The reaction of cis-protected (Me4en)Pt(SO4) (Me4en=N,N,N′,N′-tetramethylethylenediamine) with barium diallylmalonate (L) in aqueous solution exhibits both solvent-dependent linkage isomerism, ...(Me4en)Pt(O,allyl-L) and (Me4en)Pt(O,O′-L) and cyclodimerism, (Me4en)Pt(O,O′-L)2.
The isomerism and cyclodimerism of (Me4en)platinum(II) complex containing diallylmalonate ligand is dependent on the solvent system. Display omitted
•The reaction of cis-protected (Me4en)Pt(SO4) with barium diallylmalonate (L) forms (Me4en)Pt(L) complex.•The solvent-dependent linkage isomerism, (Me4en)Pt(O,allyl-L) and (Me4en)Pt(O,O'-L) was observed.•The coexistence of solvent-dependent linkage isomerism and cyclodimerism in Pt-complex has been observed.
The {Ru(NO)2}10 dinitrosylruthenium complex Ru(NO)2(PPh3)2 (1) shows photo‐induced linkage isomerism (PLI) of a special kind: the two NO ligands switch, on photo‐excitation, synchronously from the ...ground state (GS) with two almost linear RuNO functions to a metastable state (MS) which persists up to 230 K and can be populated to ≈50 %. The MS was experimentally characterised by photo‐crystallography, IR spectroscopy and DS‐calorimetry as a double‐bent variant of the double‐linear GS. The experimental results are confirmed by computation which unravels the GS/MS transition as a disrotatory synchronous 50° turn of the two nitrosyl ligands. Although 1 shows the usual redshift of the N−O stretch on bending the MNO unit, there is no increased charge transfer from Ru to NO along the GS‐to‐MS path. In terms of the effective‐oxidation‐state (EOS) method, both isomers of 1 and the transition state are Ru−II(NO+)2 species.
The picture shows the transition state (TS) which connects the double‐linear ground state (GS) with the double‐bent metastable state (MS) of the dinitrosylruthenium compound Ru(NO)2(PPh3)2 (1). The TS's strongly negative vibrational mode (−831 cm−1) traces the decay path if the photo‐generated MS is warmed above 230 K. 1 provides the first example of synchronous photo‐induced linkage isomerism (PLI) involving two ligands (see Supporting Information for an animation of the movement).
Nitrites of passage: Raman and single‐crystal photocrystallographic studies on Ni(dppe)(η1‐NO2)Cl have, for the first time, identified a system which undergoes a reversible 100 % conversion into the ...metastable isomer in the solid state, in this case the Ni(dppe)(η1‐ONO)Cl isomer.
Acetyl hydrazone oxime, (1E,2E)-2-(hydroxyimino)-1-phenylethylideneacetohydrazone (hipeahH2) and its palladium(II) and platinum(II) complexes have been synthesized and characterized. This paper ...reports structural and spectroscopic characterization of the hipeahH2 and its palladium(II) and platinum(II) complexes by using both experimental methods such as X-ray, UV–vis, IR and NMR, and DFT calculations. Display omitted
•An acetyl hydrazone oxime and its Pd(II) and Pt(II) complexes were synthesized.•The compounds have been characterized by UV–vis, IR, NMR, LC–MS and X-ray crystallography.•Linkage isomerism of palladium(II) and platinum(II) complexes were performed by DFT.•Theoretical UV–vis, IR and NMR spectra have been calculated using DFT.
Acetyl hydrazone oxime, (1E,2E)-2-(hydroxyimino)-1-phenylethylideneacetohydrazone (hipeahH2) and its palladium(II) and platinum(II) complexes, M(hipeahH)2 (M=PdII and PtII), have been synthesized and characterized by elemental analysis, UV–vis IR, NMR and LC–MS techniques. X-ray diffraction analysis of Pd(hipeahH)2 shows that the two hipeahH2 ligands are not equal; one of the ligands loses the hydrazone proton, while the other one loses the oxime proton, resulting in a different coordination behavior to form five- and six-membered chelate rings. The molecular geometries from X-ray experiments in the ground state were compared using the density functional theory (DFT) with the B3LYP method combined with the 6-311++G(d,p) basis set for the ligand and the LanL2DZ basis set for the complexes. Comprehensive theoretical and experimental structural studies on the molecule have been carried out by FT-IR, NMR and UV–vis spectrometry. In addition, the isomer studies of ligand and its complexes were made by DFT.
