Click-generated triazole based ferrocene-carbohydrate bioconjugates: a highly selective multisignalling probe for Cu(II) ions

Two Cu2+-specific colorimetric sensors, based on ferrocene-carbohydrate bioconjugates, 2, C46H56O20N6Fe and 3, C28H33O10N3Fe were designed and synthesized in good yields. Both the compounds, 2 and 3, behave as very selective and sensitive chromogenic and electrochemical chemosensor for Cu2+ ion in aqueous environment (CH3CN/H2O (2:8, v/v). The analytical detection limit (ADL) for receptor 2 was 7.5 × 10−7 M. The considerable changes in their absorption spectra of 2 and 3 are accompanied by the appearance of a new low energy (LE) peak at 630 nm (2: ε = 1600 M−1 cm−1 and 3: 822 M−1 cm−1). This is further accompanied by a strong colour change from yellow to dark green that allows the prospective for ‘naked eye’ detection of Cu2+ ion

Synthesis and reactivity of dimolybdathiaborane cluster [(Cp^*Mo)₂B₄SH₆] (Cp^∗ = η⁵-C₅Me₅)

Chemistry and reactivity of dimolybdathiaborane, [(Cp∗Mo)2B4SH6], 1, obtained from the reaction of 2-mercaptobenzothiazole, [Cp∗MoCl4] and [LiBH4.thf], has been explored with dinuclear metal carbonyl [Fe2 (CO)9]. As a result, reaction of 1 with [Fe2(CO)9] yielded heterometallathiaborane, [(Cp∗Mo)2B4H6SFe(CO)3], 2 in good yield. Both the new compounds have been characterized in solution by 1H, 11B and 13C NMR spectroscopy and the structural types were unequivocally established by X-ray crystallographic analysis of compound 2. Cluster 2 has a bicapped octahedral geometry with the {Fe(CO)3} fragment occupying one of the high-connectivity cluster vertexes rather than a capping position. Interestingly, cluster 1 undergoes geometric changes (bicapped trigonal bipyramid → bicapped octahedron) on the addition of two-electron {Fe(CO)3} fragment to 1

Reactivity of [Cp*Mo(CO)₃Me] with chalcogenated borohydrides Li[BH₂E₃] and Li[BH₃EFc] (Cp*= (η⁵-C₅Me₅); E = S, Se or Te; Fc = (C₅H₅-Fe-C₅H₄))

Reactivity of [Cp*Mo(CO)3Me], 1 with various chalcogenide ligands such as Li[BH2E3] and Li[BH3EFc] (E = S, Se or Te; Fc = (C5H5-Fe-C5H4)) has been described. Room temperature reaction of 1 with Li[BH2E3] (E = S and Se) yielded metal chalcogenide complexes [Cp*Mo(CO)2(η2-S2CCH3)], 2 and [Cp*Mo(CO)2(η1-SeC2H5)], 3. In compound 2, {Cp*Mo(CO)2} fragment adopts a four-legged piano-stool geometry with a η2-dithioacetate moiety. In contrast, treatment of 1 with Li[BH3(EFc)] (E = S, Se or Te; Fc = C5H5-Fe-C5H4) yielded borate complexes [Cp*Mo(CO)2(μ-H)(μ-EFc)BH2], 4-6 in moderate yields. Compounds 4-6 are too unstable and gradual conversion to [{Cp*Mo(CO)2}2(μ-H)(μ-EFc] (7: E = S; 8: Se) and [{Cp*Mo(CO)2}2 (μ-TeFc)2], 9 happened by subsequent release of BH 3. All the compounds have been characterized by mass spectrometry, IR, multinuclear NMR spectroscopy and structures were unequivocally established by crystallographic analysis for compounds 2, 3 and 7

Dimetallaheteroborane clusters containing group 16 elements: A combined experimental and theoretical study

Recently we described the synthesis and structural characterization of various dimetallaherteroborane clusters, namely nido-[(Cp∗Mo2B4EClxH6−x], 1–3; (1: E = S, x = 0; 2: E = Se, x = 0; 3: E = Te, x = 1). A combined theoretical and experimental study was also performed, which demonstrated that the clusters 1–3 with their open face are excellent precursors for cluster growth reaction. In this investigation process on the reactivity of dimetallaheteroboranes with metal carbonyls, in addition to [(Cp∗Mo)2B4H6EFe(CO)3] (4: E = S, 6: E = Te) reported earlier, reaction of 2 with [ Fe2(CO)9] yielded mixed-metallaselenaborane [(Cp∗Mo)2B4H6SeFe(CO)3], 5 in good yield. The quantum chemical calculation using DFT method has been carried out to probe the bonding, NMR chemical shifts and electronic properties of dimolybdaheteroborane clusters 4–6

Addition and elimination reactions of \H2\ in ruthenaborane clusters: A computational study

