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Graphical abstract A new rhodium(III) triphenylphosphine complex having the general formula [Rh(PPh 3) 2 (L)Cl] (1) was synthesized by C S bond cleavage of an ONS donor azo-thioether ligand (L-CH 2 Ph). The complex was thoroughly characterized by various spectroscopic techniques. Its single crystal X-ray structure exhibits an octahedral geometry around the rhodium(III) center. A cyclic voltammogram of the complex exhibits ligand based quasi-irreversible oxidative and reductive responses. The electronic structure, redox properties and electronic excitations in the complex were interpreted by DFT and TDDFT calculations. The complex effectively catalyzed the transfer hydrogenation reaction of ketones with high yields. Abstract A new rhodium(III) triphenylphosphine complex having the general formula [Rh(PPh 3) 2 (L)Cl] (1) was synthesized by C S bond cleavage of an ONS donor azo-thioether ligand (L-CH 2 Ph). The complex was thoroughly characterized by various spectroscopic techniques. Its single crystal X-ray structure exhibits an octahedral geometry around the rhodium(III) center. A cyclic voltammogram of the complex exhibits ligand based quasi-irreversible oxidative and reductive responses. The electronic structure, redox properties and electronic excitations in the complex were interpreted by DFT and TDDFT calculations. The complex effectively catalyzed the transfer hydrogenation reaction of ketones with high yields in i -PrOH in the presence of a base. [ABSTRACT FROM AUTHOR]

In recent years, α-imino rhodium carbene complexes derived by ring-opening of N-sulfonyl-1,2,3-triazoles have attracted much attention from organic chemists. Many transformations of these species have been reported that involve, in most cases, nucleophilic attack at the carbene center of the α-imino rhodium carbene, facilitating the synthesis of a wide range of novel and useful compounds, particularly heterocycles. This Minireview mainly focuses on advances in the transformation of N-sulfonyl-1,2,3-triazoles during the past two years. [ABSTRACT FROM AUTHOR]

The first example of efficient asymmetric hydrogenation of challenging β-aryloxyacrylic acids was realized using a RhI-complex based on the heterocombination of a readily available chiral monodentate secondary phosphine oxide (SPO) and an achiral monodentate phosphine ligand as the catalyst. Excellent enantioselectivities (92->99 % ee) were achieved for a wide variety of chiral β-aryloxypropionic acids with minor aryloxy elimination in most cases. The resultant products were readily transformed into biologically active compounds through simple synthetic manipulations. [ABSTRACT FROM AUTHOR]

Controlling the relative and absolute configuration of octahedral metal complexes constitutes a key challenge that needs to be overcome in order to fully exploit the structural properties of octahedral metal complexes for applications in the fields of catalysis, materials sciences, and life sciences. Herein, we describe the application of a proline-based chiral tridentate ligand to decisively control the coordination mode of an octahedral rhodium(III) complex. We demonstrate the mirror-like relationship of synthesized enantiomers and differences between diastereomers. Further, we demonstrate, using the established pyridocarbazole pharmacophore ligand as part of the organometallic complexes, the importance of the relative and absolute stereochemistry at the metal toward chiral environments like protein kinases. Protein kinase profiling and inhibition data confirm that the proline-based enantiopure rhodium(III) complexes, despite having all of the same constitution, differ strongly in their selectivity properties despite their unmistakably mutual origin. Moreover, two exemplary compounds have been shown to induce different toxic effects in an ex vivo rat liver model. [ABSTRACT FROM AUTHOR]

Herein we report that 1,4-dilithio-1,3-butadienes, a type of 1,3-butadienyl dianion, can act as non-innocent ligands, taking electrons from low-valent transition metals. Dilithio reagents reacted with [{RhCl(cod)}2] to give dilithio rhodacycle 3 a. Single-crystal X-ray structural analysis revealed the structure of 3 a with averaged bond lengths. XPS data suggested that the oxidation state of Rh in 3 a was more likely to be Rh3+. CDA/ECDA confirmed the electron-transfer process. 7Li NMR spectra of 3 a and theoretical calculations revealed a considerable aromatic character. In this process, the dilithio compounds behaved as non-innocent ligands and formal oxidants. These results demonstrated that organolithium compounds with suitable π-conjugation could be used as electron acceptor. [ABSTRACT FROM AUTHOR]

