Dimetallaheteroborane clusters containing group 16 elements: A combined experimental and theoretical study

Recently we described the synthesis and structural characterization of various dimetallaherteroborane clusters, namely nido-[(Cp∗Mo2B4EClxH6−x], 1–3; (1: E = S, x = 0; 2: E = Se, x = 0; 3: E = Te, x = 1). A combined theoretical and experimental study was also performed, which demonstrated that the clusters 1–3 with their open face are excellent precursors for cluster growth reaction. In this investigation process on the reactivity of dimetallaheteroboranes with metal carbonyls, in addition to [(Cp∗Mo)2B4H6EFe(CO)3] (4: E = S, 6: E = Te) reported earlier, reaction of 2 with [ Fe2(CO)9] yielded mixed-metallaselenaborane [(Cp∗Mo)2B4H6SeFe(CO)3], 5 in good yield. The quantum chemical calculation using DFT method has been carried out to probe the bonding, NMR chemical shifts and electronic properties of dimolybdaheteroborane clusters 4–6

Copper Clusters Containing Hydrides in Trigonal Pyramidal Geometry

International audienceStructurally precise copper hydrides [CuH{SP(OPr)}(C≡CR)], R = Ph (1), CHF (2), and CHOMe (3), were first synthesized from the polyhydrido copper cluster [CuH{SP(OPr)}] with nine equivalents of terminal alkynes. Later, their isolated yields were significantly improved by direct synthesis from [Cu(CHCN)](PF), [NH][SP(OPr)], NaBH, and alkynes along with NEt in THF. 1, 2, and 3 were fully characterized by single-crystal X-ray diffraction, ESI-MS, and multinuclear NMR spectroscopy. All three clustershave 11 copper atoms, adopting 3,3,4,4,4-pentacapped trigonal prismatic geometry, with two hydrides inside the Cu cage, the position of which was ascertained by a single-crystal neutron diffraction structure of cluster 1 co-crystallized with a [Cu(H){SP(OPr)}] (4) cluster. Six dithiophosphate and three alkynyl ligands stabilize the CuH core in which the two hydrides adopt a trigonal pyramidal coordination mode. This coordination mode is so far unprecedented for hydride. The H NMR resonance frequency of the two hydrides appears at 4.8 ppm, a value further confirmed by H NMR spectroscopy for their deuteride derivatives [Cu(D){SP(OPr)}(C≡CR)]. A DFT investigation allows understanding the bonding within this new type of copper(I) hydrides

B–H bond iodination of polyhedral dimolybdaborane and dimolybdathiaborane clusters

Reaction of [Cp∗MoCl4 (Cp∗ = η5-C5Me5) with excess of [LiBH4·thf] followed by pyrolysis with NaI yielded B–I inserted [(Cp∗Mo)2B5H9−nIn], 1–3 (1: n = 1; 2: n = 2; 3: n = 3). In parallel to the formation of 1–3, the reaction also produced known [(Cp∗Mo)2B5H9] and [(Cp∗Mo)2 (μ-I)4] in good yields. Under the similar reaction conditions, dimolybdathiaborane [(Cp∗Mo)2B4H4S2] yielded iodine substituted dimolybdathiaboranes, [(Cp∗Mo)2B4S2H4−nIn], 4 and 5 (4: n = 2; 5: n = 3) in good yields. All the new compounds have been characterized in solution by IR, 1H and 11B NMR as simple substituted derivatives of [(Cp∗Mo)2B5H9] and [(Cp∗Mo)2B4H4S2]. The solid state structures were established unambiguously by crystallographic analysis of compounds 1–5

Structurally Precise Dichalcogenolate-Protected Copper and Silver Superatomic Nanoclusters and Their Alloys