In a quest for effective synthetic precursors for the preparation of B-agostic complexes of ruthenium, we have shown that the reaction of Cp*RuCl22 (Cp* = η5-C5Me5) with NaBt or NaBo ...(Bt = dihydrobis(2-mercaptobenzthiazolyl)borate; Bo = dihydrobis(2-mercaptobenzoxazolyl)borate) led to the formation of B-agostic complexes Cp*RuBH2L2, 1a,b (1a: L = 2-mercaptobenzthiazol, 1b: L = 2-mercaptobenzoxazol) and Cp*RuBH3L, 2a,b (2a: L = 2-mercaptobenzthiazol, 2b: L = 2-mercaptobenzoxazol) in good yields. In parallel to the formation of 1a,b and 2a,b, this method also allowed the formation of ruthenium hydrotrisborate complexes Cp*RuBYL3, 3a–c (3a: L = 2-mercaptobenzthiazol, Y = H; 3b: L = 2-mercaptobenzoxazol, Y = H; 3c: L = 2-mercaptobenzoxazol, Y = Cl). The key feature of complexes 3a–c is the coordination of one of the 2-mercaptobenzothiazole ligand that connects to the metal and the boron centre through a common sulfur atom. Upon heating, compounds 3a,b change into their corresponding S→N linkage isomers, in which the boron atom is bonded to three nitrogen atoms. The cyclic voltammetric studies on compounds 3a–c and 4a,b suggest that a deviation in coordination of the ligand change the oxidation potential of the metal centre. All the new compounds have been characterized in solution by 1H, 11B and 13C NMR spectroscopy, mass spectrometry and the structural types of 3a–c and 4b were unequivocally established by crystallographic analysis.
Numerous B-agostic and Ru-borate complexes have been synthesized using Cp*RuCl22 as a precursor. The Ru-borate complexes show linkage isomerism under thermolytic condition. Display omitted
•Various ruthenium hydrotrisborate complexes have been synthesized.•Ligand connects to the metal and the boron centre through a common sulfur atom.•Upon heating, compounds 3a,b change into their corresponding S→N linkage isomers.
The investigation of photo‐induced effects is profoundly influenced by the characteristics of photo‐excitation sources. In this study, we present a comprehensive analysis of the structures of two ...photoinduced linkage isomers (PLI) in a ruthenium nitrosyl complex, trans‐Ru(py)4F(NO)(ClO4)2, following irradiation with both pulsed and continuous wave (CW) light sources under low temperature conditions. The X‐ray (photo)diffraction analysis shows that the resulting PLI generated from the two types of irradiation sources, an isonitrosyl configuration of the nitrosyl ligand in the so‐called metastable state MS1, and a side‐on configuration of the nitrosyl ligand in the metastable state MS2, are identical. In‐situ optical absorption spectroscopy was employed during CW and pulsed irradiation, enabling the monitoring of the population process of these PLI. The results obtained from the infrared spectroscopic analysis after pulsed irradiation give insight into the population mechanism illustrating that the generation of the isonitrosyl MS1 occurs through a two‐step process, via the second PLI, the side‐on configuration MS2.
The investigation of photo‐induced effects is profoundly influenced by the characteristics of photo‐excitation sources. We present here a comprehensive analysis of the structures of two photoinduced linkage isomers (PLI) in a ruthenium nitrosyl complex trans‐Ru(py)4F(NO)(ClO4)2, following irradiation with both pulsed and continuous wave (CW) light sources under low temperature conditions.
The solid‐state, low‐temperature linkage isomerism in a series of five square planar group 10 phosphino nitro complexes have been investigated by a combination of photocrystallographic experiments, ...Raman spectroscopy and computer modelling. The factors influencing the reversible solid‐state interconversion between the nitro and nitrito structural isomers have also been investigated, providing insight into the dynamics of this process. The cis‐Ni(dcpe)(NO2)2 (1) and cis‐Ni(dppe)(NO2)2 (2) complexes show reversible 100 % interconversion between the η1‐NO2 nitro isomer and the η1‐ONO nitrito form when single‐crystals are irradiated with 400 nm light at 100 K. Variable temperature photocrystallographic studies for these complexes established that the metastable nitrito isomer reverted to the ground‐state nitro isomer at temperatures above 180 K. By comparison, the related trans complex Ni(PCy3)2(NO2)2 (3) showed 82 % conversion under the same experimental conditions at 100 K. The level of conversion to the metastable nitrito isomers is further reduced when the nickel centre is replaced by palladium or platinum. Prolonged irradiation of the trans‐Pd(PCy3)2(NO2)2 (4) and trans‐Pt(PCy3)2(NO2)2 (5) with 400 nm light gives reversible conversions of 44 and 27 %, respectively, consistent with the slower kinetics associated with the heavier members of group 10. The mechanism of the interconversion has been investigated by theoretical calculations based on the model complex Ni(dmpe)Cl(NO2).
