Synthesis and Characterization of Novel Ruthenaferracarboranes from Photoinsertion of Alkynes into a Ruthenaferraborane

Photolysis of [{(μ₃-BH)­(Cp*Ru)­Fe­(CO)₃}₂(μ-CO)] (<b>1</b>; Cp* = η⁵-C₅Me₅) in the presence of various alkynes such as 1,2-diphenylethyne, 1-phenyl-1-propyne, 2-butyne, and 1-(diphenylphosphino)-2-phenylacetylene led to the formation of four types of novel heterometallic metallacarboranes, [1,1,1-(CO)₃-μ-2,3-(CO)-2,3-(Cp*)₂-4,6-Ph₂-<i>closo</i>-1,2,3,4,6-FeRu₂C₂BH] (<b>2</b>), [1,8-(Cp*)₂-2,2,7,7-(CO)₄-μ-2,8-(CO)-μ-7,8-(CO)-4-Me-5-Ph-<i>pileo</i>-1,2,7,4,5-RuFe₂C₂(BH)₂] (<b>3</b>), [1,8-(Cp*)₂-2,2,7,7-(CO)₄-μ-2,8-(CO)-μ-7,8-(CO)-4,5-Me₂-<i>pileo</i>-1,2,7,4,5-RuFe₂C₂(BH)₂] (<b>4</b>), and [1,2-(Cp*)₂-6,6,7,7-(CO)₄-μ-2,7-(CO)-<i>exo</i>-μ-5,6-(PPh₂)-μ₃-1,2,6-(BH)-4-Ph-<i>pileo</i>-1,2,6,7,4,5-Ru₂Fe₂C₂BH] (<b>5</b>). Cluster compound <b>2</b> exhibits an octahedral structure with adjacent carbon atoms consistent with its skeletal electron pair (sep) count of 7. The cage geometry of <b>3</b> and <b>4</b> is based on a pentagonal bipyramid with one additional {Cp*Ru} vertex capping one of its faces. The solid-state X-ray diffraction results of <b>5</b> suggest that the core geometry is a capped pentagonal bipyramid, with an Fe–C bridging PPh₂ group. All the cluster compounds <b>2</b>–<b>5</b> have been characterized by IR and ¹H, ¹¹B, and ¹³C NMR spectroscopy, and the geometries of the structures were unequivocally established by crystallographic analysis

Effect of linking groups on 2, 5-disubstituted thiophene with chalcone as the side arm containing bent-core materials

<p>Novel bent-core materials containing a central core of 2, 5-disubstituted thiophene with chalcone as the side arm were synthesized and characterized to determine the structure–property relationship. The structural difference between two materials is the linking group in the thiophene and chalcone side arm. Chalcone is linked with thiophene by ester group in material I, while ester group is replaced with imine group in material II. The change in linking group exhibited a drastic difference in their physicochemical and intramolecular behaviors. Material I exhibits a hexagonal columnar mesophase at below room temperature, whereas material II exhibits a crystalline phase. Both liquid crystalline and crystalline properties were examined from polarized optical microscopy (POM), differential scanning calorimetry (DSC), and powder X-ray diffraction (PXRD) analyses. The highlight of this work is material I revealed a hexagonal columnar phase in the temperature ranges 22–38°C and undergoes photocrosslinking in UV light; contrarily, material II exhibits neither LC phase nor photocrosslinking property.</p

Hypoelectronic Dimetallaheteroboranes of Group 6 Transition Metals Containing Heavier Chalcogen Elements

