Bidentate Bases Research Articles

Cis-bis(2,2'-bipyridyl-N-N')dichlorosilicon diiodide

The crystal and molecular structure of the title compound, C20H16Cl2N4Si2+·2I−, has been determined at 173 K. To our knowledge, this is the first crystal structure of a silicon tetrahalide complex with a bidentate base as a ligand. The two chloro ligands are cis relative to each other. The Si—N bonds trans to a chloro ligand are longer than the Si—N bonds trans to an Si—N bond. This feature is observed for the majority of M(bipy)2Cl2 (M = metal and bipy = 2,2′-bipyridyl) complexes, but it does not hold for all structures retrieved from the Cambridge Structural Database. The two pyridyl rings of each bipyridyl unit are nearly coplanar, whereas the bipyridyl units are almost perpendicular to each other. The two I− ions are more than 5 Å from the silicon centre. As a result, the compound can definitely be described as ionic. The crystal packing is stabilized by short C—H⋯I contacts.

Synthesis of nickel(II)-di(2,3-dichlorophenyl)carbazonate and its adduct formation with heterocyclic nitrogen bases

The nickel(II)-di(2,3-dichlorophenyl)carbazonate [Ni(D2,3DClPC)2] complex has been prepared and characterized by elemental and spectral studies. The NiII chelate forms adducts with heterocyclic nitrogen bases, which were studied spectrophotometrically in monophase CHCl3 media. Saturated monodentate bases such as pyrrolidine, piperidine, etc., form pentacoordinate adducts of 1:1 stoichiometry, whereas bidentate and unsaturated monodentate bases form hexacoordinated adducts with 1:1 and 1:2 metal–ligand stoichiometries respectively. The results are discussed interms of steric properties, basicity and ring structures of the heterocyclic bases.

Degradation and Modification of Metallaboranes: Reactions of the Hexaborane(10) Analoguenido-(PPh3)2(CO)OsB5H9with Phosphines and the Crystal and Molecular Structure of [2,2,2-(PPh3)2(CO)-nido-2-OsB4H7-3-BH2·PPh2Me

The reaction between the osmahexaborane [2,2,2-(PPh3)2(CO)-nido-2-OsB5H9] (1) and bases such as PPh3, PPh2Me, and PMe3 in refluxing CH2Cl2 affords unique adducts of the type [2,2,2-(PPh3)2(CO)-nido-2-OsB4H7-3-BH2·PR3] (2) for which spectroscopic data suggest the presence of a pendent boryl group. This was confirmed by a crystal structure determination for the PPh2Me adduct which shows that 2 is a nido-osmapentaborane with a terminal BH2·PPh2Me moiety on a basal boron atom adjacent to the metal. The reaction is reversible in the case of PPh3 and to a lesser extent PPh2Me, but not for PMe3. Heating the PPh3 adduct affords the osmahexaborane 1, liberating PPh3, but degradation to the osmapentaborane [2,2,2-(PPh3)2(CO)-nido-2-OsB4H8] (6) and BH3·PPh3 competes. The tendency to degrade to phosphine·borane increases markedly down the series R3 = Ph3, Ph2Me, and Me3. When the bidentate bases [1,2-(PPh2)2(CH2)2] and [1,3-(PPh2)2(CH2)3] (abbreviated as dppe and dppp, respectively) are used, two major products are o...

Classification of polar additives with respect to their influence on the microstructure in anionic polymerization of butadiene with butyllithium by transition energy measurements

A transition energy scale was established on the basis of di-Me indoaniline as org. dye for 23 mono- and bidentate polar additives. From polymn. expts. of isoprene with s-butyllithium in mixts. of n-hexane and the selected bases, the microstructure of polyisoprenes was detd. by 1H-NMR spectroscopy. The vinyl contents of these polymers could be satisfactorily correlated with the transition energy measurements. However, it turned out that esp. bidentate bases do not fit into this scheme. Obviously, besides their influence on the polarity of the reaction soln., they exhibit special interactions with the growing centers. The developed correlations allow the prediction of 1,2- and 3,4-linkages in polyisoprenes from anionic polymn. of isoprene with butyllithium in polar solvents in the presence of low concns., also of bases hitherto not investigated. The temp. dependence of the microstructure can likewise be estd. As in the case of butadiene, at least for weak bases, it was found that the vinyl contents depend primarily on the polarity of the reaction mixt. detd. by the base concn. and not on the molar ratio of base to initiator.

