Showing papers on "Carborane published in 2016"
TL;DR: This review deals with the redox properties and photoluminescence behavior of this collection of compounds, as well as their influence on the properties of materials and devices whose working principles are related to electron-transfer or electron-promotion phenomena.
Abstract: Icosahedral boranes, carboranes, and metallacarboranes are extraordinarily robust compounds with desirable properties such as thermal and redox stability, chemical inertness, low nucleophilicity, and high hydrophobicity, making them attractive for several applications such as medicine, nanomaterials, molecular electronics, energy, catalysis, environmental chemistry, and other areas. The hydrogen atoms in these clusters can be replaced by convenient groups that open the way to a chemical alternative to conventional "organic" or "organometallic" realms. Icosahedral boron cluster derivatives have been reviewed from different perspectives; however, there is a need for a review dedicated to the redox and photophysical characteristics of easily accessible borane and carborane derivatives, which are excellent materials for a wide range of applications. This review deals with the redox properties and photoluminescence behavior of this collection of compounds, as well as their influence on the properties of materials and devices whose working principles are related to electron-transfer or electron-promotion phenomena. We hope that this review will be of great value to boron cluster scientists and researchers working in the photoluminescence and electrochemistry fields who are interested in exploring the possibilities of these unique and promising systems.
355 citations
TL;DR: The development of a new class of phosphorescent zwitterionic bis(heteroleptic) Ir(III) compounds containing pyridyl ligands with weakly coordinating nido-carboranyl substituents is reported, suggesting that the use of a ligand framework containing aWeakly coordinating anionic component can provide a new avenue for designing efficient Ir( III)-based phosphorescent emitters.
Abstract: We report the development of a new class of phosphorescent zwitterionic bis(heteroleptic) Ir(III) compounds containing pyridyl ligands with weakly coordinating nido-carboranyl substituents. Treatment of phenylpyridine-based Ir(III) precursors with C-substituted ortho-carboranylpyridines in 2-ethoxyethanol results in a facile carborane deboronation and the formation of robust and highly luminescent metal complexes. The resulting nido-carboranyl fragments associate with the cationic Ir(III) center through primarily electrostatic interactions. These compounds phosphoresce at blue wavelengths (450–470 nm) both in a poly(methyl methacrylate) (PMMA) matrix and in solution at 77 K. These complexes display structural stability at temperatures beyond 300 °C and quantum yields greater than 40%. Importantly, the observed quantum yields correspond to a dramatic 10-fold enhancement over the previously reported Ir(III) congeners featuring carboranyl-containing ligands in which the boron cluster is covalently attached t...
137 citations
TL;DR: The synthesis and structure of the first 1,2-bis(NHSi)-substituted ortho-carborane (termed SiCCSi) is reported, and the strong donor character of the ligand enables [SiCCSi]NiBr2 to act as an outstanding precatalyst in the catalytic aminations of arenes, surpassing the activity of previously known molecular Ni-based precatalysts.
Abstract: The synthesis and structure of the first 1,2-bis(NHSi)-substituted ortho-carborane [(LSi:)C]2B10H10 (termed SiCCSi) is reported (NHSi=N-heterocyclic silylene; L=PhC(NtBu)2). Its suitability to serve as a reliable bis(silylene) chelating ligand for transition metals is demonstrated by the formation of [SiCCSi]NiBr2 and [SiCCSi]Ni(CO)2 complexes. The CO stretching vibration modes of the latter indicate that the SiII atoms in the SiCCSi ligand are even stronger σ donors than the PIII atoms in phosphines and CII atoms in N-heterocyclic carbene (NHC) ligands. Moreover, the strong donor character of the [SiCCSi] ligand enables [SiCCSi]NiBr2 to act as an outstanding precatalyst (0.5 mol % loading) in the catalytic aminations of arenes, surpassing the activity of previously known molecular Ni-based precatalysts (1–10 mol %).