We have synthesized and structurally characterized several dimetallaheteroborane clusters, namely, <i>nido</i>-[(Cp*Mo)₂B₄SH₆], <b>1</b>; <i>nido</i>-[(Cp*Mo)₂B₄SeH₆], <b>2</b>; <i>nido</i>-[(Cp*Mo)₂B₄TeClH₅], <b>3</b>; [(Cp*Mo)₂B₅SeH₇], <b>4</b>; [(Cp*Mo)₂B₆SeH₈], <b>5</b>; and [(CpW)₂B₅Te₂H₅], <b>6</b> (Cp* = η⁵-C₅Me₅, Cp = η⁵-C₅H₅). In parallel to the formation of <b>1</b>–<b>6</b>, known [(CpM)₂B₅H₉], [(Cp*M)₂B₅H₉], (M = Mo, W) and <i>nido</i>-[(Cp*M)₂B₄E₂H₄] compounds (when M = Mo; E = S, Se, Te; M = W, E = S) were isolated as major products. Cluster <b>6</b> is the first example of tungstaborane containing a heavier chalcogen (Te) atom. A combined theoretical and experimental study shows that clusters <b>1</b>–<b>3</b> with their open face are excellent precursors for cluster growth reactions. As a result, the reaction of <b>1</b> and <b>2</b> with [Co₂(CO)₈] yielded clusters [(Cp*Mo)₂B₄H₄E­(μ₃-CO)­Co₂(CO)₄], <b>7</b>–<b>8</b> (<b>7</b>: E = S, <b>8</b>: E = Se) and [(Cp*Mo)₂B₃H₃E­(μ-CO)₃Co₂(CO)₃], <b>9</b>–<b>10</b> (<b>9</b>: E = S, <b>10</b>: E = Se). In contrast, compound <b>3</b> under the similar reaction conditions yielded a novel 24-valence electron triple-decker sandwich complex, [(Cp*Mo)₂{μ-η⁶:η⁶-B₃H₃TeCo₂(CO)₅}], <b>11</b>. Cluster <b>11</b> represents an unprecedented metal sandwich cluster in which the middle deck is composed of B, Co, and Te. All the new compounds have been characterized by elemental analysis, IR, ¹H, ¹¹B, ¹³C NMR spectroscopy, and the geometric structures were unequivocally established by X-ray diffraction analysis of <b>1</b>, <b>2</b>, <b>4</b>–<b>7</b>, and <b>9</b>–<b>11</b>. Furthermore, geometries obtained from the electronic structure calculations employing density functional theory (DFT) are in close agreement with the solid state structure determinations. We have analyzed the discrepancy in reactivity of the chalcogenato metallaborane clusters in comparison to their parent metallaboranes with the help of a density functional theory (DFT) study

An Early–Late Transition Metal Hybrid Analogue of Hexaborane(12)

Metal assisted borane condensation method has been employed for the preparation of novel metallaborane cluster containing group 4 metal. Pyrolysis of [Cp*IrB₃H₉], <b>1</b>, with in situ generated zirconium bisborohydrate [Cp₂Zr­(BH₄)₂], produced from the fast metathesis reaction of [Cp₂ZrCl₂] and LiBH₄, and excess of BH₃·THF yielded <i>arachno</i>-[(Cp₂Zr)­(Cp*Ir)­B₄H₁₀], <b>2</b>, in 56% yield. Compound <b>2</b> constitutes the first crystallographic structure determination of hexaborane(12) metal analogue containing zirconium. The observed geometry of <b>2</b> can be generated from a dodecahedron by removing two vertices and an edge. Anticipating a straight metal fragment substitution/addition reaction, mild thermolysis of <b>2</b> with [Fe₂(CO)₉] was carried out. However, the reaction led to the formation of known trimetallic [Cp*IrFe₂(CO)₉] cluster via cluster degradation. In addition, density functional theory (DFT) calculations have been carried out for <b>2</b> and other hypothetical early–late combinations of hexaborane(12) metal analogues to reveal the electronic structures