Synthetic, Structural and Vibrational Spectroscopic Studies in Bismuth(III) Halide/N,N′-Aromatic Bidentate Base Systems. V Bismuth(III) Halide/N,N′-Bidentate Ligand (1 : 2) Systems

Syntheses and room-temperature single-crystal X-ray determinations are recorded for a number of adducts of BiX3/N,N′-bidentate 1 : 2 stoichiometry (N,N′-bidentate = 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen)). BiX3/bpy (1 : 2), X = Br, I, are isomorphous, monoclinic, P21/c, a ≈ 7·5, b ≈ 31, c ≈ 10·3 Å, β ≈ 113°, Z = 4; conventional R on |F| were 0·058, 0·055 for No 1744, 2068 independent ‘observed’ (I > 3σ(I)) reflections. BiCl3/phen (1 : 2) is monoclinic, P21/C, a 9·675(3), b 31·845(7), c 7·756(2) Å, β 109·94(2), Z = 4, R 0·071 for No 2537, while BiBr3/phen (1 : 2), also monoclinic, P21/c, has a 17·590(5), b 8·812(2), c 17·537(7) Å, β 117·58(3)°, Z = 4; R 0·083 for No 890. BiX3/phen (1 : 2).S, X/S = Br/MeCN, I/CH2Cl2, are isomorphous, orthorhombic, Pna21, a ≈ 20·7, b ≈ 14·2, c ≈ 8·9 Å, Z = 4, R 0·060, 0·046 for No 1553, 2423 respectively. All complexes are mononuclear with seven-coordinate (N2)2BiX3 bismuth environments. Bands in the far-infrared spectra due to the v(BiX) vibrations in [(phen)2BiCl3] and [(bpy)2BiX3] (X = Br, I) are assigned and discussed in relation to the structures of the complexes.

Synthetic, Structural and Vibrational Spectroscopic Studies in Bismuth(III) Halide/N,N′-Aromatic Bidentate Base Systems. I Large-Cation (2,2′-Bipyridinium and 1,10-Phenan- throlinium) Salts of Polyhalobismuthate(III) Ions