129 citations
TL;DR: For the first time, nonclassical hydrogen (H)-bonding involving a B-H···π interaction is described utilizing both quantum chemical predictions and experimental realization, and quantum chemical calculations suggest that the interaction is electrostatic and the local (B)H·ring stretching force constant is as large as the H-bond stretching force Constant in the water dimer.
Abstract: For the first time, nonclassical hydrogen (H)-bonding involving a B–H···π interaction is described utilizing both quantum chemical predictions and experimental realization. In the gas phase, a B–H···π H-bond is observed in either B2H6···benzene (ΔE = −5.07 kcal/mol) or carborane···benzene (ΔE = −3.94 kcal/mol) complex at reduced temperatures. Ir-dimercapto-carborane complexes [Cp*Ir(S2C2B10H10)] are designed to react with phosphines PR3 (R = C6H4X, X = H, F, OMe) to give [Cp*Ir(PR3)S2C2B10H10] for an investigation of B–H···π interactions at ambient temperatures. X-ray diffraction studies reveal that the interaction between the carborane BH bonds and the phosphine aryl substituents involves a BH···π H-bond (H···π distance: 2.40–2.76 A). 1H NMR experiments reveal that B–H···π interactions exist in solution according to measured 1H{11B} signals at ambient temperatures in the range 0.0 ≤ δ ≤ 0.3 ppm. These are high-field shifted by more than 1.5 ppm relative to the 1H{11B} signals obtained for the PMe3 analog...
110 citations
TL;DR: The density functional theory calculations showed that the change in electron distribution between the aryl amino group and the carborane moiety indicates the intramolecular CT character, and the emission colour changes were attributed to the HOMO-LUMO energy gap controlled by the π-extension of the phenylene linker.
Abstract: Carborane-based donor–π–acceptor triads (D–π–A–π–D) bearing triarylamine moieties were synthesised. All the monomeric triads showed a blue-green emission in a dilute solution, which was assigned as an intramolecular charge-transfer (CT) emission. The intramolecular CT emission showed large Stokes shifts at a higher solvent polarity. The intramolecular CT emission further shifted to a longer wavelength with the increase in π-conjugation. Interestingly, a strong red emission was observed in highly concentrated solutions or in the solid state, which was assigned as an aggregation-induced emission (AIE). Moreover, the AIE strongly depended on solvent polarity. A large Stokes shift in AIE was attributed to the strong CT character. The changes in the dipole moment for the AIE state and monomer emission were evaluated using the Lippert–Mataga relationship. The density functional theory calculations showed that the change in electron distribution between the aryl amino group (highest occupied molecular orbital, HOMO) and the carborane moiety (lowest unoccupied molecular orbital, LUMO) indicates the intramolecular CT character, and the emission colour changes were attributed to the HOMO–LUMO energy gap controlled by the π-extension of the phenylene linker. The electrochemical properties such as oxidation and reduction potentials were consistent with theoretical calculation results. The emission properties were affected by two main factors: solvent polarity and solubility.
68 citations
20 May 2016
TL;DR: In this paper, the synthesis and structure of polyhedral boron hydride anions and their derivatives are reviewed, which demonstrate a wide variety of structural types relating to both the metal coordination environment and coordination modes.
Abstract: Synthesis and structure of silver and copper salts and complexes with polyhedral boron hydride anions, including closo-decaborate [B10H10]2−, closo-dodecaborate [B12H12]2−, 1-carba-closo- decaborate [1-CB9H10]−, carba-closo-dodecaborate [CB11H12]−, and cobalt bis(dicarbollide) [3,3′-Co(1,2-C2B9H11)2]− anions and their derivatives, are reviewed. The complexes demonstrate a wide variety of structural types, relating to both the metal coordination environment and coordination modes of boron hydride anions. The latter can range from strong coordination via the polyhedron triangular face including formation of 3c-2e MHB bonds in the case of the [B10H10]2− dianion, the structure of which contains two four-coordinated boron atoms, to very weak M…H interactions with the hydride atoms in the case of bulky [3,3′-Co(1,2-C2B9H11)2]− monoanion.