Electrophilic, cationic Rh(III) complexes of composition [(η5-C5Me5)Rh(Ap)]+, (1+), were prepared by reaction of [(η5-C5Me5)RhCl2]2 and LiAp (Ap = aminopyridinate ligand) followed by chloride abstraction with NaBArF (BArF = B[3,5-(CF3)2C6H3]4). Reactions of cations 1+ with different Lewis bases (e.g., NH3, 4-dimethylaminopyridine, or CNXyl) led in general to monoadducts 1·L+ (L = Lewis base; Xyl = 2,6-Me2C6H3), but carbon monoxide provided carbonyl-carbamoyl complexes 1·(CO)2+ as a result of metal coordination and formal insertion of CO into the Rh-Namido bond of complexes 1+. Arguably, the most relevant observation reported in this study stemmed from the reactions of complexes 1+ with H2. ¹H NMR analyses of the reactions demonstrated a H2-catalyzed isomerization of the aminopyridinate ligand in cations 1+ from the ordinary κ²-N,N' coordination to a very uncommon, formally tridentate κ-N,η³ pseudoallyl bonding mode (complexes 3+) following benzylic C-H activation within the xylyl substituent of the pyridinic ring of the aminopyridinate ligand. The isomerization entailed in addition H-H and N-H bond activation and mimicked previous findings with the analogous iridium complexes. However, in dissimilarity with iridium, rhodium complexes 1+ reacted stoichiometrically at 20 °C with excess H2. The transformations resulted in the hydrogenation of the C5Me5 and Ap ligands with concurrent reduction to Rh(I) and yielded complexes [(η4-C5Me5H)Rh(η6, (2+), in which the pyridinic xylyl substituent is 6-bonded to the rhodium(I) center. New compounds reported were characterized by microanalysis and NMR spectroscopy. Representative complexes were additionally investigated by X-ray crystallography. [ABSTRACT FROM AUTHOR]

A series of complexes of novel chelating thione-alkene S(η2-C=C)S tridentate ligands bound to late transition metals (Ir, Rh, Pd) were isolated and characterised. Counter-anions play an important role in the binding of the alkene moiety to the metals. Different solvents were observed to affect the stability of the rhodium complexes. [ABSTRACT FROM AUTHOR]

Three rhodium(I) complexes of the types [Rh( COE)Cl(η2-L)] ( 1a, 1b) and [ RhCl(η2-L) (η1-L)] ( 1c), where L = P~N donor ligands 2-[2-(diphenylphosphino) ethyl]pyridine, ( PPh2Etpy) ( a), 2-(diphenylphosphino)pyridine ( PPh2py) ( b), and 3-(diphenylphosphino)-1-propylamine (PPh2(CH2)3NH2) ( c), have been synthesized by reacting [Rh(coe)2Cl]2 with the respective ligands in 1:2 molar ratio for 1a, 1b and 1:4 molar ratio for 1c in DCM under refluxing condition. The complexes were characterized using different analytical techniques such as FT-IR, ESI(+) mass spectrometry, 1H and 31P{ 1H} NMR spectrometry, conductivity measurements, and melting point determination. The synthesized complexes were found to exhibit good catalytic activity for the transfer hydrogenation of carbonyl compounds to corresponding alcohols with high conversion rate. [ABSTRACT FROM AUTHOR]

Rhodium(I) complexes bearing amide-functionalised NHC ligands were synthesized in high yields through various synthetic routes and from different metal precursors, showing the versatility of such systems. By changing the ancillary ligands on the rhodium from cyclooctadiene to carbonyls the coordination behaviour of the NHC-amide ligand could be influenced. When a more basic precursor was employed for complexation, bidentate behaviour with the amide in an anionic mode was observed. All reported complexes are synthesized in high yields and under ambient conditions, which shows their robustness. The monodentate rhodium(I) biscarbonyl NHC complexes were shown to be able to activate iodomethane. [ABSTRACT FROM AUTHOR]

The synthesis and structural characterization of the new olefinic complex [Rh(η5-C5H5)(coe)2] ( 2) (coe = cis-cyclooctene) is reported. The title compound could easily be prepared in good yield by reaction of [{Rh(μ-Cl)(coe)2}2] ( 1) with an appropriate amount of thallium cyclopentadienide in THF at room temperature. Single crystals of 2 were grown from n-hexane and were analyzed by X-ray crystallography. In a similar manner the compound [Rh(η5-C5H5)(cod)] ( 4) (cod = cis, cis-1.5-cyclooctadiene) was obtained from [{Rh(μ-Cl)(cod)}2] and thallium cyclopentadienide in THF at room temperature and was characterized by spectroscopic means as well as by X-ray diffraction. [ABSTRACT FROM AUTHOR]