Syntheses and room-temperature single-crystal X-ray studies are recorded for a variety of salts of cations derived from protonated 2,2′-bipyridine and 1,10-phenanthroline (bpyH+ and phenH+) with polyhalobismuthate(III) anions. ‘[(phenH)(phenH2)(H2O)2] [BiCl6]’ is triclinic, P-1, a 9·791(1), b 9·338(3), c 8·311(3) Å, α 73·46(3), β 69·71(2), γ 86·36(2)°, Z = 1; conventional R on |F| was 0·027 for No 4852 independent ‘observed’ (I > 3σ(I)) reflections. [BiCl6]3- is closely octahedral, accompanied by an interesting protonation/hydrogen-bonding array among the other moieties. The latter comment applies also to ‘[(phenH2)(H2O)][BiCl5](∞|∞)’, monoclinic, P2/c, a 8·388(1), b 12·004(1), c 17·146(3) Å, β 98·26(1)°, Z = 4, R 0·047 for No 2670, the anion array being a one-dimensional polymer with bridging chlorine atoms occupying cis sites in the pseudo-octahedral coordination sphere of the bismuth. [bpyH2]4 [Bi4Cl20] is monoclinic, P21/c, a 14·228(4), b 14·217(2), c 16·254(4) Å, β 110·14(2)°, Z = 2, R 0·045 for No 2777; in the novel centrosymmetric tetramer, the four bismuth atoms are bridged into a square array by four linearly coordinated halogen atoms at the centres of the edges, a pair of these lying cis in the pseudo-octahedral coordination sphere of each bismuth. [bpyH]3 [Bi2Cl9] is triclinic, P-1 a 19·288(7), b 14·251(3), c 7·644(3) Å, α 75·02(2), β 80·15(3), γ 72·76(2)°, Z = 2, R 0·072 for No 3600, the two pseudo-octahedrally coordinated bismuth atoms being bridged by three chlorine atoms on a mutual octahedral face, [Cl3Bi(µ-Cl)3BiCl3]3-. [phenH] [BiCl4](∞|∞),H2O is triclinic, space group P-1, a 12·119(7), b 10·169(6), c 7·247(4) Å, α 69·30(4), β 75·05(4), γ 77·92(5)°, Z = 2, R 0·035 for No 2348. The anion is a one-dimensional polymer, successive metal atoms being bridged by pairs of chlorine atoms lying cis in the pseudo-octahedral coordination sphere. [bpyH]4 [Bi2I10] is monoclinic, P21/n, a 13·426(4), b 14·396(6), c 14·539(5) Å, β 101·31(3)°, Z = 2, R 0·11 for No 1862; the anion is of the form [I4Bi(µ-I)2BiI4]4- with quasi-octahedral bismuth. [bpyH] [BiI4](∞|∞) is monoclinic, C2/c, a 12·442(5), b 18·41(2), c 7·714(2) Å, β 92·80(3)°, Z = 4, R 0·080 for No 850, with a polymeric one-dimensional anion comparable to that in [phenH] [BiCl4](∞|∞),H2O. The structure of the 2,6-dimethylpyridinium salt of [BiCl6]3- is also recorded, as its acetonitrile solvate; triclinic, P-1, a 15·025(2), b 10·357(3), c 9·964(1) Å, α 83·14(2), β 89·32(1), γ 86·61(2)°, Z = 2, R 0·046 for No 3601; there is also an isomorphous bromide, and also an isostoichiometric bromide modelled as monoclinic, Cm, a 18·128(6), b 10·348(2), c 10·241(2) Å, β 121·31(3)°, Z = 2, R 0·050 for No 1379. Bands in the far-infrared and Raman spectra due to the v(BiCl) modes are assigned in [(phenH)(phenH2)(H2O)2] [BiCl6] and [bpyH2]4 [Bi4Cl20], and are discussed in relation to the structures of the complexes.

Synthetic, Structural and Vibrational Spectroscopic Studies in Bismuth(III) Halide/N,N′-Aromatic Bidentate Base Systems. IV Bismuth(III) Halide/N,N′-Bidentate Ligand (1 : 1) Systems

Room-temperature single-crystal X-ray studies are recorded for a number of adducts of BiX3 and N,N′-bidentate ligand (2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen)), devoid of coordinated solvent. BiBr3/bpy/MeCN (1 : 1 : 1) is triclinic P-1, a 12·129(2), b 9·955(4), c 7·748(1) Å, α 73·14(2), β 77·34(1), γ 69·79(2)°, Z = 2; conventional R on |F| was 0·036 for No 2252 independent ‘observed’ (I > 3σ(I)) reflections. The phen analogue is isomorphous, a 11·586(3), b 10·839(6), c 7·769(10) Å, α 73·70(7), β 76·67(7), γ 70·34(4)°, Z = 2, R 0·042 for No 800. BiI3/bpy (1 : 1) is triclinic, P-1, a 11·742(4), b 9·261(1), c 8·261(3) Å, α 86·46(2), β 71·48(3), γ 67·25(2)°, Z = 2, R 0·043 for No 1164. All complexes are centrosymmetric binuclear [(N,N′-bidentate)X2Bi(µ-X)2BiX2(N,N′-bidentate)] with six-coordinate pseudo-octahedral bismuth(III). Attempts to produce a chloride analogue have resulted, in the case of N,N′-bidentate = bpy, in a novel adduct of BiCl3/bpy 1 : 1·5 stoichiometry, monoclinic, P21/c, a 9·377(8), b 17·699(5), c 21·58(1) Å, β 107·82(6)°, Z = 8, R 0·055 for No 1804. The complex is [(bpy)2Cl2Bi(µ-Cl)BiCl3(bpy)], containing seven- and six-coordinate bismuth. Bands in the far-infrared spectra due to the v(BiX) vibrations in [(bpy)2Cl2Bi(µ-Cl)BiCl3(bpy)] and [(bpy)I2Bi(µ-I2)BiI2(bpy)] are assigned and discussed in relation to the structures of the complexes.

