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In an attempt to isolate boron-containing tri-niobium polychalcogenide species, we have carried out prolonged thermolysis reactions of [Cp*NbCl4] (Cp* = ɳ5-C5Me5) with four equivalents of Li[BH2E3] (E = Se or S). In the case of the heavier chalcogen (Se), the reaction led to the isolation of the tri-niobium cubane-like cluster [(NbCp*)3(μ3-Se)3(BH)(μ-Se)3] (1) and the homocubane-like cluster [(NbCp*)3(μ3-Se)3(μ-Se)3(BH)(μ-Se)] (2). Interestingly, the tri-niobium framework of 1 stabilizes a selenaborate {Se3BH}− ligand. A selenium atom is further introduced between boron and one of the selenium atoms of 1 to yield cluster 2. On the other hand, the reaction with the sulfur-containing borate adduct [LiBH2S3] afforded the trimetallic clusters [(NbCp*)3(μ-S)4{μ-S2(BH)}] (3) and [(NbCp*)3(μ-S)4{μ-S2(S)}] (4). Both clusters 3 and 4 have an Nb3S6 core, which further stabilizes {BH} and mono-sulfur units, respectively, through bi-chalcogen coordination. All of these species were characterized by 11B{1H}, 1H, and 13C{1H} NMR spectroscopy, mass spectrometry, infrared (IR) spectroscopy, and single-crystal X-ray crystallography. Moreover, theoretical investigations revealed that the triangular Nb3 framework is aromatic in nature and plays a vital role in the stabilization of the borate, borane, and chalcogen units.

Despite the synthesis and structural characterization of closo-hydroborate dianions, [Bn Hn ]2- (n=6-12) more than 50 years ago, some ambiguity remains about the structure of [B8 H8 ]2- . Although the solid-state structure of [B8 H8 ]2- was established by single-crystal X-ray studies in 1969, fast rearrangements in solution at accessible temperatures prevented its detailed characterization. We therefore stabilized a derivative of [B8 H8 ]2- by using Cp2 MBH3 and structurally characterized two new octaborane analogues, [(Cp2 MBH3 )2 B8 H6 ] (Cp=η5 -C5 H5 ; M=Zr (1-Zr) and Hf (1-Hf)), so that the dynamics of the B8 skeleton were arrested. The solid-state structures of both 1-Zr and 1-Hf comprise a dodecahedron core protected by {Cp2 MBH3 } moieties on both sides of the cluster. Spectroscopic characterization (11 B NMR) validates the intactness of the B8 dodecahedron core in solution as well. Theoretical calculations establish that the two exo-{Cp2 MBH3 } fragments provide structural and electronic structural stability to the B8 core and its intact dodecahedral dianionic nature. Furthermore, we propose isodesmic equations for the formation of higher analogues of the Bn core (n>8) guarded by different group 4 transition metals. Our analysis suggests that, as we move to higher polyhedra (n>10), the formation becomes unfavourable irrespective of metal.

A series of metal-rich metallaboranes of groups 7 and 9 comprising triply bridging borylene and boride units have been isolated and structurally characterized. Thermolysis of nido-[(RhCp*)2B3H7] (1...

Isolation of planar [B

Despite the synthesis and structural characterization of closo-hydroborate dianions, [B

We have recently reported the perchlorinated diniobaborane species [(Cp*Nb)2(B2H4Cl2)2] from [(Cp*Nb)2(B2H6)2] using CCl4 as a chlorinating agent. In an attempt to isolate the vanadium analogue, we...

The room-temperature reaction of [Cp*TaCl4 ] with LiBH4 ⋅THF followed by addition of S2 CPPh3 results in pentahydridodiborate species [(Cp*Ta)2 (μ,η2 :η2 -B2 H5 )(μ-H)(κ2 ,μ-S2 CH2 )2 ] (1), a classical [B2 H5 ]- ion stabilized by the binuclear tantalum template. Theoretical studies and bonding analysis established that the unusual stability of [B2 H5 ]- in 1 is mainly due to the stabilization of sp2 -B center by electron donation from tantalum. Reactions to replace the hydrogens attached to the diborane moiety in 1 with a 2 e {M(CO)4 } fragment (M=Mo or W) resulted in simple adducts, [{(Cp*Ta)(CH2 S2 )}2 (B2 H5 )(H){M(CO)3 }] (6: M=Mo and 7: M=W), that retained the diborane(5) unit.

