Synthesis and Chemistry of Ammonioethenyl and Phosphonioethenyl Ligands in Zwitterionic Dirhenium Carbonyl Complexes.

New zwitterionic dirhenium carbonyl complexes containing ammonioethenyl and phosphonioethenyl ligands have been synthesized and studied. The reaction of Re2(CO)10 with C2H2 and Me3NO yielded the dirhenium complex Re2(CO)9(NMe3) (6) and the new zwitterionic complex Re2(CO)9[η1-E-2-CH═CH(NMe3)] (7). Compound 6 was characterized structurally and was found to have a NMe3 ligand in an equatorial coordination site cis to a long Re-Re single bond, Re-Re = 3.0938(2) Å. Compound 7 can be obtained from the reaction of 6 with ethyne (C2H2) formally by the insertion of ethyne into the Re-N bond to the NMe3 ligand. Compound 7 contains a 2-trimethylammonioethenyl ligand, -CH═CH(+NMe3), that is formally a zwitterion having a positive charge on the nitrogen atom and a negative charge on the terminal carbon atom. When coordinated to rhenium by the terminal ethenyl carbon atom, the negative charge on the -CH═CH(+NMe3) carbon atom is formally transferred to the rhenium atom. The reaction of Re2(CO)10 with C2H2 and NEt3 in the presence of Me3NO yielded the new dirhenium complex Re2(CO)9[η1-E-2-CH═CH(NEt3)] (8) together with some 6 and 7. Compound 8 is structurally similar to 7, but it contains a NEt3 group in the ammonioethenyl ligand in the place of the NMe3 group in 7. Reactions of 7 with PMePh2 and PPh3 yielded the zwitterionic 2-arylphosphonioethenyl-coordinated dirhenium carbonyl complexes, Re2(CO)9[η1-E-2-CH═CH(PPh2Me)] (9a) and Re2(CO)9[η1-E-2-CH═CH(PPh3)] (9b), and the zwitterionic 1-phosphonioethenyl ligand in the dirhenium carbonyl complexes, Re2(CO)9[η1-1-C(PPh2Me)(═CH2)] (10a), Re2(CO)8[µ-η2-1-C(PPh2Me)(═CH2)] (11a), and Re2(CO)8[[µ-η2-1-C(PPh3)(CH2)] (11b). Compound 10a was converted to 11a and the new compound Re2(CO)7(µ-H)[µ-η2-1-(CH2C)P(Ph)(Me)(o-C6H4)], (12) by decarbonylation using Me3NO. Compound 12 contains an ortho-metalated phenyl ring. The new products 6,7, 8, 9b, 10a, 11a, 11b and 12 were characterized structurally by single-crystal X-ray diffraction analyses.

"Broken-hearted" carbon bowl via electron shuttle reaction: energetics and electron coupling.

Unprecedented one-step C[double bond, length as m-dash]C bond cleavage leading to opening of the buckybowl (π-bowl), that could provide access to carbon-rich structures with previously inaccessible topologies, is reported; highlighting the possibility to implement drastically different synthetic routes to π-bowls in contrast to conventional ones applied for polycyclic aromatic hydrocarbons. Through theoretical modeling, we evaluated the mechanistic pathways feasible for π-bowl planarization and factors that could affect such a transformation including strain and released energies. Through employment of Marcus theory, optical spectroscopy, and crystallographic analysis, we estimated the possibility of charge transfer and electron coupling between "open" corannulene and a strong electron acceptor such as 7,7,8,8-tetracyanoquinodimethane. Alternative to a one-pot solid-state corannulene "unzipping" route, we reported a nine-step solution-based approach for preparation of novel planar "open" corannulene-based derivatives in which electronic structures and photophysical profiles were estimated through the energies and isosurfaces of the frontier natural transition orbitals.

Synthesis, Structures, and Transformations of Bridging and Terminally-Coordinated Trimethylammonioalkenyl Ligands in Zwitterionic Pentaruthenium Carbido Carbonyl Complexes.

