Eleonora Rivarola

Synthesis and characterization of triorganotin(IV) complexes of 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids. - Crystal and molecular structures of a series of triphenyltin 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoates (aryl=phenyl, 2-methylphenyl, 3-methylphenyl and 4-methoxyphenyl)

Abstract The triphenyltin and tri-n-butyltin complexes of some 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids have been synthesized and characterized by 1H-, 13C-, 119Sn-NMR, IR and 119mSn Mossbauer spectroscopic techniques in combination with elemental analysis. The crystal structures of triphenyltin 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoates (aryl=phenyl, 2-methylphenyl, 3-methylphenyl and 4-methoxyphenyl) are reported. Both X-ray and 119Sn Mossbauer data indicate that the triphenyltin complexes adopt a monomeric distorted tetrahedral configuration with the carboxylate ligand coordinating in a monodentate mode. By contrast, 119Sn Mossbauer spectroscopy shows that each tributyltin complex is polymeric and features a trans-trigonal bipyramidal geometry with a planar SnBu3 unit and two apical carboxylate oxygen atoms derived from bidentate bridging carboxylate ligands. This is a solid-state effect, as both 119Sn-NMR and 1J(13C–119/117Sn) coupling constant data indicate tetrahedral geometries in solution for the triphenyl and tri-n-butyl complexes.

Synthesis and spectroscopic investigations (IR, NMR and Mössbauer) of tin(IV) and organotin(IV) derivatives of bis(pyrazol-1-yl) alkanes: X-ray crystal structures of bis(4-methylpyrazol-1-yl) methane and its dimethyltin(IV) dichloride adduct

A series of 1:1 adducts of the type [(L)RnSnX4−n]·zH2O (L ≡ bis(4-methylpyraazol-1-yl)ethane (L4), bis(3,4,5-timethylpyrazol-1-yl)methane (LT), 1,2-bis(pyrazol-1-yl)ethane (LA) or 1,2-bis(3,5-dimethylpyrazol-1-yl)ethane (LB); R ≡ Me, Et, Bu or Ph; X ≡ I, Br or Cl; n = 0, 1 or 2; z = 1, 1.5 or 2), and the likely polynuclear [(LA)5(SnCl4)4]·(H2O)5 and [(LB)2(SnCl4)3]·12[Et2O] have been characterized in the solid state and in solution by analyses, spectral (IR, Mossbauer, and 1H, 13C and 119Sn NMR) data and conductivity measurements. When LT reacts with SnCl4, cleavage of a carbon (sp3)-nitrogen bond was observed and the adduct [(3,4,5-trimethyl-pyrazole)2SnCl4] was obtained. The diorganotin(IV) complexes generally dissociate in chloroform or in acetone solution, while the trichlorotin(IV) and tetrachlorotin(IV) adducts probably retain the hexacoordinate configuration. The crystal structures of L4 and of the adduct [(L4)(CH3)2SnCl2] have been determined by X-ray analysis. In the adduct the tin atom is coordinated to two halide atoms, two methyl groups and two N atoms, with trans-(CH3)2Sn in a slightly distorted octahedral configuration. The long SnN bond distance (2.436(6)A) indicated weak donor ability of the N2 donor L4. Comparison is made with the X-ray crystal structures of several R2SnX2N2-type compounds.

Investigations on organoantimony compounds II. Preparation and configuration of organo(oxinato)antimony(V) compounds RnSbCl4−nOx (n = 1−4)

Abstract Organo(oxinato)antimony(V) compounds of the types RSbCl 3 Ox, R 2 SbCl 2 Ox, R 3 SbClOx and R 4 SbOx (R = alkyl and phenyl) have been synthesized and and investigated by spectroscopic (UV, PMR, IR) methods. All the compounds are monomeric in benzene. In all the compounds except R 3 SbClOx (R = alkyl), which contains penta-coordinate antimony, the oxinato group acts as a bidentate ligand in benzene solution. The compounds RSbCl 3 Ox and R 2 SbCl 2 Ox are also hexa-coordinate in ethanol (100%) and chloroform, but partial or complete rupture of the SbN coordinate bond in Ph 3 SbClOx and R 4 SbOx takes place in these polar solvents. The stability of the SbN coordinate bond in R 4 SbOx follows the order of the I -effect of the group R. Low-temperature PMR experiments show the occurence of rapid pseudorotation for hexa-coordinate Me 4 SbOx in toluene above − 70°. At − 100° two types of methyl groups can be distinguished, but even at this temperature a limiting spectrum is not obtained. In methylene dichloride rapid pseudo-rotation takes place even at − 100°. Similar results are obtained for the − 100° PMR spectra of Me 4 SbAcac in these solvents. The spectral results are used in discussions of the possible configurations of the organo(oxinato)antimony(V) compounds.

