Treatment of group 5 metal polychlorides such as [CpnMCl 4-x] (M = Nb: n = 1, x = 0; M = V: n, x = 2), (Cp = η5-C5H5) with [LiBH4·THF] followed by thermolysis in presence of diphenyl dichalcogenide ligands, E 2Ph2 (E = Se or Te) yielded dimetallaheteroborane clusters [(CpNb)2BH(Se)4], 1 and [(CpV)2B 3H9(μ3-Te)], 2 in modest yields. Compound 1 can be considered as an edge fused cluster in which a trigonal bipyramidal unit [Nb2Se2B] has been fused with a tetrahedral core [Nb 2Se2] by means of a common [Nb2] edge. Compound 2 can be described as a dimetallaheteroborane built from two edge-fused V 2B2 tetrahedra, in which one of the BH3 units is replaced by an isoelectronic Te ligand. All the compounds have been characterized by mass spectrometry, 1H, 11B, 13C, 51V and 77Se NMR spectroscopy. In addition the geometry of compound 1 has been established by crystallographic analysis. © 2012 Elsevier B.V. All rights reserved.

Sundargopal Ghosh

Department Of Chemistry

Babu Varghese

Chalcogens

CRYSTALLOGRAPHIC ANALYSIS

Metallaboranes

Structural characterization

Trigonal bipyramidal

Ligands

Mass spectrometry

Niobium

Nuclear magnetic resonance spectroscopy

selenium

Sodium compounds

Tellurium

Tellurium compounds

Vanadium

Niobium compounds

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IIT Madras

Journal of Organometallic Chemistry

In an attempt to synthesize expanded-cage metallaheteroboranes containing heavier chalcogen atoms, the reaction of diruthenaborane analogue of pentaborane(9), nido-[1,2-(Cp*RuH)2B3H7] (1) with phenyl-chalcogenoborates Li[BH3(EPh)] (E = S, Se or Te) was carried out. Thermolysis of nido-1 with Li[BH3(SPh)] led to the formation of the dimetalla-pentaborane(11) analogue arachno-[(Cp*Ru)2B3H8(SPh)] (2). In parallel to the formation of 2, the reaction also yielded three B-H functionalized compounds, namely [(Cp*Ru)2B4H7(Ph)] (3), [(Cp*Ru)2B4H7(Cl)] (4) and [(Cp*Ru)2B4H6(SPh)(Cl)] (5). On the other hand, reaction of 1 with Li[BH3(SePh)] led to the formation of the diruthenium analogue of hexaborane(10) nido-[(Cp*Ru)2B4H9(SePh)] (6), whereas Li[BH3(TePh)] yielded the capped nido-pentagonal-pyramidal [(Cp*Ru)2B4H6Te] (7). Compound 7 is a rare ruthenaborane cluster containing a heavier chalcogen element (Te). All the compounds were characterized by mass spectrometry and 1H, 1H{11B}, 11B{1H} and 13C{1H}NMR spectroscopy. The solid state X-ray structures of all the compounds were unequivocally established by crystallographic analysis. Additionally, the electronic properties of compound 2 were analyzed. © 2017 Elsevier B.V.

Fulltext

Synthesis and characterization of diruthenaborane analogues of pentaborane(11) and hexaborane(10)

In an objective to synthesize metallaheteroboranes containing heavier chalcogen atoms, we performed the reaction of dimetallaborane analogues of pentaborane(9) with various chalcogen sources. As a result, the thermolysis of nido-[1,2-(Cp∗RuH)2B3H7], 1 (Cp∗ = η5-C5Me5) with mixture of S and Se powder was carried out, that led to the isolation of half sandwich dimetallaheteroborane arachno-[(1,2-Cp∗Ru)2B2H6S2], 2. On the other hand, the reaction of nido-1 with diorganyldichalcogenide ligands, [Ph2E2] afforded chalcogen bridged half sandwich complexes [(2,3-Cp∗Ru)2B3H6(μ-η1-EPh)], 4a-c (4a: E = S; 4b: E = Se and 4c: E = Te). Compound 2 can be derived from a closo-snub disphenoid by removing a 5-connect vertex followed by the removal of a 3-connect vertex. Compound 4a-c can be described as nido-square pyramidal structures, isoelectronic and isostructural with nido-1. All the compounds have been characterized by mass spectrometry, 1H, 11B and 13C spectroscopy. Further, the geometry of compounds 2, 3, 4b and 4c were unequivocally established by crystallographic analysis. © 2014 Elsevier B.V. All rights reserved.