Reactions of the pentaruthenium cluster complexes Ru5(µ5-C)(CO)15 (5), Ru5(µ5-C)(CO)14[µ-η2-O═C(NMe2)](µ-H) (6), and Ru5(µ5-C)(CO)15Cl(µ-H) (7) with ethyne (C2H2) in the presence of Me3NO yielded the zwitterionic complexes Ru5(µ5-C)(CO)13[µ-η2-CHCH(NMe3)] (8), Ru5(µ5-C)(CO)13[µ-η2-O═C(NMe2)](η1-E-CH═CH(NMe3)(µ-H) (9), and Ru5(µ5-C)(CO)13Cl[η1-E-CH═CH(NMe3)](µ-H) (11). Each product contains a positively charged trimethylammonioethenyl ligand, CH═CH(+NMe3), that is derived from a 2-trimethylammonioethenide, -CH═CH(+NMe3), zwitterion that formally has a positive charge on the nitrogen atom and a negative charge on the terminal enyl carbon atom. The trimethylammonioethenyl ligand, CH═CH(+NMe3) in 8 is a η2-ligand that bridges a Ru-Ru bond on a basal edge of the square-pyramidal Ru5 cluster by a combination of σ + π cooordination of the ethenyl group. Compounds 9 and 11 each contain a η1-terminally coordinated [η1-E-CH═CH(+NMe3)] ligand with an E stereochemistry at the C═C double bond in open Ru5 cluster complexes. Compound 9 was decarbonylated to yield the compound Ru5(µ5-C)(CO)12[µ-η2-O═C(NMe2)][µ-η2-CH═CH(NMe3)](µ-H) (10) containing a η2-bridging CHCH(+NMe3) ligand. Compound 10 was converted back to 9 by the addition of CO. Two zwitterionic products, Ru5(µ5-C)(CO)14[η1-E-CH═CH(NMe3)] (12) and Ru5(µ5-C)(CO)15[η1-E-CH═CH(NMe3)] (13), were obtained by the addition of CO to 8. Compound 12 is an intermediate en route to 13. Compound 12 contains a terminally coordinated η1-E-CH═CH(+NMe3) ligand on one of the basal Ru atoms of a square-pyramidal Ru5 cluster. Compound 13 also contains a terminally coordinated η1-E-CH═CH(+NMe3) ligand on the wing-tip bridging Ru atom of a butterfly Ru4C cluster. Treatment of 6 with methyl propiolate (HC≡CCO2Me) yielded the zwitterionic complex Ru5(µ5-C)(CO)13[µ-η2-O═C(NMe2)][η1-E-(MeO2C)C═C(H)NMe3](µ-H) (14) that is structurally similar to 9 but contains a η1-E-(MeO2C)C═C(H)(+NMe3) ligand. Compound 14 eliminated the NMe3 group to yield the compounds Ru5(µ5-C)(CO)13[µ-η2-O═C(NMe2)][µ-η2-(MeO2C)HC═CH] (15) which contains a bridging methoxycarbonyl-substituted alkenyl ligand and the known compound Ru5(µ5-C)(CO)13[µ-η2-O═C(NMe2)](HNMe2)(µ-H) (16).

Zwitterionic Ammoniumalkenyl Ligands in Metal Cluster Complexes. Synthesis, Structures, and Transformations of Zwitterionic Trimethylammoniumalkenyl Ligands in Hexaruthenium Carbido Carbonyl Complexes.

Ru6(µ6-C)(CO)17, 1, has been shown to react with C2H2 when activated by Me3NO to yield the complexes Ru6C(CO)15(µ-η2-C2H2NMe3), 2, and Ru6C(CO)14(µ3-η4-C4H4NMe3), 3, containing a bridging 2-trimethylammoniumethenyl (C2H2NMe3) ligand and a triply bridging 4-trimethylammoniumbutadienyl (C4H4NMe3) ligand, respectively. Complexes 2 and 3 are formally zwitterionic by virtue of the positive charge on the nitrogen atom and a negative charge that must be assigned formally to the Ru6 cluster. Compound 2 added CO at room temperature to yield the compound Ru6C(CO)16(η1-E-C2H2NMe3), 4, that contains a terminally coordinated zwitterionic 2-trimethylammoniumethenyl ligand. Compounds 2 and 3 eliminated the NMe3 grouping, reversibly, when heated to yield the ethyne cluster complex Ru6C(CO)15(µ3-C2H2), 5, and the butadiendiyl cluster complex Ru6C(CO)14(µ3-η4-C4H4), 6, respectively. Compound 3 was obtained from 2 by addition of C2H2 in the presence of Me3NO. Reaction of 1 with methyl propiolate, HC2CO2Me, yielded the CO2CH3 substituted zwitterionic complex Ru6C(CO)16[η1-E-(C(CO2Me)═C(H)NMe3], 7, which contains the terminally coordinated zwitterionic ligand, C(CO2Me)═C(H)NMe3. Compound 7 eliminated NMe3 and CO when heated to 83 °C to yield the methoxycarbonyl alkyne complex Ru6C(CO)15[µ3-HC2(CO2Me)], 8. All new products, 2-8, were characterized structurally by single-crystal X-ray diffraction analyses.