International audienceRuthenaborane clusters have been modelled by performing density functional theory calculations using the \B3LYP\ functional. The calculations gain insights into hydrogen storage and the H-H bond activation by ruthenaboranes. To study the nature of the chemical bond of \H2\ molecules attached to ruthenaboranes, we carried out structural optimizations for different ruthenaborane clusters and determined transition state structures for their hydrogenation addition/elimination reactions. Calculations of the reaction pathways yielded different transition-state structures involving molecular hydrogen bonded to the cluster or formation of metal hydrides. The H-H bond of \H2\ seems to be activated by the ruthenaborane clusters as activation energies of 24-42 kcal/mol were calculated for the \H2\ addition reaction. The calculated Gibbs free energy for the \H2\ addition reaction is 14-27 kcal/mol. The calculated activation energies and the molecular structures of the [(C5Me5)Ru2B10H16], [(C5Me5)Ru2B8H14] and [(C5Me5)Ru2B8H12] clusters with different degree of hydrogenation are compared. The mechanisms of the \H2\ addition and elimination reactions of the studied clusters suggest that they might be useful as hydrogen storage materials due to their ability to activate the H-H bond. They also serve as an example of the ability of hypoelectronic metallaboranes to reversibly or irreversibly bind hydrogen

Trimetallaborides as starting points for the syntheses of large metal-rich molecular borides and clusters

Treatment of an anionic dimanganaborylene complex ([{Cp(CO)2Mn}2B]–) with coinage metal cations stabilized by a very weakly coordinating Lewis base (SMe2) led to the coordination of the incoming metal and subsequent displacement of dimethylsulfide in the formation of hexametalladiborides featuring planar four-membered M2B2 cores (M = Cu, Au) comparable to transition metal clusters constructed around four-membered rings composed solely of coinage metals. The analogies between compounds consisting of B2M2 units and M4 (M = Cu, Au) units speak to the often overlooked metalloid nature of boron. Treatment of one of these compounds (M = Cu) with a Lewis-basic metal fragment (Pt(PCy3)2) led to the formation of a tetrametallaboride featuring two manganese, one copper and one platinum atom, all bound to boron in a geometry not yet seen for this kind of compound. Computational examination suggests that this geometry is the result of d10-d10 dispersion interactions between the copper and platinum fragments

Heterometallic cubane-type clusters containing group 13 and 16 elements

Heterometallic cubane-type clusters were synthesized from the reaction of group 6 and 8 metallaboranes using transition-metal carbonyl compounds. Structural and spectroscopic study revealed the existence of novel “capped-cubane” geometry. In addition, the crystal structure of these clusters distinctly confirms the presence of boride unit as one of the vertices. These clusters possess 60 cluster valence electrons (cve) and six metal–metal bonds. A plausible pathway for the formation of ruthenium-capped cubane has been described

Chemical bonding in oblatonido ditantalaboranes and related compounds

The recently discovered ditantalaboranes Cp2Ta2BnHn+6 (n = 4, 5) are isoelectronic with the previously discovered dimetallaboranes Cp2M2BnHn+4 of the group 6 metals Cr, Mo, and W where Cp = η5-cyclopentadienyl or substituted cyclopentadienyl. Their oblatonido polyhedral structures can be derived from the oblate (flattened) deltahedra of the oblatocloso dirhenaboranes Cp2Re2Bn+1Hn+1 by removal of an equatorial BH vertex with adjustment of the skeletal electron count by changing the metal atoms and adding hydrogen atoms. In these oblatocloso dirhenaborane deltahedra, the approximately antipodal rhenium atoms are close enough together to form a formal Re=Re double bond with lengths in the range 2.69–2.82 Å. Similarly, short M=M distances are maintained in the related oblatonido derivatives Cp2Ta2BnHn+6 (n = 4, 5) and Cp2M2BnHn+4 (M=Cr, Mo, W). However, the synthesis of Cp2Ta2BnHn+6 (n = 4, 5) from CpTaCl4 + LiBH4/BH3 also gives a less-reduced product Cp2Ta2Cl2B5H11 with a longer Ta–Ta distance of ~3.2 Å. This may be regarded as a formal single bond bridged by one of the hydrogen atoms. Vertices of degree 5 (excluding terminal atoms/groups but not edge-bridging hydrogens) are sites of highest stability/lowest chemical reactivity not only in metal-free boranes but also in the dimetallaboranes discussed in this paper. For example, all four boron vertices in Cp2Ta2B4H10 have the favorable degree or 5

A highly selective redox, chromogenic, and fluorescent chemosensor for Hg²⁺ in aqueous solution based on ferrocene–glycine bioconjugates

The synthesis, electrochemical, optical, and metal-cation-sensing properties of ferrocene–glycine conjugates C₃₀H₃₈O₈N₈Fe (2) and C₂₀H₂₄O₄N₄Fe (3) have been documented. Both compounds 2 and 3 behave as very selective redox (ΔE_1/2 = 217 mV for 2 and ΔE_1/2 = 160 mV for 3), chromogenic, and fluorescent chemosensors for Hg²⁺ cations in an aqueous environment. The considerable changes in their absorption spectra are accompanied by the appearance of a new low-energy peak at 630 nm (2, ε = 1600 M^–1cm^–1; 3, ε = 822 M^–1cm^–1). This is also accompanied by a strong color change from yellow to purple, which allows a prospective for the “naked eye” detection of Hg²⁺ cations. These chemosensors present immense brightness and fluorescence enhancement (chelation-enhanced fluorescence = 91 for 2 and 42 for 3) following Hg²⁺ coordination within the limit of detection for Hg²⁺ at 7.5 parts per billion