67 citations
TL;DR: A review of recent advances in this interesting research field can be found in this article, where a 3-dimensional relative of benzyne, 1,2-dehydro- o -carborane ( o -carboryne), has been utilized as a powerful synthon for generating a wide range of cage carbon functionalized o-carboranes over the past 25 years.
47 citations
TL;DR: This general and simple procedure provides a metal-free alternative for the synthesis of 3-(hetero)arylated-o-carboranes.
Abstract: A visible-light-mediated in situ generation of a boron-centered carboranyl radical (o-C2 B10 H11(.)) has been described. With eosin Y as a photoredox catalyst, 3-diazonium-o-carborane tetrafluoroborate [3-N2-o-C2B10H11][BF4] was converted into the corresponding boron-centered carboranyl radical intermediate, which can undergo efficient electrophilic substitution reaction with a wide range of (hetero)arenes. This general and simple procedure provides a metal-free alternative for the synthesis of 3-(hetero)arylated-o-carboranes.
45 citations
TL;DR: The reaction of Os3 (CO)10 (NCMe)2 with closo-o-C2 B10 H10 has yielded two interconvertible isomers that contains two triosmium triangles attached to the same carborane cage.
Abstract: The reaction of Os3 (CO)10 (NCMe)2 with closo-o-C2 B10 H10 has yielded two interconvertible isomers Os3 (CO)9 (μ3 -4,5,9-C2 B10 H8 )(μ-H)2 (1 a) and Os3 (CO)9 (μ3 -3,4,8-C2 B10 H8 )(μ-H)2 (1 b) formed by the loss of the two NCMe ligands and one CO ligand from the Os3 cluster. Two BH bonds of the o-C2 B10 H10 were activated in its addition to the osmium cluster. A second triosmium cluster was added to the 1 a/1 b mixture to yield the complex Os3 (CO)9 (μ-H)2 (μ3 -4,5,9-μ3 -7,11,12-C2 B10 H7 )Os3 (CO)9 (μ-H)3 (2) that contains two triosmium triangles attached to the same carborane cage. When heated, 2 was transformed to the complex Os3 (CO)9 (μ-H)(μ3 -3,4,8-μ3 -7,11,12-C2 B10 H8 )Os3 (CO)9 (μ-H) (3) by a novel opening of the carborane cage with loss of H2 .
42 citations
TL;DR: This work has synthesized and crystallized carboranes containing Br atoms in two different positions, namely, bound to C- and B-vertices, and found that halogen bonding in carborane can be much stronger than in organic architectures.
Abstract: Halogen bonds are a subset of noncovalent interactions with rapidly expanding applications in materials and medicinal chemistry. While halogen bonding is well known in organic compounds, it is new in the field of boron cluster chemistry. We have synthesized and crystallized carboranes containing Br atoms in two different positions, namely, bound to C- and B-vertices. The Br atoms bound to the C-vertices have been found to form halogen bonds in the crystal structures. In contrast, Br atoms bound to B-vertices formed hydrogen bonds. Quantum chemical calculations have revealed that halogen bonding in carboranes can be much stronger than in organic architectures. These findings open new possibilities for applications of carboranes, both in materials and medicinal chemistry.
42 citations
TL;DR: The syntheses of the first carboranyl N-heterocyclic carbene complexes with transition metals are reported, and it is indicated that replacement of an adamantyl group by a hydride substituted icosahedral carborane anion results in a 3.7% increase in %Vbur.
Abstract: The syntheses of the first carboranyl N-heterocyclic carbene complexes with transition metals are reported. Both unsymmetrical mono-anionic and symmetrical dianionic NHCs readily react with ClAuSMe2 to afford unusual zwitterionic and anionic Au(I) dimethyl sulfide adducts. The compounds are characterized by NMR, mass spectrometry, and single crystal X-ray diffraction studies. Percent buried volume (%Vbur) calculations indicate that replacement of an adamantyl group by a hydride substituted icosahedral carborane anion results in a 3.7% increase in %Vbur.
