Borole Ligand Research Articles

Agostic hydrogen atoms versus cobalt-cobalt multiple bonding in binuclear borole cobalt carbonyls

The (C4H4BH)2Co2(CO)n (n = 4, 3, 2, 1) systems have been examined by density functional theory for comparison with the analogous (C4H4BCH3)2Co2(CO)n systems. For the tetracarbonyl (C4H4BH)2Co2(CO)4 a higher energy unbridged structure is found at ∼7 kcal/mol above the lowest energy doubly bridged structure similar to (C4H4BCH3)2Co2(CO)4. The lowest energy structures for the unsaturated derivatives (C4H4BH)2Co2(CO)n (n = 3, 2, 1) have bridging borole ligands with agostic hydrogen atoms from their B–H groups to a cobalt atom. Structures without agostic hydrogens analogous to the low-energy structures for the corresponding methylborole derivatives (C4H4BCH3)2Co2(CO)n are higher energy (C4H4BH)2Co2(CO)n structures.

Bridging hydrogen atoms versus iron–iron multiple bonding in binuclear borole iron carbonyls

The geometries and energetics of the binuclear unsubstituted borole iron carbonyls (C4H4BH)2Fe2(CO)n (n=5, 4, 3, 2, 1) have been studied by density functional theory for comparison with the previously studied related substituted borole iron carbonyls (C4H4BR)2Fe2(CO)n [R=CH3, (CH3)2N] having different substituents on the boron atoms. The lowest energy (C4H4BH)2Fe2(CO)n (n=5, 4, 3) structures have terminal borole ligands related to those in the (C4H4BR)2Fe2(CO)n [R=CH3, (CH3)2N] systems as well the isoelectronic (η5-C5H5)2Mn2(CO)n systems. However, the lowest energy structure of the dicarbonyl (C4H4BH)2Fe2(CO)2 is an unusual quintet spin state structure with one of the borole ligands bridging the central Fe2 unit by forming a three-center two-electron BHFe bond to one iron atom as well as functioning as a pentahapto ligand to the other iron atom. For the (C4H4BR)2Fe2(CO)n [R=CH3, (CH3)2N] systems the tricarbonyls (n=3) having formal FeFe triple bonds of lengths ∼2.2Å analogous to the experimentally known (η5-Me5C5)2Mn2(μ-CO)3 structure appear to be favorable structures. An analogous (C4H4BH)2Fe2(μ-CO)3 structure is found for the unsubstituted borole ligand. However, this structure appears to be disfavored relative to disproportionation into (C4H4BH)2Fe2(CO)n+1+(C4H4BH)2Fe2(CO)n−1.

Metallacarboranes and triple-decker complexes with the (C 4Me 4)Pt fragment

Complex Cp∗PtCl 2 (Cp∗ = η-C 4Me 4) reacts with the carborane anions [7,8-C 2B 9H 11] 2− and [9-SMe 2-7,8-C 2B 9H 10] − giving platinacarboranes Cp∗Pt(η-7,8-C 2B 9H 11) ( 1) and [Cp∗Pt(η-9-SMe 2-7,8-C 2B 9H 10)] + ( 2), respectively. Reactions of the [Cp∗Pt] 2+ fragment (as a labile nitromethane solvate) with the sandwich compounds Cp∗Fe(η-C 5H 3Me 2BMe) and Cp∗Rh(η 5-C 4H 4BPh) afford the triple-decker cations [Cp∗Pt(μ-η:η-C 5H 3Me 2BMe)FeCp∗] 2+ ( 3) and [Cp∗Pt(μ-η 5:η 5-C 4H 4BPh)RhCp∗] 2+ ( 4) with bridging boratabenzene and borole ligands. The structures of 1 and 3(CF 3SO 3) 2 were determined by X-ray diffraction.

Triple-decker complexes with a central borole ligand C4H4BR

The review summarizes the results of the recent author’s research on the synthesis of triple-decker complexes with bridging borole ligand. Electrophilic stacking of sandwich compounds with [(ring)M] n+ (n = 1, (ring)M = (C5R5)Ru, (C4Me4)Co; n = 2, (ring)M = Cp*Co, Cp*Rh, etc.) cationic fragments were used as a general method of synthesis of the complexes. The influence of the substituent at the boron atom on the course of stacking reactions is discussed. The spectral, structural, and electrochemical properties of the complexes synthesized are also considered.

