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1-Alkyl-1H-Benzimidazolium Sulfonates as Non-Competitive Inhibitors of Polyphenol Oxidase
(Wiley, 2026) Ergun, Adem; Cikrikci, Kubra; Gencer, Nahit; Arslan, Oktay; Uslu, Harun; Goktas, Bunyamin; Karatas, Mert Olgun
Polyphenol oxidase (PPO) has been the subject of many inhibition studies due to its presence in many species, causing enzymatic browning in fruits and vegetables, and its pigmentation role in mammalian species. In the present study, the inhibitory properties of twelve 1-alkyl-1H-benzimidazolium sulfonates and two 1-alkyl-1H-benzimidazolium iodides on PPO activity have been investigated. The PPO enzyme was purified from banana using Sepharose 4B-tyrosine-p-aminobenzoic acid affinity gel chromatography. The effects of 14 different synthesized benzimidazole derivatives on the PPO enzyme were investigated, and they were found to significantly inhibit the enzyme in question. When ADME predictions were examined, it was seen that all compounds that include methylbenzenesulfonate structure showed good pharmacokinetic properties; only compounds 3a and 3b, which contain iodide, violated the Ghose rules. These compounds, which were effective at low concentrations, may serve as promising lead molecules for the development of PPO inhibitors with potential applications in food preservation, cosmetic formulations, and pharmaceutical research, pending further in vivo and formulation-based studies.
Benzotriazole functionalized N-heterocyclic carbene-silver(I) complexes: Synthesis, cytotoxicity, antimicrobial, DNA binding, and molecular docking studies
(Pergamon-Elsevier Science Ltd, 2018) Onar, Gulnihan; Karatas, Mert Olgun; Balcioglu, Sevgi; Tok, Tugba Taskin; Gurses, Canbolat; Kilic-Cikla, Isin; Ozdemir, Namik
In this study, six [Ag(NHC)(2)](+)[AgCl2](-) type silver complexes were synthesized by the reaction of corresponding carbene precursor and Ag2O. One [Ag(NHC)(2)]+NO3- type complex was synthesized by the anion exchange reaction of corresponding silver-NHC and NaNO3. The synthesized complexes were characterized by H-1 NMR, C-13 NMR and IR spectroscopic methods, and elemental analysis. X-ray crystal structure of 5a was also reported. Cytotoxicities of all compounds were evaluated against human breast (MCF-7) and colorectal (Caco-2) cancer cell lines and non-cancer mouse fibroblast (L-929) cell lines. All complexes performed stronger activity against both cancer cell lines than standard compound cisplatin while complex 3b performed nearly equal cytotoxicity to cisplatin against non-cancer L-929. Antimicrobial effects of all compounds were evaluated against Escherichia coli, Bacillus subtilis and Candida albicans and good activities were observed. The docking results indicated that complex 3b might be classified as druggable molecule in drug design. DNA binding study also demonstrates that 3b complex has an interaction ability to DNA. Combination of experimental and molecular docking results revealed that reported complexes are promising structures and deserve further research as anticancer drugs. (C) 2018 Elsevier Ltd. All rights reserved.
Comparison of the catalytic performances of bridged bi-metallic and non-bridged mono-metallic PEPPSI type palladium N-heterocyclic carbene complexes
(Elsevier, 2020) Karatas, Mert Olgun; Alici, Bulent
Palladium-N-heterocyclic carbene complexes are widely investigated catalysts in cross-coupling reactions. However, studies about the catalytic activities of bridged bi-metallic complexes are quite rare. Therefore, in this study, anthracene-substituted one mono-metallic and one bridged bi-metallic PEPPSI-type Pd-NHC complexes were synthesized in order to compare their catalytic activities in Suzuki-Miyaura and Mizoroki-Heck reactions. Both complexes were fully characterized by H-1 and C-13 NMR, LC-MS, IR spectra and elemental analyses. The results of catalytic reactions clearly revealed that mono-metallic complex performs better catalytic activity than bi-metallic analogue in the use of same amount of palladium.