The synthesis and structural characterization of some triorganotin(IV) complexes of 2-{[(E)-1-(2-hydroxyaryl)alkylidene]amino}acetic acid. Crystal and molecular structures of Ph3Sn(2-OHC6H4C(H)NCH2COO) and Me3Sn(2-OHC6H4C(CH3)NCH2COO)

Abstract Triorganotin(IV) derivatives of 2-{[(E)-1-(2-hydroxyaryl)alkylidene]amino}acetic acid have been synthesized and characterized by 1H, 13C, 119Sn-NMR, 119Sn Mossbauer and IR spectroscopic techniques in combination with elemental analyses. The crystal structures of triphenyltin 2-{[(E)-1-(2-hydroxyphenyl)methylidene]amino}acetate and trimethyltin 2-{[(E)-1-(2-hydroxyphenyl)ethylidene]amino}acetate are reported. The X-ray structures reveal that the complexes adopt a polymeric trans-O2SnC3 trigonal bipyramidal configuration with the R groups in the equatorial positions and the axial locations occupied by a carboxylate oxygen from the ligand and the phenolic oxygen of the ligand on an adjacent complex. The ligands coordinate in the zwitterionic form with the phenolic proton moved to the nearby nitrogen atom. There is hydrogen bonding between this proton and the phenolic oxygen. The carboxylate group is unidentate. The spectroscopic evidence in combination with 119Sn Mossbauer data suggest that the other complexes adopt similar polymeric structures in the solid state.

Adducts of tin(IV) and organotin(IV) derivatives with 2,2′-azopyridine II. Crystal and molecular structure of SnMe2Br2AZP and further mössbauer and photoelectronic spectroscopic studies

Abstract A series of adducts of tin(IV) derivatives with 2,2′-azopyridine, AZP, has been studied by Mossbauer and X-ray photoelectronic spectroscopies and the crystal and molecular structure of SnMe2Br2- AZP has been determined. The linear correlation of the Mossbauer parameter isomer shift with partial atomic charge on tin suggests the occurrence of a single homologous series of isostructural adducts. The correlation of the Mossbauer parameter quadrupole splitting and C-Sn-C bond angle permits their calculation in SnMe2X2AZP adducts (X = Cl, Br). The N1s binding energies, obtained by XPS data, pointed out two slightly different values for both pyridinic and azo-group nitrogens. The crystallographic study of the SnMe2Br2AZP adduct shows a new structure in which the Sn atom is seven-coordinated.

Tin(IV) and organotin(IV) complexes containing mono or bidentate N-donor ligands: III. 1-methylimidazole derivatives: synthesis, spectroscopic and structural characterization

Abstract A series of adducts of the type [(L # ) y R n SnX 4− n ]· z H 2 O (L # =1-methylimidazole, y =1 or 2, R=Me, Et, Bu n or Ph, n =1, 2 or 3, X=Cl, Br or I, z =0, 1/2 or 1) has been characterized in the solid state and in solution by analyses, spectral (IR, 119 Sn Mossbauer, and 1 H, 13 C and 119 Sn NMR) data and conductivity measurements. The molecular weight determinations and the NMR data indicate that these organotin(IV) complexes partly dissociate in chloroform and acetone solution. The donor L # interacts with [(CH 3 ) 3 SnNO 3 ], yielding the 2:1 ionic complex [(L # ) 2 (CH 3 ) 3 Sn]NO 3 . The derivative [(L # ) 2 (CH 3 ) 2 SnCl 2 ] reacts with NaClO 4 , AgNO 3 , NaBPh 4 and KSCN in ethanol and diethyl ether giving the complexes [(L # ) 2 (CH 3 ) 2 Sn(ClO 4 ) 2 ], [(L # )(CH 3 ) 2 Sn(NO 3 ) 2 (H 2 O)], [(L # )(CH 3 ) 2 SnCl(H 2 O) 2 ]BPh 4 and [(L # ) 2 (CH 3 ) 2 Sn(NCS) 2 ], respectively, whereas when [(L # )(CH 3 ) 3 SnCl] interacts with an equimolar quantity of NaClO 4 , [(L # ) 2 (CH 3 ) 3 Sn]ClO 4 ·1/2H 2 O and (CH 3 ) 3 Sn(ClO 4 ) in 1:1 ratio are obtained. The stability towards self-decomposition of the complexes obtained decreases with increasing number of the Sn-bonded aryl or alkyl groups. The derivative [(L # ) 2 (CH 3 ) 2 SnBr 2 ] reacts with 1,10-phenanthroline (Phen), yielding immediately the complex [(Phen)(CH 3 ) 2 SnBr 2 ], whereas from the reaction between [(L # ) 2 (CH 3 ) 2 Sn(ClO 4 ) 2 ] and Phen, the mixed ligand complex [(L # )(Phen)(CH 3 ) 2 Sn](ClO 4 ) 2 is obtained. A different behaviour has been shown from the diiodide complex [(L # ) 2 (C 2 H 5 ) 2 SnI 2 ] which reacts with Phen, yielding the compound with the 3:2 stoichiometry [(Phen) 3 {(C 2 H 5 ) 2 SnI 2 } 2 ]. Both the crystal structures of [(L # ) 2 (CH 3 ) 2 SnBr 2 ] and [(L # ) 2 (C 2 H 5 ) 2 SnI 2 ] show the tin atom in an all- trans octahedral regular configuration, whereas in [(L # )(C 6 H 5 ) 3 SnCl] the tin atom exhibits a distorted trigonal bipyramidal geometry, with the phenyl groups in the equatorial positions. A comparison was made with structural data of other R 3 SnXN-type derivatives. The molecular parameters of 1-methylimidazole in the tin(IV) complexes were used, together with other structural data in literature, to derive empirical rules concerning the imidazole donor.