TL;DR: In this paper, the carborane-fused azaborolyl radical cation [{(Dipp)NC(But)C2B10H10}B(NHC)]•+ ([2]•+) is delocalized over the BNC unit and the two fused five-membered rings in 3 form a sort of π-conjugated system.
TL;DR: A combination of the electron-accepting properties of a carborane cage and steric enforcement of close interatomic contacts represent a new synthetic strategy for the activation of strong B-H bonds in carboranes.
Abstract: An unusual 12-vertex-closo-C2 B10 /12-vertex-nido-C2 B10 biscarborane cluster was synthesized through an unprecedented regioselective metal-free B-H activation by a sterically hindered P(III) center under mild conditions accompanied by cage-opening rearrangement. A combination of the electron-accepting properties of a carborane cage and steric enforcement of close interatomic contacts represent a new synthetic strategy for the activation of strong B-H bonds in carboranes.
TL;DR: A phosphine containing a 10-vertex carborane anion substituent and its subsequent ligation to a Rh(I) carbonyl complex is reported, characterized by NMR spectroscopy and a single crystal X-ray diffraction study.
TL;DR: The bonding of the carborane clusters to two stilbene units preserves their PL behavior in solution, but produces significant changes in the solid state, and iodinated species can be considered to be promising precursors for theranostic agents in which both imaging and therapeutic functions could possibly be combined.
Abstract: A set of triads in which o- and m-carborane clusters are bonded to two stilbene units through Ccluster−CH2 bonds was synthesized, and their structures were confirmed by X-ray diffraction. A study on the influence of the o- and m- isomers on the absorption and photoluminescence properties of the stilbene units in solution revealed no charge-transfer contributions in the lowest excited state, as confirmed by (TD)DFT calculations. The presence of one or two B−I groups in m-carborane derivatives does not affect the emission properties of the stilbenes in solution, probably due to the rather large distance between the iodo substituents and the fluorophore. Nevertheless, a significant redshift of the photoluminescence (PL) emission maximum in the solid state (thin films and powder samples) compared to solution was observed; this can be traced back to PL sensitization, most probably due to more densely packed stilbene moieties. Remarkably, the PL absolute quantum yields of powder samples are significantly higher than those in solution, and this was attributed to the restricted environment and the aforementioned sensitization. Thus, the bonding of the carborane clusters to two stilbene units preserves their PL behavior in solution, but produces significant changes in the solid state. Furthermore, iodinated species can be considered to be promising precursors for theranostic agents in which both imaging and therapeutic functions could possibly be combined.
TL;DR: The strongest carborane acid, H(CHB11F11), protonates CO2 while traditional mixed Lewis/Brønsted superacids do not and is therefore the strongest known acid.
Abstract: The strongest carborane acid, H(CHB11F11), protonates CO2 while traditional mixed Lewis/Bronsted superacids do not. The product is deduced from IR spectroscopy and calculation to be the proton disolvate, H(CO2)2(+). The carborane acid H(CHB11F11) is therefore the strongest known acid. The failure of traditional mixed superacids to protonate weak bases such as CO2 can be traced to a competition between the proton and the Lewis acid for the added base. The high protic acidity promised by large absolute values of the Hammett acidity function (H0) is not realized in practice because the basicity of an added base is suppressed by Lewis acid/base adduct formation.
TL;DR: Versatile coordination of the ligands to Rh(I) is demonstrated, in which both NHC and carborane moieties covalently coordinate a metal centre.
TL;DR: In this paper, a robust conjugation with electron-accepting ability of o-carborane was proposed. But it was not shown that the electronic delocalization should occur on the rigid template.