Coumarin or benzoxazinone based novel carbonic anhydrase inhibitors: synthesis, molecular docking and anticonvulsant studies
(Taylor & Francis Ltd, 2016) Karatas, Mert Olgun; Uslu, Harun; Sari, Suat; Alagoz, Mehmet Abdullah; Karakurt, Arzu; Alici, Bulent; Bilen, Cigdem
Among many others, coumarin derivatives are known to show human carbonic anhydrase (hCA) inhibitory activity. Since hCA inhibition is one of the underlying mechanisms that account for the activities of some antiepileptic drugs (AEDs), hCA inhibitors are expected to have anti-seizure properties. There are also several studies reporting compounds with an imidazole and/or benzimidazole moiety which exert these pharmacological properties. In this study, we prepared fifteen novel coumarin-bearing imidazolium and benzimidazolium chloride, nine novel benzoxazinone-bearing imidazolium and benzimidazolium chloride derivatives and evaluated their hCA inhibitory activities and along with fourteen previously synthesized derivatives we scanned their anticonvulsant effects. As all compounds inhibited purified hCA isoforms I and II, some of them also proved protective against Maximal electroshock seizure (MES) and ScMet induced seizures in mice. Molecular docking studies with selected coumarin derivatives have revealed that these compounds bind to the active pocket of the enzyme in a similar fashion to that previously described for coumarin derivatives.
Cycloheptyl substituted N-heterocyclic carbene PEPPSI-type palladium complexes with different N-coordinated ligands: Involvement in Suzuki-Miyaura reaction
(Elsevier Science Sa, 2019) Karatas, Mert Olgun
In the present study, synthesis and catalytic properties of palladium PEPPSI type complexes of cycloheptyl substituted N-heterocyclic carbene ligand were reported. Different N-coordinate ligands including pyridine, imidazole and thiazole derivatives were used to stabilize the complexes. Structures of complexes were established by H-1 NMR, C-13 NMR, IR spectroscopic methods and elemental analyses. All complexes were applied to Suzuki-Miyaura cross coupling reaction in aqueous media. After the optimization of reaction conditions, all complexes were tested on the cross coupling of five different aryl chloride derivatives and phenylboronic acid. Pyridine containing complex, 3a performed stronger catalytic performance than others. (C) 2019 Elsevier B.V. All rights reserved.
Cytotoxic effects of coumarin substituted benzimidazolium salts against human prostate and ovarian cancer cells
(Indian Acad Sciences, 2019) Karatas, Mert Olgun; Tekin, Suat; Alici, Bulent; Sandal, Suleyman
Coumarin and benzimidazole derivatives have individual biological activities including anticancer. In this study, we aimed to synthesize coumarin-benzimidazole hybrids in order to investigate their anticancer properties. For this purpose, six 6-substituted-4-chloromethylene coumarin derivatives were synthesized. Sixteen coumarin substituted benzimidazolium chlorides were synthesized by the reaction of 4-chloromethylene coumarin and N-benzylbenzimidazole derivatives. All of the synthesized compounds were characterized by 1H and 13C NMR, IR spectroscopic techniques and elemental analyses. Cytotoxicities of all compounds were tested by [ 3-(4,5-dimethylthiazole)-2-yl]-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay against human prostate (PC-3) and ovarian (A2780) cancer cells. All compounds performed significant cytotoxicities at 100 mu Magainst both cancer cell lines. Moreover, some compounds performed significant activities at 1 mu M against both cancer cell lines and the obtained results suggest that this type of compounds are promising candidates for the treatment of human prostate and ovarian cancers.
Cytotoxic potential of silver, palladium, rhodium, ruthenium, and iridium complexes of a cycloheptyl-substituted lipophilic N-heterocyclic carbene ligand
(Taylor & Francis Ltd, 2023) Karatas, Mert Olgun; Sekerci, Guldeniz; Tekin, Suat; Sandal, Suleyman; Kucukbay, Hasan
Lipophilicity is a crucial parameter for cytotoxicity of metal complexes, in many cases associated with increased activity. In the present study, we synthesized a series of N-heterocyclic carbene (NHC) complexes of different metals with a lipophilic benzimidazolium chloride to investigate and compare their cytotoxicity. Rh- (4), Ru- (5), and Ir-NHC (6) complexes of a cycloheptyl-substituted benzimidazole-based NHC ligand (1) have been prepared by transmetalation reaction between Ag-NHC and the corresponding metal compound. The newly synthesized complexes have been characterized by NMR, IR, LC-MS spectroscopy, and elemental analyses. The anti-growth effects of the newly synthesized Rh-, Ru-, and Ir-NHC complexes and previously reported NHC precursor (1), Ag- (2), and Pd-NHC (3) complexes against human breast (MCF-7), colorectal (Caco-2), ovarian (A2780), and prostate (LNCaP) cancer cell lines have been investigated by MTT assay. The results revealed that the compounds provide stronger anti-growth effects against all cell lines compared to standard drug cisplatin. Among the compounds, benzimidazolium chloride, and Ag-NHC complex showed promising activities.