RhC30H25Cl2NO2P, orthorhombic P212121 (no. 19), a=7.6656(5) Å, b=16.6097(11) Å, c=20.9423(14) Å, V =2666.4(3) ų Z =4, Rgt(F)=0.0649, wRref(F²)=0.1632, T=100 K. [ABSTRACT FROM AUTHOR]

The (β-ketiminato)rhodium complex [Rh{κ2-( N, O)-( tBu)( O)CCHC( tBu) N(C6F5)}(cod)] ( 1) [cod = (1 Z,5 Z)-1,5-cyclooctadiene] and (β-diketiminato)rhodium complexes [Rh{κ2-( N, N)-(Ar) NC(Me)CHC(Me) N(Ar)}(L1)(L2)] [ 2: Ar = C6F5, (L1)(L2) = cod; 3: Ar = C6F5, L1 = L2 = C2H4; 4: Ar = C6F5, L1 = L2 = CN tBu; 5: Ar = 2,6-MeC6H3, L1 = L2 = CN tBu; 6a: Ar = C6F5, L1 = L2 = CO; 7a: Ar = C6F5, L1 = CO, L2 = NCMe; 8a: Ar = C6F5, L1 = CO, L2 = PEt3; 9a: Ar = C6F5, L1 = CO, L2 = NH3] were synthesized. Treatment of [Rh{κ2-( N, N)-(C6F5) NC(Me)CHC(Me) N(C6F5)}(CO)(NCMe)] ( 7a) with tertiary silanes HSiR3 gave the (β-diketiminato)(hydrido)(silyl)rhodium complexes [Rh{κ2-( N, N)-(C6F5) NC(Me)CHC(Me) N(C6F5)}(H)(SiR3)(CO)] ( 10a: R = Me; 11: R = Et; 12: R = iPr; 13: R = Ph; 14: R = OMe; 15: R = OEt). When using an excess amount of HSiMe3 the dihydridobis(silyl) complex [Rh{κ2-( N, N)-(C6F5) NC(Me)CHC(Me) N(C6F5)}(H)2(SiMe3)2] ( 16) was formed in addition to 10a. [ABSTRACT FROM AUTHOR]

A monoanionic, bidentate phosphaalkenyl–phosphidoligandwas designed, synthesized, and used for the complexation of a rhodiumcarbonyl fragment. The characterization of the latter revealed delocalizedπ electrons on the phosphaalkenyl–phosphide moiety. Thecatalytic activity of this rhodium carbonyl complex has been demonstratedin a hydrosilylation reaction. [ABSTRACT FROM AUTHOR]

Copper(I) complexes with phenanthro-annulated N-heterocyclic carbene ligands were prepared by reaction of imidazolium salts with copper(I) oxide. Transmetalation of the copper complexes with [RhCl(cod)]2 in usual solvents like CH2Cl2 led to an equilibrium between the reactants and the products. For rhodium complexes 4 and 5 this equilibrium could be shifted to the product side by carrying out the reaction in acetonitrile. The ester functionalized rhodium complex 6 was prepared in a two phase mixture of chloroform and aqueous CaCl2 starting from copper complex 3c. The rhodium complexes were characterized by NMR and X-ray measurements. [ABSTRACT FROM AUTHOR]

Highlights: [•] Synthesis of Rh(I) and Ir(I) carbonyl complexes of tetradentate phosphine ligand. [•] Spectroscopic and X-ray structural characterization of the synthesized complexes. [•] Catalytic activity of the complexes towards the hydroformylation of alkenes. [ABSTRACT FROM AUTHOR]

