Water-soluble NNN-pincer complexes of cobalt, nickel and palladium: Solid-state structures and catalytic activity

Polyhedron ◽  
2018 ◽  
Vol 143 ◽  
pp. 138-143 ◽  
Author(s):  
Joshua Heidebrecht ◽  
Chris Gendy ◽  
Benjamin S. Gelfand ◽  
Roland Roesler
Keyword(s):  
Catalytic Activity ◽  
Solid State ◽  
Water Soluble ◽  
Pincer Complexes ◽  
Cobalt Nickel ◽  
Solid State Structures

Reactions of a pincer proligand with copper iodide: bridging instead of C–H metalation

2020 ◽  
Vol 98 (9) ◽  
pp. 524-530
Author(s):  
Taghrid Chahrour ◽  
Annie Castonguay ◽  
Paul O. Oguadinma ◽  
Frank Schaper ◽  
Davit Zargarian
Keyword(s):  
Solid State ◽  
The Other ◽  
Strong Preference ◽  
Pincer Complexes ◽  
Divalent Copper ◽  
Copper Iodide ◽  
Tetrahedral Geometry ◽  
Central Carbon ◽  
Copper Center ◽  
Solid State Structures

Various precursors of divalent copper have been treated with the meta-disubstituted phenylene-based proligand POC(H)OP (1,3-(i-Pr2PO)2C6H4) with the objective of preparing classical pincer complexes (POCOP)CuX. However, in no case was such species obtained, presumably owing to the difficult C–H metallation step. Analogous reactions of monovalent precursors were also unsuccessful, whereas reaction of POC(H)OP with CuI under different conditions gave the non-metallated adducts {(μ, κP, [Formula: see text]-POC(H)OP)Cu(μ-Ι)}2, 1, {(μ, κP, [Formula: see text]-POC(H)OP)Cu2(μ-Ι)2(DMAP)2}, 2 (DMAP = 4-dimethylaminopyridine), and {(μ, κP, [Formula: see text]-POC(H)OP)Cu2(μ3-Ι)2}2, 3. Treating 1 with DMAP gave the adduct 2, whereas 3 could be obtained by treating 1 with BuLi or by sublimation of 1. The solid state structures of these complexes revealed the tetrahedral geometry that might be anticipated for the d10 Cu(I) centers, in addition to fairly close I–H distances; on the other hand, no C–H interaction (agostic or otherwise) was observed with the Cu centers in any of these structures. The unsuccessful metallation of the C(2)–H moiety is thought to be a result of the strong preference of monovalent copper center to form bridging interactions with iodide and the POC(H)OP ligand; this appears to prevent the approach of the central carbon of the ligand to the Cu centers.

scholarly journals Late Transition Metal Complexes of Pentafluorophenylphosphino-Pincer Ligands

2021 ◽  
Author(s):  
◽  
Bradley George Anderson
Keyword(s):  
Catalytic Activity ◽  
Coordination Chemistry ◽  
Solid State ◽  
Nucleophilic Attack ◽  
Pincer Complexes ◽  
Pincer Ligands ◽  
Late Transition Metals ◽  
Suzuki Reactions ◽  
Pincer Complex ◽  
Late Transition