Selective Activation of CH Bonds in Polar Vinyl Olefins and Coupling of Ethylene to the Activated Carbon Atoms in Pentaruthenium Complexes.

Ru5(µ5-C)(CO)15, 1, has been found to activate CH bonds in the vinyl group of polar vinyl olefins, methyl acrylate (MA), and vinyl acetate (VAc), through a cluster opening process to yield the complexes Ru5(µ5-C)(CO)14[η2-O═C(OMe)CH═CH](µ-H), 2, and Ru5(µ5-C)(CO)14[η2-(MeCO2)C═CH2](µ-H), 4, respectively. The site of CH activation is dependent on the olefin substituent. In 2, the site of CH activation is the ß-carbon atom of the vinyl group, while in 4 the CH activation has occurred exclusively at the α-carbon atom of the vinyl group. Compound 2 can be further decarbonylated to yield the complex Ru5(µ5-C)(CO)13[µ-η3-O═C(OMe)CHCH](µ-H), 3, which contains a η3-bridging acryloyl ligand. Compound 2 reacts with ethylene in the presence of Me3NO to yield three new Ru5 products: Ru5(µ5-C)(CO)13[η4-1- anti,3- syn-{O═C(OMe)}C(H)C(H)C(H)Me](µ-H), 5, Ru5(µ5-C)(CO)12(C2H4)[µ-η3- O═C(OMe)C(H)C(H)](µ-H), 6, and Ru5(µ5-C)(CO)13[η4- anti-O═C(OMe)H2CHCHCH2](µ-H), 7. Compounds 5 and 7 are isomers containing substituted η3-allyl ligands formed by the coupling of the ethylene to the CH-activated ß-carbon atom of the acryloyl ligand accompanied by some metal-mediated H-shifts. Compound 6 contains an uncoupled π-coordinated ethylene ligand. Compound 7 was isomerized to 5 thermally at 80 °C. Compound 4 reacts with ethylene in the presence of Me3NO to yield two new Ru5 products: Ru5(µ5-C)(CO)13[η4-1,1- anti- syn-[(O2CMe)C(Me)CHCH2](µ-H), 8, and Ru5(µ5-C)(CO)13[η4-1- anti-CH(Me)C(O2CMe)(CH2)](µ-H), 9. Compounds 8 and 9 both contain substituted η3-allyl ligands formed by the coupling of the ethylene to the CH-activated α-carbon atom of the vinyl acetyl ligand. Compound 8 was isomerized to 9 thermally at 80 °C. All new products were characterized structurally by single-crystal X-ray diffraction analyses.

Multiple activations of CH bonds in arenes and heteroarenes.

The activation of CH bonds in arenes and heteroarenes has attracted considerable attention in recent years. Examples of the activation of two or more CH bonds in arenes or heteroarenes are rare. In recent studies it has been found that certain polynuclear metal carbonyl complexes, such as Re2(CO)8(µ-C6H5)(µ-H), 1 and Os3(CO)10(NCMe)2, can react two or more times with selected arenes and heteroarenes through a series of CH activations to yield interesting new multiply-CH activated arenes and heteroarenes and can lead to the opening of ring systems in the case of heteroarenes. A summary of these novel reactions and new products is presented in this Frontier article.

Activation of Heteroaromatic C-H Bonds in Furan and 2,5-Dimethylfuran.