Synthesis and Structure of Dirhodium Analogue of Octaborane-12 and Decaborane-14

We present the results of our investigation of a thermally driven cluster expansion of rhodaborane systems with BH₃·THF. Four novel rhodaborane clusters, for example, <i>nido</i>-[(Cp*Rh)₂B₆H₁₀], <b>1</b>; <i>nido</i>-[(Cp*Rh)­B₉H₁₃], <b>2</b>; <i>nido</i>-[(Cp*Rh)₂B₈H₁₂], <b>3</b>; and <i>nido</i>-[(Cp*Rh)₃B₈H₉(OH)₃], <b>4</b> (Cp* <b>=</b> η⁵-C₅Me₅), have been isolated from the thermolysis of [Cp*RhCl₂]₂ and borane reagents in modest yields. Rhodaborane <b>1</b> has a <i>nido</i> geometry and is isostructural with [B₈H₁₂]. The low temperature ¹¹B and ¹H NMR data demonstrate that compound <b>1</b> exists in two isomeric forms. The framework geometry of <b>2</b> and <b>3</b> is similar to that of [B₁₀H₁₄] with one BH group in <b>2</b> (3-position), and two BH groups in <b>3</b> (3, 4-positions) are replaced by an isolobal {Cp*Rh} fragment. The 11 vertex cluster <b>4</b> has a <i>nido</i> structure based on the 12 vertex icosahedron, having three rhodium and eight boron atoms. In addition, the reaction of rhodaborane <b>1</b> with [Fe₂(CO)₉] yielded a condensed cluster [(Cp*Rh)₂{Fe­(CO)₃}₂B₆H₁₀], <b>5</b>. The geometry of <b>5</b> consists of [Fe₂B₂] tetrahedron and an open structure of [(Cp*Rh)₂B₆], fused through two boron atoms. The accuracy of these results in each case is established experimentally by spectroscopic characterization in solution and structure determinations in the solid state

Chemistry of Homo- and Heterometallic Bridged-Borylene Complexes

Thermolysis of [(Cp*RuCO)₂B₂H₆] (<b>1</b>; Cp* = η⁵-C₅Me₅) with [Ru₃(CO)₁₂] yielded the trimetallaborane [(Cp*RuCO)₃(μ₃-H)­BH] (<b>2</b>) and a number of homometallic boride clusters: [Cp*RuCO­{Ru­(CO)₃}₄B] (<b>3</b>), [(Cp*Ru)₂{Ru₂(CO)₈}­BH] (<b>4</b>), and [(Cp*Ru)₂{Ru₄(CO)₁₂}­BH] (<b>5</b>). Compound <b>2</b> is isoelectronic and isostructural with the triply bridged borylene compounds [(μ₃-BH)­(Cp*RuCO)₂(μ-CO)­{Fe­(CO)₃}] (<b>6</b>) and [(μ₃-BH)­(Cp*RuCO)₂(μ-H)­(μ-CO)­{Mn­(CO)₃}] (<b>7</b>), where the [μ₃-BH] moiety occupies the apical position. To test if compound <b>2</b> undergoes hydroboration reactions with alkynes, as observed with <b>6</b>, we performed the reaction of <b>2</b> with the same set of alkynes under photolytic conditions. However, neither <b>2</b> nor <b>7</b> undergoes hydroboration to yield a vinyl–borylene complex. On the other hand, thermolysis of <b>6</b> with trimethylsilylethylene yielded the novel diruthenacarborane [1,1,7,7,7-(CO)₅-2,3-(Cp*)₂-μ-2,3-(CO)-μ₃-1,2,3-(CO)-5-(SiMe₃)-<i>pileo</i>-1,7,2,3,4,5-Fe₂Ru₂C₂BH] (<b>8</b>). The solid-state X-ray diffraction results suggest that <b>8</b> exhibits a pentagonal -bipyramidal geometry with one additional CO capping one of its faces. Cluster <b>3</b> is a boride cluster where boron is in the interstitial position of a square-pyramidal geometry, whereas compound <b>4</b> can be described as a tetraruthenium boride in which the Ru₄ butterfly skeleton has an interstitial boron atom. Electronic structure calculations of compound <b>2</b> employing density functional theory (DFT) generate geometries in agreement with the structure determinations. The existence of a large HOMO–LUMO gap in <b>2</b> is in agreement with its high stability. Bonding patterns in the structure have been analyzed on the grounds of DFT calculations. Furthermore, the B3LYP-computed ¹¹B and ¹H chemical shifts for compound <b>2</b> precisely follow the experimentally measured values. All the compounds have been characterized by IR and ¹H, ¹¹B, and ¹³C NMR spectroscopy, and the geometries of the structures were unambiguously established by crystallographic analyses of <b>2</b>–<b>4</b> and <b>8</b>