The field of diborinane is sparsely explored area, and not many compounds are structurally characterized. The room-temperature reaction of [{Cp*RuCl(μ-Cl)}2] (Cp* = η5-C5Me5) with Na[BH3(SCHS)] yie...

Polyhedral boron cluster chemistry has been dominated over the last six decades by icosahedral borate dianions, carboranes, metallacarboranes and metallaboranes owing to their high stabilities and rich chemistry. After the first isolation of the closo-borate dianion [B10H10]2− in 1959, many other closo-[BnHn]2− anions (n = 5–9, 11 and 12) were synthesized by Hawthorne, Lipscomb, Muetterties and others. However, the first crystallographic characterization of icosahedral K2[B12H12] by Lipscomb in 1960 stimulated the chemistry and bonding investigations of these closo-[BnHn]2− (n = 6–12) anions. Interestingly, although the closo-[B7H7]2− was synthesized and partially characterized, the X-ray structure of the heptaborane dianion was not established until very recently. Bernhardt and co-worker have fully characterized closo-[B7H7]2− very recently and subsequently, we have isolated a transition metal guarded closo-heptaborane. After exploring the lower borane series, chemists have started envisaging supraicosahedral boranes. Although theoretical calculations by Lipscomb, Jemmis and Schleyer suggested that closo-borate dianions beyond icosahedron [BnHn]2− (n ˃ 12) are stable, the parent closo-borate dianions [BnHn]2− (n ˃12) have not been isolated yet. Following the first isolation of a supraicosahedral metallacarborane in 1971, carboranes, metallacarboranes and metallaboranes have been synthesized with supraicosahedral geometries. The bonding and characteristic electron counts of these supraicosahedral clusters are quite different from those of the lower nuclearity clusters. This chapter describes the synthesis, structural features and electron counts of 13–16-vertex borane, carborane, metallacarborane and metallaborane polyhedral molecules.

International audience; A series of triborane and tetraborane analogues have been isolated and structurally characterized utilizing chalcogenatoborate ligancis Li[BH3(EPh)] (E = S or Se). Thermolysis of [Cp*TaCl4] in the presence of Li[BH3(SPh)] afforded bimetallic tantallaheteroborane [(Cp*Ta)(2)(mu-eta(3):eta(3)-B2H4S)(mu-eta(2):eta(2)-SBH3)] (1) and hexasulfido trimetallic complex [(Cp*Ta)(2)(mu-S)(4)(mu-SPh)(2)] (2). Compound 1 is a fused ditantallaheteroborane, in which both di- and triborane analogues are stabilized by two tantalum atoms. In an attempt to synthesize the selenium analogues of 1 and 2, room-temperature reaction of [Cp*TaCl4] with Li[BH3(SePh)] was carried out, which afforded bimetallic tantallaheteroborane [(Cp*Ta)(2){mu-eta(3):eta(3)-B3H6(SePh)}{mu-SePh}(2)] (3), monometallic tantal- laheteroboranes [Cp*Ta(SePh)(2){B4H8-n(SePh)(2)}] (4: n = 0, 5: n = 1), and trimetallic species [(Cp*Ta)(3)(mu-Se)(4){mu-Se-2(Se)}] (6). Compound 3 is the rarest example of triborane analogue {B3H6(SePh)} in the coordination sphere of two tantalum atoms. Whereas compounds 4 and 5 are examples of unsaturated metallaheteroboranes, in which the tetraborane analogues are stabilized in the coordination sphere of tantalum. One of the unique features of 3 and 5 is the presence of terminal B-SePh. Compound 6 has similar Ta3Se6 trisbutterfly core as that of 2 with additional bridging selenide unit. All the compounds have been characterized by NMR spectroscopy, mass spectrometry, IR spectroscopy and single-crystal X-ray diffraction studies.