International audienceThe chalcogenolato silver and copper superatoms are currently a topic of cutting edge research besides the extensively studied Au (SR) clusters. Crystal structure analysis is an indispensable tool to gain deep insights into the anatomy of these sub-nanometer clusters. The metal framework and spatial arrangement of the chalcogenolates around the metal core assist in unravelling the structure-property relationships and fundamental mechanisms involved in their fabrication. In this Account, we discuss our contribution toward the development of dichalcogenolato Ag and Cu cluster chemistry covering their fabrication and precise molecular structures. Briefly introducing the significance of the single crystal structures of the atomically precise clusters, the novel dichalcogenolated two-electron superatomic copper and its alloy systems are presented first. The [Cu{SCNR}{C≡CR'}] is so far the first unique copper cluster having Cu centered cuboctahedra, which is a miniature of bulk fcc structure. The galvanic exchange of the central Cu with Ag or Au results in a similar anatomy of formed bimetallic [Au/Ag@Cu(SCN Bu)(C≡CPh)][CuCl] species. This is unique in the sense that other contemporary M cores in group 11 superatomic chemistry are compact icosahedra. The central doping of Ag or Au significantly affects the physiochemical properties of the bimetallic Cu-rich clusters. It is manifested in the dramatic quantum yield enhancement of the doped species [Au@Cu(SCN Bu)(C≡CPh)] with a value of 0.59 at 77 K in 2-MeTHF. In the second part, the novel eight-electron dithiophosphate- and diselenophosphate-protected silver systems are presented. A completely different type of architecture was revealed for the first time from the successful structural determination of [Ag{SP(O Pr)}], [Ag{SP(O Pr)}] and [Au@Ag{SP(OPr)}]. They exhibit a nonhollow M (Ag or AuAg) icosahedron, capped by 8 and 7 Ag atoms in the former and latter two species, respectively. The overall metal core units are protected by 12 dithiophosphate ligands and the metal-ligand interface structure was found to be quite different from that of Au (SR) . Notably, the [Ag{SP(O Pr)}] cluster provides the first structural evidence of a silver superatom with a chiral metallic core. This chirality arises through the simple removal of one of capping Ag cations of [Ag{SP(O Pr)}] present on its C axis. Further, the effects of the ligand exchange on the structures of [Ag{SeP(O Pr)}], [Ag{SeP(OEt)}], and [AuAg{SeP(OEt)}] are studied extensively. The structure of the former species is similar to its dithiophosphate counterpart ( C symmetry). The latter two ( T symmetry) differ in the arrangement of 8 capping Ag atoms, as they form a cube engraving the Ag (AuAg) icosahedron. The blue shifts in absorption spectra and photoluminescence further indicate the strong influence of the central Au atom in the doped clusters. Finally, the first paradigm of unusual heteroatom doping induced size-structure transformations is discussed by presenting the case of formation of [AuAg{SeP(O Pr)}] upon Au doping into [Ag{SeP(O Pr)}]. Finally, before concluding this Account, we discuss the possibility of many unique structural isomers with different physical properties for the aforementioned Ag superatoms which need to be explored extensively in the future

Synthesis, characterization and crystal structure analysis of cobaltaborane and cobaltaheteroborane clusters

Cluster expansion reactions of cobaltaboranes were carried out using mono metal-carbonyls, metal halides and dichalcogenide ligands. Thermolysis of an in situ generated intermediate, obtained from the reaction of [Cp*CoCl]₂ (Cp* = C₅Me₅) and [LiBH₄·thf], with three equivalents of [Mo(CO)₃(CH₃CN)₃] followed by the reaction with methyl iodide yielded isocloso-[(Cp*Co)₃B₆H₇Co(CO)₂] (1) and closo-[(Cp*Co)₂B₂H₅Mo₂(CO)₆I] (2). Cluster 1 is ascribed to the isocloso structure based on a 10-vertex bicapped square antiprism geometry. In a similar manner, the reaction of [Cp*CoCl]₂ with [LiBH₄·thf] and the dichalcogenide ligand RS–SR (R = 1-OH-2,6-(tBu)₂-C₆H₂) yielded nido cluster [(Cp*Co)₂B₂H₂S₂] (3). In parallel with the formation of the compounds 1–3, these reactions also yielded known cobaltaboranes [(Cp*Co)₂B₄H₆] (4) and [(Cp*Co)₃B₄H₄] in good yields. After the isolation of compound 4 in good yield, we verified its reactivity with PtBr₂, which yielded closo-[(Cp*Co)₂B₄H₂Br₄] (5). To the best of our knowledge this is the second perhalogenated metallaborane cluster which has been recognized. All the new compounds were characterized by elemental analysis, IR, ¹H, ¹¹B and ¹³C NMR spectroscopy, and the geometric structures were unequivocally established by the X-ray diffraction analysis of compounds 1, 2, 3 and 5. Geometries obtained from the electronic structure calculations employing density functional theory (DFT) are in close agreement with the solid state X-ray structures. In addition, we analyzed the variation in the stability of the model compounds 1′ (1′: Cp analogue of 1, Cp = C₅H₅), [(CpCo)₄B₆H₆] (1a) and [(CpRh)₄B₆H₆] (1b)

Hypoelectronic dimetallaheteroboranes of group 6 transition metals containing heavier chalcogen elements

We have synthesized and structurally characterized several dimetallaheteroborane clusters, namely, nido-[(Cp*Mo)₂B₄SH₆], 1; nido-[(Cp*Mo ₂B₄SeH₆], 2; nido-[(Cp*Mo)₂B₄TeClH₅], 3; [(Cp*Mo)₂B₅SeH₇], 4; [(Cp*Mo)₂B₆SeH₈], 5; and [(CpW)₂B₅Te₂H₅], 6 (Cp* = η⁵-C₅Me₅, Cp = η⁵-C₅H₅). In parallel to the formation of 1–6, known [(CpM)₂B₅H₉], [(Cp*M)₂B₅H₉], (M = Mo, W) and nido-[(Cp*M)₂B₄E₂H₄] compounds (when M = Mo; E = S, Se, Te; M = W, E = S) were isolated as major products. Cluster 6 is the first example of tungstaborane containing a heavier chalcogen (Te) atom. A combined theoretical and experimental study shows that clusters 1–3 with their open face are excellent precursors for cluster growth reactions. As a result, the reaction of 1 and 2 with [Co₂(CO)₈] yielded clusters [(Cp*Mo₂B₄H₄E(μ³-CO)Co₂(CO)₄], 7–8 (7: E = S, 8: E = Se) and [(Cp*Mo)₂B₃H₃E(μ-CO)₃Co₂(CO) ₃], 9–10 (9: E = S, 10: E = Se). In contrast, compound 3 under the similar reaction conditions yielded a novel 24-valence electron triple-decker sandwich complex, [(Cp*Mo)₂{μ-η⁶:η⁶-B₃H₃TeCo₂(CO)₅}], 11. Cluster 11 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 1, 2, 4–7, and 9–11. 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

