A neutral metallaborane comprising a Rh4B12 polyhedron with icosioctahedron geometry with 16 vertices and 28 triangular faces was prepared (see structure; Rh: red, B: green). The cage has the shape of a 12-membered truncated tetrahedron with four capped hexagonal faces. © 2013 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Sundargopal Ghosh

Department Of Chemistry

Bijan Mondal

Venkatachalam Ramkumar

Cage compounds

Metallaboranes

boron

geometry

Rhodium

Rhodium compounds

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IIT Madras

Angewandte Chemie - International Edition

Density functional theory studies on the experimentally known Cp∗3Rh3B12H12Rh(B4H9RhCp∗) as well as the model compounds Cp4Rh4B12H12 and Cp3Rh3B12H12Rh(η3-C3H5) indicate low energy structures with central Rh4B12 tetracapped tetratruncated tetrahedra (TTT) for these 32 Wadean skeletal electron systems. This skeletal electron count corresponds to 2k2 (k = 4) skeletal electrons suggesting a spherical aromatic system with filled 1s + 1p + 1d + 1f molecular orbitals as well as an isocloso 2n (= 32 for n = 16) skeletal electron count. Similar TTT structures are found for the valence isoelectronic 32 skeletal electron systems [Cp4M′′4B12H12]4+ (M′′ = Ni, Pd, Pt) and [Cp4M′4B12H12]4- (M′ = Fe, Ru, Os). The preferred structures of the 34 skeletal electron systems [Cp4M4B12H12]2- (M = Co, Rh, Ir), [Cp4M′′4B12H12]2+ (M′′ = Ni, Pd, Pt) are not the most spherical TTT despite their 2n + 2 skeletal electron count (= 34 for n = 16) for a closo structure by the Wade-Mingos rules. Instead they are prolate (elongated) polyhedra with two degree 6 and two degree 5 metal vertices with a central M4 macrobutterfly having one long M⋯M distance of ∼5.0 Å between the wingtips. The preferred structures for the still electron richer 36 skeletal electron systems Cp4M′′4B12H12 (M′′ = Pd, Pt) are derived from triple square antiprisms with two open M′′2B2 square faces. A distorted version of this polyhedron is the deltahedral structure with four degree 5 metal vertices and four degree 6 boron vertices found in the valence isoelectronic 36 skeletal electron first row transition metal derivatives Cp4Ni4B12H12 and [Cp4Co4B12H12]4-. However, this polyhedron is not found in the 36 skeletal electron [Cp4M4B12H12]4- (M = Rh, Ir), that instead have symmetrical central M4B12 TTTs. For some 16-vertex [Cp4M4B12H12]z systems deviating from the favored 32 skeletal electron count, low-energy structures are found in which hydrogen atoms migrate to bridge B-B edges or bend over to bridge M-B edges. In addition, the hypoelectronic hexacations [Cp4M4B12H12]6+ (M = Co, Rh, Ir; Ni, Pd, Pt) are found to have low-energy structures in which three of the four Cp rings are hydrogenated to give tetrahapto cyclopentadiene η4-C5H6 rings. © the Owner Societies.

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Physical Chemistry Chemical Physics

The tetracapped truncated tetrahedron in 16-vertex tetrametallaborane structures: Spherical aromaticity with an: Isocloso rather than a closo skeletal electron count

In an effort to synthesize metallaheteroborane complexes of ruthenium, we carried out the reaction of ruthenium methanedithiolate complex, [(Cp∗Ru)2(B3H8)(CS2H)], (Cp∗ = η5-C5Me5) 1 with [BH3SPh]Li at elevated temperature that yielded a dinuclear bridged thiolate complex [Cp∗Ru(µ-SPh)2(µ-η1-S2)RuCp∗], 2. In a similar fashion, reaction of [Cp∗IrCl2]2 with [BH3TePh]Li yielded tellurolato-bridged diiridium half sandwich complex [Cp∗IrH(µ-TePh)2HIrCp∗], 5. All the compounds have been characterized by various spectroscopic techniques and the structures were unequivocally established by crystallographic analysis. Further, the density functional theory (DFT) calculations were performed to investigate the bonding and electronic properties of 2′ and 5′ (Cp analogues of 2 and 5). © 2018

Inorganica Chimica Acta

Chalcogenolato-bridged dinuclear half sandwich complexes of ruthenium and iridium

In an attempt to synthesize expanded-cage metallaheteroboranes containing heavier chalcogen atoms, the reaction of diruthenaborane analogue of pentaborane(9), nido-[1,2-(Cp*RuH)2B3H7] (1) with phenyl-chalcogenoborates Li[BH3(EPh)] (E = S, Se or Te) was carried out. Thermolysis of nido-1 with Li[BH3(SPh)] led to the formation of the dimetalla-pentaborane(11) analogue arachno-[(Cp*Ru)2B3H8(SPh)] (2). In parallel to the formation of 2, the reaction also yielded three B-H functionalized compounds, namely [(Cp*Ru)2B4H7(Ph)] (3), [(Cp*Ru)2B4H7(Cl)] (4) and [(Cp*Ru)2B4H6(SPh)(Cl)] (5). On the other hand, reaction of 1 with Li[BH3(SePh)] led to the formation of the diruthenium analogue of hexaborane(10) nido-[(Cp*Ru)2B4H9(SePh)] (6), whereas Li[BH3(TePh)] yielded the capped nido-pentagonal-pyramidal [(Cp*Ru)2B4H6Te] (7). Compound 7 is a rare ruthenaborane cluster containing a heavier chalcogen element (Te). All the compounds were characterized by mass spectrometry and 1H, 1H{11B}, 11B{1H} and 13C{1H}NMR spectroscopy. The solid state X-ray structures of all the compounds were unequivocally established by crystallographic analysis. Additionally, the electronic properties of compound 2 were analyzed. © 2017 Elsevier B.V.

