Structural information from the Mössbauer quadrupole splitting of tint(IV) chloride complexes

An empirical linear relationship has been found between the Sn-Cl distance in octahedral tin(IV) chloride complexes and the Mössbauer partial quadrupole splitting of the ligands. The correlationd(Sn-Cl)=(–0.044±0.002) (4 PQS)+(2.420±0.003) Å can be used to predict Sn-Cl distances and get information about the tin-ligand bond strength and the sign of the quadrupole splitting. The relationship suggests that bond distances are strongly affected by rehybridization at the tin atom. The cis or trans structure of tin(IV) chloride complexes cannot be assigned on the basis of the resolvable or unresolvable nature of the Mössbauer doublets, which are rationalized by means of the correlation with the Sn-Cl distances.Deceased on December 4, 1987.     

Mössbauer studies of complexes of diorganotin diisothiocyanates with tridentate ligands

Mössbauer and infrared spectra have been obtained for terpyridylcomplexes of dimethyl-, di-n-butyl- and diphenyltindiisothiocyanates and the corresponding[R₂Sn(NCS)·terpyridyl]⁺ [BPh₄]- compounds, and for the8-(2-pyridylmethylene-amino)quinoline, PMAQ, complexes withdi-n-butyl- and diphenyltin diisothiocyanates. Infrared spectra ofthe neutral complexes indicate seven-coordination for tin and theMössbauer parameters indicate axial C Sn bondshaving a greater tin s-character than in trans octahedralcomplexes. The largest quadrupole splitting, 4.73 mm/sec, wasobtained for the terpyridyl complex with di-n-butyltindiisothiocyanate.     

Molecular orbital calculation of Mössbauer parameters for Sn(CH3)nH4−n (n=0, 1, 2, 3) and their photoproducts in low temperature matrices

Mössbauer parameters of tin compounds, Sn(CH₃)₂H_4–n (n=0, 1, 2, 3, 4), isolated in low temperature matrices were related to electronic properties at the tin nuclei obtained by molecular orbital calculations. Structures of novel species, Sn(CH₃)₂ and Sn(CH₃)H, produced via photodissociation of matrix-isolated Sn(CH₃)₃H and Sn(CH₃)₂H₂, respectively, were determined on the basis of molecular orbital calculations as compared with Mössbauer parameters. The correlations between Mössbauer quadrupole splitting and calculated electric field gradient using STO-3G or MINI-4 were found to depend on the valence of tin atoms because of poor allowance for basis sets in describing highly polar molecules.     

Molecular orbital calculation of Mössbauer parameters for tin compounds in low temperature matrices

Mössbauer parameters of tin compounds, Sn(CH₃)_nCl_4–n (n=0, 1, 2, 3, 4), isolated in low temperature matrices are correlated with electronic properties at the tin nuclei obtained by molecular orbital calculations. The Mössbauer isomer shift and quadrupole splitting show good correlation with electron density and electric field gradient estimated by molecular orbital calculations, respectively. Structures of novel species (Sn(CH₃)₂CH₂ and [Sn(CH₃)₂CH₂]₂) produced via photodissociation of Sn(CH₃)₄ in low temperature matrices were estimated by means of molecular orbital calculations as compared with Mössbauer parameters.     

Photochemical reactions of tetramethylstannane isolated in low temperature argon matrix

Photolytic products of tetramethylstannane in low temperature argon matrix were studied by Mössbauer, IR, and UV spectroscopy. At an early stage of the reaction, an unstable tin compound possibly with a tin-carbon double bond was formed in low temperature argon matrix, which might not exist in ordinary conditions. In subsequent reaction, cyclic tin compounds with large quadrupole splittings might be produced.     

Preparation and structural studies on organotin(IV) complexes with flavonoids

Fourteen complexes of di-n-butyltin(IV)²⁺ cations with flavonoid glycosides (rutin, hesperidin, 2′,4′,3-trihydroxy-5′,4-dimetoxychalkone 4-rutinoside) and flavonoid aglycones (quercetin, morin, hesperitin and sorte flavones) were prepared. The composition of the complexes was determined by standard analytical methods. The results showed that complexes containing diorganotin(IV)²⁺ moiety and the ligand in 1∶1, 2∶1 or 3∶1 ratio are formed. The FTIR spectra were consistent with the presence of Sn-O (phenol or carbohydrate) vibration in the compounds. The structure of the complexes was measured by Mössbauer spectroscopy. Comparison of the experimental quadrupole splitting with those calculated on the basis of partial quadrupole splitting concept revealed that the complexes are of four types: with the central tin atoms surrounded by donor atoms in a purely trigonal-bipyramidal, octahedral+trigonal-bipyramidal, trigonal-bipyramidal+tetrahedral and octahedral+tetrahedral arrangement. This procedure also distinguished between the different structural isomers of both trigonal-bipyramidal and octahedral complexes. Conclusions could therefore be drawn on the factors determining which of the isomers are formed in the systems. The Mössbauer parameters obtained for organotin(IV)-flavonoid complexes were compared with those measured for organotin(IV)-carbohydrate complexes.     