Dinuclear Rhodium(I)-N-Heterocyclic Carbene Complexes as Alkyne Hydropyridonation Catalysts
(Wiley-V C H Verlag Gmbh, 2026) Espanol-Sanchez, Belinda; Karatas, Mert Olgun; Di Giuseppe, Andrea; Togaev, Ulugbek; Passarelli, Vincenzo; Oro, Luis A.; Perez-Torrente, Jesus J.
A series of new RhI-N-Heterocyclic carbene dinuclear complexes of type [Rh(mu -Cl)(eta 2-coe)(NHC)]2, containing IPrBIAN, IPrCl, and IPr* ligands, has been prepared. The crystal structure of the IPrCl functionalized rhodium-dinuclear complex reveals an intermolecular ClCl halogen bond. The chlorido-bridges can be cleaved by pyridine to afford the corresponding mononuclear derivatives RhCl(eta 2-coe)(NHC)(py). These complexes are efficient alkyne hydropyridonation catalysts, with the IMes complex exhibiting the highest reactivity within the series.
Efficiency enhancement with chloride to iodide ion exchange of benzimidazolium salt as a redox mediator
(Tubitak Scientific & Technological Research Council Turkey, 2021) Dayan, Serkan; Karatas, Mert Olgun; Alici, Bulent; Kalaycioglu Ozpozan, Nilgun
The new benzimidazolium derivative (SM-1) salt with ion exchange from the (SM-0) was fabricated and characterized by proton-nuclear magnetic resonance (H-1-NMR), carbon-nuclear magnetic resonance (C-13-NMR), Fourier-transform infrared spectroscopy (FTIR), electrospray ionization (EIS-MS), thermal analysis (TG), cyclic voltammetry (CV), and ultraviolet-visible spectroscopy (UV-vis), for electrolytes (liquid or dried) in the DSSC charge transportation mechanism. Also, the influence of ion exchange from chloride to iodine in the synthesized electrolytes, compared to other electrolytes (conventional or commercial), was investigated about DSSC performance efficiency. When using as a liquid electrolyte (SM-1), the power conversion efficiency (eta) of the working DSSC device was recorded as 1.980% and it was observed that the performances of DSSCs increased up to 56% when comparing dried electrolyte for SM-1 without conventional redox material (I-/I3-). In the future, different molecular modifications of this type of benzimidazole derivatives or mixtures with conventional redox couples may further improve the performance of DSSC devices.
Functionalized imidazolium and benzimidazolium salts as paraoxonase 1 inhibitors: Synthesis, characterization and molecular docking studies
(Pergamon-Elsevier Science Ltd, 2016) Karatas, Mert Olgun; Uslu, Harun; Alici, Bulent; Gokce, Basak; Gencer, Nahit; Arslan, Oktay; Arslan, N. Burcu
Paraoxonase (PON) is a key enzyme in metabolism of living organisms and decreased activity of PON1 was acknowledged as a risk for atherosclerosis and organophosphate toxicity. The present study describes the synthesis, characterization, PON1 inhibitory properties and molecular docking studies of functionalized imidazolium and benzimidazolium salts (1a-5g). The structures of all compounds were elucidated by IR, NMR, elemental analysis and structures of compounds 2b and 2c were characterized by single-crystal X-ray diffraction. Compound 1c, a coumarin substituted imidazolium salt showed the best inhibitory effect on the activity of PON1 with good IC50 value (6.37 mu M). Kinetic investigation was evaluated for this compound and results showed that this compound is competitive inhibitor of PON1 with K-1, value of 2.39 mu M. Molecular docking studies were also performed for most active compound 1c and one of least active compound 2c in order to determine the probable binding model into active site of PON1 and validation of the experimental results. (C) 2016 Elsevier Ltd. All rights reserved.
