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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. [ABSTRACT FROM AUTHOR]

In a quest for efficient precursors for the synthesis of boratrane complexes of late transition metals, we have developed a useful synthetic method using [L′M(μ-Cl)Clx]2 as precursors (L′=η6-p-cymene, M=Ru, x=1; L′=COD, M=Rh, x=0 and L′=Cp*, M=Ir or Rh, x=1; COD=1,5-cyclooctadiene, Cp*=η5-C5Me5). For example, treatment of Na[(H3B)bbza] or Na[(H2B)mp2] (bbza=bis(benzothiazol-2-yl)amine; mp=2-mercaptopyridyl) with [L′M(μ-Cl)Clx]2 yielded [(η6-p-cymene)RuBH{(NCSC6H4)(NR)}2] (2; R=NCSC6H4), [{N(NCSC6H4)2}RhBH{(NCSC6H4)(NR)}2] (3; R=NCS-C6H4), [(η6-p-cymene)RuBH(L)2] (5; L=C5H4NS), and [Cp*MBH(L)2] (6 and 7; L=C5H4NS, M=Ir or Rh). In order to delineate the significance of the ligands, we studied the reactivity of [(COD)Rh(μ-Cl)]2 with Na[(H3B)bbza], which led to the formation of the isomeric agostic complexes [(η4-COD)Rh(μ-H)BHRh(C14H8N3S2)3], 4 a and 4 b, in parallel to the formation of 16-electron square-pyramidal rhodaboratrane complex 3. Compounds 4 a and 4 b show two different geometries, in which the Rh−B bonds are shorter than in the reported Rh agostic complexes. The new compounds have been characterized in solution by various spectroscopic analyses, and their structural arrangements have been unequivocally established by crystallographic analyses. DFT calculations provide useful insights regarding the stability of these metallaboratrane complexes as well as their M→B bonding interactions. [ABSTRACT FROM AUTHOR]

Several early-late heterodimetallaborane clusters have been isolated and structurally characterized through spectroscopic and crystallographic analysis. The thermolysis of [Cp2Zr(BH4)2] (Cp = η5-C5H5) with [Cp*IrB3H9] (Cp* = η5-C5Me5) and [(Cp*Rh)2B2H6] yielded arachno-[(Cp2Zr)(Cp*Ir)B3H9] ( 2) and arachno-[(Cp2Zr)(Cp*Rh)B4H10] ( 4), respectively. In a similar fashion, the reaction of [Cp2Hf(BH4)2] was performed with the same set of group 9 metallaboranes that led to the formation of arachno-[(Cp2Hf)(Cp*M′)B4H10] ( 5: M′ = Ir; 6: M′ = Rh). To the best of our knowledge, 2 is the first structurally characterized pentaborane(11) analogue containing zirconium, while the clusters 5 and 6 are the first examples with Hf in a hexaborane(12) core. The bonding between the Zr atoms and the boron ring was studied computationally by DFT methods, and 2 can be defined as a dimetallic analogue of arachno-B5H11 on the basis of the combined experimental and computational results. [ABSTRACT FROM AUTHOR]

Treatment of [M2(μ-Cl)2(cod)2] (M=Ir and Rh) with Na[H2B(bt)2] (cod=1,5-cyclooctadiene and bt=2-mercaptobenzothiazolyl) at low temperature led to the formation of dimetallaheterocycles [(Mcod)2(bt)2], 1 and 2 ( 1: M=Ir and 2: M=Rh) and a borate complex [Rh(cod){κ2-S,S′-H2B(bt)2}], 3. Compounds 1 and 2 are structurally characterized metal analogues of 1,5-cyclooctadiene. Metal-metal bond distances of 3.6195(9) Å in 1 and 3.6749(9) Å in 2 are too long to consider as bonding. In an attempt to generate the Ru analogue of 1 and 2, that is [(Rucod)2(bt)2], we have carried out the reaction of [Ru(Cl)2(cod)(CH3CN)2] with Na[H2B(bt)2]. Interestingly, the reaction yielded agostic complexes [Ru(cod)L{κ3-H,S,S′-H2B(bt)2}], 4 and 5 ( 4: L=Cl; 5: L=C7H4NS2). One of the key differences between 4 and 5 is the presence of different ancillary ligands at the metal center. The natural bond orbital (NBO) analysis of 1 and 2 shows that there is four lone pairs of electrons on each metal center with a significant amount of d character. Furthermore, the electronic structures and the bonding of these complexes have been established on the ground of quantum-chemical calculations. All of the new compounds were characterized by IR, 1H, 11B, 13C NMR spectroscopy, and X-ray crystallographic analysis. [ABSTRACT FROM AUTHOR]

