Arachno Cluster Research Articles

Kinetic and computational investigation on the reaction of Os5C(CO)15 with (Z)-Ph2PCH=CHPPh2 (dppen): Stepwise conversion to nido Os5C(CO)13(κ2-Pa,Pb-dppen)

The reaction of the pentaosmium cluster Os5C(CO)15 (1) with the diphosphine (Z)-Ph2PCHCHPPh2 (dppen) has been studied over the temperature range 328–358 K. Diphosphine addition to Os5C(CO)15 yields the arachno cluster Os5C(CO)15(κ1-Peq-dppen) (2) as the initially observed product. Cluster 2 transforms to the arachno cluster Os5C(CO)14(κ2-Peq,Peq-dppen) (3) upon CO loss and chelation of the pendent phosphine moiety. The loss of a second CO in cluster 3 is accompanied by polyhedral contraction to give the square pyramidal nido cluster Os5C(CO)13(κ2-Pa,Pb-dppen) (4). Clusters 2–4 were characterized in solution by IR and NMR spectroscopies, and the molecular structure of each new cluster was established by X-ray crystallography. The kinetics for the formation of 2 from 1 and dppen support a bimolecular process involving dppen addition to 1 analogous to the reported ligand additions to the family of M5C(CO)15 clusters (where M = Fe, Ru). Cluster 2 is labile and serves as the precursor to 3 + CO, which undergoes conversion to 4 + CO. The kinetics for these reactions have been explored, and these data, in conjunction with DFT calculations, have provided mechanistic insight into the stepwise conversion of 1 and dppen to 4 + 2CO.

Ten-vertex closo-carboranes react with “wet” fluoride: A direct closo-to-arachno transformation as a result of a hydride transfer

On the basis of the experimentally observable transformation of closo-1,6-C2B8H10 to arachno-4,6-C2B7H12− with NBu4F, the DFT computational protocol has been used to examine the corresponding reaction pathway. Therefore, this work is a joint synthetic/computational attempt to describe the formation of such a 9-vertex arachno cluster. Analogous experimental transformations of closo-1,2-C2B8H10 and closo-1,10-C2B8H10 have been attempted and the corresponding arachno clusters have been afforded only computationally as the results of energetically demanding processes. For comparison, the identical reaction of icosahedral carboranes provided the fluoroborate anions BF4− and BHxF4−x− (x = 1–3) similarly as in the course of the reactions under scrutiny, but in the case of the 1,2- and 1,10-isomers as the only detectable products. The negative charge of the arachno-4,6-C2B7H12− product with respect to the neutral arachno-4,6-C2B7H13 is caused by a CH group instead of two CH2, detected for the latter.

Salts of octabismuth(2+) polycations crystallized from Lewis-acidic ionic liquids

Abstract The reaction of Bi and BiCl3 with RbCl or CsCl in the Lewis-acidic ionic liquid (IL) [BMIm]Cl·4AlCl3 at T = 200 °C yielded air-sensitive, shiny black crystals. X-ray diffraction on single crystals revealed the hexagonal structures of two new salts (Bi8)M[AlCl4]3 (M = Rb, Cs), which are isostructural to the high-temperature form of (Bi8)Tl[AlCl4]3. The known (Bi8)2+ polycation is a square antiprism and can be interpreted as an arachno cluster following modified Wade rules. The crystal structure is a complex variant of the hexagonal perovskite structure type ABX 3 with A = (Bi8)2+, B = M + and X = [AlCl4]–. Chiral strands ∞ { M [ AlCl 4 ] 3 } 2 − ∞ 1 $\infty {}_{\infty }{}^{1}{\left\{M{\left[{\text{AlCl}}_{4}\right]}_{3}\right\}}^{2-}$ (M = Rb, Cs) run along [001]. The (Bi8)2+ polycations are only weakly coordinated inside a cage of 24 chloride ions and show dynamic rotational disorder at room temperature. Upon slow cooling to 170 K, the reorientation of the clusters was frozen, yet no long-range order was established.