In vitro inhibition effect of some coumarin compounds on purified human serum paraoxonase 1 (PON1)
(Taylor & Francis Ltd, 2016) Gokce, Basak; Gencer, Nahit; Arslan, Oktay; Karatas, Mert Olgun; Alici, Bulent
Human serum paraoxonase 1 (PON1; EC 3.1.8.1) is a high-density lipoprotein associated, calcium-dependent enzyme that hydrolyses aromatic esters, organophosphates and lactones and can protect the low-density lipoprotein against oxidation. In this study, in vitro effect of some hydroxy and dihydroxy ionic coumarin derivatives (1-20) on purified PON1 activity was investigated. Among these compounds, derivatives 11-20 are water soluble. In investigated compounds, compounds 6 and 13 were found the most active (IC50 = 35 and 34 mu M) for PON1, respectively. The present study has demonstrated that PON1 activity is very highly sensitive to studied coumarin derivatives.
Inhibition of paraoxonase 1 by coumarin-substituted N-heterocyclic carbene silver(I), ruthenium(II) and palladium(II) complexes
(Wiley, 2019) Karatas, Mert Olgun; Calgin, Gamze; Alici, Bulent; Gokce, Basak; Gencer, Nahit; Tok, Tugba Taskin; Arslan, Oktay
We synthesized three coumarin-substituted benzimidazolium chlorides and their silver(I), ruthenium(II) and palladium(II) N-heterocyclic carbene (NHC) complexes. All compounds were characterized using appropriate spectroscopic techniques and elemental analyses. Single-crystal X-ray structure of a Pd(II)-NHC complex (6b) was also determined. The inhibitory properties of all compounds were tested on the activity of human paraoxonase 1 (PON1). All complexes exhibited weaker inhibitory properties than their corresponding benzimidazolium salts except for complex 6b which is the most active inhibitor with an IC50 value of 3.01 mu M among the compounds reported in this study. A kinetic evaluation showed that this complex inhibits PON1 activity in a non-competitive manner. Molecular docking studies were also performed for 6b in order to obtain more insight into the binding mode.
Microwave-Assisted Synthesis of Novel Perimidinium Salts as N-Heterocyclic Carbene Precursors: Involvement in Palladium-Catalyzed Cross-Coupling Reactions
(Springer, 2015) Onar, Gulnihan; Karatas, Mert Olgun; Alici, Bulent; Cetinkaya, Engin
In the current study, five novel perimidinium chlorides were synthesized in good yields by reaction of 1-(3-methylbenzyl)perimidine with five different alkyl chlorides under microwave irradiation in 30 minutes. Synthesized compounds were characterized by IR, H-1, C-13 NMR spectroscopic methods and elemental analyses. Performance of in situ formed catalytic system which consist of the perimidinium salts and Pd(OAc)(2) was investigated for Heck and Suzuki reactions in aqueous media, and desired products were obtained in good yields.
N-heterocyclic carbene palladium complexes with different N-coordinated ligands: Comparison of their catalytic activities in Suzuki-Miyaura and Mizoroki-Heck reactions
(Pergamon-Elsevier Science Ltd, 2020) Karatas, Mert Olgun; Ozdemir, Namik; Alici, Bulent; Ozdemir, Ismail
In this paper, we have reported the synthesis and catalytic activities of four new anthracene substituted imidazole-based palladium N-heterocyclic carbene complexes. The synthesized complexes, 2a-d, were stabilized with different N-heterocycles, namely pyridine, N-methylimidazole, N-vinylimidazole and 4,5-dimethylthiazole, respectively. The complexes were completely characterized using H-1 NMR, C-13 NMR, IR, LC-MS spectroscopic methods and elemental analyses. The crystal structures of 2a, 2c and 2d were also reported. The catalytic activities of all the complexes were tested for Suzuki-Miyaura and Mizoroki-Heck cross-coupling reactions in aqueous medium. According to the results, for the Suzuki-Miyaura reaction, the pyridine bearing complex 2a, and for the Mizoroki-Heck reaction, the 4,5-dimethylthiazole bearing complex 2d were found to be the most active catalysts. (C) 2019 Elsevier Ltd. All rights reserved.
New coumarin derivatives as carbonic anhydrase inhibitors
(Taylor & Francis Ltd, 2014) Karatas, Mert Olgun; Alici, Bulent; Cakir, Umit; Cetinkaya, Engin; Demir, Dudu; Ergun, Adem; Gencer, Nahit
In the current study, a series of 4-chloromethyl-7-hydroxy-coumarin derivatives containing imidazolium, benzimidazolium, bisbenzimidazolium and quaternary ammonium salts were synthesized, characterized and the inhibition effects of the derivatives on human carbonic anhydrases (hCA I and hCA II) were investigated as in vitro. Structures of these coumarins were confirmed by FT-IR, (1)H NMR, (13)C NMR and LC-MS analyses. Structure activity relationship study showed that 3d (IC50: 79 mu m M for hCA I and 88 m M for hCA II) performed higher inhibitory activity than others.