Treatment of [Cp*IrCl2]2 (Cp* = pentamethylcyclopentadienyl) with Li[BH3(SePh)] at room temperature led to the isolation of a dimetala analogue of hexaborane(10), nido-[(Cp*Ir)(µ-SePh)2Ir{(Cp*Ir)SePh}B4H8] ( 1). Solid-state X-ray structure analysis of 1 showed an extended sandwich molecule with two iridium atoms between Cp* and a [B4Ir] ring. Further, in an effort to synthesize the Rh analogue of 1 under similar reaction conditions, we isolated arachno-[{(Cp*Rh)(µ-SePh)3}Rh(µ-SePh)B3H6] ( 2), a rhodium analogue of tetraboarane(10) in which the {RhB3} unit shows geometric equivalence with a metal π-allyl {MC3} species. Ir complex 1, having an Ir-Ir bond, can be considered similar to the dizinc sandwich complex [Cp*Zn-ZnCp*] in terms of the valence electron count at the metal centers. [ABSTRACT FROM AUTHOR]

Trinuclear complexes of group 6, 8, and 9 transition metals with a (μ3-BH) ligand [(μ3-BH)(Cp*Rh)2(μ-CO)M′(CO)5], 3 and 4 ( 3: M′=Mo; 4: M′=W) and 5- 8, [(Cp*Ru)3(μ3-CO)2(μ3-BH)(μ3-E)(μ-H){M′(CO)3}] ( 5: M′=Cr, E=CO; 6: M′=Mo, E=CO; 7: M′=Mo, E=BH; 8: M′=W, E=CO), have been synthesized from the reaction between nido-[(Cp*M)2B3H7] ( nido- 1: M=Rh; nido- 2: M=RuH, Cp*=η5-C5Me5) and [M′(CO)5 ⋅thf] (M′=Mo and W). Compounds 3 and 4 are isoelectronic and isostructural with [(μ3-BH)(Cp*Co)2(μ-CO)M′(CO)5], (M′=Cr, Mo and W) and [(μ3-BH)(Cp*Co)2(μ-CO)(μ-H)2M′′H(CO)3], (M′′=Mn and Re). All compounds are composed of a bridging borylene ligand (B−H) that is effectively stabilized by a trinuclear framework. In contrast, the reaction of nido- 1 with [Cr(CO)5 ⋅thf] gave [(Cp*Rh)2Cr(CO)3(μ-CO)(μ3-BH)(B2H4)] ( 9). The geometry of 9 can be viewed as a condensed polyhedron composed of [Rh2Cr(μ3-BH)] and [Rh2CrB2], a tetrahedral and a square pyramidal geometry, respectively. The bonding of 9 can be considered by using the polyhedral fusion formalism of Mingos. All compounds have been characterized by using different spectroscopic studies and the molecular structures were determined by using single-crystal X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