The addition of aminoalkyl-substituted 2,6-bis(imino)pyridine (or pyridine diimine, PDI) ligands to [(COD)RhCl]2 (COD = 1,5-cyclooctadiene) resulted in the formation of rhodium monochloride complexes with the general formula (NPDI)RhCl (NPDI = iPr2NEtPDI or Me2NPrPDI). The investigation of ( iPr2NEtPDI)RhCl and (Me2NPrPDI)RhCl by single-crystal X-ray diffraction verified the absence of amine arm coordination and a pseudo square-planar geometry about rhodium. Replacement of the chloride ligand with an outer-sphere anion was achieved by adding AgBF4 directly to ( iPr2NEtPDI)RhCl to form [( iPr2NEtPDI)Rh][BF4]. Alternatively, this complex was prepared by chelate addition following the salt metathesis reaction between AgBF4 and [(COD)RhCl]2. Using the latter method, both [(NPDI)Rh][BF4] complexes were isolated and found to exhibit κ4- N, N, N, N-PDI coordination regardless of arm length or steric bulk. In contrast, the metallation of PPDI chelates featuring alkylphosphane imine substituents (PPDI = Ph2PEtPDI or Ph2PPrPDI) resulted in the formation of cationic complexes featuring κ5- N, N, N, P, P-PDI coordination in all instances, [(PPDI)Rh][X] (X = Cl, BF4). Adjusting the metallation stoichiometry allowed the preparation of [(Ph2PPrPDI)Rh][(COD)RhCl2], as validated by multinuclear NMR spectroscopy and single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

Condensation of homochiral primary amines with 1-methyl-1H-imidazole-2-carbaldehyde affords the corresponding imidazolyl-imine compounds (L1–L3) which have been employed as ligands for the preparation of half-sandwich rhodium and iridium complexes of the formula [(η5-C5Me5)MClLn][SbF6]. Treatment of these chloride compounds with AgSbF6 renders dicationic aqua-complexes [(η5-C5Me5)MLn(H2O)] [SbF6]2 which act as catalysts for the Diels–Alder reaction between methacrolein and cyclopentadiene. Catalysis occurs with good exo : endo selectivity and poor enantioselectivity. All the compounds have been completely characterized by analytical and spectroscopic methods. Characterization includes the molecular structure determination of the complexes [(η5-C5Me5)MClLn][SbF6] (Ln = L1, M = Rh, (1) Ir (4); Ln = L3, M = Ir (6)) and [(η5-C5Me5)ML1(H2O)][SbF6]2 (M = Rh (7), Ir (10)) using X-ray diffraction. From the stereochemical properties of the organometallic precursors the catalytic outcome is discussed. [ABSTRACT FROM AUTHOR]

The N-heterocyclic carbene NHC/thione ligand precursors 1-[(3-R-2-thioxo-2 H-imidazol-1-yl)methyl]-3-R-2 H-imidazol-2-ium hexafluorophosphate, [HCSR]PF6 (R = methyl, benzyl) have been prepared and used in the synthesis of the complexes [Rh(CSR)(cod)][PF6] (R = methyl, benzyl; cod = 1,5-cyclooctadiene). The coordination and structural features of the novel ditopic NHC/thione ligands have been explored. [ABSTRACT FROM AUTHOR]

The C–C bond of cyclobutanones undergoes oxidative addition to a T-shape rhodium(I) complex possessing a PBP pincer ligand at room temperature. The remarkable propensity of the rhodium complex for oxidative addition is attributed to the highly electron-donating nature of the boron ligand as well as the unsaturation on the rhodium center. [ABSTRACT FROM AUTHOR]

The bis(pentalene) complexes M2(pent†)2(M = Rh (1), Pd (2); pent†= 1,4-bis(triisopropylsilyl)pentalene) have been synthesizedand structurally characterized. In both 1and 2the metals have a formal electron count in excess of 18 per metalcenter, and DFT calculations indicate antibonding metal–metalinteractions are present in 1, whereas 2involves antibonding metal–ligand interactions. [ABSTRACT FROM AUTHOR]

The design and synthesis of an intensely blue rhodium(III) complex [ 3]+ of a new N,N-donor ligand, 8-(quinolin-8-ylamino)pyrido[2,1- c][1,2,4]benzotriazin-11-ium, [ 2]+, which contains a planar pendant triazinium arm, is described. Structural characterization for [ 3]+ was carried out by using various spectroscopic techniques and single-crystal X-ray crystallography. The organometallic rhodium(III) compound shows a ligand-based reversible reduction at -0.65 V. The electrochemically reduced compound displays a single-line EPR spectrum that signifies the formation of ligand-based free radicals. Compound [ 3]+ shows a binding propensity to calf thymus DNA to give a Kapp value of 6.05 × 105 M-1. The parent triazinium salt, pyrido[2,1- c][1,2,4]benzotriazin-11-ium [ 1]+ and the ligand salt [ 2]+ exhibit photoinduced cleavage of DNA in UV-A light, whereas the reference Rh complex [ 3]+ photocleaves DNA with red light (647.1 nm). The compounds show photonuclease activities under both aerobic and anaerobic conditions. Mechanistic investigations under aerobic conditions with several inhibitors indicate the formation of hydroxyl radicals by means of a photoredox pathway. Under anaerobic conditions, it is believed that a photoinduced oxidation of DNA mechanism is operative. Compound [ 3]+ exhibits photocytotoxicity in HeLa cervical cancer cells to give IC50 values of (12 ± 0.9) μ M in UV-A light at 365 nm and (31.4 ± 1.1) μ M in the dark. [ABSTRACT FROM AUTHOR]