New silver, rhodium and iridium complexes with anthracene-functionalized N-heterocyclic carbene ligands: Crystal structures, cytotoxicity and fluorescence studies
(Pergamon-Elsevier Science Ltd, 2024) Bekci, Hatice; Ozdemir, Namuk; Sahin, Zeynel; Mumcu, Akun; Dayan, Serkan; Karatas, Mert Olgun
In the present study, we have synthesized anthracene-functionalized metal complexes to investigate their cytotoxicity and photophysical properties. In this context, firstly, an Ag - NHC (NHC = N -heterocyclic carbene) complex ( 2a ) has been synthesized by the interaction of Ag 2 O and N -(2-methylbenzyl)- N -((anthracen-9-yl) methyl)benzimidazolium chloride ( 1a ). Corresponding Rh - ( 3a ) and Ir - NHC ( 4a ) complexes have also been synthesized by the transmetalation reaction between 2a and corresponding metal compounds. Additionally, for comparison purposes, an ether-functionalized Ag - NHC complex ( 2b ) with N -(methoxyethyl)- N -((anthracene-9- yl)methyl)benzimidazole-2-ylidene ligand, and [AgL 2 ]NO 3 type complex ( 2c ) with a N -coordinated N - ((anthracen-9-yl)methyl)benzimidazole ligand have been synthesized. All complexes have been characterized by the combination of NMR and mass spectroscopic techniques, and elemental analyses. Moreover, solid state structures of 2a , 2b and 4a have been determined by the single crystal X-ray diffraction analysis. Cytotoxic potentials of all compounds have been tested against human lung adenocarcinoma alveolar basal epithelial cell line (A549) using the MTT assay, and all complexes performed strong anti-proliferative activity. Stability studies have disclosed that only 1a and 2c are able to retain their structure in the culture medium (DMEM) that biological assays were carried out. Photophysical measurements revealed that all compounds have similar emission bands because of the conjugation of anthracene group. Finally, 1a and 2c have been visualized by fluorescence confocal microscopy to investigate cellular uptake and subcellular distribution of the complexes, and the findings indicated that both compounds dispersed along the cell membranes nuclear regions.
Palladium(II) and ruthenium(II) complexes of benzotriazole functionalized N-heterocyclic carbenes: Cytotoxicity, antimicrobial, and DNA interaction studies
(Elsevier Science Sa, 2019) Onar, Gulnihan; Gurses, Canbolat; Karatas, Mert Olgun; Balcioglu, Sevgi; Akbay, Nuriye; Ozdemir, Namik; Ates, Burhan
In the present study, four palladium and four ruthenium complexes were synthesized with benzotriazole substituted N-heterocyclic carbene ligands. The structures of complexes were established by appropriate spectroscopic methods and elemental analyses. In addition, the crystal structure of a Pd-NHC complex (1c) was reported. Anticancer, antimicrobial and DNA interaction properties of the complexes were examined. Antimicrobial effects of the complexes were tested against two bacteria strains and one fungi strain. Cytotoxic effects of the complexes were tested against human breast (MCF-7) and colorectal (Caco-2) cancer cell lines and non-cancer mouse fibroblast (L-929) cell lines. Ruthenium complexes were found as more cytotoxic than palladium complexes against cancer cell lines. Especially, benzyl containing, benzimidazole-based ruthenium complexes (3c and 3d) were found as non-cytotoxic against non-cancer L-929 cell lines while performing comparable cytotoxicity against Caco-2 cancer cell lines with cisplatin. In addition, DNA interaction studies were performed with pBR322 plasmid DNA and ctDNA and results showed that both palladium and ruthenium complexes have weaker ability to interact with DNA than cisplatin. The results from this study showed that although the cytotoxic properties of the complexes are not stronger than cisplatin, selectivity of benzyl containing benzimidazole-based ruthenium-NHC complexes against Caco-2 cell lines provides them an advantage, and they deserve further research in the treatment of human colorectal cancer. (c) 2019 Elsevier B.V. All rights reserved.