In an effort to isolate the chalcogen-rich niobium analogue of [(Cp*Ta)3(μ-S)3(μ3-S)3BH], the room temperature reaction of [Cp*NbCl4] (Cp* = η5-C5Me5) with Li[BH2S3] was carried out. Although the objective of isolating the niobium analogue was not achieved, the reaction yielded a homocubane-type cluster [(Cp*Nb)3(μ-S)3(μ3-S)3(μ-S)BH], 1, and a hexa-sulfido cluster [(Cp*Nb)3(μ-S)6], 2. Cluster 1 is a notable example of a homocubane-type cluster in which one of the vertices of the homocubane is missing. Compound 1 may be considered as a hypo-electronic cluster with an electron count of 64 cve (cve = cluster valence electrons), whereas compound 2 shows the presence of two doubly bridging η1-S around each Nb-Nb bond. On the other hand, the room temperature reaction of [Cp*TaCl4] with selenaborate ligand, [LiBH2Se3], led to the formation of [(Cp*Ta)3(μ-Se)4{μ-Se2(Se2)}], 3. Compound 3 is one of the rarest examples having a Ta3Se6 core structure with a unique diselenide bridging fragment. The presence of a short Se-Se bond of this diselenide unit makes this molecule of further interest. All these compounds were characterized by 1H, 11B{1H} and 13C{1H} NMR spectroscopy, infrared spectroscopy, mass spectrometry, and single-crystal X-ray crystallography. Density functional theory (DFT) calculations were carried out to provide insight into the bonding and electronic structures of these chalcogen-rich trimetallic clusters.

The reactions of dimetallaoctaboranes(12) [(Cp*M)2B6H10] [M = Co (1) or Rh (2); Cp* = η5-C5Me5] with different chalcogen sources, such as Li[BH2E3] and Li[BH3EPh] (E = S, Se, or Te), led to two unique reaction outcomes. For example, the formation of 10-vertex nido-[(Cp*M)2B6E2H6] (3, M = Co, E = S; 4, M = Co, E = Se; 5, M = Co, E = Te; 6, M = Rh, E = Se) from compounds 1 and 2 is a typical representation of a cluster growth reaction, while the formation of arachno-[(Cp*Co)2B6H9(EPh)] [E = S (9), Se (10), or Te (11)] is a rare method that yielded arachno clusters, keeping the core geometry identical. The formation of arachno-9-11 is a unique method that converts disobedient cluster 1 to obedient clusters 9-11. Further, the reactivity of nido-4 with various metal carbonyls presented sequential cluster growth reactions, which afforded 11-vertex nido-[(Cp*Co)2B6Se2H6{Fe(CO)3}] (7) and 13-vertex fused closo-[(Cp*Co)2B6Se2H6{Ru3(CO)8}] (8). The core geometry of nido-7 is uncommon and very similar to that of [C2B9H11]2- with a unique open pentahapto-coordinating five-membered face.

In an effort to isolate the 16-vertex supraicosahedral cobaltaborane [(Cp*Co)3B12H12Co{Cp*CoB4H9}] (Cp* = η5-C5Me5), we have pyrolyzed an in situ generated intermediate, obtained from the fast metathesis of [Cp*CoCl]2 and [LiBH4·THF], with an excess amount of [BH3·THF]. Although the objective of isolating the 16-vertex cobalt analogue was not achieved, the reaction yielded a closo-19-vertex face-fused cluster presenting icosahedral {Co3B9}, tetrahedral {B4}, and 10-vertex {CoB9} units. The reaction also yielded a 20-vertex face-fused cluster that contains icosahedral {Co4B8}, square-pyramidal {CoB4}, tetrahedral {Co2B2}, and nido-{CoB7} units.

In an attempt to isolate some electron precise early transition metal borate complexes, we have explored the reactions of [Cp*TaCl4] (Cp* = η5-C5Me5) with chalcogen-based borate ligand Li[BH3(SPh)]. The room-temperature reaction yielded bimetallic borate complex [(Cp*Ta)2(μ-SPh){S(BH3)}{SPh(BH3)}] (1) that present two types of borate ligands, i.e., {BH3(SPh)} and {BH3(S)} ligands having unique coordination with the tantalum atoms. Interestingly, the {BH3(S)} ligand is coordinated to both the Ta centers in µ-η1:η2 fashion. On the other hand, thermolysis of [Cp*TaCl4] in the presence of Li[BH3(SPh)] yielded a bimetallic borate species [(Cp*Ta)2(µ-η3:η3-B2H4S){µ-η2:η2-S(C6H4)BH3}] (2). Compound 2 contains a triborane analog and a borate ligand, which are coordinated to two Ta atoms. This can also be considered as a notable example of C H activated molecule, in which a B-C bond formation took place. Both the borate species have been characterized by mass spectrometry, IR spectroscopy, NMR spectroscopy, and single-crystal X-ray diffraction studies. The density functional theory (DFT) calculations further provided insights into the bonding and electronic structures of these bimetallic borate species.