TL;DR: A new family of amphiphilic biodegradable boron-enriched polycarbonates was synthesized by ring-opening polymerization of a carborane-installed cyclic carbonate monomer, and it was demonstrated that larger nanoparticles (PN150) were more easily subjected to protein adsorption and captured by the liver, and smaller nanoparticles were more likely to enter cancer cells and accumulate at the tumor site.
TL;DR: In this article, a simple and efficient method for selective cage B(3) multiple functionalization of o-carborane is described, which may serve as another efficient [18F]-radiolabeling method of carborane clusters for positron emission tomography applications.
Abstract: A simple and efficient method for selective cage B(3) multiple functionalization of o-carborane is described. Reaction of [3-N2-o-C2B10H11][BF4] with various kinds of nucleophiles gave a very broad spectrum of cage B(3)-substituted o-carborane derivatives, 3-X-o-C2B10H11 (X = OH, SCN, NH2, NO2, N3, CF3, PO(C6H5)2, etc). This reaction may serve as another efficient [18F]-radiolabeling method of carborane clusters for positron emission tomography applications.
TL;DR: In this article, a review describes the recent progress on the research of half-sandwich late transition metal complexes with functionalized carborane ligands, which are of great interest because of their rich coordination mode, novel reactivity and promising applications in a variety of important fields.
TL;DR: Two benzoxazine precursors bearing carborane moiety (1 and 2) were designed and synthesized successfully by the Mannich reaction of corresponding bisphenol (3 and 4) with aniline and formaldehyde in 1,4-dioxane.
Abstract: Two benzoxazine precursors bearing carborane moiety (1 and 2) were designed and synthesized successfully by the Mannich reaction of corresponding carborane bisphenol (3 and 4) with aniline and formaldehyde in 1,4-dioxane The obtained precursors were characterized by using multiple spectroscopic techniques including GPC, FTIR, 1H NMR, 13C NMR, and 11B NMR Nonisothermal DSC studies showed that precursor 1 owned lower apparent activation energies (Ea) than 2 The optimum curing processes of benzoxazine precursors were also obtained on the basis of DSC data TGA analyses manifested that the incorporation of carborane moiety endowed the obtained benzoxazine resins (cured 1 and 2) with excellent thermal stability and unique thermo-oxidative stability The Td data showed that the initial degradation of both cured 1 and 2 under nitrogen and air was postponed to some extent owing to the shielding effect of carborane moiety on adjacent organic fragments At higher temperature three-dimensional polymer networks with B-O-B and B–C linkages were formed as chars by the reaction of carborane cage with atmospheric moisture, degradation products such as phenolic hydroxyl, and oxygen (under air) Under nitrogen this network hindered the motion of radicals formed at elevated temperature and thus inhibited further polymer degradation processes While under air, the formed boron-rich networks could hardly be further oxidized into carbon dioxide so that the carborane-containing benzoxazine resins also showed very high char yields © 2016 Wiley Periodicals, Inc J Appl Polym Sci 2016, 133, 43488
TL;DR: Examination of the Ir complexes in the transfer hydrogenation of acetophenone to 1-phenylethanol reveals that cyclometallation of the carborane moiety is important for catalytic efficacy, indicating a bifunctional mechanism and involvement of the dicarbadodecaborane anion.
Abstract: Imidazolium salts linked by an ethyl tether to closo-dicarbadodecaboranes were reacted with [IrCp*Cl2]2, [RhCp*Cl2]2 or [Ru(p-cymene)Cl2]2 in the presence of Ag2O to prepare complexes of the type [MCp*(NHC)Cl2] (M = Ir, Rh; NHC = N-heterocyclic carbene) or [Ru(p-cymene)(NHC)Cl2]. When the NHC contained an N-tBu substituent, C–H activation of the tBu and subsequent alkyl coordination was observed at Ir. Coordination of the closo-dicarbadodecaborane moiety to Ir was possible to give 7-membered metallacycles, coordinated through the carbenic carbon of the NHC and either a carbon atom or a boron atom of the carborane. Examination of the Ir complexes in the transfer hydrogenation of acetophenone to 1-phenylethanol reveals that cyclometallation of the carborane moiety is important for catalytic efficacy, indicating a bifunctional mechanism and involvement of the dicarbadodecaborane anion.