Diruthenium analogues of Hexaborane(12) and Pentaborane(9): Synthesis and structural characterization of [(1,2-Cp∗Ru)2B2H6S2] and [(2,3-Cp∗Ru)2B3H6(μ-η1-EPh)], (E = S, Se and Te) (Cp∗ = η5-C5Me5)

Metal-metal bonds are found in wide varieties of dinuclear and polynuclear species with or without bridging ligands. This chapter reviews the synthesis, structure, and reactivity of distinct group 5 metal-metal bonded dinuclear and coordinatively unsaturated organodimetallic complexes. In spite of a large amount of work in the area of divanadium compounds-preparation, nonorganometallic metal-metal bonded divanadium complexes are limited due to the absence of suitable metal-metal bonded divanadium precursors. The area of niobium hydride chemistry continues to be an extremely important area. It has been observed that hydrides, supported by bulky aryloxo ligands, catalyze homogenous hydrogenation of arenes. The field of hydride complexes of Ta is a prosperous area in organometallic chemistry. Recent progress has shown that electrophilic mono-and binuclear tantalum hydride complexes are capable of reducing CO and N2, whereas the alkyl/aryl complexes are important in organic and organometallic chemistry. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.

Molecular Metal-Metal Bonds: Compounds, Synthesis, Properties

Group 5 Metal-Metal Bonds

The reaction of nido-[1,2-(Cp*RuH)2B3H 7] (1 a, Cp*=Î·5-C5Me 5) with [Mo(CO)3(CH3CN)3] under mild conditions yields the new metallaborane arachno-[(Cp*RuCO) 2B2H6] (2). Compound 2 catalyzes the cyclotrimerization of a variety of internal- and terminal alkynes to yield mixtures of 1,3,5- and 1,2,4-substituted benzenes. The reactivities of nido-1 a and arachno-2 with alkynes demonstrates that a change in geometry from nido to arachno drives a change in the reaction from alkyne-insertion to catalytic cyclotrimerization, respectively. Density functional calculations have been used to evaluate the reaction pathways of the cyclotrimerization of alkynes catalyzed by compound 2. The reaction involves the formation of a ruthenacyclic intermediate and the subsequent alkyne-insertion step is initiated by a [2+2] cycloaddition between this intermediate and an alkyne. The experimental and quantum-chemical results also show that the stability of the metallacyclic intermediate is strongly dependent on the nature of the substituents that are present on the alkyne. Everything changes but Ru: The reactivities of nido-[1,2-(Cp*RuH)2B3H7] and arachno-[(Cp*RuCO)2B2H6] with alkynes show that a change in geometry (nido to arachno) drives a change from alkyne-insertion to catalytic cyclotrimerization, respectively. Copyright © 2012 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Chemistry - A European Journal

A mechanistic study of the utilization of arachno-diruthenaborane [(Cp*RuCO)2B2H6] as an active alkyne-cyclotrimerization catalyst

The reaction of [CpnMCl4-x] (M=V: n=2, x=2; M=Nb: n=1, x=0; Cp=Î·5-C5H5) with LiBH4·THF followed by thermolysis in the presence of dichalcogenide ligands E2R2 (E=S, Te; R=2,6-(tBu) 2-C6H2OH, Ph) and 2-mercaptobenzothiazole (C7H5NS2) yielded dimetallaheteroboranes [{CpV(μ-TePh)}2(μ3-Te)BH·thf] (1), [(CpV)2(BH3S)2] (2), [(CpNb)2B 4H10S] (3), [(CpNb)2B4H 11S(tBu)2C6H2OH] (4), and [(CpNb)2B4H11TePh] (5). In cluster 1, the V2BTe atoms define a tetrahedral framework in which the boron atom is linked to a THF molecule. Compound 2 can be described as a dimetallathiaborane that is built from two edge-fused V2BS tetrahedron clusters. Cluster 3 can be considered as an edge-fused cluster in which a trigonal-bipyramidal unit (Nb2B2S) has been fused with a tetrahedral core (Nb2B2) by means of a common Nb2 edge. In addition, thermolysis of an in-situ-generated intermediate that was produced from the reaction of [Cp2VCl2] and LiBH 4·THF with excess BH3·THF yielded oxavanadaborane [(CpV)2B3H8(μ3- OEt)] (6) and divanadaborane cluster [(CpV)2B5H 11] (7). Cluster 7 exhibits a nido geometry with C2v symmetry and it is isostructural with [(Cp*M)2B 5H9+n] (M=Cr, Mo, and W, n=0; M=Ta, n=2; Cp*=Î·5-C5Me5). All of these new compounds have been characterized by 1H NMR, 11B NMR, and 13C NMR spectroscopy and elemental analysis and the structural types were established unequivocally by crystallographic analysis of compounds 1-4, 6, and 7. Group 5 alive: Divanadatellura- and divanadathiaboranes were obtained from the treatment of Group 5 metal polychlorides with dichalcogenides and monoboranes. The treatment of [Cp2VCl2] with monoboranes yielded an oxavanadaborane and a divanadaborane (see structures). Copyright © 2012 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Synthesis and structural characterization of new divanada- and diniobaboranes containing chalcogen atoms

