Intramolecular Pericyclic Re-hydroboration via Six-Membered Transition State: Synthesis of Fused Borolo[3,2-b]siloles.

We experimentally demonstrate a new type of the intramolecular reaction between non-activated alkyne units and the dialkylboryl group (9-BBN), which was previously only hypothesized and studied on a calculational level. The reaction described here can formally be classified as a 1,2-hydroboration reaction, but, in contrast to the classical mechanism via a cyclic four-membered transition state, the reaction proceeds by a pericyclic mechanism involving a six-membered transition state. In practice, the reaction allows the synthesis of a new class of the borolenes fused with silole or dihydrosilole units.

Experimental and Computational Se NMR Spectroscopic Study on Selenaborane Cluster Compounds.

Calculated and measured Se nuclear magnetic resonance (NMR) chemical shift data on a diverse collection of 13 selenaborane cluster compounds, containing a total of 19 selenium centers, reveals a correlation between chemical shifts and the intracluster coordination of selenium atoms within their borane frameworks. A plot of the measured against calculated Se NMR chemical shifts shows an approximately linear relationship that can serve as a predictive tool in assessing the chemical shift range in which a selenium vertex from a particular compound might be expected to be found, thereby reducing expensive experimental time. Furthermore, the relative chemical shifts between selenium vertices in clusters containing more than one selenium atom are consistent across the range, thus allowing the assignment of the selenium resonances with a high degree of confidence even in relatively low-level density functional theory calculations.

Expanding Luminescence Horizons in Macropolyhedral Heteroboranes.

Luminescence is observed in three novel macropolyhedral nineteen- and eighteen-vertex chalcogenaboranes: SeBH (1), SeBH (3) and SeBH (4). This led us to the recognition that previously published macropolyhedral heteroborane species might also exhibit luminescence. Thus, the known nineteen- and eighteen-vertex dithiaboranes SBH (2), n-SBH (5) and i-SBH (6) were synthesised and also found to exhibit a range of luminescent properties.

Simple Route to [PSH][BH] and a Contemporary Study of Its Solid-State Dynamic Behavior.

The 1,8-bis(dimethylamino)naphthalenium ([PSH]) decaborane salt, [PSH][BH], has been found to react in ethanol to form [PSH][BH] (), affording a simple route to the synthesis of the -nonaborate anion. This new polyhedral salt is characterized by NMR spectroscopy and X-ray diffraction. The measurement of diffusion coefficients by NMR methods demonstrates that the [PSH] cation and the [BH] anion form ion pairs in a non-coordinating solvent such as CHCl, whereas in CDCN the formation of ion pairs was not observed.

Macropolyhedral -BH, the "Forgotten" Isomer.

The chemistry and physics of macropolyhedral BH clusters have attracted significant attention due to the interesting photophysical properties of -BH (blue emission, laser properties) and related potential applications. We have focused our attention on the "forgotten" -BH isomer, which has received very little attention since its discovery compared to its -BH isomer, presumably because numerous studies have reported this isomer as nonluminescent. In our study, we show that in crystalline form, -BH exhibits blue fluorescence and becomes phosphorescent when substituted at various positions on the cluster, associated with peculiar microstructural-dependent effects.

A Window into the Workings of -BH Luminescence-Blue-Fluorescent Isomeric Pair 3,3'-Cl-BH and 3,4'-Cl-BH (and Others).

The action of AlCl on room-temperature tetrachloromethane solutions of -BH () results in a mixture of fluorescent isomers, 3,3'-Cl-BH () and 3,4'-Cl-BH (), together isolated in a 76% yield. Compounds and are capable of the stable emission of blue light under UV-excitation. In addition, small amounts of other dichlorinated isomers, 4,4'-Cl-BH (), 3,1'-Cl-BH (), and 7,3'-Cl-BH () were isolated, along with blue-fluorescent monochlorinated derivatives, 3-Cl-BH () and 4-Cl-BH (), and trichlorinated species 3,4,3'-Cl-BH () and 3,4,4'-Cl-BH ().

The Impact of Visual Impairment on Completion of Cognitive Screening Assessments: A Post-Hoc Analysis from the IVIS Study.

Aim: The aim of this study was to evaluate completed cognitive screens in stroke survivors with and without visual impairment to explore whether the presence of visual impairment impacts on completion of cognitive screening.

Materials And Methods: Cognitive screening assessment was undertaken using the Oxford Cognitive Screen (OCS). Data from visual function assessments (inclusive of visual acuity, visual fields, eye movements and visual perception evaluation) were analysed to determine whether presence and/or type of visual impairment impacted on cognitive screening scores achieved.

Macropolyhedral Chalcogenaboranes: Insertion of Selenium into the Isomers of BH.

High yields of novel macropolyhedral selenaboranes are reported. Reactions of the monoanions of the - and -isomers of BH with powdered selenium in THF variously give new macropolyhedral selenaboranes: 19-vertex [SeBH] anion , 19-vertex [SeBH] anion , 20-vertex [SeBH] anion , and 19-vertex [SeBH] anion . Single-cluster [-SeBH] anion and neutral -SeBH also result.