<p>This thesis details the synthesis of new examples of electron-poor pincer ligands, featuring bis(pentafluorophenyl)phosphine donors attached to 1,3-substituted phenylene or 2,6-substituted pyridine backbones, to create tridentate PCP and PNP ligands. The effect of the ligands’ electronic nature on the coordination chemistry and ease of pincer complex synthesis with late transition metals is discussed, as is the catalytic activity of the resultant palladium pincer complexes in the Heck and Suzuki reactions. Symmetric PCP and PNP ligands possessing bis(pentafluorophenyl)phosphinite and bis(pentafluorophenyl)phosphoramine functionalities were synthesised by reaction of bis(pentafluorophenyl)phosphine bromide with resorcinol, 3-hydroxybenzyl-di- tert -butylphosphine, 2,6-diaminopyridine, or 2,6-dihydroxypyridine, affording 1,3- [(C6F5)2PO]2C6H4 (POCOPH, 1), 1-[(C6F5)2PO]-3-(tBu2PCH2)2C6H4 (POCCPH, 3), 2,6-[(C6F5)2PNH]2C6H3N (PNNNP, 10), and 2,6-[(C6F5)2PO]2C6H3N (PONOP, 11) respectively. The previously reported 1,3-[(C6F5)2PCH2]2C6H4 (PCCCPH, 2) was also synthesised, with the literature yield improved upon by the use of magnesium-anthracene to generate the required Grignard reagent. The coordination chemistry of the POCOPH ligand 1 with platinum(0) alkene and platinum(II) dimethyl precursors revealed an affinity for the formation of cis-bridged oligomeric structures. The dimer [(POCOPH)Pt(nb)]2 (14, nb = norbornene) was isolated and crystallographically characterised from the reaction between 1 and [Pt(nb)3]. The solid state structure revealed the presence of stabilising - interactions between the aromatic ligand backbones, which were also observed in solution by 1H NMR spectroscopy. Reactions of ligand 1 with platinum and palladium dichloride or chloromethyl starting materials led to rare examples of cis,trans-dimers of the type cis,trans-[(POCOPH)MClX]2 (M = Pd, Pt; X = Cl, Me). In part due to facile dimer formation with 1, metallation of the ligand backbone to form the tridentate pincer complex [(POCOP)PtCl] (25) required long reaction times and high temperatures. It was observed that platinum dichloride starting materials with more strongly binding ancillary ligands were less prone to oligomer formation, and could facilitate more rapid metallation to from 25. More facile pincer complex formation was also observed for more electron-rich ligands with both PCP and PNP pincer ligands. The electron poor platinum and palladium POCOP, PCCCP, and POCCP pincer complexes (where the free ligand had been deprotonated upon metallation) were synthesised and subsequently converted into the metal carbonyl species [(PCP)M(CO)]+. Analysis of C−O stretching frequencies by infrared spectroscopy confirmed complexes of POCOP ligand 1 were the most electron poor, while those of POCCP ligand 3 were the most electron rich. Decarbonylation of the palladium pincer complexes was observed in solution and in the solid state, and was more facile for complexes with a higher wavenumber C−O stretch. Reaction of the [(PCP)PtCl] pincer complexes with methyl nucleophiles revealed that treatment with methylmagnesium iodide resulted in halide exchange, while methyllithium promoted nucleophilic attack at phosphorus. Spectroscopic data indicated that in one instance this led to pentafluorophenyl migration to the metal centre to form a [(PCP)Pt(C6F5)] complex. Dimethylzinc was successful in methylating the platinum PCP complexes; however, it was observed to degrade the palladium PCP pincer complexes. Treatment of the rhodium PNP pincer complex [(PNNNP)RhCl] (49) with dimethylzinc also resulted in degradation, which spectroscopic evidence indicated proceeded via ligand deprotonation and the formation of a zinc adduct of 49. Low temperature protonolysis of the [(PCP)PtMe] species did not reveal any information about possible interactions between the metal and liberated methane. The catalytic activity of the electron-poor [(PCP)PdCl] complexes were assessed in the Heck and Suzuki cross-coupling reactions. The complexes of 1, 2, and 3 were all found to possess only modest activity in the Heck reaction, functioning as precatalysts which decomposed to give catalytically-active Pd(0) colloids. Under milder Suzuki reaction conditions, the most electron-poor complex, [(POCOP)PdCl] (28) proved to be one of the most active pincer catalysts known for this reaction, able to achieve a turnover number of 176,000 for the coupling of electronically-deactivated aryl bromides and phenylboronic acid. Mercury poisoning tests revealed that Suzuki reactions catalysed by 28 proceeded via a homogeneous active species.</p>

scholarly journals Crystal Structure of Burgess Inner Salts and their Hydrolyzed Ammonium Sulfaminates