Among the series of stable closo-borate dianions, [BnHn]2−, the X-ray crystallographic structure of [B7H7]2− was determined only in 2011. To explore its chemistry and stability, we have isolated and structurally characterized two new transition metal complexes of the heptaborane, [(Cp2M)2B9H11] (Cp = η5-C5H5; M = Zr or Hf). The structures of [(Cp2M)2B9H11] contain a pentagonal bipyramidal B7 core, coordinated by two {Cp2M} and two {BH2} units equatorially. Structural and spectroscopic characterizations and DFT calculations show that [(Cp2M)2B9H11] complexes are substantially more stable than the parent dianion, in either [B7H7]2− or (nBu4N)2[B7H7]. Our theoretical study and chemical bonding analyses reveal that the surprising stability of the two new heptaborane metal complexes is due to multi-center covalent bonds related to the two exo-{Cp2M} units, as well as electrostatic interactions between the {Cp2M} units and the B7 core. The facile syntheses of the heptaborane metal-complexes will allow further exploration of their chemistry.

International audience; Triply-bridging bis-{hydrido(borylene)} and bis-borylene species of groups 6, 8 and 9 transition metals are reported. Mild thermolysis of [Fe-2(CO)(9)] with an in situ produced intermediate, generated from the low-temperature reaction of [Cp*WCl4] (Cp*=eta(5)-C5Me5) and [LiBH4.THF] afforded triply-bridging bis-{hydrido(borylene)}, [(mu(3)-BH)(2)H-2{Cp*W(CO)(2)}(2){Fe(CO)(2)}] (1) and bis-borylene, [(mu(3)-BH)(2){Cp*W(CO)(2)}(2){Fe(CO)(3)}] (2). The chemical bonding analyses of 1 show that the B-H interactions in bis-{hydrido (borylene)} species is stronger as compared to the M-H ones. Frontier molecular orbital analysis shows a significantly larger energy gap between the HOMO-LUMO for 2 as compared to 1. In an attempt to synthesize the ruthenium analogue of 1, a similar reaction has been performed with [Ru-3(CO)(12)]. Although we failed to get the bis-{hydrido(borylene)} species, the reaction afforded triply-bridging bis-borylene species [(mu(3)-BH)(2){WCp*(CO)(2)}(2){Ru(CO)(3)}] (2 '), an analogue of 2. In search for the isolation of bridging bis-borylene species of Rh, we have treated [Co-2(CO)(8)] with nido-[(RhCp*)(2)(B3H7)], which afforded triply-bridging bis-borylene species [(mu(3)-BH)(2)(RhCp*)(2)Co-2(CO)(4)(mu-CO)] (3). All the compounds have been characterized by means of single-crystal X-ray diffraction study; H-1, B-11, C-13 NMR spectroscopy; IR spectroscopy and mass spectrometry.

As per the World Health Organization, cancer is the second leading cause of death globally and is responsible for an estimated 9.6 million deaths in 2018. More than 2 million cases of lung and breast cancer have been reported in 2018. Paclitaxel is a natural product based anti-mitotic agent useful for the treatment of lung cancer, ovarian cancer and breast cancer. Paclitaxel exhibits low oral bioavailability due to poor aqueous solubility and poor permeability. Paclitaxel is the first blockbuster anticancer drug with annual sales of more than US $1 billion in 1997. Taxol®, Abraxane® and Genexol PM® are commercial injectable preparations of paclitaxel with a drug loading of not more than 17% w/w. The toxicity issues of Cremophor® EL used in Taxol® led to the development of different delivery systems sans Cremophor® EL. The maximum tolerated dose of Taxol® is 135 mg/m2. Taxol® exhibited hypersensitivity reactions and required use of special IVEX-2 filter to avoid leaching of plasticizer into the product. Genexol PM® was physically unstable and was ineffective against multidrug-resistant tumor treatment. Abraxane® exhibited limited tumor exposure, tumor uptake, tumor regression and higher half-maximal inhibitory concentration.