Synthetic, Structural and Vibrational Spectroscopic Studies in Bismuth(III) Halide/N,N ′-Aromatic Bidentate Base Systems. III Some Novel Bismuth(III) Halide/N,N ′-Bidentate Ligand (1 : 1)

Syntheses and single-crystal room-temperature X-ray structure determinations are recorded for a number of adducts obtained by the crystallization of bismuth(III) halides with 2,2′-bipyridine (bpy) or 1,10- phenanthroline (phen) from dimethyl sulfoxide (dmso) solution. [(phen)BiX3(O-dmso)2].dmso, X = Cl, Br, are triclinic, P-1,a ≈ 14·6, b ≈ 9·7, c ≈ 9·5 Å, α ≈ 96, β ≈ 96, γ ≈ 98°, Z = 2; conventional R on | F| were 0·057, 0·037 for No 5775, 4847 independent ‘observed’ (I > 3σ(I)) reflections respectively. The metal atom coordination environments are seven-coordinate pentagonal bipyramidal with axial halides and the two O-dmso ligands cis in the equatorial plane. BiI3/phen/dmso (1 : 1 : 1 ) is orthorhombic, Pmc21, a 12·745(3), b 9·697(3), c 18·335(5) Å, Z = 4, R 0·049 for No 2012. The complex is ionic [(phen)BiI2(O-dmso)3]+[(phen)BiI4]-, the halide atoms being axial in a pentagonal bipyramidal array about the metal in the cation, with a quasi-octahedral coordination environment in the anion. With bpy, by contrast, BiI3/bpy/dmso (1 : 1 : 1) is obtained, orthorhombic, Pnma, a 17·86(2), b 12·87(1), c 8·47(1) Å, Z = 4, R 0·058 for No 1194, a neutral mononuclear complex [(bpy)BiI3(O-dmso)] with a six-coordinate array about the metal, O-dmso trans to an iodine atom. Bands in the far-infrared and Raman spectra due to the vibrations of the O2N2BiX3 cores in [(phen)BiX3(O-dmso)2] (X = Cl, Br) are assigned, and discussed in relation to the structures of the complexes.

Nickel(II) complexes of substituted diphenylcarbazones and their adducts with heterocyclic nitrogen bases

The complexing behaviour of novel 1,5-di(4-chloro-2- methylphenyl)carbazone and 1,5-di(2,4-dichlorophenyl)carbazone towards nickel(II) ions has been investigated by elemental analysis, magnetic susceptibility, u.v. -vis., i.r. and 1H-n.m.r. spectral studies. The ligands act as bidentate N,O donors and form 1:2 complexes with the metal ions. The adducting behaviour of nickel(II) complexes with nitrogen bases has been studied spectrophotometrically in a chloroform monophase. The nickel(II) di(4-chloro-2-methylphenyl)carbazonate forms hexacoordinate adducts with monodentate and bidentate bases with 1:2 and 1:1 chelate:base stoichiometries, respectively, whilst, nickel(II) di(2,4-dichloro-phenyl)carbazonate forms penta- and hexacoordinate adducts of 1:1 chelate:base stoichiometry with monodentate and bidentate bases, respectively. The results are discussed on the basis of steric properties and the basicity of the nitrogen bases.