Pentacoordinated Rhodium(I) Complexes Supported by Coumarin-Functionalized N-Heterocyclic Carbene Ligands
(Amer Chemical Soc, 2018) Karatas, Mert Olgun; Di Giuseppe, Andrea; Passarelli, Vincenzo; Alici, Bulent; Perez-Torrente, Jesus J.; Oro, Luis A.; Ozdemir, Ismail
New coumarin-tethered benzimidazolium (BzICou(R)HCl) and imidazolium (ICou(R)HCl) salts have been prepared as precursors for coumarin-NHC rhodium(I) complexes RhCl(NHC)(cod). Trigonal bypiramidal pentacoordinated bis-coumarin-NHC rhodium(I) species, RhCl(NHC)(2), can be obtained by heating rhodium-cod derivatives in the presence of coumarin-azolium salts and a base. These unusual species are stabilized by coordination of the unsaturated bond of both coumarin moieties by the same enantioface. The allyl substituent on doubly functionalized NHC competes for coordination with coumarin wingtips. DFT calculations upon coordination of the olefin moieties support the experimental results.
Rhodium(i) complexes with proton-responsive anionic tethered N-heterocyclic carbene ligands: synthesis and application in alkyne dimerization
(Royal Soc Chemistry, 2025) Karatas, Mert Olgun; Hinojosa, Diego R.; Passarelli, Vincenzo; Oro, Luis A.; Perez-Torrente, Jesus J.; Castarlenas, Ricardo
A series of rhodium(i) complexes of formula Rh{kappa 2C,X-(IDippR)}(cod) and Rh{kappa 2C,X-(IDippR)}(CO)2 {IDippR = 1-(R)-3-(2,6-diisopropylphenyl)-imidazolin-2-carbene; X = N, O; R = (6-yl-2-pyridone), (CH2CH2NC( 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 O)Ph), (CH2CH2COO); (cod = 1,5-cyclooctadiene)} containing anionic-tethered NHC-functionalized ligands, including pyridonato, amidato or carboxylato groups at the N-wingtip, has been prepared and their application to alkyne homocoupling has been investigated. The chelate coordination of the NHC-functionalized ligand generates 5, 6 and 7-membered metallacycles for pyridonato, amidato and carboxylato substituents, respectively. Preparation of the mixed bis-NHC derivative Rh{kappa 2C,O-(IDippCarbx)}(CO)(IPr) {IPr = 1,3-bis-(2,6-diisopropylphenyl)-imidazolin-2-carbene} is possible due to lability of one of the CO ligands in the bis-CO precursor. Reversible protonation is observed for pyridonato and carboxylato moieties but not for amidato counterpart. Alkyne dimerization catalytic activity is reported for N-based anionic groups whereas carboxylato counterparts are inefficient. A proton transfer mechanism is invoked for the gem-selectivity observed for cod-based catalysts whereas alkyne insertion is the regioselectivity-determining step for CO-containing analogues.
Ruthenium, rhodium and iridium complexes of a silyl-substituted N-heterocyclic carbene ligand and their catalytic performance in hydrosilylation of terminal alkynes
(Elsevier Science Sa, 2023) Mumcu, Akin; Karatas, Mert Olgun; Ozdemir, Namik; Erdogan, Ali; Kucukbay, Hasan
Herein, [Ru(NHC)(p-cymene)Cl-2] (3) and [MCl(NHC)(cod)] (M=Rh (4) or Ir (5)) (cod=1,5-cyclooctadiene) complexes of a silyl-substituted N-heterocyclic carbene ligand (NHC) have been prepared by the transmetalation reaction between Ag-NHC (2) and corresponding starting metal compound. The characterization of the complexes has been completed by NMR spectroscopy and elemental analyses. Solid state structures of Ag- (2) and Rh-NHC (4) have also been determined by single crystal X-ray analysis. [RhCl(NHC)(CO)(2)] type bis-carbonyl complex (6) has also been prepared and CO stretching frequencies pointed the strong s-donor ability of the silyl-substituted NHC. The catalytic activity of all complexes have been examined in hydrosilylation of terminal alkynes. Among the complexes, Ir-NHC has been found out as active catalyst with around 90% conversion and beta-(Z) selectivity at room temperature. Further studies revealed that this complex is able to maintain its stability in catalytic reaction conditions, chemoselective to alkynes in the presence of alkenes, and operable in scale-up reactions. In contrast, bis-carbonyl Rh-NHC performed 82% beta-(Z) selectivity with full conversion of alkyne in first 4 h of reaction, but when reaction time was extended to 24 h, almost all beta-(Z) vinylsilane isomerised to thermodynamically more stable beta-(E). (c) 2023 Elsevier B.V. All rights reserved.

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