2019 ◽  
Vol 72 (11) ◽  
pp. 867 ◽  
Author(s):  
Anthony J. Arduengo III ◽  
Yosuke Uchiyama ◽  
David A. Dixon ◽  
Monica Vasiliu
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Crystal Structures ◽  
Ethyl Ester ◽  
Crystallographic Analysis ◽  
Water Soluble ◽  
X Ray ◽  
Dative Bond ◽  
Solid State Structures

The solid-state structures of the Burgess reagent, and its analogous ethyl ester reveal structures indicative of triethylamine solvated sulfonyl imides rather than the more commonly depicted triethylammonium sulfonyl amidate. The existence of a reversibly formed hydrate of Burgess reagent is not supported by present studies, but rather a hydrosylate that does not revert to the Burgess reagent with gentle warming under vacuum was isolated and characterised. Structures of the hydrosylates from both the methyl- and ethyl-amidate esters were determined from X-ray crystallographic analysis and are reported. The crystal structures of the Burgess inner salts exhibit geometries at the sulfur atoms that are intermediate between a planar O2S=NCO2R unit and tetrahedral 4-coordinate sulfur centres that would be expected from a strong single (dative) bond between the triethylamine nitrogen and sulfur. The hydrolysed ammonium sulfaminates are water soluble intermolecular salts composed of triethylammonium ions, Et3NH+, and N-(alkoxycarbonyl)sulfaminate, O(−)SO2NHCO2R {R=CH3 or C2H5}.

scholarly journals Late Transition Metal Complexes of Pentafluorophenylphosphino-Pincer Ligands

2021 ◽  
Author(s):  
◽  
Bradley George Anderson
Keyword(s):  
Catalytic Activity ◽  
Coordination Chemistry ◽  
Solid State ◽  
Nucleophilic Attack ◽  
Pincer Complexes ◽  
Pincer Ligands ◽  
Late Transition Metals ◽  
Suzuki Reactions ◽  
Pincer Complex ◽  
Late Transition