A combined experimental and quantum-chemical study of a series of homometallic metallaheteroboranes [(Cp*M)2-E6B2H2] (M = Rh or RuH; E = S or Se; Cp* = η5-C5Me5), which are analogues of 1,3-bishomocubane, is reported. The thermolysis of nido-[(Cp*Rh)2B3H7] (1) in the presence of S or Se powder in toluene yielded bishomocubane clusters [(Cp*Rh)2-(μ-E)2(μ3-E)4B2H2], (3: E = S; 4: E = Se). In a similar fashion, the treatment of nido-[(Cp*RuH)2B3H7] (2) with S or Se powder in p-xylene yielded [(Cp*Ru)2(μ-E)2(μ3-E)4B2H2] (5: E = S; 6: E = Se) and [(Cp*Ru)2(μ3-Se)(μ4-Se)B3H5] (7). One of the noteworthy features of 3-6 is the presence of an electronprecise trichalcogenoborato ligand. All of the compounds have been characterized by mass spectrometry; IR spectroscopy; and 1H, 11B, and 13C NMR spectroscopy. The structures of 3, 4, 6, and 7 were established unequivocally by Xray crystallographic analysis. Quantum-chemical calculations by DFT methods for 3, 4, and 6 showed reasonable agreement with the experimentally observed structural parameters. The large HOMO-LUMO gaps are consistent with the high stabilities of these complexes. [ABSTRACT FROM AUTHOR]

A high-yielding synthetic route for the preparation of group 9 metallaboratrane complexes [Cp*MBH(L)2], 1 and 2 ( 1, M=Rh, 2, M=Ir; L=C7H4NS2) has been developed using [{Cp*MCl2}2] as precursor. This method also permitted the synthesis of an Rh-N,S-heterocyclic carbene complex, [(Cp*Rh)(L2)(1-benzothiazol-2-ylidene)] ( 3; L=C7H4NS2) in good yield. The reaction of compound 3 with neutral borane reagents led to the isolation of a novel borataallyl complex [Cp*Rh(L)2B{CH2C(CO2Me)}] ( 4; L=C7H4NS2). Compound 4 features a rare η3-interaction between rhodium and the B-C-C unit of a vinylborane moiety. Furthermore, with the objective of generating metallaboratranes of other early and late transition metals through a transmetallation approach, reactions of rhoda- and irida-boratrane complexes with metal carbonyl compounds were carried out. Although the objective of isolating such complexes was not achieved, several interesting mixed-metal complexes [{Cp*Rh}{Re(CO)3}(C7H4NS2)3] ( 5), [Cp*Rh{Fe2(CO)6}(μ-CO)S] ( 6), and [Cp*RhBH(L)2W(CO)5] ( 7; L=C7H4NS2) have been isolated. All of the new compounds have been characterized in solution by mass spectrometry, IR spectroscopy, and 1H, 11B, and 13C NMR spectroscopies, and the structural types of 4- 7 have been unequivocally established by crystallographic analysis. [ABSTRACT FROM AUTHOR]

Building upon our earlier results on the synthesis of electron-precise transition-metal-boron complexes, we continue to investigate the reactivity of pentaborane(9) and tetraborane(10) analogues of ruthenium and rhodium towards thiazolyl and oxazolyl ligands. Thus, mild thermolysis of nido-[(Cp*RuH)2B3H7] ( 1) with 2-mercaptobenzothiazole (2-mbtz) and 2-mercaptobenzoxazole (2-mboz) led to the isolation of Cp*-based (Cp*=η5-C5Me5) borate complexes 5 a, b [Cp*RuBH3L] ( 5 a: L=C7H4NS2; 5 b: L=C7H4NOS)) and agostic complexes 7 a, b [Cp*RuBH2(L)2], ( 7 a: L=C7H4NS2; 7 b: L=C7H4NOS). In a similar fashion, a rhodium analogue of pentaborane(9), nido-[(Cp*Rh)2B3H7] ( 2) yielded rhodaboratrane [Cp*RhBH(L)2], 10 (L=C7H4NS2). Interestingly, when the reaction was performed with an excess of 2-mbtz, it led to the formation of the first structurally characterized N,S-heterocyclic rhodium-carbene complex [(Cp*Rh)(L2)(1-benzothiazol-2-ylidene)] ( 11) (L=C7H4NS2). Furthermore, to evaluate the scope of this new route, we extended this chemistry towards the diruthenium analogue of tetraborane(10), arachno-[(Cp*RuCO)2B2H6] ( 3), in which the metal center possesses different ancillary ligands. [ABSTRACT FROM AUTHOR]