Synthesis and spectroscopic studies (Mo¨ssbauer, IR and NMR) of [R2SnCl2bipym] (R = butyl or phenyl) and the crystal and molecular structure of [Ph2SnCl2bipym]

Abstract The complexes [R 2 SnCl 2 bipym] (R = phenyl or butyl, bipym = 2,2′,6,6′-bipyrimidine) were synthesized and studied in solution by 1 H- and 13 C-NMR spectroscopy and in the solid state by IR and Mo¨ssbauer spectroscopy. The latter was also performed in frozen ethanolic solution. The structure of the phenyl complex was determined by single crystal diffraction methods. The value obtained for the angle C-SN-C in the phenyl compound is 169.3(2)° (X-ray) and 151° (Mo¨ssbauer), but the assignment of an octahedral configuration by Mo¨ssbauer spectroscopy is consistent with the structure determined by diffraction. The butyl complex is also octahedral and the two techniques show better agreement. The value of the C-SN- C angle is 171° (Mo¨ssbauer in the solid state), 163° (Mo¨ssbauer in frozen solution) and 175.1(6)° (X-ray). The NMR coupling constant, 1 J ( 119 Sn- 13 C), was also used to estimate the C-SN-C angle. The 13 C-NMR spectrum for the butyl complex is markedly concentration-dependent. At the highest concentration, this angle is 138° (Lockhart) and 145° (Holecˇek); for less concentrated samples the angle tends to decrease. This suggests that the coordination number of tin in solution is less than six.

Synthesis and structural studies by infrared and Mössbauer spectroscopy of adducts of tin(IV) and organotin(IV) derivatives with 2,2′-azopyridine

Abstract A number of complexes have been prepared by the reaction between 2,2′-azopyridine(AZP) and tin(IV) halides and organotin(IV) halides, and characterized by elemental analysis and infrared and variable temperature 119Sn Mossbauer spectroscopies. All of the new compounds have 1:1 stoichiometry, with the AZP ligand occupying two coordination sites by bonding through one of the ring and one of the azo group nitrogen atoms, to give rise to distorted octahedral structures. In the diorganotin complexes the two organic groups occupy trans positions. The infrared and Mossbauer spectroscopic data suggest that these compounds are monomeric in the solid state.

Complexes of organometallic compounds. XLVIII. Mössbauer and other studies on pyrazine derivatives of tin(IV) compounds. A relationship between isomer shift and charge on tin

Abstract Adducts RSnCl 3 ·pyz (R = Me, Bu n , Oct n , Ph; pyz = pyrazine) have been synthesized and characterized in the solid state. It has been determined that RSnCl 3 ·pyz are polymeric compounds, where the ligand acts as bridging bis-monodentate and the tin atoms attain the coordination number six. This has been duduced from: i) temperature dependent Mossbauer spectroscopy; ii) the correlation between Mossbauer isomer shift, δ, and electrical charge on tin, Q Sn , concerning pyrazine adducts of RSnCl 3 and others; iii) an infrared study of the coordinated ligand in RSnCl 3 ·pyz. Other implications of the Mossbauer T dependent study ( e.g. , the decrease of the Debye temperature in RSnCl 3 ·pyz with increasing of R), as well as of the δ/Q Sn correlation ( e.g. , the occurence of linear dependences as function of the Sn coordination number, using Q Sn from the method of Jolly and Perry [11, 12], are presented and discussed. The skeletal configuration around tin is lastly studied by point-charge model calculations of Mossbauer partial quadrupole splitting due to pyz/2, and of ΔE of RSnCl 3 ·pyz. A structure with meridional Cl 3 and trans -N 2 is proposed.

Synthesis, spectroscopic studies (Mössbauer and infrared), and the crystal and molecular structure of the organotin(IV)-pyrazine adducts [Sn(CH3)2Cl2]2pyz and [Sn(CH3)2Br2pyz]

Two adducts [Sn(CH 3 ) 2 Cl 2 ] 2 pyz ( Ia ) and Sn- (CH 3 ) 2 Br 2 pyz] ( Ib ) (pyz = pyrazine) have been synthesized and characterized in the solid state. Infrared and Mossbauer spectroscopies suggest a five- coordinated species for the Ia complex with an angular CSnC bond and a six-coordinated compound with a linear CSnC bond for the Ib complex. X-ray diffraction studies confirm a distorted trigonal bipyramidal geometry with N, Cl axial atoms and Cl and methyls in the equatorial plane for Ia where the Cl ax SnN bond angle is the lowest one reported to date and the Cl eq Sn bond distance the longest one with regard to similar complexes. This molecule has a short contact of 3.47 A between the tin and the axial chlorine atoms. The molecular structure of complex Ib points out all equivalent bonds in the trans position arising from a polymeric chain with bridged pyrazine ligand. The complex Ib is centro- symmetric at the tin atom.