A simple and high-yield route to iridium, rhodium, osmium and ruthenium -6-metalladecaborane compounds.

We report a high-yield heterogeneous solid/liquid phase synthetic method to a series of -6-metalladecaboranes. The hydridoirida- and hydridorhoda-decaboranes, [6,6,6-H(PPh)--6-MBH] [M = Ir (1), Rh (2)] are isolatable in 98% yields from the reaction of the square-planar M(I) complexes, [MCl(PPh)] (M = Rh, Ir), with K[BH]. The same synthetic procedure, but using [MCl(CO)H(PPh)] (M = Ru, Os) as metal starting reagents produces the CO-ligated clusters, [6,6,6-(CO)(PPh)--6-MBH] [M = Ru (3), Os (4)], in yields of 83% and 95%, respectively.

One-Pot Synthesis of 2,5-Dihydrosiloles and Their Silole-Annulated Analogs Starting from Alkynylsilanes with a Terminal Alkynyl Group.

In contrast to the reaction of vinyl(alkynyl)silanes with 9-BBN-H, leading to the quantitative formation of 5-R-4-(9-BBN)-2,3-dihydro-1-siloles, treatment of bis(alkynyl)silanes bearing one terminal alkynyl group with 2 equiv of 9-BBN-H followed by methanolysis afforded 5-R-4-(9-BBN)-2,5-dihydro-1-siloles with yields of 85-90% (by NMR integration). The reaction proceeds via a double 1,2-hydroboration of the terminal triple bond with the formation of the geminal diborane followed by ring closure via intramolecular 1,1-carboboration of the remaining alkynyl fragment. Depending on the nature of the substituent R in position 5, the allylic BBN group locates in position 3 (R = Ph) or position 5 (R = SiHMe, SiMe) to give 2,3- or 2,5-dihydrosiloles, respectively.

The Photostability of Novel Boron Hydride Blue Emitters in Solution and Polystyrene Matrix.

In recent work, the boron hydride -BH was announced in the literature as a new laser dye, and, along with several of its derivatives, its solutions are capable of delivering blue luminescence with quantum yields of unity. However, as a dopant in solid polymer films, its luminescent efficiencies reduce dramatically. Clarification of underlying detrimental effects is crucial for any application and, thus, this contribution makes the initial steps in the use of these inorganic compounds in electrooptical devices based on organic polymer thin films.

Ligand Lability Driven by Metal-to-Borane Pseudorotation: A Mechanism for Ligand Exchange.

The discovery of systems that interact with small molecules plays a vital facilitating role in the development of devices that show sensitivity to their surroundings and an ability to quickly relay chemical and physical information. Herein, we report on the reaction of [NiCl(dppe)] with decaborane that produces in usable yield a new 11-vertex nickelaborane, [7,7-(dppe)--7-NiBH] (), which shows interesting reactivity and functionality toward carbon monoxide and ethylisonitrile. This contribution describes the synthesis and full structural characterization of and its small-molecule EtNC and CO adducts, and , and delineates the dynamic molecular behavior of all of these species in solution.

A Series of Ultra-Efficient Blue Borane Fluorophores.

We present the first examples of alkylated derivatives of the macropolyhedral boron hydride, -BH, which is the gain medium in the first borane laser. This new series of ten highly stable and colorless organic-inorganic hybrid clusters are capable of the conversion of UVA irradiation to blue light with fluorescence quantum yields of unity. This study gives a comprehensive description of their synthesis, isolation, and structural characterization together with a delineation of their photophysical properties using a combined theoretical and experimental approach.

A Reversible NO-Triggered Multiple Metallaborane Cluster Fusion by Ligand Expulsion/Addition from (PMePh)PtBH to Afford (PMePh)PtBH and (PMePh)PtBH.

The dimetallic boron hydride cluster, (PMePh)PtBH (-Pt), is known to reversibly sequester small molecules (e.g., O, CO, and SO) across its Pt-Pt cluster vector.

Swollen Polyhedral Volume of the -BH Cluster via Extensive Methylation: -BHClMe.

Methylation of -BH () affords the first example of alkyl substitution of terminal hydrogen atoms on the fluorescent octadecaborane-22 molecule to give highly methylated 2,2'-Cl-1,1',3,3',4,4',7,7',8,8',10,10'-Me--BH (). This extensive chemical substitution leads to a swelling in the polyhedral volume of the 18-vertex boron atomic skeleton of the molecule and an enhancement of the absorption and solubility characteristics of this highly fluorescent molecule. We propose this "swollen polyhedral volume" to be the result of a marked increase in the relative positivity of the "cluster-only total charge" of the boron atomic skeleton caused by the combined electron-withdrawing capacity of the 12 methyl groups.

Macropolyhedral Nickelaboranes from the Metal-Assisted Fusion of KBH.