Journal of Organometallic Chemistry

Synthesis and characterization of diruthenaborane analogues of pentaborane(11) and hexaborane(10)

To build upon our earlier results of heterometallic metallaboranes employing metal carbonyls, we performed the reaction of nido-[(Cp*Rh)2B3H7] (1) (nido-1) with [M(CO)5·THF] (M = Mo or W) that yielded the trimetallic metallaborane clusters [(Cp*Rh)2M(CO)3(μ-CO)(μ3-BH)(B2H4)] (3: M = Mo; 4: M = W) having a capped borylene fragment and trimetallic triply bridging borylene complexes [(Cp*Rh)2(μ3-BH)(μ-CO)M(CO)5] (5: M = Mo; 6: M = W). The chemistry of trimetallic triply bridging borylene complexes (5 and 6) were explored with Lewis bases such as tert-butyl isocyanide and bisphosphine ligands. Photolysis of 5 and 6 with tert-butyl isocyanide yielded [(Cp*Rh)2(μ3-BH)(μ-CO)M(CO)4(CN-tBu)] (7: M = Mo; 8: M = W) and with phosphines, PPh2(CH2)nPPh2 (n = 1, 2) they resulted in the formation of [(Cp*Rh)2(μ3-BH)(μ-CO)M(CO)4((PPh2)2(CH2)n)] (9: n = 1, M = Mo; 10: n = 1, M = W; 11: n = 2, M = Mo; 12: n = 2, M = W). All the new compounds have been characterized in solution by mass spectrometry and NMR spectroscopic techniques. The structural aspects were unambiguously established by X-ray crystallographic analysis of 3–4 and 7–10. © 2018 Elsevier B.V.

Synthesis and ligand substitution of tri-metallic triply bridging borylene complexes

Treatment of a dirhodium analogue of pentaborane(9), [(Cp*Rh)2B3H7] (nido-1; Cp* = η5-C5Me5), with [Fe2(CO)9] at room temperature led to the formation of [(Cp*Rh)2Fe(CO)3(µ-CO)B3H2Cl] (2) and the metal-rich metallaborane [(Cp*Rh)2Fe(CO)3Fe(CO)2(µ-CO)2B2H2] (3). When the same reaction was carried out at moderate temperature, two metal-rich metallaboranes, [(Cp*Rh)3Fe(CO)2(µ3-CO)2B2HX] 4 (X = H) and 5 (X = Cl), and a heterometallic µ9-boride cluster, [(Cp*Rh)3(RhCO)3Fe(CO)3(µ-CO)3B3H2] (6), were obtained. Compounds 4 and 5 can be viewed as cubane clusters with 62 cluster valence electrons (cves) and five metal–metal bonds. In another reaction, the treatment of nido-1 with [Mn2(CO)10] yielded the heterometallic µ9-boride cluster [(Cp*Rh)3Rh(CO)2{Mn(CO)3}2B4H3] (7). The cluster cores of both 6 and 7 are comprised of tricapped trigonal prisms containing a µ9-B atom bonded to seven/six metals and two/three boron atoms, respectively. All the new compounds have been characterized by mass spectrometry, IR, 1H, 11B{1H}, and 13C{1H} NMR spectroscopy, and X-ray crystallographic analysis. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

European Journal of Inorganic Chemistry

Metal-Rich Metallaboranes: Structures and Geometries of Heterometallic µ9-Boride Clusters

We present the results of our investigation of a thermally driven cluster expansion of rhodaborane systems with BH 3·THF. Four novel rhodaborane clusters, for example, nido-[(CpRh) 2B 6H 10], 1; nido-[(CpRh)B 9H 13], 2; nido-[(CpRh) 2B 8H 12], 3; and nido-[(CpRh) 3B 8H 9(OH) 3], 4 (Cp* = η 5-C 5Me 5), have been isolated from the thermolysis of [CpRhCl 2] 2 and borane reagents in modest yields. Rhodaborane 1 has a nido geometry and is isostructural with [B 8H 12]. The low temperature 11B and 1H NMR data demonstrate that compound 1 exists in two isomeric forms. The framework geometry of 2 and 3 is similar to that of [B 10H 14] with one BH group in 2 (3-position), and two BH groups in 3 (3, 4-positions) are replaced by an isolobal {CpRh} fragment. The 11 vertex cluster 4 has a nido structure based on the 12 vertex icosahedron, having three rhodium and eight boron atoms. In addition, the reaction of rhodaborane 1 with [Fe 2(CO) 9] yielded a condensed cluster [(CpRh) 2{Fe(CO) 3} 2B 6H 10], 5. The geometry of 5 consists of [Fe 2B 2] tetrahedron and an open structure of [(CpRh) 2B 6], 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. © 2012 American Chemical Society.

Journal	Angewandte Chemie - International Edition
ISSN	14337851
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