{Sn10 [Si(SiMe3 )3 ]4 }(2-) : A highly reactive metalloid tin cluster with an open ligand shell.

The reaction of a Sn(I) Cl solution with LiSi(SiMe3 )3 gave the anionic metalloid tin cluster {Sn10 [Si(SiMe3 )3 ]4 }(2-) (7) in good yield. The arrangement of the ten tin atoms in the cluster core can be described as a distorted centaur polyhedron. Quantum chemical calculations suggest that there are 26 bonding electrons in the cluster core, which may be described as an arachno cluster in agreement with Wade's rules. NMR and mass spectrometric investigations showed that 7 is highly reactive, which may be due to the open ligand shell. The easily available tin atoms in 7 thereby open the door to further subsequent reactions, in which 7 may act as a building block to larger cluster aggregates.

Preparations of cobalt-containing phosphines and reactions toward dicobalt octacarbonyl

Treatments of bis(diphenylphosphino)methylene (dppm) bridged dicobalt complex, Co 2(CO) 6(μ-Ph 2PCH 2PPh 2), with alkynes, Ph 2PCCR ( 2: R=CMe 3; 3: R=SiMe 3), at 60 °C in THF for 6 h gave alkyne-bridged complexes [(μ-Ph 2PCH 2PPh 2)Co 2(CO) 4][(μ-Ph 2PCCR)] ( 4: R=CMe 3; 5: R=SiMe 3). Further reactions of 4 and 5 with Co 2(CO) 8 at 80 °C in toluene for 3 h resulted in the formations of unexpected tetra-cobalt clusters, [(μ-Ph 2PCH 2PPh 2)(μ-PPh 2)Co 4(CO) 7(μ 4,μ 2-CCR)] ( 6: R=CMe 3; 7: R=SiMe 3). All these compounds were characterized by spectroscopic means; 5, 6 and 7 were studied by X-ray diffraction methods as well. The structure of 6 (or 7) can be looked upon as a tetra-cobalt arachno cluster being coordinated with phosphine ligands and linked by organic moiety.

Transition-Metal-Substituted Dichlorobismuthanes as Starting Materials for Novel Bismuth−Transition-Metal Clusters

The reaction of [{Cp(CO)2Fe}BiCl2] (1a) with [Co(CO)4]- leads to the formation of the first heteroleptic substituted bismuthane, [(μ3-Bi){Co(CO)4}2{Fe(CO)2Cp}] (2). When the “open” complex 2 is irradiated, the heterocubane [Bi4{Co(CO)3}4] (3) is formed. [{Cp‘ ‘(CO)2Fe}BiCl2] (1b; Cp‘ ‘ = η5-C5H3-tBu2) reacts with [Fe(CO)4]2- to give the nido cluster [{Fe3(CO)9}{μ-BiFe(CO)2Cp‘ ‘}2] (4) and to give the complex [Bi4{μ3-Fe(CO)3}3{Fe(CO)2Cp‘ ‘}2] (5); the latter contains a distorted-tetrahedral Bi4 cluster core in which three of the faces are capped by Fe(CO)3 moieties. The reaction of 1b with Na2[W2(CO)10] yields the Bi-bridged tetrahedral W2Bi2 cluster [{W2(CO)8}(μ,η2-Bi2){μ-BiFe(CO)2Cp‘ ‘}] (6). In contrast to this, the molybdenum-substituted analogue [{Cp‘ ‘(CO)3Mo}BiCl2] (7) reacts with Na2[Fe(CO)4] to yield the arachno cluster [{Fe2(CO)6}{Fe(CO)4}{μ3-BiMo(CO)3Cp‘ ‘}2] (9). When 7 is reacted with Na2[W(CO)5], the complex [{Cp‘ ‘(CO)3Mo}2BiCl] (10) is obtained. The decomposition of compound 7 in THF leads ...