International audience; A new synthetic route for the synthesis of diruthenium boryl complexes has been established. Thermolysis of an arachno-ruthenaborane, [(Cp*Ru)(2)B3H8(CS2H)] (1; Cp* = eta(5)-C5Me5), with phenylacetylene led to the formation of the bridging boryl borylene complex [(Cp*Ru)(2) (mu-HBS2CH2-kappa B-2:kappa S-2){mu-B(C6H4)C(CH3)-kappa B-2:kappa C-2)] (2). In parallel to the formation of 2, the reaction also yielded [(Cp*Ru)(mu-H)BH-{HC=C(H)Ph}{SC(H)S}] (3a) and [(Cp*Ru)(mu-H)BH-(PhC=CH2){SC(H)S}] (3b). To understand the reaction pathways for the formation of 2, we have thermolyzed 1 in toluene, which afforded the ruthenium bridging bis(boryl) complex [(Cp*Ru)(2)(mu-HBS2CH2-kappa B-2:kappa S-2){mu,eta(2):eta(2)-SBH}] (4) along with the nido-ruthenathiaborane [(Cp*Ru)(2)(Me)(S2B2H3)] (5). nido-5 is structurally and electronically similar to nido-[(Cp+Ru)(2)(S2C2Ph2)] (Cp+ = eta(5)-C5Me4Et), which can be generated from the room-temperature reaction of [(Cp+Ru)(2)(mu, eta(1):eta(1)-S-2)(mu, eta(2):eta(1)-S-2)] with diphenylacetylene. Thus, nido-5 can be defined as a true mimic of the organometallic cluster nido-[(Cp+Ru)(2)(S2C2Ph2)]. The complex [(Cp*Ru)(2)(mu-eta(1):eta(1)-S-2)(mu, eta(2):eta(1)-S-2)] (6), the Cp* analogue of [(Cp+Ru)(2)(mu-eta(1):eta(1)-S-2)(mu, eta(2):eta(1)-S-2)], can be isolated from the reaction of Li[BH2S3] with [Cp*RuCl2](2) along with the diruthenium boryl complex [(Cp*Ru)(2)(mu-eta(1):eta(1)-S-2)(mu-(SBH)-B-2-kappa B-1:kappa S-2:kappa S-2')] (7), in which the boryl unit (S2BH) possesses no bulky heterocyclic ligand. Theoretical studies were performed to shed light on the bonding of these borylene and boryl complexes. The theoretical calculations reveal that the stability of these complexes is due to the strong interaction between the borylene and boryl units and the ruthenium centers.

The room-temperature reaction of [Cp*TaCl

In an effort to isolate the chalcogen-rich niobium analogue of [(Cp*Ta)3(μ-S)3(μ3-S)3BH], the room temperature reaction of [Cp*NbCl4] (Cp* = η5-C5Me5) with Li[BH2S3] was carried out. Although the objective of isolating the niobium analogue was not achieved, the reaction yielded a homocubane-type cluster [(Cp*Nb)3(μ-S)3(μ3-S)3(μ-S)BH], 1, and a hexa-sulfido cluster [(Cp*Nb)3(μ-S)6], 2. Cluster 1 is a notable example of a homocubane-type cluster in which one of the vertices of the homocubane is missing. Compound 1 may be considered as a hypo-electronic cluster with an electron count of 64 cve (cve = cluster valence electrons), whereas compound 2 shows the presence of two doubly bridging η1-S around each Nb-Nb bond. On the other hand, the room temperature reaction of [Cp*TaCl4] with selenaborate ligand, [LiBH2Se3], led to the formation of [(Cp*Ta)3(μ-Se)4{μ-Se2(Se2)}], 3. Compound 3 is one of the rarest examples having a Ta3Se6 core structure with a unique diselenide bridging fragment. The presence of a short Se-Se bond of this diselenide unit makes this molecule of further interest. All these compounds were characterized by 1H, 11B{1H} and 13C{1H} NMR spectroscopy, infrared spectroscopy, mass spectrometry, and single-crystal X-ray crystallography. Density functional theory (DFT) calculations were carried out to provide insight into the bonding and electronic structures of these chalcogen-rich trimetallic clusters.

