Thallium(I) bis(mercaptoimidazolyl)borates

The Role of Prussian Blue-Thallium and Potassium Similarities and Differences in Crystal Structures of Selected Cyanido Complexes of W, Fe and Mo

The synthesis and single X-ray crystal structures of Tl2[W(CN)6(bpy)]·H2O, Tl[W(CN)6(bpy)], Tl57[{Fe(CN)6}12{NO3}9]·9H2O, Tl4[W(CN)8] and Tl4[Mo(CN)8] are described. Salts crystalize in the monoclinic or trigonal (Fe) space group. For all complexes, the very unusual “side-on” coordination of Tl to C and N of cyanido ligands is observed and compared to potassium cations. The very strong bonding to cyanido ligands with an 8–13 coordination number of thallium is described and discussed. The difference between potassium and thallium bonding is an indication of the biological activity of thallium and the role of Prussian blue in the thallium detoxification procedure.

Three-dimensional organometallic thallium(I) supramolecular polymer nanostructures synthesized with sonochemical process

A new three-dimensional thallium(I) supramolecular polymer, [Tl₂(μ₂-ATA)]_n (1), [H₂ATA=2-aminoterephthalic acid]_, has been synthesized and characterized. The single-crystal X-ray data of compound 1 shows one type of Tl^I ion with a low coordination number. Compound 1 was self-assembled from Tl⋯C, Tl⋯O and Tl⋯N secondary interactions in thallium(I) coordination and the active lone pair on Tl^I in this compound may be involved in donor bonding. Two sides of the aromatic ring of ATA^2- anion have been involved in two types of secondary Tl⋯C approaches. Three samples of 1 were synthesized with three different concentrations of initial reagents under ultrasonic irradiation. The thermal stability of compound 1 samples were studied by thermo gravimetric (TG) and differential thermal analyses (DTA). These nano-structures were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM).

Bis- and Tris(2-oxobenzimidazolyl)hydroborato Complexes of Sodium and Thallium: New Classes of Bidentate and Tridentate Oxygen Donor Ligands

A series of bis- and tris(oxobenzimidazolyl)hydroborato compounds, namely, [Bo^RBenz]Na and [To^RBenz]-Na (R = Me, Bu^t, Ad), which feature uncommon sterically demanding LX [O₂] and L₂X [O₃] donor ligands, have been obtained via the reactions of NaBH₄ with 1-R-1,3-dihydro-2H-benzimidazol-2-ones. Evidence that the alkyl substituents are suitably located to have a significant impact on the coordination environment is provided by the observation that the methyl derivative [To^MeBenz]Na(κ³-diglyme) exhibits κ³-coordination of the diglyme, whereas the t-butyl and adamantyl derivatives, [To^ButBenz]Na(κ²-diglyme) and [To^AdBenz]Na(κ²-diglyme), exhibit κ²-coordination. The [Bo^RBenz] and [To^RBenz] ligands also allow for isolation of discrete mononuclear thallium compounds, [Bo^RBenz]Tl and [To^RBenz]Tl, for which the steric demands of the ligands have been quantified in terms of both cone angle and buried volume concepts.

Studies the effects of ultrasonic irradiation and dielectric constants of solvents on formation of lead(II) supramolecular polymer; new precursors for synthesis of lead(II) oxide nanoparticles

In order to evaluation the effects of ultrasonic irradiations and dielectric constants of solvents on formation [Pb₂(5-Clq-8-ol)₂(OAc)₂]_n (1), [H5-Clq-8-ol=5-chloroquinolin-8-ol and OAc^-=acetate]_, we designed some experiments and synthesized six samples of 1 under different conditions. Microrods of a lead(II) supramolecular polymer, were synthesized under these conditions. These microstructures were characterized by IR spectroscopy, X-ray powder diffraction (XRD) and Scanning Electron Microscopy (SEM). The results indicated that compound 1 with the best crystallinity can be obtained in the presence of MeCN and H₂O (as the bulk sample) and in the presence of MeCN and EtOH (by sonochemical process). The least agglomeration of microrods was observed in H₂O which is due to high dielectric constant of it. By considering all of the factors consist of crystallinity and agglomeration of the products and their corresponding histograms, it seems that MeCN is the best solvent for synthesis of 1. The samples which were synthesized in the presence of MeCN, had been used as new precursors for fabricating lead(II) oxide nanoparticles via thermal decomposition in oleic acid (OA).

Molecular structures of tris(2-mercapto-1-tert-butylimidazolyl)hydroborato and tris(2-mercapto-1-adamantylimidazolyl)hydroborato sodium complexes: analysis of [Tm(R)] ligand coordination modes and conformations

The tris(mercaptoimidazolyl)hydroborato complexes, [κ(3)-S2H-Tm(Bu(t))]Na(THF)3 and [κ(3)-S2H-Tm(Ad)]Na(THF)3, which feature t-butyl and adamantyl substituents, have been synthesized via the reactions of the respective 1-R-1,3-dihydro-2H-imidazole-2-thiones with NaBH4 in THF (R = Bu(t), 1-Ad). X-ray diffraction studies indicate that the compounds are monomeric and that the [Tm(R)] ligands coordinate to the metal in a κ(3)-S2H manner via two of the sulfur donors and the hydrogen attached to boron, a combination that is unprecedented for sodium derivatives. Analysis of the tris(mercaptoimidazolyl)hydroborato compounds that are listed in the Cambridge Structural Database has allowed for the formulation of a set of criteria that enables κ(x)-S(x) and κ(x+1)-S(x)H coordination modes to be identified. Furthermore, the various κ(x)-S(x) and κ(x+1)-S(x)H coordination modes have also been analyzed with respect to the conformations of the [Tm(R)] ligands, which differ by rotation of the imidazolethione moieties about the B-N bond.