Synthesis,Mössbauer,and IP spectroscopic studies and thermal behavior of diorganotin(IV) complexes with carbohydrate ligands

A series of diethyltin(IV) complexes with carbohydrate ligands (aldoses, polyalcohols, sugar acids, sugar amines, and di- and trisaccharides] was prepared. The compositions of the complexes were determined by standard analytical methods. The results showed that complexes formed containing the diethyltin moiety and the carbohydrate ligand in 11 ratio. The IR spectra were consistent with the presence of tin—carbohydrate oxygen vibrations in the compounds. The comparison of experimental quadrupole splitting values with those calculated on the basis of the partial quadrupole splitting (PQS) concept revealed the compounds to be of three types: complexes in with the central tin(IV) atoms are present in purely trigonal bipyramidal surroundings, ones with the tin(IV) atoms present in purely octahedral surroundings, or ones with both octahedral and trigonal bipyramidal arrangements in approximately 11 ratio. The thermal decompositions showed that some of the complexes decompose via the reduction of tin(IV) to SnO as the final tin-containing product, some of them decompose without reduction, to give SnO₂, and some decompose to give indefinite final tin-containing products.     

Determination of the Mössbauer parameters of rare-earth nitroprussides: Evidence for new light-induced magnetic excited state (LIMES) in nitroprussides

Nitroprussides of the rare-earth elements and some mixed rare-earth-sodium nitroprussides are studied by Mössbauer spectroscopy at ambient and lower temperatures. The high precision Mössbauer measurements reveal fine changes in the electronic configurations of the nitroprusside anions. A small increase of the quadrupole splitting reveals charge polarization effects in the nitroprusside anion caused by the oblate or prolate shape of the rare-earth ion and the lanthanide contraction. Despite the very large magnetic moment of holmium a magnetic phase transition is not observed down to 300 mK. The population of the metastable states SI and SII are evidenced in europium and scandium nitroprussides, and most likely they can be populated in all rare-earth nitroprussides. No distinct correlation between the Mössbauer parameters and the decay temperatures T_c of the metastable states are found. In a very thin surface layer strong color change, which remains stable at room temperature, is detected. A quadrupole doublet with Mössbauer parameters typical for Fe(III), low spin S=1/2 state is related to a new colored photoproduct. The photoproduct is called light-induced magnetic excited state (LIMES) and explained with a photochemical redox reaction, which changes the valence, spin, and magnetic state of 4f-3d bimetallic complexes.     

Mössbauer study of mixed-ligand complexes of europium(III)

A series of europium(III) mixed complexes was prepared containing 1,10-phenanthroline or 2,2-bipyridine as neutral ligand and simple inorganic anions or benzoate and its derivatives as ionic ligands. The Mössbauer spectra of the products indicated that both types of ligands were directly coordinated to the central europium(III) atom. The Mössbauer isomer shift values reflected both electron shifting and steric effects of the substituents on the ligand. The quadrupole splitting values pointed to the similar symmetry of the electron shell of the europium in almost all complexes with analogous composition. The IR spectra provided evidence of the binding mode of the carboxylate groups in the complexes containing benzoate or its derivatives. The x-ray photoelectron spectra of the compounds demonstrated the effects of electrophilic and nucleophilic substituents on the electron binding energies in the europium, oxygen, and nitrogen orbitals.     

Preparation and structural studies on dibutyltin(IV) complexes with pyridine mono- and dicarboxylic acids