TL;DR: Several stable internally charge-compensated zwitterionic complexes were obtained and characterized and an attempt to measure the dipole moments in solution failed due to insufficient solubility in solvents of low polarity.
Abstract: The anionic nitriles 1-R-12-NC–CB11H10– (R = H, CH3, I, COOH), 12-NC-1-H–CB11Me10–, and 12-NC-1-H–CB11F10– were prepared, and three of them were examined for complex formation with (Et3P)2Pt(II) and (Et3P)2Pd(II). Several stable internally charge-compensated zwitterionic complexes were obtained and characterized. RI-BP86/SV(P) calculations suggest that their dipole moments exceed 20 D. An attempt to measure the dipole moments in solution failed due to insufficient solubility in solvents of low polarity.
04 May 2016
TL;DR: In this article, the synthesis and coordination chemistry of a series of carboranyl ligands containing N,O donors are summarized and the properties of such complexes are described in detail.
Abstract: This review summarizes the synthesis and coordination chemistry of a series of carboranyl ligands containing N,O donors. Such carborane-based ligands are scarcely reported in the literature when compared to other heteroatom-containing donors. The synthetic routes for metal complexes of these N,O-type carborane ligands are summarized and the properties of such complexes are described in detail. Particular attention is paid to the effect that the incorporation of carboranes has into the coordination chemistry of the otherwise carbon-based ligands and the properties of such materials. The reported complexes show a variety of properties such as those used in magnetic, chiroptical, nonlinear optical, catalytic and biomedical applications.
TL;DR: A unique mechanism for this fluxionality is proposed and is shown to be fully consistent with the observed fluxionsality or nonfluxionality of a series of previously reported 14-vertex dicobaltacarboranes.
Abstract: Two-electron reduction of 1,1'-bis(o-carborane) followed by reaction with [Ru(η-mes)Cl2 ]2 affords [8-(1'-1',2'-closo-C2 B10 H11 )-4-(η-mes)-4,1,8-closo-RuC2 B10 H11 ]. Subsequent two-electron reduction of this species and treatment with [Ru(η-arene)Cl2 ]2 results in the 14-vertex/12-vertex species [1-(η-mes)-9-(1'-1',2'-closo-C2 B10 H11 )-13-(η-arene)-1,13,2,9-closo-Ru2 C2 B10 H11 ] by direct electrophilic insertion, promoted by the carborane substituent in the 13-vertex/12-vertex precursor. When arene=mesitylene (mes), the diruthenium species is fluxional in solution at room temperature in a process that makes the metal-ligand fragments equivalent. A unique mechanism for this fluxionality is proposed and is shown to be fully consistent with the observed fluxionality or nonfluxionality of a series of previously reported 14-vertex dicobaltacarboranes.
TL;DR: The 10-vertex carborane cage was introduced in this article as a new fundamental spacer type in PCP chemistry, due to a combination of a lower steric demand compared to the 12-vertices analogue, a preferred orientation angle of 45° between the carboxylate planes and a moderately low rotation barrier.
Abstract: 1,10-Dicarboxy-1,10-dicarba-closo-decaborane, a classical dicarboxylate spacer ligand type similar to the prototypical terephthalic acid, proved to be different not only from the latter, but also from its closest relative compound, 1,12-dicarboxy-closo-1,12-dicarbadecaborane, with regard to the topology of its derived PCPs. Highly porous and robust compounds of zinc (rob net) and cobalt (‘quasi’ pcu) as well as a topologically unexpected copper compound (lvt) define the individuality of the 10-vertex carborane cage as a new fundamental spacer type in PCP chemistry. A combination of a lower steric demand compared to the 12-vertex analogue, a preferred orientation angle of 45° between the carboxylate planes and a moderately low rotation barrier are held responsible for the uniqueness of the 10-vertex analogue.