Benzannulated tris(2-mercapto-1-imidazolyl)hydroborato ligands: tetradentate κ4-S3H binding and access to monomeric monovalent thallium in an [S3] coordination environment

The benzannulated tris(mercaptoimidazolyl)borohydride sodium complex, [Tm(Bu(t)Benz)]Na, has been synthesized via the reaction of NaBH4 with 1-tert-butyl-1,3-dihydro-2H-benzimidazole-2-thione, while [Tm(MeBenz)]K has been synthesized via the reaction of KBH4 with 1-methyl-1,3-dihydro-2H-benzimidazole-2-thione. The molecular structures of the solvated adducts, {[Tm(Bu(t)Benz)]Na(THF)}2(μ-THF)2 and [Tm(MeBenz)]K(OCMe2)3, have been determined by X-ray diffraction, which demonstrates that the [Tm(R)] ligands in these complexes adopt different coordination modes to that in {[Tm(MeBenz)]Na}2(μ-THF)3. Specifically, while the [Tm(MeBenz)] ligand of the sodium complex {[Tm(MeBenz)]Na}2(μ-THF)3 adopts a κ(3)-S3 coordination mode, the potassium complex [Tm(MeBenz)]K(OCMe2)3 adopts a most uncommon inverted κ(4)-S3H coordination mode in which the potassium binds to all three sulfur donors and the hydrogen of the B-H group in a linear KH-B manner. Furthermore, the [Tm(Bu(t)Benz)] ligand of {[Tm(Bu(t)Benz)]Na(THF)}2(μ-THF)2 adopts a κ(3)-S2H coordination mode, thereby demonstrating the flexibility of this ligand system. The monovalent thallium compounds, [Tm(MeBenz)]Tl and [Tm(Bu(t)Benz)]Tl, have been obtained via the corresponding reactions of [Tm(MeBenz)]Na and [Tm(Bu(t)Benz)]Na with TlOAc. X-ray diffraction demonstrates that the three sulfur donors of the [Tm(RBenz)] ligands of both [Tm(MeBenz)]Tl and [Tm(Bu(t)Benz)]Tl chelate to thallium. This coordination mode is in marked contrast to that in other [Tm(R)]Tl compounds, which exist as dinuclear molecules wherein two of the sulfur donors coordinate to different thallium centers. As such, this observation provides further evidence that benzannulation promotes κ(3)-S3 coordination in this system.

Synthesis and structural characterization of bis(2-oxoimidazolyl)hydroborato complexes: a new class of bidentate oxygen-donor ligands

A new class of bidentate ligands that feature oxygen donors, namely, the bis(2-oxo-1-tert-butylimidazolyl)hydroborato and bis(2-oxo-1-methylbenzimidazolyl)hydroborato ligands, [Bo(Bu(t))] and [Bo(MeBenz)], have been synthesized via the reactions of MBH4 with 2 equiv of the respective 2-imidazolone. Chelation of [Bo(Bu(t))] and [Bo(MeBenz)] to a metal center results in a flexible eight-membered ring that is capable of adopting a "boatlike" conformation that allows for secondary M···H-B interactions.

Synthesis and structural characterization of bis and tris(2-mercapto-1-methylbenzimidazolyl)hydroborato complexes: benzannulation promotes κ³-coordination

The benzannulated bis and tris(mercaptoimidazolyl)borohydride compounds, [BmMeBenz]Na and [TmMeBenz]Na, have been synthesized via the reactions of NaBH4 with two and three equivalents of 1-methyl-1,3-dihydro-2H-benzimidazole-2-thione, respectively. X-ray diffraction studies on the THF adducts, {μ-[BmMeBenz]Na(THF)₂}₂ and {[TmMeBenz]Na}₂(μ-THF)₃, indicate that both compounds are dinuclear but differ according to the nature of the bridging ligand. Specifically, {μ-[BmMeBenz]Na(THF)₂}₂ possesses bridging [BmMeBenz] ligands and terminal THF ligands, while {[TmMeBenz]Na}₂(μ-THF)₃ possesses terminal [TmMeBenz] ligands and bridging THF ligands. The tris(mercaptoimidazolyl)borohydride ligand of {[TmMeBenz]Na}₂(μ-THF)₃ coordinates in a κ³-manner, which is in marked contrast to the κ²-, κ¹- and κ⁰-modes that have been reported for various [TmMe]Na derivatives. Density functional theory (DFT) geometry optimization calculations of the anions [TmMeBenz]⁻ and [TmMe]⁻ in the gas phase indicate that the conformation required for κ³-S₃ coordination, i.e. one in which the three sulfur donors point away from the B-H group, is relatively more stable for [TmMeBenz]⁻ than for [TmMe]⁻, and thus provides a rationalization for the observation that benzannulation enables κ³-coordination of tris(mercaptoimidazolyl)borohydride ligand in {[TmMeBenz]Na}₂(μ-THF)₃. Furthermore, comparison of the molecular structure and IR spectroscopic properties of [TmMeBenz]Re(CO)₃ with those of [TmMe]Re(CO)₃ indicates that benzannulation reduces the electron donating properties of the ligand, but has little effect on its steric properties. {μ-[BmMeBenz]Na(THF)₂}₂ and {[TmMeBenz]Na}₂(μ-THF)₃ react with [Me₃PCuCl]₄ to give [BmMeBenz]CuPMe₃ and [TmMeBenz]CuPMe₃, the first pair of structurally related bis and tris(mercaptoimidazolyl)hydroborato copper(I) compounds.