A number of organotin(IV) complexes with pyridine mono- and dicarboxylic acids (containing ligating -COOH group(s) and aromatic {N} atoms) were prepared in the solid state. The bonding sites of the ligands were determined by means of FT-IR spectroscopic measurements. It was found that in most cases the -COO⁻ groups form bridges between two central {Sn} atoms, thereby leading to polymeric (oligomeric) complexes. On this basis, the experimental ¹¹⁹Sn Mössbauer spectroscopic data were treated with partial quadrupole splitting approximations. The calculations predicted the existence of complexes with octahedral (oh) and trigonal-bipyramidal (tbp) structures, but the formation of complexes with pentagonal-bipyramidal (pbp) structures could not be ruled out. Single-crystals of 2-picolinic and pyridine-2,6-dicarboxylic acid Bu₂Sn(IV)²⁺ complexes were obtained. The X-ray diffraction studies revealed that the central {Sn} atoms are in a pbp environment with bond distances characteristic of organotin(IV) compounds. The two butyl groups are located in axial positions. ¹¹⁹Sn NMR measurements in dmso solution and in the solid state indicated that the polymeric structures of the complexes are not retained in solution. The results of the solid-state ¹¹⁹Sn NMR measurements for compounds 1a, 2a and 6a are in agreement with the structures predicted by Mössbauer spectroscopy and revealed by X-ray diffraction.     

Mössbauer spectra of dimethenylbiferrocenediamine compounds

Summary ⁵⁷Fe Mössbauer studies of mono- and dibiferrocene derivatives and their triiodide salts of oxidized ferrocene derivatives show that there are small changes in the isomer shift and quadrupole splitting of these compounds. The mixed valence salt of dimethenylbiferrocenyl-p-phenylene-diamine is localized within the Mössbauer timescale.     

Quantum chemical analysis of parameters of mössbauser spectra of tetracoordinate Fe-porphyrin complexes in different spin states

We present the results of quantum chemical calculations of the electronic structure and parameters of the Mössbauer spectra for tetracoordinate iron porphyrin (FeP) complexes in different spin states. We compare the results obtained with experimental data and results of other quantum chemical calculations. The calculated values of the quadrupole splitting and the isomer shift in the ³Eg term are close to the experimental values in tetraphenyl-FeP and in octaethyl-FeP. The Mössbauer parameters in the term ⁵Eg are close to the experimental values in octamethyltetrabenz-FeP.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 5, pp. 601–606, September–October, 1989.     

Preparation and structural characterization of organotin(IV) complexes with ligands containing a hetero {N} atom and a hydroxy group or hydroxy and carboxyl groups

Twenty-two n-butyltin(IV) and t-butyltin(IV) complexes of ligands containing an -OH (-CO) group or -OH and -COOH groups and an aromatic {N} donor atom were prepared by metathetical reactions. On the basis of the FT-IR and Mössbauer spectroscopic data, molecular structures were assigned to these compounds. The binding sites of the ligands were identified by means of FT-IR spectroscopic measurements, and it was found that in most cases the organotin(IV) moiety reacts with the phenolic form of these ligands. In the complexes with -OH and -COOH functions, the -COOH group is coordinated to the organotin(IV) centres in a monodentate manner. The ¹¹⁹Sn Mössbauer and the FT-IR studies support the formation of trigonal bipyramidal (TBP) and octahedral (O_h) molecular structures. Furthermore, X-ray diffraction analysis has been performed on the n-butyltin(IV)- and t-butyltin(IV)-8-quinol 8-olato-O,N single crystals. The hexacoordinated tin centres exhibit cis-octahedral geometry in both complexes.     

Structural investigations on diorgano- and triorganotin(IV) derivatives of [meso-tetra(4-sulfonatophenyl)porphine] metal chlorides

Several new complexes of organotin(IV) moieties with MCl_n[meso-tetra(4-sulfonatophenyl)porphine], (R₂Sn)₂MCl_n[meso-tetra(4-sulfonatophenyl)-porphinate]s and (R₃Sn)₄MCl_n [meso-tetra(4-sulfonatophenyl)porphinate]s, [M = Fe(III), Mn(III): n = 1, R = Me, n-Bu; Ph; M = Sn(IV): n = 2, R = Me, n-Bu] have been synthesized and their solid state configuration investigated by infrared (IR) and Mössbauer spectroscopy, and by ¹H and ¹³C NMR in D₂O.The electron density on the metal ion coordinated inside the porphyrin ring is not influenced by the organotin(IV) moieties bonded to the oxygen atoms of the side chain sulfonatophenyl groups, as it has been inferred on the basis of Mössbauer spectroscopy and, in particular, from the invariance of the isomer shift of the Fe(III) and Sn(IV) atoms coordinated into the porphyrin square plane of the newly synthesized complexes, with respect to the same atoms in the free ligand.As far as the coordination polyhedra around the peripheral tin atoms are concerned, infrared spectra and experimental Mössbauer data would suggest octahedral and trigonal bipyramidal environments around tin, in polymeric configurations obtained, respectively, in the diorganotin derivatives through chelating or bridging sulfonate groups coordinating in the square plane, and in triorganotin(IV) complexes through bridging sulfonate oxygen atoms in axial positions.The structures of the (Me₃Sn)₄Sn(IV)Cl₂[meso-tetra(4-sulfonatophenyl)porphinate] and of the two model systems, Me₃Sn(PS)(HPS) and Me₂Sn(PS)₂ [HPS = phenylsulfonic acid], have been studied by a two layer ONIOM method, using the hybrid DFT B3LYP functional for the higher layer, including the significant tin environment. This approach allowed us to support the structural hypotheses inferred by the IR and Mössbauer spectroscopy analysis and to obtain detailed geometrical information of the tin environment in the compounds investigated.¹H and ¹³C NMR data suggested retention of the geometry around the tin(IV) atom in D₂O solution.     