Stacking reactions of the borole complex Cp*Rh(η5-C4H4BPh) with the dicationic fragments [Cp*M]2+ (M = Rh or Ir)

The reaction of the (borole)rhodium iodide complex [(η-C4H4BPh)RhI]4 with Cp*Li afforded the sandwich compound Cp*Rh(η-C4H4BPh) (4). The reactions of compound 4 with the solvated complexes [Cp*M(MeNO2)3]2+(BF 4 − )2 gave triple-decker cationic complexes with the central borole ligand [Cp*Rh(η-η5:η5-C4H4BPh)MCp*]2+(BF 4 − )2 (M = Rh (5) or Ir (7)). The structure of complex 4 was established by X-ray diffraction.

The first metallacarborane triple-decker complexes with a bridging borole ligand

The (borole)iodide complex [(η 5-C 4H 4BPh)RhI] 4 reacts with the carborane anion [Carb′] − (Carb′ = 9-SMe 2-7,8-C 2B 9H 10) giving (Carb′)Rh(η 5-C 4H 4BPh) ( 2). Reactions of 2 with dicationic fragments [LM] 2+ afford the μ-borole triple-decker complexes [(Carb′)Rh(μ-η 5:η 5-C 4H 4BPh)ML] 2+ [LM = Cp ∗Ir ( 4), (Carb′)Rh ( 7)] or the arene-type complexes [(Carb′)Rh(μ-η 5:η 6-C 4H 4BPh)ML] 2+ [LM = Cp ∗Rh ( 3), (Carb′)Ir ( 8)]. The structure of 4(BF 4) 2 was determined by X-ray diffraction.

Rhodium-containing triple-decker complexes with a central borole ligand

Triple-decker complexes with a bridging borole ligand (C 4H 4BPh)Rh(μ-C 4H 4BPh)ML (ML = RuCp, 2a; RuCp ∗, 2b; FeCp ∗, 3; Co(C 4Me 4), 4; Ir(cod), 5) were synthesized by stacking reactions of [Rh(C 4H 4BPh) 2] − ( 1) with cationic [ML] + fragments. The structures of 2a, b and (C 4H 4BPh)Rh(μ-C 4H 4BPh)Rh(C 4H 4BPh) ( 6) were determined by X-ray diffraction.

Reactions of the B‐Phenylborole Complex [CpRh(η5‐C4H4BPh)] with Metalloelectrophiles [(ring)M]2+

AbstractThirty‐valence‐electron dicationic triple‐decker complexes with a bridging borole ligand [CpRh(μ‐η5:η5‐C4H4BPh)M(ring)]2+ [M(ring) = CoCp* (3), IrCp* (6), Ru(η‐C6H3Me3‐1,3,5) (8a), Ru(η‐C6Me6) (8b)] were obtained by stacking reactions of [CpRh(η5‐C4H4BPh)] (2) with the corresponding half‐sandwich fragments [M(ring)]2+. Minor formation of arene‐type complexes [CpRh(μ‐η5:η6‐C4H4BPh)M(ring)]2+ was observed for M(ring) = IrCp* and Ru(arene). On the contrary, the arene‐type complex [CpRh(μ‐η5:η6‐C4H4BPh)RhCp*]2+ (5) was isolated as the sole product from the reaction of 2 with the fragment [RhCp*]2+; an intermediate formation of the triple‐decker complex [CpRh(μ‐η5:η5‐C4H4BPh)RhCp*]2+ (4) in this reaction was detected by 1H NMR spectroscopy. Heating 6 in nitromethane gives the symmetrical triple‐decker complex [Cp*Ir(μ‐η5:η5‐C4H4BPh)IrCp*]2+ (10). The cations were isolated as salts with the BF4– anion. The structures of 2, 5(BF4)2, 6(BF4)2 and 8a(BF4)2 were determined by X‐ray diffraction. The electrochemical properties of the complexes were also investigated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

ChemInform Abstract: Synthesis of Dicationic Triple‐Decker Complexes with a Central B‐Cyclohexyl‐Substituted Borole Ligand.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of dicationic triple-decker complexes with a central B-cyclohexyl-substituted borole ligand

Stacking reactions of the dicationic fragments [LM]2+ (LM = (η-C6H6)Ru, (η-C6H3Me3)Ru, or (η-C5Me5)Rh) with the complex (η-C5H5)Co(η-C4H4BCy) (Cy = cyclo-C6H11) afforded new dicationic 30-electron triple-decker complexes [(η-C5H5)Co(μ-η:η-C4H4BCy)ML](BF4)2 containing a cyclohexyl-substituted borole ligand in the central position.