A convenient route to carbon-substituted derivatives of nido-5,6-C 2B 8H 12

An alternative route to the parent nido-5,6-C 2B 8H 12 dicarbaborane is reported together with a convenient synthesis of its carbon-substituted derivatives. The method is based on reactions between 4-(Me 2S)- arachno-B 9H 13 and alkynes R 1R 2C 2 (where R 1R 2=H,H; Me, Me; Ph,H, and Ph,Ph) in toluene at reflux. The characteristic reaction mode is a dicarbon insertion into the 9-vertex arachno cluster to produce a series of the 5,6-R 1R 2- nido-5,6-C 2B 8H 10 species combined with concomitant elimination of one {BH} vertex. The products were characterised by high-field 1H and 11B NMR spectroscopy and mass spectrometry associated with [ 11B– 11B]-COSY and 1H{ 11B(selective)} measurements that permitted complete assignments of all resonances to individual cluster {BH} units.

Synthesis and Bonding in Hybrid Diborolyl/Boranyl and Thiaboranyl Triple‐Decker Compounds – Electronic Contribution of Heteroborane Cluster Ligands in Complexes

AbstractThe three‐component reaction of [(η5‐C5H5)Co(η5‐(CEt)2(BEt)2CMe)]−, CoCl2 and B9H−14 (7) yields the triple‐decker complex [(η5‐C5H5)Co{μ,η5‐(CEt)2(BEt)2CMe}‐6‐Co(B9H13)] (8) with a terminal B9H13 ligand contaning two cobalt–boron‐bridging hydrogen atoms. Analogously, (6‐H)−, CoCl2, and arachno‐6‐SB9H−12 (10) react to give the triple‐decker [(η5‐C5H5)Co{μ,η5‐(CEt)2(BEt)2CMe}‐1‐Co‐2‐(SB9H9)] (11). The analogous reaction with the heteroboranyl anion arachno‐6,8‐S2B7H8− leads to the loss of one boron atom, forming the air‐stable triple‐decker complex [(η5‐ C5H5)Co{μ,η5‐(CEt)2(BEt)2CMe}‐7‐Co‐6,8‐(S2B6H8)] (12). The X‐ray structure determination shows that the dithiacobaltaborane fragment in 12 has an arachno cluster geometry. The three‐component reaction of (6‐H, CoCl2, and arachno‐2,3‐S2B9H10− yields the expected triple‐decker [(η5‐C5H5)Co{μ,η5‐(CEt)2(BEt)CMe}Co‐6,8‐(S2B9H9)] (15), and surprisingly the sandwich complex (η5‐C5H5)Co‐6,8‐(S2B9H9) (16). The constitutions of the new compounds are based on NMR and MS data. A rule is described regarding the electron donation of heteroboranyl cluster ligands in metal complexes.

Thiaaza‐arachno‐pentaboran SNB3H2tBu3R

Thiaaza‐arachno‐pentaborane SNB3H2tBu3RThe azadiboriridine [‐B(tBu)‐N(tBu)‐B(tBu)‐] (1) gives 1:1 adducts with the mercaptoboranes BH2(SR), which can be generated from their cyclotrimers by the action of THF. The adduct 4a (R = Ph), a nido cluster with an NB3 skeleton, forms an equilibrium with an adduct 5a, an arachno cluster with an SNB3 skeleton, whose S‐bound ligand Ph is found in an endo position by an X‐ray structural analysis. The equilibrium 4a · 5a involves a Lewis acid‐base reaction, which is electronically coupled to a reduction of a three‐center to give a two‐center π bond. The reaction of 1 with BH2(SPr) gives the corresponding arachno cluster 5b only.

Synthesis of the thermally unstable arachno cluster Fe 2(CO) 6(μ 3-S) 2Ni(1, 5-COD observation of facile decomposition to FeNiS

The reaction between Fe 2(CO) 6(μ 2-S) 2 and (1,5-COD) 2Ni gives the arachno cluster Fe 2(CO) 6(μ 3-S) 2Ni(1,5-COD) at −78 °C in toluene. This new cluster is stable at low temperature and has been characterized by low-temperature IR spectroscopy. Cluster decomposition occurs upon warming to yield amorphous FeNiS, which has been characterized by energy- dispersive X-ray analysis (EDAX).