Synthetic, Structural and Vibrational Spectroscopic Studies in Bismuth(III) Halide/N,N′-Aromatic Bidentate Base Systems. IV. Bismuth(III) Halide/N,N′-Bidentate Ligand (1 : 1) Systems

The generation of a number of 1,2-diarylcyclopropane-1,2-diols is reported. Reaction of these in situ with acid gives, primarily, an α,β-unsaturated ketone in which the aryl substituent attached to the double bond is that which is best able to stabilize a benzylic cation. It is proposed that the reaction proceeds by O-protonation of the cyclopropane-1,2-diol, followed by loss of water and opening of the resulting cyclopropyl cation and final deprotonation. Such initial O-protonation contrasts with the C-protonation normally observed in the acidolysis of cyclopropanols and other dialkyl- and alkylaryl-cyclopropane-1,2-diols.

Synthesis of nickel(II)-di(5-chloro-2-methylphenyl)carbazonate and its adduct formation with heterocyclic nitrogen bases

The title complex has been synthesized and characterized by elemental and spectral analysis. The NiII chelate forms adducts with heterocyclic nitrogen bases, which were characterized spectrophotometrically in solution. Bidentate and unsaturated monodentate bases form hexacoordinate adducts with 1∶1 and 1∶2 metal∶ligand stoichiometries, respectively, whilst saturated nitrogen bases form pentacoordinate adducts with 1∶1 stoichiometry. The results are discussed in terms of basicities and steric properties of the bases.

Lewis-Base Adducts of Lead(II) Compounds. XVI. Synthetic and Structural Studies of Some Adducts of 2-Aminomethylpyridine With Lead(II) Compounds

Syntheses and room-temperature single-crystal X-ray structure determinations are recorded for 2:1 adducts of 2-aminomethylpyridine ('amp') with lead(II) nitrate and thiocyanate . [(amp)2Pb(NO3)2]2 is triclinic, Pī, a 11.616(4), b 11.145(6), c 7.341(3) Ǻ, α 83.87(4), β 89.17(3), γ 64.12(3)°, Z = 1 dimer ; R was 0.043 for No 3529 independent 'observed' (I > 3σ(I)) reflections. [(amp)2Pb(SCN)2]2 is also triclinic, Pī , a 12.121(9), b 9.301(14), c 8.615(8) Ǻ, α 70.11(10), β 84.00(7), γ 79.38(10)°, Z = 1 dimer (R 0.033 for No 3467). Both complexes are centrosymmetric dimers ; the coordination environment is made up in each case of a pair of N,N°-bidentate bases, one terminally bound anion (O,O°-chelating nitrate or S-bonded thiocyanate ) and bridging anions. In the case of the thiocyanates, these bridge end-on, so that the lead(II) environment is seven-coordinate PbN5S2; in the nitrate, the anion chelates through two of its oxygen atoms, bridging via the third, so that the lead(II) environment is nine-coordinate PbN4O5. A 'problem structure', [(amp)2Pb(ClO4)2], monoclinic, C2/c (?), a 14.528(3), b 8.203(3), c 15.495(6) Ǻ, β 91.14(3)°, Z = 4 f.u ., R 0.044 for No 1775, is also recorded, the crystal seemingly a disordered aggregate of [(N, N′-amp)2Pb(OClO3)2] moieties.