Heterometallic complexes with borole ligands †‡

The borole-containing carbonylmetalates [(η-C4H4BPh)Re(CO)3]– ([Re]–) and [(η-C4H4BPh)Fe(CO)2H]– ([Fe]–) were used for the synthesis of heterometallic complexes with Re–Hg, Re–Cu, Re–Ag, Re–Au or Fe–Pt metal–metal bonds, respectively. The complex [Re]–Hg–[Re] 1 was characterized by X-ray diffraction and contains a linear metal chain. In the presence of HgCl2, redistribution reactions were observed, leading to [Re]–Hg–Cl 2 which was independently prepared from [Re]– and an excess of HgCl2. The reaction of [Fe]– with trans-[PtBr2(4-Mepy)2] (4-Mepy = 4-methylpyridine) afforded the trinuclear complex trans-[Pt[Fe]2(4-Mepy)2] 6 which was characterized by X-ray diffraction and contains two hydrido ligands which bridge the Fe–Pt bonds.

Tantalum Borollide Trichloride: A Versatile Entry into Tantalum Borollide Complexes

The reaction of Li2[C4H4B-N(CHMe2)2]·THF with 2 equiv of AlCl3 and 1 equiv of TaCl5 gives mononuclear [C4H4B-N(CHMe2)2]TaCl3 (1) in 47% yield. Alkylation of 1 with 3 equiv of MeMgCl gives methylated species in conjunction with the triple decker complex [C4H4B-N(CHMe2)2]Me2Ta[μ-C4H4B-N(CHMe2)2]TaMe4 (2). Monoalkylation is possible with LiCH(SiMe3)2 to give [C4H4B-N(CHMe2)2]TaCl2[CH(SiMe3)2] (3) which contains a Ta−Cα−H agostic interaction. Addition of H2NAr (Ar = 2,6-iPr2-C6H3) and triethylamine to 1 affords [C4H4B-NH(CHMe2)2]Ta(NAr)Cl2 (4). When 2 equiv of acetone are added to 1, the result is [C4H4B-NH(CHMe2)2]TaCl3[Me2C(O)CH2C(O)Me] (5). Reaction with LiCp* (Cp* = C5Me5) gives Cp*[C4H4B-N(CHMe2)2]TaCl2 (6). Reduction of 6 with Mg under an atmosphere of CO produces Cp*[C4H4B-N(CHMe2)2]Ta(CO)2 (7) which can be protonated with [H(OEt2)2][B(C6H3(CF3)2)4] to form {Cp*[C4H4B-NH(CHMe2)2]Ta(CO)2}{[B(C6H3(CF3)2)4]} (8). Reaction of 1 with excess LiCp‘ (Cp‘ = C5H4Me) affords Cp‘2[η2-C4H4B-N(CHMe2)2]TaCl (10) in which the borole ligand is η2-bound. Addition of Li[C5H5B-R] to 1 results in the formation of [C4H4B-N(CHMe2)2][C5H5B-R]TaCl2 (11, R = Ph; 12, R = NMe2). Methylation of 11 affords [C4H4B-N(CHMe2)2][C5H5B-Ph]TaMe2 (14), which reacts with H2 in the presence of PMe3 to give [C4H4B-N(CHMe2)2][C5H5B-Ph]Ta(PMe3)2 (16). For PEt3, the product is [C4H4B-N(CHMe2)2][C5H5B-Ph]Ta(H)2PEt3 (17). Reduction of 1 in the presence of PMe3 under nitrogen gives {[C4H4B-N(CHMe2)2](Me3P)2ClTaN}2 (18). Under an argon atmosphere the reduced product is [C4H4B-N(CHMe2)2]Ta(PMe3)3Cl (19). Complex 19 reacts with hydrogen to give the asymmetric dinuclear complex [([C4H4B-N(CHMe2)2]Ta(H)(PMe3)Cl)μ-H([C4H4B-N(CHMe2)2]Ta(PMe3)2Cl) (20). The crystallographic characterization of complexes 1, 3, 4, 5, 7, 10, 11, 12, 16, 17, 18, 19, and 20 is also presented. These data give important insight into the metal−borollide relationship under a variety of ligand environments and different oxidation states. They also allow for an estimation of the contribution from the possible resonance forms.