The field of diborinane is sparsely explored area, and not many compounds are structurally characterized. The room-temperature reaction of [{Cp*RuCl(μ-Cl)}

Metal-rich metallaborane clusters, having triply and tetra bridging borylenes, and multicentred boride units are demanding renewed interest because of their diverse reactivity and unique structural features. Recent years have witnessed significant progress in the field of metal-rich metallaborane clusters. In spite of high instability of free borylene species, modern synthetic strategies utilizing transition metals have enabled to the isolation of borylene species, particularly as triply bridging borylene species. On the other hand, naked boron ‘boride’ has been encapsulated inside different types of transition metal and metallaborane clusters. The unique bonding ability of the boron of borylene and boride with multiple transition metals afforded a series of metal-rich metallaboranes. In this review, we have discussed the history of the synthesis of metal-rich clusters containing triply bridging borylene and boride moieties and their structure, bonding, and electron count. The reactivity of these metal-rich metallaboranes toward various substrates has also been discussed.

Dimetallaoctaborane(12) of Ru, Co, and Rh have been well-characterized by a range of spectroscopic techniques and X-ray diffraction studies. Thus, reinvestigation of the Ir-system became of interest. As a result, a slight modification in the reaction conditions enabled us to isolate the missing Ir analogue of octaborane(12), [(Cp*Ir)2B6H10], 1. Compound 1 adapts a geometry similar to that of its parent octaborane(12) and Ru, Co, and Rh analogues. In [M2B6H10+x](M = Ru, x = 2; M = Co and Rh, x = 0), there exist two M–H–B protons. However, a significant difference observed in [(Cp*Ir)2B6H10] is the presence of two Ir–H instead of Ir–H–B protons that eventually controls the reactivity of this molecule. For example, unlike [M2B6H10](M = Co or Rh), the Ir-analogue does not react with metal carbonyl compounds or [Au(PPh3)Cl]. Along with 1, a closo trimetallic 8-vertex iridaborane [(Cp*Ir)3B5H4Cl], 2 was also isolated. Additionally, from another reaction, 12-vertex closo iridaboranes [(Cp*Ir)2B10Hy(OH)z], 3a and...

Department of Chemistry, Indian Institute of Technology Madras, Chennai-600 036, India E-mail: sghosh@iitm.ac.in Fax: 91-44-22574202 Manuscript received 28 June 2018, accepted 16 July 2018 In an effort to isolate the heavier chalcogen-rich metallaheteroborane analogue of [(Cp*Ta)3(µ-S)3(µ3-S)3BH], thermolysis of [Cp*TaCl4] (Cp* = ŋ5-C5Me5) and Li[BH2Se3] was carried out that afforded cubane-type cluster [(Cp*Ta)3(µ-Se)3(µ3- Se)3B(OBuCl)], 1. Compound 1 is an example of cubane-type organotantalum selenido cluster, in which one of the vertices of the cubane is missing. Compound 1 is a hypo-electronic cluster with an electron count of 50 cve (cve = cluster valence electrons). In parallel to the formation of 1, trimetallic selenide cluster [(Cp*Ta)3(µ,-Se)6], 2 has also been isolated and struc­turally characterized. All these compounds were characterized by the multi-nuclear NMR spectroscopy, mass spectrometry and single crystal X-ray crystallography. The density functional theory (DFT) calculations were also performed to provide in­sight into the bonding and electronic structures of these novel clusters.

In an effort to synthesize chalcogen-rich metallaheteroborane clusters of group 5 metals, thermolysis of [Cp*TaCl4] (Cp* = η5-C5Me5) with thioborate ligand Li[BH2S3] was carried out, affording trimetallic clusters [(Cp*Ta)3(μ-S)3(μ3-S)3B(R)], 1-3 (1, R = H; 2, R = SH; and 3, R = Cl). Clusters 1-3 are illustrative examples of cubane-type organotantalum sulfido clusters in which one of the vertices of the cubane is missing. In parallel to the formation of 1-3, the reaction also yielded tetrametallic sulfido cluster [(Cp*Ta)4(μ-S)6(μ3-S)(μ4-O)], 6, having an adamantane core structure. Compound 6 is one of the rarest examples containing the μ4-oxo unit with a heavier early transition metal, i.e., tantalum. In an effort to isolate selenium analogues of clusters 1-3, we have isolated the trimetallic cluster [(Cp*Ta)3(μ-Se)3(μ3-Se)3B(H)], 4, from the thermolytic reaction of [Cp*TaCl4] and Li[BH2Se3]. In contrast, the thermolysis of [Cp*TaCl4] with Li[BH2Te3] under the same reaction conditions yielded tantalum telluride complex [(Cp*Ta)2(μ-Te)2], 5. Compounds 1-4 are hypo-electronic clusters with an electron count of 50 cluster valence electrons. All these compounds have been characterized by 1H, 11B{1H}, and 13C{1H} NMR spectroscopy; infrared spectroscopy; mass spectrometry; and single-crystal X-ray crystallography. The density functional theory calculations were also carried out to provide insight into the bonding and electronic structures of these molecules.