Dibenzyltin(IV) complexes of the 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-olates: Synthesis and an investigation of structures by X-ray diffraction, solution and solid-state tin NMR, Sn Mössbauer and electrospray ionization MS

A series of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}dibenzyltin(IV) complexes have been synthesized by reacting sodium salts of 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-ol (LH) and dibenzyltin dichloride. These complexes have been characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, ESI-MS in solution and by IR and ^119mSn Mössbauer, ¹¹⁷Sn CP-MAS NMR spectroscopy in solid state. In addition, the structures of three of the dibenzyltin(IV) complexes, viz., Bz₂Sn(L²)₂ (2), Bz₂Sn(L³)₂ (3), and Bz₂Sn(L⁵)₂ (5) (L = 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-ol: aryl = 4′-methylphenyl- (L²H), 4′-methoxylphenyl- (L³H) and 4′-bromophenyl- (L⁵H)) were determined by single-crystal X-ray diffraction. In general, the complexes were found to adopt a distorted cis-octahedral arrangement around the tin atom in both solution and solid state.     

Mössbauer and X-ray diffraction study of an aluminium-magnesium-silicon alloy containing Pb and Sn

The Mössbauer parameters of tin in aluminium matrix were studied and published in an earlier paper¹. The aim of this work was to carry out investigations on tin in an aluminium alloy containing magnesium, silicon and lead beside the Mössbauer active tin. The effect of heat treatments on the formation of intermetallic compounds was studied by X-ray diffraction and by the Mössbauer spectra of¹¹⁹Sn.     

Mössbauer study of Al6 (Fe,Mn) formation in Al-rich Al−Fe−Mn alloys

Al–Fe–Mn alloys containing 0.5 wt. % iron and 0–3.0 wt. % manganese were prepared at different cooling rates from 0.1 to 500 K/s and studied by Mössbauer spectroscopy. Beyond the usual phase analysis, it was found that the presence of manganese is responsible for the decrease of the quadrupole splitting and isomer shift of the Al₆(Fe,Mn) phase, compared to those of Al₆Fe. It was also shown that the Mössbauer parameters are characteristic of the average manganese content of Al₆(Fe,Mn) only if there are no substantial fluctuations of the Fe/Mn ratio in the Al₆(Fe,Mn) phase. Accurate Mössbauer parameters for the Al₆Fe phase were also determined.     

Mössbauer, vibrational and electronic spectroscopy of trinuclear μ-oxo iron(III) acetate clusters with pyridine and derivatives as ligands

In this study we have investigated eight complexes of the general composition [Fe₃O(OOCCH₃)₆(L)₃]NO₃, where L is a heterocyclic ligand, viz. a 4-substituted pyridine. The Mössbauer spectra of the complexes showed isomer shifts and quadrupole splittings that are characteristic of iron(III) high-spin complexes. The Mössbauer quadrupolar doublets showed asymmetries that are attributed principally to the Goldanskii-Karyagin effect. A correlation is proposed between the Mössbauer parameters, and between the energy of the charge transfer band spectra, and the pK_a values of the N-heterocyclic ligands.     

On the quadrupole splitting of a low-spin Iron(III)-Dithio Chelate

The magnetically perturbed Mössbauer spectra of iron(III) (dithioacetylacetonate)₃ show V_zz<0 corresponding to a d_xy hole and a²A ground term. These results support a recent study of the temperature dependence of the quadrupole splitting and suggest that the origin of the quadrupole splitting is primarily in the distribution of non-bonding electrons.     

A119Sn-Mössbauer study of tetramethylstannane isolated in low temperature argon matrix

Unusually broad¹¹⁹Sn-Mössbauer absorption was observed in pure Sn(CH₃)₄ or Sn(CH₃)₄/argon condensed at low temperatures by pulsed deposition. Such broadening of the Mössbauer linewidth suggested the presence of large quadrupole splitting due to possible distortion of molecular structure as deposited in the argon matrix.