Applications of Tripodal [S(3)] and [Se(3)] L(2)X Donor Ligands to Zinc, Cadmium and Mercury Chemistry: Organometallic and Bioinorganic Perspectives

The tripodal tris(2-mercapto-1-R-imidazolyl)hydroborato ligand system, [Tm(R)], and its selenium counterpart, [Tse(R)], provide useful platforms for investigating organometallic and bioinorganic aspects of the chemistry of zinc, cadmium and mercury in sulfur-rich and selenium-rich coordination environments. For example, the tridentate [Tm(R)] ligand provides an [S(3)] donor array that is of use for mimicking aspects of zinc enzymes and proteins that have sulfur-rich active sites, such as the Ada DNA repair protein. With respect to mercury, an interesting application of the [Tm(Bu(t) )] ligand is the synthesis of the mercury alkyl compounds [Tm(Bu(t) )]HgR (R = Me, Et) that react with PhSH to yield [Tm(Bu(t) )]HgSPh and RH, a reaction that emulates mercury detoxification by the organomercurial lyase, MerB. In addition to the tridentate [Tm(R)] and [Tse(R)] ligands, applications of the bidentate counterparts, [Bm(R)] and [Bse(R)] are also described.

Bis- and tris(2-seleno-1-methylimidazolyl)hydroborato complexes, {[BseMe]ZnX}2(X = Cl, I), [BseMe]2Zn and [TseMe]Re(CO)3: Structural evidence that the [BseMe] ligand is not merely a “heavier” version of the sulfur counterpart, [BmMe]

New bidentate and tridentate ligands that feature selenium donors, namely the bis- and tris(2-seleno-1-methylimidazolyl)hydroborato ligands [BseMe] and [TseMe], have been constructed via the reaction of MBH4(M=Na, K) with 1-methylimidazole-2-selone. Comparison of the structure of {[BseMe]ZnI}2 with its sulfur counterpart, [BmMe]ZnI, demonstrates that the seleno ligand exhibits a greater tendency than the mercapto ligand to bridge two metal centers, while comparison of [TseMe]Re(CO)3 and [TseMes]Re(CO)3 indicates that the [TseMe] ligand is more electron donating and less sterically demanding than the [TseMes] ligand.

Niobium and Tantalum Tris(methimazolyl)borate Complexes [M(NC6H3iPr2-2,6)Cl2{HB(mt)3}] (M = Nb, Ta; mt = Methimazolyl)

The first early transition metal tris(methimazolyl)borate com-plexes [M(=NR)Cl2{HB(mt)3}] (M = Nb, Ta; R = C6H3(i)Pr(2)-2,6; mt = methimazolyl) have been obtained from the reactions of [Nb(=NR)Cl3(DME)] or [Ta(=NR)Cl3(THF)2] (DME = dimethyl ether; THF = tetrahydrofuran) with Na[HB(mt)3] and structurally characterized, illustrating that the HB(mt)3 ligand can indeed be compatible with "hard" metals in high oxidation states.

Manganese(i) poly(mercaptoimidazolyl)borate complexes: spectroscopic and structural characterization of Mn⋯H–B interactions in solution and in the solid state

The manganese(I) tricarbonyl complexes (Bm(R))Mn(CO)3(R = Me, Bz, But, p-Tol) and (PhBmMe)Mn(CO)3, the first bis(mercaptoimidazolyl)borate derivatives for this metal, have been readily prepared and fully characterized. In particular, the presence of three-center-two-electron Mn...H-B interactions in these species, both in solution and in the solid state, has been investigated using a combination of IR and NMR spectroscopies and, in the case of the methyl-, tert-butyl- and para-tolyl-substituted derivatives, by X-ray crystallography. To complement these synthetic and structural studies, the tris(mercaptoimidazolyl)borate complexes (TmMe)Mn(CO)3(R = Me, Bz, But, p-Tol) and (PhTm(Me))Mn(CO)3, as well as the related pyrazolylbis(mercaptoimidazolyl)borate (pzBmMe)Mn(CO)3, have also been synthesized and characterized by a combination of analytical and spectroscopic techniques.