Lewis-Base Adducts of Lead (II) Compounds. XI. Synthetic and Structural Studies of Some 1:1 Adducts of 2,2'-Bipyridine and 1,10-Phenanthroline With Lead(II) Oxoanion Salts

Syntheses and room-temperature single-crystal X-ray structure determinations are recorded for 1 : 1 adducts of 1,10-phenanthroline ('phen') with lead(II) nitrate (as a monohydrate; the structure of the isomorphous 2,2'-bipyridine (' bpy ') analogue is also recorded) and of its lead(II) acetate ('ac') analogue (as a dihydrate ). [( bpy ) Pb (NO3)2](∞|∞).H2O is monoclinic, P 21/c; a 7.244(9), b 9.872(2), c 20.395(5) Ǻ, β 109.08(7)°, Z = 4 f.u ., R being 0.048 for No = 3447 independent 'observed' (I > 3σ(I)) reflections. [( phen ) Pb (NO3)2](∞|∞).H2O has a 7.168(2), b 9.972(1), c 21.069(3) Ǻ, β 99.47(1)°, R 0.034 for No 3596. [( phen ) Pb (ac)2]2.4H2O is triclinic, Pī , a 13.932(3), b 12.904(4), c 12.716(5) Ǻ, α 62.37(2), β 71.16(2), γ 60.55(2)°, Z = 2 ( dimers ); R was 0.029 for No 5457. The nitrates are one-dimensional polymers along b, successive lead atoms being linked by one oxygen of one of the nitrate groups, each of the other oxygen atoms completing a chelate to either side; the lead environment is completed as N2PbO7 by the other nitrate (as a chelate ), the bidentate base, and the water molecule. In the acetate which is a centrosymmetric dimer (manifested in two distinct independent dimers ) the two lead atoms are linked by bridging oxygen atoms derived from pairs of chelating acetate moieties about each lead atom. The coordination sphere of each lead atom is completed by the bidentate aromatic base. The two dimers differ significantly in parallel comparison of their geometrical descriptors.

NMR and Other Spectroscopic Studies of Isonicotinoyl Based Hydrazones and Their Ternary Complexes

Abstract The three isonicotinoyl hydrazone Schiff bases viz. anisaldehyde isonicotinoyl hydrazone(AINH), 2-furaldehyde isonicotinoyl hydrazone(FINH), 2-thi ophenealdehyde isonicotinoyl hydrazone(TINH) have been synthesized and characterized on the basis of their elemental analysis, magnetic susceptibility, IR, electronic and nmr spectral studies. The ternary complexes of Ni(II) and Cu(II) with these hydrazones and neutral bidentate base phen and bipy are octahedral and the presence of acetate and/ or water molecule is revealed by the study of their IR spectra, force constants and thermal degradation pattern. Suitable structures have been assigned to these ternary complexes.

NMR Investigation of the interaction between monodentate and bidentate nitrogen bases and tungsten(VI) fluoride and oxide fluorides

NMR spectroscopy proved to be an invaluable tool to study the interaction between monodentate and bidentate nitrogen bases and tungsten(VI) fluoride and oxide fluorides in solution. 1H, 19F, and 13C spectra including 2D COSY experiments were used for these studies. Pyridine, and 2,F-pyridine were used as monodentate bases and 2,2′- bipyridyl as a bidentate base. The results obtained are discussed in terms of the chemistry and structural features of the species present in these systems.

Structure and equilibria in triorganolead halide adduct formation

The Lewis acidities of triorganolead halides have been studied by 31P and 207Pb NMR spectroscopy and by calorimetry. The formation of 1:1 adducts with a variety of mono- and bidentate bases was demonstrated by the linearity of the plots of chemical shift versus (shift/conc.) 1 2 . The 207Pb chemical shifts of the bidentate adducts indicated only 5-coordinate lead and hence the absence of chelation. Towards triphenyllead chloride basicities varied in the order triethylphosphine oxide > tributylphosphine oxide ⩾ triphenylphosphine oxide > DMSO > tributylphosphine ⩾ pyridine. Triphenyllead chloride was found to be a stronger acid (larger K) than both triphenyllead bromide and triethyllead chloride. The effects of solvent on the equilibrium constants paralleled the trend reported previously for organotin halides. The equilibrium constant for adduct formation with triphenylphosphine oxide (TPPO) is slightly larger for triphenyllead chloride relative to triphenyltin chloride, confirming the expected increase in acidities down Group 14. X-Ray diffraction studies of triphenylphosphine oxide adducts of triphenyllead bromide and triphenyltin chloride showed both structures to be trigonal bipyramidal with the phenyl groups on the equatorial positions. Additionally, the structures are crystallographically isomorphous.