We have isolated and structurally characterized two new transition metal complexes of the heptaborane, [(Cp2M)2B9H11] (Cp = η5-C5H5; M = Zr or Hf)., Among the series of stable closo-borate dianions, [BnHn]2–, the X-ray crystallographic structure of [B7H7]2– was determined only in 2011. To explore its chemistry and stability, we have isolated and structurally characterized two new transition metal complexes of the heptaborane, [(Cp2M)2B9H11] (Cp = η5-C5H5; M = Zr or Hf). The structures of [(Cp2M)2B9H11] contain a pentagonal bipyramidal B7 core, coordinated by two {Cp2M} and two {BH2} units equatorially. Structural and spectroscopic characterizations and DFT calculations show that [(Cp2M)2B9H11] complexes are substantially more stable than the parent dianion, in either [B7H7]2– or (nBu4N)2[B7H7]. Our theoretical study and chemical bonding analyses reveal that the surprising stability of the two new heptaborane metal complexes is due to multi-center covalent bonds related to the two exo-{Cp2M} units, as well as electrostatic interactions between the {Cp2M} units and the B7 core. The facile syntheses of the heptaborane metal-complexes will allow further exploration of their chemistry.

Here, we present the draft genome (377.3 Mbp) of Corchorus olitorious cv. JRO-524 (Navin), which is a leading dark jute variety developed from a cross between African (cv. Sudan Green) and indigenous (cv. JRO-632) types. We predicted from the draft genome a total of 57,087 protein-coding genes with annotated functions. We identified a large number of 1765 disease resistance-like and defense response genes in the jute genome. The annotated genes showed the highest sequence similarities with that of Theobroma cacao followed by Gossypium raimondii. Seven chromosome-scale genetically anchored pseudomolecules were constructed with a total size of 8.53 Mbp and used for synteny analyses with the cocoa and cotton genomes. Like other plant species, gypsy and copia retrotransposons were the most abundant classes of repeat elements in jute. The raw data of our study are available in SRA database of NCBI with accession number SRX1506532. The genome sequence has been deposited at DDBJ/EMBL/GenBank under the accession LLWS00000000, and the version described in this paper will be the first version (LLWS01000000).

Purpose To develop a magnetic resonance imaging (MRI)-based method to monitor in vivo trafficking of bone marrow (BM) cells to atherosclerotic lesions. Materials and Methods BM cells from LacZ-transgenic mice were labeled with a superparamagnetic iron oxide (Feridex) and then transplanted into ApoE–/– recipient mice that were fed an atherogenic diet. Twenty-four ApoE–/– mice were divided into three study groups: 1) group I with Feridex-labeled BM transplantation (BMT) cells (N = 9), 2) group II with unlabeled BMT cells (N = 10), and 3) group III with no BMT cells (N = 5). Migrated Feridex/LacZ-BM cells to atherosclerotic aortic walls were monitored in vivo using a 4.7T MR scanner and correlated with histopathological findings. Results In group I with Feridex-BMT cells, histology examination displayed plaques in five of nine animals. In four of these five animals, in vivo MRI showed large MR signal voids of the aorta walls (due to the “blooming” effect of migrated Feridex-BM cells in plaques), which were correlated with Feridex- and/or LacZ-positive cells detected in the atherosclerotic lesions. No signal voids could be visualized in the two control animal groups (groups II and III). Conclusion This study demonstrates the potential use of in vivo MRI to monitor the trafficking of magnetically labeled BM cells to atherosclerotic lesions. J. Magn. Reson. Imaging 2007. © 2007 Wiley-Liss, Inc.

