed through a solution of 2 (100 mg, 0.20 mmol) in 20 mL of benzene for 20 min at room temperature. After the solution was stirred for another 20 min, the solvent was removed and the oily residue dissolved in 3 mL of pentane. Column chromatography on Al2O3 (neutral, activity grade V) gave upon elution with pentane an orange fraction which was brought to dryness in vacuo. The solid was recrystallized from pentane (-78°C) to afford orange crystals: yield 48 mg (41%).(5) Selected spectroscopic data for 5, 6a, 6b, and 7a (omitting the 1 H and 13 C NMR data for isopropyl and phenyl groups) are as follows. 5: 1 H NMR (200 MHz, C6D6) δ 5.1 (m, 4H, C5H4), 4.8 (m, 1H, CHPh2); 31 P NMR (81.0 MHz, C6D6) δ 119.4 (ddq, 1 J(PF) ) 849.3, 1 J(RhP) ) 446.3, 2 J(PP) ) 77.6 Hz, PF3), 79.0 (dd, 1 J(RhP) ) 221.0, 2 J(PP) ) 77.6 Hz, PiPr3). 6a: 1 H NMR (400 MHz, C6D6) δ 5.72 (d, 3 J(RhH) ) 2.9 Hz, 1H, CHPh2), 5.1, 4.4 (both m, 2H each, C5H4), -12.21 (dd, 1 J(RhH) ) 35.1, 2 J(PH) ) 13.8 Hz, 1H, RhH); ...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.