An AB initio molecular orbital study of the structure, energetics and bond activation of Al + complexes

The structures and stabilities of Al + complexes of mono- and bidentate bases have been examined by ab initio molecular orbital theory. Equilibrium structures were obtained at the 6-31G ∗ level and correlation effects were evaluated at the fourth-order (MP4SDTQ) Møller-Plesset theory. The structures of the Al + complexes investigated closely resemble those of the corresponding protonated species rather than those of analogous Li + complexes. We have shown that the Al + − base interaction, although essentially electrostatic, has some covalent component through the contribution of the low-lying empty p orbitais of Al +. Our results also show that a correct description of these interactions requires the inclusion of polarization functions in the basis set. A topological analysis of the electronic charge density of the complexes and the corresponding neutral bases permits quantitative discussion of both substituent effects on the complex stability and bond activation within the base. Charge redistribution of the base upon Al + association is in agreement with the calculated shift for the stretching frequencies of the A-B bond.

Bond activation by protonation in the gas phase

The structures of different first-row bases and their protonated species are compared using ab initio quantum-mechanical techniques at the 6-31G* and 6-31+G(d, p) levels of accuracy. A topological analysis of the Laplacian of the electronic charge density offers quantitative information on bond activation upon protonation. We have shown that protonation can be accompanied by bond breaking in cases where the basic center is highly electronegative as in alcohols or fluoroalkanes. In bidentate bases, protonation produces opposite effects depending on the center which undergoes protonation.

The formation of organotin halide adducts with 1,2-bis(diphenylphosphine oxy)ethane and methyldiphenylphosphine oxide

The acidities of a series of organotin halides toward the bidentate base 1,2-bis(diphenylphosphine oxy)ethane ([C 6H 5) 2P(O)CH 2] 2, EDPO) were determined by monitoring the 31P chemical shift of equimolar mixtures of acid and base as a function of concentration in chloroform. Additional studies used the analogous Lewis monodentate base methyldiphenylphosphine oxide (MPPO) and the Lewis base triphenylphosphine oxide (TPPO). In all cases, formation of a 1 1 adduct was found to predominate. Comparison of the equilibrium constants for specific organotin halides showed that EDPO and MPPO have comparable base strengths in chloroform. TPPO is a weaker base than either EDPO or MPPO in chloroform. Tin-119 NMR indicated that the organotin halide-EDPO adducts have 5-coordination at tin with no chelation of the base.

ChemInform Abstract: Thermochemical Study of the Reactions of Lewis Bases with Bis(ethane‐1,2‐dithiolato)tin(IV) in Benzene Solution

Thermodynamic data have been obtained by calorimetric titration in benzene solution at 30°C for reacton of Lewis bases with bis(ethane-1,2-dithiolato)tin(IV) (SnS4). Unidentate bases form simultaneously 1:1 and 1:2 adducts with SnS4, and bidentate bases form 1:1 adducts. The enthalpies of formation of the 1,10-phen adducts are similar to those of 1:2 adducts with py or 4-mepy and the stability of the TMEN adducts is similar to 1:2 adducts of piperidine with similar enthalpies of formation. Pyridine N-oxide is the only non-nitrogen donor observed to form 1:2 adducts with smaller enthalpy changes but a rather big equilibrium constant, due to the smaller steric effect of the pointed NO ligand. The Lewis acidity of Sn(IV) compounds is according to the following order: Ph2SnS2<SnS4<SnI4< SnCl4.