The reaction of [Cp*TaCl4], 1 (Cp* = η5-C5Me5), with [LiBH4· THF] at -78 °C, followed by thermolysis in the presence of excess [BH 3·THF], results in the formation of the oxatantalaborane cluster [(Cp*Ta)2B4H10O], 2 in moderate yield. Compound 2 is a notable example of an oxatantalaborane cluster where oxygen is contiguously bound to both the metal and boron. Upon availability of 2, a room temperature reaction was performed with [Fe2(CO) 9], which led to the isolation of [(Cp*Ta)2B 2H4O{H2Fe2(CO)6BH}], 3. Compound 3 is an unusual heterometallic boride cluster in which the [Ta 2Fe2] atoms define a butterfly framework with one boron atom lying in a semi-interstitial position. Likewise, the diselenamolybdaborane, [(Cp*Mo)2B4H4Se2], 4 was treated with an excess of [Fe2(CO)9] to afford the heterometallic boride cluster [(Cp*MoSe)2Fe6(CO) 13B2(BH)2], 5. The cluster core of 5 consists of a cubane [Mo2Se2Fe2B2] and a tricapped trigonal prism [Fe6B3] fused together with four atoms held in common between the two subclusters. In the tricapped trigonal prism subunit, one of the boron atoms is completely encapsulated and bonded to six iron and two boron atoms. Compounds 2, 3, and 5 have been characterized by mass spectrometry, IR, 1H, 11B, 13C NMR spectroscopy, and the geometric structures were unequivocally established by crystallographic analysis. The density functional theory calculations yielded geometries that are in close agreement with the observed structures. Furthermore, the calculated 11B NMR chemical shifts also support the structural characterization of the compounds. Natural bond order analysis and Wiberg bond indices are used to gain insight into the bonding patterns of the observed geometries of 2, 3, and 5. © 2011 American Chemical Society.

Inorganic Chemistry

Synthesis, characterization, and electronic structure of new type of heterometallic boride clusters

Reaction of [CpFe(CO)2I], 1 (Cp = η5-C 5H5) and di(organyl)dichalcogenides, E2R 2 (E = S, Se; R = Ph, CH2Ph, 2,6-(tBu) 2-C6H2OH) with [LiBH4·thf] at -70 °C in toluene, followed by stirring at room temperature for 18 h yielded heteroferraboranes, [CpFe(CO)B2H4(μ-L)], 2-4 (2: L = SePh; 3: SeCH2Ph and 4: S(2,6-(tBu) 2-C6H2OH). Compounds 2-4 are highly unstable and concurrent lose of boron atoms yielded organochalcogenolato-bridged complexes, [CpFe(CO)(μ-L)]2, 5-7, respectively (5: L = SePh; 6: SeCH2Ph and 7: S(2,6-(tBu)2-C6H 2OH). In contrast, the reaction of 1 with di(2-furyl)ditelluride, (C4H3O)2Te2, yielded organotellurato-bridged complex, [CpFe(CO)(μ-TeC4H 3O)]2, 8 and all of our attempts to isolate the boron precursor [CpFe(CO)B2H4(μ-TeC4H 3O)] in pure form failed. The accuracy of these predictions in each case is established by IR, 1H, 11B, 13C, 77Se, 125Te NMR and mass spectrometry and complex 8 is further structurally confirmed by X-ray crystallography. © 2011 Elsevier B.V. All rights reserved.

Inorganica Chimica Acta

A new entry into ferraborane chemistry: Synthesis and characterization of heteroferraborane complexes

C-H activation of arenes and heteroarenes has been achieved by a hydrogen rich tantalaborane cluster [(Cp*Ta)2B5H 11] that leads to the formation of C-H functionalized products. Furthermore, we examined the reaction of substituted thiophene and pyrrole derivatives with tantalaborane which provided a convenient and efficient route to regio-defined C-H functionalized heteroarenes. © 2011 The Royal Society of Chemistry.

Journal	Journal of Organometallic Chemistry
ISSN	0022328X
Open Access	No