Thermolysis of an in situ generated intermediate [(Cp*Ta)2(BH3)2Cl2], 1 generated from the reaction of [Cp*TaCl4], (Cp* = η5-C5Me5) and [LiBH4·thf], in presence of [Ru3(CO)12] yielded pileo-[Cp*TaCl(μ-Cl)-B2H4Ru3(CO)8], 2 having two electrons fewer than seven pairs required for the observed square pyramidal geometry. Cluster 2 is the first example of an unsaturated cluster comprising early and late transition metals in a square pyramid core. This reaction also yielded [(Cp*Ta)2(B2H6)(B2H4Cl2)], 3 as a by-product. In addition, the reaction of [Cp*MoCl4] (Cp* = η5-C5Me5) with [LiBH4.thf] in presence of excess [MeI] at mild condition led to the isolation of periodinated dimolybdatetraborane [(Cp*Mo)2B4H3I5], 4 that hints a possible existence of [(Cp*Mo)2B4H8]. After the isolation of periodinated 4, we extended this chemistry towards the late transition metallaborane [(Cp*Rh)3B4H4], 5 using [PtBr2] as brominating source. Although all the attempts to isolate perbrominated rhodaborane failed, we have isolated partially brominated rhodaborane clusters [(Cp*Rh)3(BH)-(BBr)3], 6 and [(Cp*Rh)3(BH)3(BBr)], 7. All the compounds were characterized by IR and 1H, 11B and 13C NMR spectroscopy in solution, and the solid-state structures of 2, 4 and 6 were established by crystallographic analysis. [ABSTRACT FROM AUTHOR]

A series of novel Cp*-based (Cp*=η5-C5Me5) agostic, bis(σ-borate), and boratrane complexes have been synthesized from diruthenium and dirhodium analogues of pentaborane(9). The synthesis and structural characterization of the first neutral ruthenadiborane(6) analogue are also reported. This new route offers a very efficient method for the isolation of bis(σ-borate) and agostic complexes from diruthenapentaborane(9). [ABSTRACT FROM AUTHOR]

The recent achievements and progress in the field of high-nuclearity supraicosahedral metallaborane chemistry are reviewed and compared to those made in borane, carborane and metallacarborane chemistry. In contrast to metallacarboranes, characterized large supraicosahedral metallaboranes only adopt isocloso deltahedral structural arrangements with n vertices and a non-Wadean n skeletal-electron-pair count. This anomaly can be rationalized by the preference of metal atoms for 6-connect vertices present in the cluster cages. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A comparative reactivity study of two isoelectronic nido ‐ dimetallapentaboranes with 2 ‐ mercaptobenzothiazole demonstrates the influence of metal change from Group 8 to Group 9. The former leads to the formation of B ‐ agostic, whereas the later affords a boratrane complex. In addition, the first example of a structurally characterized N,S ‐ heterocyclic carbene complex of rhodium is reported. For more details see the Full Paper by S. Ghosh et al. on page 3640 ff. [ABSTRACT FROM AUTHOR]