<p>This thesis details the synthesis of new examples of electron-poor pincer ligands, featuring bis(pentafluorophenyl)phosphine donors attached to 1,3-substituted phenylene or 2,6-substituted pyridine backbones, to create tridentate PCP and PNP ligands. The effect of the ligands’ electronic nature on the coordination chemistry and ease of pincer complex synthesis with late transition metals is discussed, as is the catalytic activity of the resultant palladium pincer complexes in the Heck and Suzuki reactions. Symmetric PCP and PNP ligands possessing bis(pentafluorophenyl)phosphinite and bis(pentafluorophenyl)phosphoramine functionalities were synthesised by reaction of bis(pentafluorophenyl)phosphine bromide with resorcinol, 3-hydroxybenzyl-di- tert -butylphosphine, 2,6-diaminopyridine, or 2,6-dihydroxypyridine, affording 1,3- [(C6F5)2PO]2C6H4 (POCOPH, 1), 1-[(C6F5)2PO]-3-(tBu2PCH2)2C6H4 (POCCPH, 3), 2,6-[(C6F5)2PNH]2C6H3N (PNNNP, 10), and 2,6-[(C6F5)2PO]2C6H3N (PONOP, 11) respectively. The previously reported 1,3-[(C6F5)2PCH2]2C6H4 (PCCCPH, 2) was also synthesised, with the literature yield improved upon by the use of magnesium-anthracene to generate the required Grignard reagent. The coordination chemistry of the POCOPH ligand 1 with platinum(0) alkene and platinum(II) dimethyl precursors revealed an affinity for the formation of cis-bridged oligomeric structures. The dimer [(POCOPH)Pt(nb)]2 (14, nb = norbornene) was isolated and crystallographically characterised from the reaction between 1 and [Pt(nb)3]. The solid state structure revealed the presence of stabilising - interactions between the aromatic ligand backbones, which were also observed in solution by 1H NMR spectroscopy. Reactions of ligand 1 with platinum and palladium dichloride or chloromethyl starting materials led to rare examples of cis,trans-dimers of the type cis,trans-[(POCOPH)MClX]2 (M = Pd, Pt; X = Cl, Me). In part due to facile dimer formation with 1, metallation of the ligand backbone to form the tridentate pincer complex [(POCOP)PtCl] (25) required long reaction times and high temperatures. It was observed that platinum dichloride starting materials with more strongly binding ancillary ligands were less prone to oligomer formation, and could facilitate more rapid metallation to from 25. More facile pincer complex formation was also observed for more electron-rich ligands with both PCP and PNP pincer ligands. The electron poor platinum and palladium POCOP, PCCCP, and POCCP pincer complexes (where the free ligand had been deprotonated upon metallation) were synthesised and subsequently converted into the metal carbonyl species [(PCP)M(CO)]+. Analysis of C−O stretching frequencies by infrared spectroscopy confirmed complexes of POCOP ligand 1 were the most electron poor, while those of POCCP ligand 3 were the most electron rich. Decarbonylation of the palladium pincer complexes was observed in solution and in the solid state, and was more facile for complexes with a higher wavenumber C−O stretch. Reaction of the [(PCP)PtCl] pincer complexes with methyl nucleophiles revealed that treatment with methylmagnesium iodide resulted in halide exchange, while methyllithium promoted nucleophilic attack at phosphorus. Spectroscopic data indicated that in one instance this led to pentafluorophenyl migration to the metal centre to form a [(PCP)Pt(C6F5)] complex. Dimethylzinc was successful in methylating the platinum PCP complexes; however, it was observed to degrade the palladium PCP pincer complexes. Treatment of the rhodium PNP pincer complex [(PNNNP)RhCl] (49) with dimethylzinc also resulted in degradation, which spectroscopic evidence indicated proceeded via ligand deprotonation and the formation of a zinc adduct of 49. Low temperature protonolysis of the [(PCP)PtMe] species did not reveal any information about possible interactions between the metal and liberated methane. The catalytic activity of the electron-poor [(PCP)PdCl] complexes were assessed in the Heck and Suzuki cross-coupling reactions. The complexes of 1, 2, and 3 were all found to possess only modest activity in the Heck reaction, functioning as precatalysts which decomposed to give catalytically-active Pd(0) colloids. Under milder Suzuki reaction conditions, the most electron-poor complex, [(POCOP)PdCl] (28) proved to be one of the most active pincer catalysts known for this reaction, able to achieve a turnover number of 176,000 for the coupling of electronically-deactivated aryl bromides and phenylboronic acid. Mercury poisoning tests revealed that Suzuki reactions catalysed by 28 proceeded via a homogeneous active species.</p>

Water soluble biguanide salts and their 1,3,5-triazine derivatives as inhibitors of acetylcholinesterase and α-glucosidase

2020 ◽  
Vol 235 (10) ◽  
pp. 465-475
Author(s):  
Ozge Gungor ◽  
Seda Nur Kertmen Kurtar ◽  
Muhammet Kose
Keyword(s):  
Spectroscopic Method ◽  
Substitute Aniline ◽  
Water Soluble ◽  
X Ray Diffraction ◽  
Nucleophilic Reaction ◽  
X Ray ◽  
Triazine Derivatives ◽  
Acidic Conditions ◽  
Approved Drugs ◽  
Solid State Structures

AbstractSeven biguanide derivatives were prepared by the nucleophilic reaction between dicyandiamide and p-substitute aniline derivatives or memantine or adamantine under acidic conditions. The cyclization of the biguanide compounds were also conducted via acetone to give 1,3,5-triazine derivatives. The structures of the synthesized compounds were characterized by analytical methods. The solid state structures of [HL5]Cl, [H2L7]Cl2, [HL1a]Cl and [HL5a]Cl were investigated by X-ray diffraction study. The acetylcholinesterase and α-glucosidase inhibitor properties of the compounds were then evaluated by the spectroscopic method. The compounds were found to show considerable acetylcholinesterase and α-glucosidase inhibitory activities compared to the approved drugs. The cyclization of biguanide derivatives with acetone did not affect inhibition of acetylcholinesterase, yet increased the α-glucosidase inhibition.

Sign in / Sign up

Export Citation Format

Share Document