The neutral rhodium(I) square-planar complexes [RhX(CO)2(L)] [X = Cl (3), I (4)] bearing a nitrogen-containing ligand L [diethylamine (a), triethylamine (b), imidazole (c), l-methylpyrazole (d), pyrazole (e), l-methyipyrazole (f), 3,S-dimethyIpyrazole (g)] are straightforwardly obtained from L and [Rh(µ-X)(CO)2]2 [X = CI (1), I (2)] precursors. The synthesis is extended to the diethylsulfide ligand h for 3h and 4h. According to the CO stretching frequency of 3 and 4, the ranking of the electronic density on the rhodium center follows the order b>a≈d>c>g>f≈h>e. The X-ray molecular structures of 3a, 3d--3f, 4a, and 4d--4f were determined. Results from variable-temperature 1H and 13C{1H} NMR experiments suggest a fluxional associative ligand exchange for 4c∼4h and a supplementary hydrogen-exchange process in 4e and 4g. The oxidative addition reaction of CH3I to complexes 4c--4g affords the neutral dimeric iodo-bridged acetylrhodium(III) complexes [RhI(µ-I)(COCH3)(CO)(L)]2 (6c--6g) in very good isolated yields, whereas 4a gives a mixture of neutral 6a and dianionic [RhI2(µ-I)(COCH3)(CO)][NHMeEt2]2 and 4h exclusively provides the analogue dianionic complex with [SMeEt2]+ as the counterion. X-ray molecular structures for 6d2 and 6e reveal that the two apical CO ligands are in mutual cis positions, as are the two apical d and e ligands, whereas Isomer 6d, is centrosymmetric. Further reactions of 6d and 6e with CO or ligand e gave quantitatively the monomeric complexes [RhI2(COCH3)(CO)2(d)] (7d) and [RhI2(COCH3)(CO)(e)2] (8e), respectively, as confirmed by their X-ray structures. The initial rate of CH3I oxidative addition to 4 as determined by IR monitoring is dependent on tlie nature of the nitrogen-containing ligand. For 4a and 4h, reaction rates similar to those of the well-known rhodium anionic [RhI2(CO)2]- spedes are observed and are consistent with tlie fonnation of this intermediate species through methylation of die a and h ligands. The reaction rates are reduced significantly when using imidazole and pyrazole ligands and involve the direct oxidative addition of CH3I to the neutral complexes 4c--4g. Complexes 4c and 4d react around 5-10 times fester than 4e--4g mainly because of electronic effects. The lowest reactivity of 4f toward CH3I is attributed to the steric effect of the coordinated ligand, as supported by the X-ray structure. [ABSTRACT FROM AUTHOR]

The mixed-ligand di-m-chloro-bridged rhodium dimers [(h2-C8H14)(h4-2-methylbuta-1,3-diene)Rh(m-Cl)]2 and [(h2-C8H14)(h4-2,3- dimethylbuta-1,3-diene)Rh(m-Cl)]2 were synthesized and characterized. These compounds are key precursors in the preparative syn- thesis of the acyclic (p-allyl)-closo-rhodacarborane complexes [3-{p-(R”-allyl)}-1-R-2-R’-closo-3,1,2-RhC2B9H9], which were obtained earlier via the one-pot metallation of the K+ salts of the [7-R-8-R’-nido-7,8-C2B9H10]– anions with [(h2-C8H14)4Rh2(m-Cl)2] in the presence of substituted buta-1,3-diene ligands. [ABSTRACT FROM AUTHOR]

Rh(III) complexes with a bidentate N-heterocyclic carbene ligand bearing flexible dendritic frameworks have been synthesized and fully characterized by X-ray crystallographic analysis, NMR measurements and theoretical calculations. [ABSTRACT FROM AUTHOR]