Thermolysis of [Ru 3 (CO) 12 ] with an in-situ generated intermediate, obtained from the reaction of [Cp*MoCl 4 ] and [LiBH 4 .THF], led to the formation of [{Cp*Mo(CO) 2 }(μ 4 -B){Ru(CO) 3 } 3 (μ-H) 2 ], 2 and [{Cp*Mo(CO) 2 } 2 (μ 4 -B){Ru(CO) 3 } 2 (μ-H)], 3 (Cp* = η 5 -C 5 Me 5 ). In a similar fashion, when [Ru 3 (CO) 12 ] was thermalized with [(Cp*Rh) 2 B 2 H 6 ], obtained from a fast metathesis reaction of [Cp*RhCl 2 ] 2 , 4 and [LiBH 4 .THF], yielded a novel heterometallic boride cluster [(Cp*Rh)(μ 6 -B){Ru(CO) 3 } 4 {RuH(CO) 2 }], 5 . Both compounds 2 and 3 can be described as 50-cluster valence electron (cve) hetero-metallic boride clusters, in which the boron atom is in semi-interstitial position of a M 4 -butterfly geometry. Compound 5 contains 86 cluster valence-electrons, in which the boron atom is inside of an octahedral hole composed of one rhodium and five ruthenium atoms. Computational studies on the ground of density functional theory has been undertaken to analyze the bonding of 2 , 3 and 5 . The structural optimization yields geometries in agreement with the structure determinations and computed 11 B chemical shifts accurately reflect the observed shifts. The molecular orbital analysis of them shows that all the valence orbitals of boron have been participated in bonding and therefore provides the “encapsulation” picture of the boron atom. All the compounds have been characterized by IR and 1 H, 11 B, and 13 C NMR spectroscopy, and the geometries of the structures were unequivocally established by crystallographic analyses of compounds 2 , 3 and 5 . [ABSTRACT FROM AUTHOR]

Building on our earlier results, the condensation of rhodium polychlorides with borane reagents (LiBH 4 ·thf, BH 3 ·thf, BHCl 2 ·SMe 2 etc.), we continue to explore the chemistry of the same system with metal carbonyl compounds. As a result, the reaction of [(Cp*Rh) 2 B 2 H 6 ], generated from fast metathesis of [Cp*RhCl 2 ] 2 and LiBH 4 , with heavier group 8 metal carbonyl compounds, yielded [(Cp*Rh) 2 B 4 H 4 Rh{Cp*RhB 3 H 8 }], 1 , [(Cp*Rh)B 3 H 7 {Ru(CO) 2 }(Cp*RhCO) 2 ], 2 [(Cp*Rh) 2 B 3 H 3 {Ru(CO) 3 } 2 ], 3 and [(Cp*Rh) 2 {Os 4 (CO) 12 }(B)H], 4 . Further, these reaction also generated two mixed-metal tetrahedral hydrido clusters [(Cp*Rh){Os(CO) 3 } 3 (μ-H) 4 ], 5 and [(Cp*Rh) 2 {Os(CO) 3 } 2 (μ-CO) (μ-H) 2 ], 6 as minor products. Compound 1 is an octahedra and a square pyramid fused cluster, whereas for 2 a square pyramid and a triangle are fused through a vertex. Both 1 and 2 follow Mingos's formalism for fused clusters. Cluster 4 is an interstitial boride composed of one boron, two rhodium and four osmium atoms. Based on its compositions, compound 4 is a rare example of heteronuclear borides. All the compounds have been characterized by IR, 1 H, 11 B, 13 C NMR spectroscopy in solution and the solid state structures were established by crystallographic analysis of 1 – 5 . [ABSTRACT FROM AUTHOR]

• Syntheses and structural characterization of group 9 triple decker sandwich complexes comprising a planar 5-membered middle-deck with coinage metal. • Density functional theory calculations provided a well-defined picture about the bonding of these heterometallic triple decker complexes. • The experimental results have been accompanied and rationalized using DFT studies. Earlier accounts of triple-decker complexes comprising main group elements and transition metals in the middle-deck, motivated us to synthesize triple-decker complexes containing coinage metals in the middle-deck. As a result, we have explored the reactivity of open-cage nido ‑ [(Cp*M) 2 { μ -B 2 H 2 E 2 }], 1 – 3 (Cp* = η 5-C 5 Me 5 , 1 : M = Co, E = S ; 2 : M = Co, E = Se; 3 : M = Rh, E = Se) with [CuBr(SMe 2)]. All the reactions yielded triple-decker complexes, [(Cp*M) 2 { μ -B 2 H 2 E 2 CuBr}], 4 – 6 (4 : M = Co, E = S ; 5 : M = Co, E = Se; 6 : M = Rh, E = Se) having [CuBr] in the middle-deck. The removal of the SMe 2 ligand resulted in the formation of complexes 4 – 6 as a single product. These complexes are examples of triple-decker species having a planar 5-membered [B 2 E 2 Cu] (E = S or Se) middle deck, in which the Cu exists as Cu(I) with an elongated M-Cu bonding interaction. Synthesized complexes have been established by ESI-MS, multinuclear nuclear magnetic resonance (NMR), and IR spectroscopy. The solid-state structures of 5 and 6 were confirmed by single-crystal X-ray diffraction analyses. Density functional theory (DFT) analyses of these complexes have presented a high electron donation from the [B 2 E 2 ] (E = S or Se) fragment of the middle ring to the axial metals and a weak bonding interaction between group 9 metals and Cu. [Display omitted] [ABSTRACT FROM AUTHOR]