Hypoelectronic metallaboranes: Synthesis, structural characterization and electronic structures of metal-rich cobaltaboranes

Reaction of [Cp∗CoCl]2 (Cp∗ = η5-C5Me5) with [LiBH4·THF] in toluene at −70 °C, followed by thermolysis with 2-mercaptobenzothiazole (C7H5NS2) in boiling toluene led to the isolation of a range of cobaltaborane clusters, [(Cp∗Co)2B7H6OMe], 1; [(Cp∗Co)3B8H7R], 2a, b (2a: R = H; 2b: R = Me); [(Cp∗Co) 3B8H8S], 3 and [(Cp∗Co)2B4H4RR′], 4a–d (4a: R, R′ = H; 4b: R = Me, R′ = H; 4c: R = H, R′ = Me and 4d: R, R′ = Me). In parallel to the formation of compounds 1–4, the reaction also yielded known [(Cp∗Co)3B4H4] in good yield. Compound 1 may be considered as 9-vertex hypoelectronic cluster with C1 symmetry, where cobalt atoms occupy the degree 5 vertices. All the dicobaltaboranes 4a–d contains two μ3-H protons and found to be very reactive. As a result, one of them (4a) when reacted with Fe2(CO)9 and sulfur powder yielded, almost immediately, [(Cp∗Co)2B4H5SFe3(CO)9], 5 and [(Cp∗Co)2B3H3(μ-CO)Fe(CO)3], 6. All the new compounds have been characterized in solution by mass, 1H, 11B, 13C NMR spectroscopy and elemental analysis. The structural types were unequivocally established by X-ray crystallographic analysis of compounds 1–6. Density functional theory (DFT) calculations on the model compounds 1′ and 2′ (1′, and 2′ are the Cp analog of 1, and 2a respectively, Cp = C5H5) yield geometries in agreement with the structure determinations. The existence of large HOMO–LUMO gap of these molecules rationalizes the isocloso description for 2a. Bonding patterns in the structure have been analyzed on the grounds of DFT calculations

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

New heteronuclear bridged borylene complexes that were derived from [{Cp*CoCl}₂] and mono-metal&#x2014;carbonyl fragments

The synthesis, structural characterization, and reactivity of new bridged borylene complexes are reported. The reaction of [{Cp*CoCl}₂] with LiBH₄⋅THF at −70 °C, followed by treatment with [M(CO)₃(MeCN)₃] (M=W, Mo, and Cr) under mild conditions, yielded heteronuclear triply bridged borylene complexes, [(μ₃-BH)(Cp*Co)₂ (μ-CO)M(CO)₅] (1–3; 1: M=W, 2: M=Mo, 3: M=Cr). During the syntheses of complexes 1–3, capped-octahedral cluster [(Cp*Co)₂ (μ-H)(BH)₄{Co(CO)₂}] (4) was also isolated in good yield. Complexes 1–3 are isoelectronic and isostructural to [(μ₃-BH)(Cp*RuCO)₂ (μ-CO){Fe(CO)₃}] (5) and [(μ₃-BH)(Cp*RuCO)₂(μ-H)(μ-CO){Mn(CO)₃}] (6), with a trigonal-pyramidal geometry in which the μ₃-BH ligand occupies the apical vertex. To test the reactivity of these borylene complexes towards bis-phosphine ligands, the room-temperature photolysis of complexes 1–3, 5, 6, and [{(μ₃-BH)(Cp*Ru)Fe(CO)₃}₂(μ-CO)] (7) was carried out. Most of these complexes led to decomposition, although photolysis of complex 7 with [Ph₂P(CH₂)nPPh₂] (n=1–3) yielded complexes 9–11, [3,4-(Ph₂P(CH₂)nPPh₂)-closo-1,2,3,4-Ru₂Fe₂ (BH)₂] (9: n=1, 10: n=2, 11: n=3). Quantum-chemical calculations by using DFT methods were carried out on compounds 1–3 and 9–11 and showed reasonable agreement with the experimentally obtained structural parameters, that is, large HOMO–LUMO gaps, in accordance with the high stabilities of these complexes, and NMR chemical shifts that accurately reflected the experimentally observed resonances. All of the new compounds were characterized in solution by using mass spectrometry, IR spectroscopy, and ¹H, ¹³C, and ¹¹B NMR spectroscopy and their structural types were unequivocally established by crystallographic analysis of complexes 1, 2, 4, 9, and 10