Construction of a Borole Ligand from Coordinated Diene and B(C6F5)3via Successive C−H Activation Steps: A Case of Catalyst Self-Activation

Construction of a Borole Ligand from Coordinated Diene and B(C₆F₅)₃via Successive C−H Activation Steps: A Case of Catalyst Self-Activation

Heterometallic Borole Complexes of Iron and Gold

The first heterometallic borole complexes of Fe and Au have been prepared by reaction of [HFe{η5-(1-phenylborole)}(CO)2]- (1) with [AuCl(PPh3)] in CH2Cl2, and the crystal structure of [(OC)2{η5-(1-phenylborole)}Fe{Au(PPh3)}2] (2) reveals an interesting orientation of the borole ligand. This complex reacts with [AuCl(PPh3)]/TIPF6 in CH2Cl2 to give the new cationic FeAu3 cluster [(OC)2{η5-(1-phenylborole)}Fe{Au(PPh3)}3]PF6 (4) which has a tetrahedral metal core, as established by a wide angle X-ray scattering study.

Borole Derivatives. 22. Iodine Degradation of the Triple-Decker Complexes (μ-C4H4BR)[Rh(C4H4BR)]2 (R = Ph, Me): Synthesis and Structural Characterization of Heterocubanes [Rh(μ3-I)(C4H4BR)]4 and of Bis(borole)rhodium Complexes RhI(C4H4BR)21

The triple-decker complexes (μ-C4H4BR)[Rh(C4H4BR)]2 (R = Ph, Me) (1) react with elemental iodine in toluene or dichloromethane to produce heterocubanes [Rh(μ3-I)(C4H4BR)]4 (2) and bis(borole)iodorhodium complexes RhI(C4H4BR)2 (3). The heterocubanes 2 exchange fragments RhI(C4H4BR) at rates which are fast with respect to the NMR time scale. The bis(borole) compounds 3 exist in an equilibrium of rotational isomers Cs-3 = C2v-3 with ΔRH = (−1.7 ± 0.2) kJ mol-1 and ΔRS = (−16 ± 1) J mol-1 K-1 for 3b. Activation parameters for the forward and reverse isomerization reactions are reported. The isomerization takes place by the mechanism of ring−ring rotation; this is demonstrated for 3b by TOCSY NMR spectra (1H NMR, −80 °C, mixing time 150 ms). Crystal structure determinations of 2a, 2b, and 3b are reported. The higher-energy isomer Cs-3b is found in the crystal of 3b. One borole ligand of Cs-3b is planar and η5-bonded with a normal Rh−B1 bond distance [236.7(6) pm]. The second ligand shows an unusual folding of ...

Electronic structure and bonding in triple-decker complexes of Mn and Co with borole ligand(s). Photoelectron spectra and molecular orbital calculations

The electronic structures of μ-(C 4H 4BCH 3) [Mn(CO) 3] 2 ( 5) and (C 4H 4BCH 3)Co-μ-(C 4H 4BCH 3)Mn(CO) 3 ( 6) have been derived by correlating the frontier MOs of the metal dimers [Mn(CO) 3] 2 2+ and [Co(C 4H 4BCH 3) Mn(CO) 3] 2+ with those of the central borole dianion C 4H 4BCH 3 2−. It is found that the interaction between the metal dimer and central borole ligand in 5 is stronger than in 6. This finding is supported by the He (I) PE spectra of 5 and 6. The interpretation of the spectra is based on INDO calculations, in which relaxation and correlation effects are taken into account by means of the Green's function method.

Sandwich and triple-decker complexes of cobalt and rhodium involving the borole ligand: photoelectron spectroscopic investigations and ab initio CI calculations on the photoelectron spectra

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSandwich and triple-decker complexes of cobalt and rhodium involving the borole ligand: photoelectron spectroscopic investigations and ab initio CI calculations on the photoelectron spectraIsabella Hyla-Kryspin, Rolf Gleiter, Gerhard E. Herberich, and Marc BenardCite this: Organometallics 1994, 13, 5, 1795–1805Publication Date (Print):May 1, 1994Publication History Published online1 May 2002Published inissue 1 May 1994https://doi.org/10.1021/om00017a042RIGHTS & PERMISSIONSArticle Views93Altmetric-Citations9LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Borole derivatives. 20. Three-center Fe-H-B bonding in (borole)(cyclopentadienyl)hydridoiron derivatives