The reaction of K[BH] with [NiCl(dppe)] produces four new 19-vertex macropolyhedral metallaboranes that result from borane cluster fusion: [9'-(dppe)-9'-Ni--BH] () and isomeric [11'-(dppe)-11'-Ni--BH] (), together with the chlorine-substituted derivative of , [5'-Cl-9'-(dppe)-9'-Ni--BH] (), and the 18-vertex cluster compound [7'-(dppe)-7'--NiBH] (). Two 10-vertex single-cluster species, [1-(dppe)-1-NiBHCl] () and [1-(dppe)-1--NiBHCl(OH)] (), were also isolated from the reaction. The production of the metalated -octadecaborane isomer from the fusion of two -nonaborate clusters is the first such case to be observed; in all other reported cases fusion has resulted in products with the octadecaboranyl configuration.

Effect of Iodination on the Photophysics of the Laser Borane -BH: Generation of Efficient Photosensitizers of Oxygen.

Treatment of the laser borane -BH (compound ) with iodine in ethanol gives the monoiodinated derivative 7-I--BH (compound ) in 67% yield, or, by reaction with iodine or ICl in the presence of AlCl in dichloromethane, the diiodinated derivative 4,4'-I--BH (compound ) in 85% yield. On excitation with 360 nm light, both compounds and give strong green phosphorescent emissions (λ = 525 nm, Φ = 0.41 and λ = 545 nm, Φ = 0.

Tuning the photophysical properties of anti-B18H22: efficient intersystem crossing between excited singlet and triplet states in new 4,4'-(HS)2-anti-B18H20.

The tuning of the photophysical properties of the highly fluorescent boron hydride cluster anti-B18H22 (1), by straightforward chemical substitution to produce 4,4'-(HS)2-anti-B18H20 (2), facilitates intersystem crossing from excited singlet states to a triplet manifold. This subsequently enhances O2((1)Δg) singlet oxygen production from a quantum yield of ΦΔ ∼ 0.008 in 1 to 0.

Facile two-electron reduction of a closo-rhodathiadecaborane.

Closo-to-arachno redox flexibility in metallaheteroboranes may be viewed as a metal-to-ligand cooperative action with application in catalysis. The treatment of [PSH][arachno-4-SB(8)H(11)] with [RhCl(PPh(3))(3)] affords, after chromatography, three new 10-vertex rhodathiaboranes, [2,2,2-(H)(PPh(3))(2)-closo-2,1-RhSB(8)H(8)] (3), [6,6,9-(PPh(3))(3)-arachno-6,5-RhSB(8)H(9)] (4) and [2,2,2-(Cl)(H)(PPh(3))-6-(PPh(3))-closo-2,1-RhSB(8)H(7)] (5). 3 reacts quantitatively with PPh(3) to form 4, which, in turn, reacts with chlorinated solvents to give the chloro-ligated cluster 5.

Decaborane thiols as building blocks for self-assembled monolayers on metal surfaces.

Three nido-decaborane thiol cluster compounds, [1-(HS)-nido-B(10)H(13)] 1, [2-(HS)-nido-B(10)H(13)] 2, and [1,2-(HS)(2)-nido-B(10)H(12)] 3 have been characterized using NMR spectroscopy, single-crystal X-ray diffraction analysis, and quantum-chemical calculations. In the solid state, 1, 2, and 3 feature weak intermolecular hydrogen bonding between the sulfur atom and the relatively positive bridging hydrogen atoms on the open face of an adjacent cluster. Density functional theory (DFT) calculations show that the value of the interaction energy is approximately proportional to the number of hydrogen atoms involved in the interaction and that these values are consistent with a related bridging-hydrogen atom interaction calculated for a B(18)H(22)·C(6)H(6) solvate.

Distinct photophysics of the isomers of B18H22 explained.

The photophysics of the two isomers of octadecaborane(22), anti- and syn-B(18)H(22), have been studied by UV-vis spectroscopic techniques and theoretical computational methods. In air-saturated hexane, anti-B(18)H(22) shows fluorescence with a high quantum yield, Φ(F) = 0.97, and singlet oxygen O(2)((1)Δ(g)) production (Φ(Δ) ∼ 0.

Reversible capture of small molecules on bimetallaborane clusters: synthesis, structural characterization, and photophysical aspects.

Metallaborane compounds containing two adjacent metal atoms, [(PMe(2)Ph)(4)MM'B(10)H(10)] (where MM' = Pt(2), 1; PtPd, 7; Pd(2), 8), have been synthesized, and their propensity to sequester O(2), CO, and SO(2) and to then release them under pulsed and continuous irradiation are described. Only [(PMe(2)Ph)(4)Pt(2)B(10)H(10)], 1, undergoes reversible binding of O(2) to form [(PMe(2)Ph)(4)(O(2))Pt(2)B(10)H(10)] 3, but solutions of 1, 7, and 8 all quantitatively take up CO across their metal-metal vectors to form [(PMe(2)Ph)(4)(CO)Pt(2)B(10)H(10)] 4, [(PMe(2)Ph)(4)(CO)PtPdB(10)H(10)] 10, and [(PMe(2)Ph)(4)(CO)Pd(2)B(10)H(10)] 11, respectively. Crystallographically determined interatomic M-M distances and infrared CO stretching frequencies show that the CO molecule is bound progressively more weakly in the sequence {PtPt} > {PtPd} > {PdPd}.