The aim of this study was to test the feasibility of using MRI to detect magnetically labeled, intravenously injected bone marrow (BM) cells homing to injured arteries. In the first phase, BM cells from LacZ-transgenic or green fluorescent protein (GFP)-transgenic mice were transplanted into eight recipient mice. The left femoral arteries of recipient mice were injured using a cuff-constriction or endothelium-damage approach, and the right femoral arteries were uninjured to serve as controls. The location and distribution of migrated LacZ-BM or GFP-BM cells were confirmed with histology. In the second phase, BM-derived cells from LacZ-transgenic mice were labeled with superparamagnetic iron oxide (Feridex) and then transplanted into eight recipient mice with cuff-induced injuries in the left femoral arteries. Migrated Feridex/LacZ-BM cells were monitored in vivo using a 4.7 T MR scanner. Subsequently, high-resolution ex vivo MRI was performed on 9.4 T and 11.7 T. LacZ-positive or GFP-positive cells in the thickened adventitia of the injured arteries were evident on histology. Both in vivo and ex vivo MRI showed larger regions of hypointensity with Feridex-labeled cells at the sites of the injured arteries compared with control arteries (P

This study was to develop a percutaneous optical imaging system for tracking fluorescent reporter gene expression in vasculatures. We built a percutaneous optical imaging system that primarily comprised a 1.5-mm, semi-rigid, two-port optical probe. The performance of the optical probe was first tested in vitro with cell phantoms, and then the feasibility of the percutaneous optical imaging system was validated in vivo in eight femoral artery segments of two pigs. Green fluorescent protein (GFP) gene was locally delivered into four arterial segments, while saline was delivered to the four contralateral arterial segments as controls. The targeted arteries were localized using color Doppler, and thereafter the optical probe was positioned to the target arterial segments under ultrasound guidance. Optical imaging captures were obtained using different exposure times from 10–60 seconds. Subsequently, the GFP- and saline-targeted arteries were harvested for fluorescent microscopy confirmation. The percutaneous optical probe was successfully positioned at a distance of approximately 2 mm from the targets in all eight arteries. The in vivo imaging showed higher average signal intensity in GFP-treated arteries than in saline-treated arteries. This study demonstrates the potential using the percutaneous optical imaging system to monitor, in vivo, reporter gene expression from vasculatures.

Rationale and Objectives We evaluated the potential of using intravascular magnetic resonance (MR)/radiofrequency (RF) to enhance vascular endothelial growth factor (VEGF) gene therapy of in-stent neointimal hyperplasia. Materials and Methods By using a catheter-based approach, VEGF/lentivirus was locally transferred into 10 (five paired) bilateral femoral-iliac arteries of five hypercholesterolemic pigs, whereas the right arteries were heated up to approximately 41°C by using an intravascular MR/RF system. Then, identical stents were placed immediately into the bilateral VEGF-targeted arteries to create in-stent neointimal hyperplasia. At day 60 after gene/stent interventions, the targeted arteries were harvested for histological correlation. Results X-Ray angiography–detectable in-stent stenoses were found in three of the arteries treated with VEGF genes only, whereas there were no in-stent stenoses in arteries treated by using MR/RF-heated VEGF genes. Correlative histological examination confirmed a 138% reduction in average thickness of neointimal hyperplasia in VEGF/RF-treated arteries compared with VEGF-only–treated arteries ( P Conclusion We report a potential method of using an intravascular MR/RF heating technique to enhance gene therapy of in-stent restenosis.

The purpose of this study was to develop a standard 0.014-inch intravascular magnetic resonance imaging guidewire (MRIG), a coaxial cable with an extension of the inner conductor, specifically designed for use in the small vessels. After a theoretical analysis, the 0.014-inch MRIG was built by plating/cladding highly electrically conductive materials, silver or gold, over the inside and outside of the coaxial conductors. The conductors were made of superelastic, nonmagnetic, biocompatible materials, Nitinol or MP35N. Then, in comparison with a previously designed 0.032-inch MRIG, the performance of the new 0.014-inch MRIG in vitro and in vivo was successfully evaluated. This study represents the initial work to confirm the critical role of highly conductive and superelastic materials in building such small-size MRIGs, which are expected to generate high-resolution MR imaging of vessel walls/plaques and guide endovascular interventional procedures in the small vessels, such as the coronary arteries.