(Borole)tricarbonyliron complexes Fe(CO)3(3,4-R12C4H2BPh) (3a, R1 = H; 3b, R1 = Me) react with cyclopentadiene under irradn. to give the hydrides CpFeH(3,4-R12C4H2BPh) (1a, b). Deprotonation by NaH in THF produces the borataferrocene anions [CpFe(3,4-R12C4H2BPh)]- (5a, b). These can be alkylated in the 2-/5-position by alkyl iodides in the presence of NaH to give 2,5-dialkyl hydride derivs.: e.g. CpFeH(2,5-R22C4H2BPh) [1c, R2 = Me, 1g, R2 = CH2:CH(CH2)4; 1h, R2 = (CH2)2CHCH2]. The structures of CpFeH(2,3,4,5-Me4C4BPh) (1d) and (C5H4Me)FeH(2,5-Me2C4H2BPh) (1f) as detd. by low-temp. x-ray diffraction show the presence of an Fe-H-B three-center bond with a weak B-H interaction. In soln. 1a establishes a mobile equil. between the ground state with Fe-H-B three-center bonding and the agostic isomer with Fe-H-C-2(C4H4B) three-center bonding with an estd. DG = 1.4 kcal/mol. The hydridic proton and the 2-/5-protons of the borole ring undergo fast intramol. exchange. A merry-go-round of the three H atoms involved with one hydrogen crossing the exo face of the borole ligand is proposed as an exchange mechanism. The bonding of CpFeH(C4H4BH) is analyzed by means of extended Hueckel calcns., which confirm the Fe-H-B three-center bonding. Exploratory extended Hueckel calcns. also support the existence of agostic isomers as well as the proposed exchange mechanism. Cyclic voltammetry revealed the existence of the 17e complex CpFe(C4H4BPh) (5a), which is characterized by its EPR and paramagnetic 1H NMR spectra. 1A reacts with CNBut to give the boracyclopentenyl complex CpFe(CNBut)(C4H5BPh) and, probably via the intermediate Fe(CNBut)(C4H4BPh)(C5H6), the borole complex Fe(CNBut)3(C4H4BPh) and 1 equiv of cyclopentadiene. Labeling expts. show that the shift of the hydride hydrogen to the borole and Cp ligands, resp., is an intramol. process. 1C reacts analogously.

Synthetic and mechanistic studies on tripledecker complexes with bridging 1 H-borole ligands

A mechanistic model for the nucleophilic degradation of tripledecker complexes like μ-(η 5-C 4H 4BPh)[Rh(η-C 4H 4BPh)] 2 is proposed. The rate-determining step is a lateral nucleophilic attack at one of the metal centres which is followed by fast addition of two further ligand molecules. The nucleophilic degradation of μ-(η 5-C 4H 4BPh)[Rh(η 5-C 4H 4BPh)] 2 by e.g. PMe 3, P(OMe) 3, CNBu t and NH 3 is reversible. Stacking reactions, mainly by means of electrophilic addition to 1-pheynylborataferrocene ion, provide a strategy for the synthesis of new heterobimetallic tripledecker complexes including e.g. the group 5 compounds μ-(η 5-C 4H 4BPh)[M(CO) 4](FeCp) (M = V, Nb, Ta) and the group 6 anions [μ-(η 5-C 4H 4BPH)[M(CO) 3](FeCp)] − (M = Cr, Mo, W). In this context the electron count of tripledecker complexes is discussed. In the presence of strong σ-donor/gp-aceptor ligands as outer ligands these complexes obey a strict 30e rule. The combination of an electrophilic stacking reaction and a nucleophilic degradation reaction may result in a net ligand transfer. Examples demonstrate the transfer of borole ligands from Fe to Re, from Co to Ru and Ir via tripledecker intermediates.

Borole derivatives: XI. 1-(Diisopropylamino)borole as ligand in transition metal complexes. Crystal and molecular structures of cis-Cr(CO) 2(C 4H 4BNP 12) 2 and Mn(CO)(C 4H 4BNPr i2) 2

X-ray diffraction studies on two 1-(diisopropylamino)borole complexes, cis- Cr(CO) 2(C 4H 4BNr i 2) 2 (I) and Mn(CO)(C 4H 4BNPr i 2) 2 (II), are reported. The major changes caused by the presence of an amino substituent at the boron atom are the larger bending angles for the borole ligands (14.4° (av.) for I and 16.4° (av.) for II), increased slip distortions (19.5 pm for I and 13.6 pm for II), and lengthened metal-boron distances (CrB 258.7 pm (av.) and MnB 251.5 pm (av.)). These structural effects are largely caused by π-interactions between the boron and the amino group, and the aminoborole is essentially bonded as a diene ligand, with only weak direct metal-boron interaction. ESR data for II also show close similarity to corresponding diene complexes MnL(η 4-C 4H 6) 2 (L = CO, PMe 3).