All or none: The factors that favour high levels of photoconversion between linkage isomers in a series of Group 10, square‐planar nitro complexes were investigated. The highest levels of reversible conversions between the linkage isomers are observed for the kinetically labile NiII complexes in which the change in reaction cavity size upon interconversion is smallest (see scheme).
Metal coordination to N9-substituted adenines, such as the model nucleobase 9-methyladenine (9MeA), under neutral or weakly acidic pH conditions in water preferably occurs at N1 and/or N7. This ...leads, not only to mononuclear linkage isomers with N1 or N7 binding, but also to species that involve both N1 and N7 metal binding in the form of dinuclear or oligomeric species. Application of a trans-(NH3)2Pt(II) unit and restriction of metal coordination to the N1 and N7 sites and the size of the oligomer to four metal entities generates over 50 possible isomers, which display different feasible connectivities. Slowly interconverting rotamers are not included in this number. Based on (1)H NMR spectroscopic analysis, a qualitative assessment of the spectroscopic features of N1,N7-bridged species was attempted. By studying the solution behavior of selected isolated and structurally characterized compounds, such as trans-PtCl(9MeA-N7)(NH3)2ClO4⋅2H2O or trans,trans-{PtCl(NH3)2}2(9MeA-N1,N7)ClO42⋅H2O, and also by application of a 9MeA complex with an (NH3)3Pt(II) entity at N7, Pt(9MeA-N7)(NH3)3NO32, which blocks further cross-link formation at the N7 site, basic NMR spectroscopic signatures of N1,N7-bridged Pt(II) complexes were identified. Among others, the trinuclear complex trans-Pt(NH3)2{μ-(N1-9MeA-N7)Pt(NH3)3}2ClO46⋅2H2O was crystallized and its rotational isomerism in aqueous solution was studied by NMR spectroscopy and DFT calculations. Interestingly, simultaneous Pt(II) coordination to N1 and N7 acidifies the exocyclic amino group of the two 9MeA ligands sufficiently to permit replacement of one proton each by a bridging heterometal ion, Hg(II) or Cu(II), under mild conditions in water.
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•The substitution reactions of dinuclear complex with sulfur-containing species.•The substituted complexes were verified by some spectroscopies and X-ray diffraction.•The linkage ...isomerism of a dmso ligand on the dinuclear complex was revealed.
The substitution reactions of a NO-ligated dinuclear ruthenium complex with ammonium thiocyanate (NH4SCN), sulfur, and dimethyl sulfoxide (DMSO) gave the corresponding mononitrosyl dinuclear complexes, except for reaction with sulfur, where diastereomers of a S2-bridged tetranuclear complex along with a NO- and S2-bridged dinuclear complex were obtained. According to the scan rate dependent cyclic voltammograms, linkage isomerism of a dmso ligand on the dinuclear complex was revealed, and the linkage isomer was obtained from the chemical oxidation.
The substitution kinetics and specific binding modes of the dithiooxamide (dto) ligand at the metal surface have been investigated and interpreted on the light of theoretical and experimental Raman ...studies. By monitoring the vibrational properties of this ligand, it was shown that gold nanoparticles employed as surface‐enhanced effects (SERS) probes are strongly dependent on the coordination chemistry of the ligands at the metal interface. The binding of dto to the gold nanoparticles led to linkage isomers, and at low concentrations, the bidentate form, corresponding to bis‐thione‐Au bond in cis configuration {Au‐S(NH2)CC(NH2)S‐Au}, was the predominating species. Even at high concentrations, the cis‐configuration was observed first; but as the ligand competition dynamics proceeded, the binding mode gradually changed into a monodentate thione‐Au mode {AuS(NH2)CCS(NH2)}. In this mode, the dto ligand adopts a thermodynamically favorable trans‐conformation geometry, producing dramatic changes in the SERS spectra. Such dynamic behavior of the ligand at the metal plasmonic surface is of crucial importance, as one of the possible factors associated with lack of reproducibility of the SERS spectra frequently reported in the literature.
The dynamics of dithiooxamide coordinated to gold nanoparticles shows cis‐trans conformation changing the SERS profiles even after the end of the aggregation process. The substitution kinetics and specific binding modes of the dithiooxamide ligand at the metal surface have been investigated and interpreted on the light of theoretical and experimental Raman studies.
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