Chloro-rhodaboratrane [(Cp*Rh)(L 2 )BCl] 4 has been synthesized from rhodium N,S-heterocyclic carbene complex [(Cp*Rh)(L 2 )(1-benzothiazol-2-ylidene)], 1 , (L = C 7 H 4 NS 2 ) and borane reagent BHCl 2 .SMe 2 . The Rh B bond in 4 is buttressed between two benzothiazolyl units in [3.3.0] fashion. The presence of B Cl bond allowed us to explore the chemistry of boratrane 4 at the boron centre. The reaction of ethynylmagnesium bromide with 4 yielded η 1 -vinyl complex [Cp*RhBr(C 2 H 2 )L] 5 , containing a five membered metallaheterocycle. In an objective to abstract the chloride, alike borylene synthesis from haloboryl, we performed the reaction of 4 with NaBAr F 4 that resulted the thiolato bridged bimetallic compound [Cp*Rh(μ-L) 3 RhCp*][BAr F 4 ] 6 (Ar F : C 6 H 3 (CF 3 ) 2 -3,5). [ABSTRACT FROM AUTHOR]

Thermolysis of an in situ generated intermediate [(Cp*Ta)2(BH3)2Cl2], 1 generated from the reaction of [Cp*TaCl4], (Cp* = η5-C5Me5) and [LiBH4·thf], in presence of [Ru3(CO)12] yielded pileo-[Cp*TaCl(μ-Cl)-B2H4Ru3(CO)8], 2 having two electrons fewer than seven pairs required for the observed square pyramidal geometry. Cluster 2 is the first example of an unsaturated cluster comprising early and late transition metals in a square pyramid core. This reaction also yielded [(Cp*Ta)2(B2H6)(B2H4Cl2)], 3 as a by-product. In addition, the reaction of [Cp*MoCl4] (Cp* = η5-C5Me5) with [LiBH4.thf] in presence of excess [MeI] at mild condition led to the isolation of periodinated dimolybdatetraborane [(Cp*Mo)2B4H3I5], 4 that hints a possible existence of [(Cp*Mo)2B4H8]. After the isolation of periodinated 4, we extended this chemistry towards the late transition metallaborane [(Cp*Rh)3B4H4], 5 using [PtBr2] as brominating source. Although all the attempts to isolate perbrominated rhodaborane failed, we have isolated partially brominated rhodaborane clusters [(Cp*Rh)3(BH)-(BBr)3], 6 and [(Cp*Rh)3(BH)3(BBr)], 7. All the compounds were characterized by IR and 1H, 11B and 13C NMR spectroscopy in solution, and the solid-state structures of 2, 4 and 6 were established by crystallographic analysis. [ABSTRACT FROM AUTHOR]

Abstract: The reactivity of two isoelectronic and isostructural metallaboranes, nido-[(Cp*Rh)2B6H10], 1 and nido-[(Cp*Ru)2B6H12], 2 with alkynes demonstrates that a change in metal from group 9 to group 8 creates difference in the reactivity pattern. Compound 1 catalyzes the cyclotrimerization of a variety of internal and terminal alkynes to yield 1,3,5- and 1,2,4-substituted benzene. In contrast, compound 2 shows no reactivity toward alkynes. A set of alkynes have been verified with nido-1 that yielded several benzene derivatives in satisfactory yields. [Copyright &y& Elsevier]