TL;DR: Using infrared (IR) spectroscopy and density functional theory (DFT) calculations, interaction of CO with the strongest known pure Brønsted carborane superacids, H(CHB11Hal11) (Hal = F, Cl), was studied.
Abstract: Using infrared (IR) spectroscopy and density functional theory (DFT) calculations, interaction of CO with the strongest known pure Bronsted carborane superacids, H(CHB11Hal11) (Hal = F, Cl), was studied. CO readily interacted at room temperature with H(CHB11F11) acid, forming a mixture of bulk salts of formyl and isoformyl cations, which were in equilibrium An(-)H(+)CO COH(+)An(-). The bonding of CO to the surface Bronsted centers of the weaker acid, H(CHB11Cl11), resulted in breaking of the bridged H-bonds of the acid polymers without proton transfer (PT) to CO. The binding occurred via the C atom (blue shift ΔνCO up to +155-167 cm(-1), without PT) or via O atom (red shift ΔνCO up to -110 cm(-1), without PT) always simultaneously, regardless of whether H(+) is transferred to CO. IR spectra of all species were interpreted by B3LYP/cc-pVQZ calculations of the simple models, which adequately mimic the ability of carborane acids to form LH(+)CO, LH(+)CO, COH(+)L, and COH(+)L compounds (L = bases). The CO bond in all compounds was triple. Acidic strength of the Bronsted centers of commonly used acid catalysts, even so-called superacidic catalysts, is not sufficient for the formation of the compounds studied.
TL;DR: In this article, the structure of [Me 3 NH][7-(1′,2′- closo -C 2 B 10 H 11 -1′-)-9-X-7,8- nido -c 2 B 9 H 10 ] was determined by single-crystal X-ray diffraction.
TL;DR: The results suggest that an important factor in a 3,1,2 to 4, 1,2 isomerisation is the relief gained from steric crowding, whereas a 3-1, 2 to 2,1-8 isomerization appears to be favoured by strongly electron-donating ligands on the metal.
Abstract: Metalation of the [7-(1'-1',2'-closo-C2B10H11)-7,8-nido-C2B9H10](2-) dianion with various {NiPP(2+)} or {NiP2(2+)} fragments (PP = chelating diphosphine; P = monodentate phosphine or phosphite) leads either to unisomerised 3,1,2-NiC2B9 species or to isomerised 4,1,2-NiC2B9 or 2,1,8-NiC2B9 species, all with a pendant C2B10 substituent. The products [1-(1'-1',2'-closo-C2B10H11)-3-dppe-3,1,2-closo-NiC2B9H10] (1), [2-(1'-1',2'-closo-C2B10H11)-4-dppe-4,1,2-closo-NiC2B9H10] (2), [8-(1'-1',2'-closo-C2B10H11)-2-dmpe-2,1,8-closo-NiC2B9H10] (3), [1-(1'-1',2'-closo-C2B10H11)-3,3-(PMe3)2-3,1,2-closo-NiC2B9H10] (4), [1-(1'-1',2'-closo-C2B10H11)-3,3-(PMe2Ph)2-3,1,2-closo-NiC2B9H10] (6), [1-(1'-1',2'-closo-C2B10H11)-3,3-{P(OMe)3}2-3,1,2-closo-NiC2B9H10] (9) and [1-(1'-1',2'-closo-C2B10H11)-2,2-{P(OMe)3}2-2,1,8-closo-NiC2B9H10] (10) were fully characterised spectroscopically and crystallographically, whilst [2-(1'-1',2'-closo-C2B10H11)-4,4-(PMePh2)2-4,1,2-closo-NiC2B9H10] (8) was characterised spectroscopically. Overall the results suggest that an important factor in a 3,1,2 to 4,1,2 isomerisation is the relief gained from steric crowding, whereas a 3,1,2 to 2,1,8 isomerisation appears to be favoured by strongly electron-donating ligands on the metal.