Nine-vertex polyhedral monocarbaplatinaborane chemistry. Isolation, molecular structure and nuclear magnetic resonance properties of [6,6-(PPh3)2-arachno-6,4-PtCB7H11

Reaction between [Pt(PPh3)4] and nido-1-CB8H121 results in the formation of [6,6-(PPh3)2-arachno-6,4-PtCB7H11]2 as a yellow crystalline solid in 26% yield. The product 2 is characterised by NMR spectroscopy and single-crystal X-ray diffraction analysis. Crystals (from CH2Cl2–hexane) are triclinic, space group P, with a= 974.3(2), b= 1237.5(2), c= 1771.3(3) pm, α= 95.26(1), β= 95.43(1), γ= 110.10(1)° and Z= 2. The structure has been refined to R(R′)= 0.0256 (0.0394) for 6324 reflections [Fo > 2.0σ(Fo)]. The molecular structure is based on a nine-vertex arachno cluster with the platinum and carbon atoms in projecting open face 6- and 4-positions respectively. The 11B, 1H and 31P NMR parameters have been measured and assigned to structural positions, and the 11B and 1H shielding patterns are compared to those of the related non-platinum species arachno-4,5-C2B7H137 and arachno-4,6-C2B7H138. Incidental to this work the previously unreported 1H shielding behaviour of the carbaboranes 1, 7 and 8 have also been measured and assigned.

Dalton communications. The first example of a direct closo to arachno cluster expansion reaction in boron cluster chemistry

The reaction between closo-1,2-C2B8H10 and NH2But resulted in a straightforward cluster expansion to give the 11-vertex azadicarbaborane anti-11-But-arachno-5,10,11-C2NB8H12, characterized by NMR and mass spectroscopy, together with the accompanying syn isomer.

ChemInform Abstract: Synthesis and Redox Reactivity of the Thermally Unstable Mixed‐Metal Arachno Cluster Fe2(CO)6(μ3‐S)2Cu(η5‐Cp*).

AbstractThe solvated Cu complex (II) is an excellent low‐temp.

Synthesis and redox reactivity of the thermally unstable mixed-metal arachno cluster Fe 2(CO) 6(μ 3-S) 2Cu(η 5-Cp*)

The reaction between Fe 2(CO) 6(μ 2-S) 2 ( 1) and (THF)Cu(η 5-Cp*) (where Cp* = C 5Me 5) has been examined in THF at −78 °C. Rapid and efficient insertion of the carbene like fragment Cu(η 5-Cp*) into the SS bond of 1 affords the mixed-metal arachno cluster Fe 2(CO) 6(μ 3-S) 2Cu(η 5-Cp*) ( 2). Reaction of 1 with LiEt 3BH and MeLi at −78 °C gives the corresponding cluster radical anion Fe 2(CO) 6(μ 3-S) 2Cu(η 5-Cp*) ·− ( 3) without the spectroscopic intermediacy of CO-based reduction products. The thermal stability of 2 and 3 is described.

Hydroformylation of cyclohexene under low pressure with Rh 4(CO) 12: evidence in favor of homogeneous cluster catalysis

The hydroformylation of cyclohexene at low pressure (34 atm CO/H 2 = 1) and 125 °C temperature has been studied using Rh 4(CO) 12 cluster as catalyst. The kinetic study supports the rate equation: ▪ The order of the reaction found for the catalyst suggests that no fragmentation of the carbonyl cluster to lower nuclearity, nor to mononuclear species, occurs. A cyclic mechanism and an intermediate arachno cluster species based on H 2Rh 4(CO) 12 are proposed to explain the experimental results.

Electron-rich carboranes. Studies of a stereochemically novel system, (CH3)4C4B7H9, an 11-vertex arachno cluster

Electron-rich carboranes. Studies of a stereochemically novel system, (CH3)4C4B7H9, an 11-vertex arachno cluster