The reaction of Re2(CO)8(µ-C6H5)(µ-H) (1) with furan in CH2Cl2 at 40 °C yielded two new isomeric dirhenium compounds, Re2(CO)8(µ-η2-2,3-C4H3O)(µ-H) (2) and Re2(CO)8(µ-η2-3,2-C4H3O)(µ-H) (3), which contain a bridging (σ + π)-coordinated furyl ligand formed by activation of the C-H bond at the 2 and 3 positions of furan, respectively. Compound 3 is the first example of a compound formed by C-H bond activation at the 3 position of a furan ring. Compound 3 was isomerized to 2 by heating to 80 °C for 7 days. The reaction of compound 2 with a second 1 equiv of 1 in CH2Cl2 at 40 °C yielded the doubly metalated furan-bis[Re2(CO)8(µ-H)] product [Re2(CO)8(µ-H)]2(µ-η2-2,3-µ-η2-5,4-C4H2O) (4) containing a 2,5-furdiyl ligand that is (σ + π)-coordinated to two Re2(CO)8(µ-H) groups by activation of the C-H bond at the 5 position of the furyl ligand in 2. Compound 2 can also be formed as the major isomer, together with a small quantity of 4 by heating furan with Re2(CO)8(µ-H)[µ-η2-C(H)═C(H)Bu n] in toluene to reflux. An isomer of 4, [Re2(CO)8(µ-H)]2(µ-η2-2,3-µ-η2-4,5-C4H2O) (5), was obtained from the reaction of 3 with 1 through C-H activation at the 4 position of the furyl ring in 3. Compound 4 was also obtained from 5 by heating to 110 °C for 24 h. The reaction of 1 with 2,5-dimethylfuran (DMFUR) in CH2Cl2 at 40 °C yielded the new compound [Re2(CO)8(µ-η2-3,2-(CH3)2C4H2O)](µ-H) (6), which contains a bridging (σ + π)-coordinated 2,5-dimethylfuryl ligand formed by activation of the C-H bond at the 3 position of DMFUR. All of the new compounds were characterized structurally by single-crystal X-ray diffraction analysis.

Multiple C-H Bond Activations in Corannulene by a Dirhenium Complex.

The reaction of Re2 (CO)8 (µ-C6 H5 )(µ-H), 1 with corannulene (C20 H10 ) yielded the product Re2 (CO)8 (µ-H)(µ-η2 -1,2-C20 H9 ), 2 (65 % yield) containing a Re2 metalated corannulene ligand formed by loss of benzene from 1 and the activation of one of the CH bonds of the nonplanar corannulene molecule by an oxidative-addition to 1. The corannulenyl ligand has adopted a bridging η2 -σ+π coordination to the Re2 (CO)8 grouping. Compound 2 reacts with a second equivalent of 1 to yield three isomeric doubly metalated corannulene products: Re2 (CO)8 (µ-H)(µ-η2 -1,2-µ-η2 -10,11-C20 H8 )Re2 (CO)8 (µ-H), 3 (35 % yield), Re2 (CO)8 (µ-H)(µ-η2 -2,1-µ-η2 -10,11-C20 H8 )Re2 (CO)8 (µ-H), 4 (12 % yield), and Re2 (CO)8 (µ-H)(µ-η2 -1,2-µ-η2 -11,10-C20 H8 )Re2 (CO)8 (µ-H), 5 (12 % yield), by a second CH activation on a second rim double bond on the corannulene molecule. The isomers differ by the relative orientations of the coordinated Re2 (CO)8 (µ-H) groupings. All new products were characterized structurally by single crystal X-ray diffraction analysis.

Multiple Aromatic C-H Bond Activations by an Unsaturated Dirhenium Carbonyl Complex.

Reactions of Re2(CO)8(µ-C6H5)(µ-H), 1, with naphthalene and anthracene have yielded the first multiply-CH activated arene products through the reductive elimination of benzene from 1 and multiple oxidative-additions of the dirhenium octacarbonyl grouping to these polycyclic aromatic compounds under very mild conditions. In addition, compound 1 was found to react with itself to yield the bis-Re2-metalated C6H4 bridged compound Re2(CO)8(µ-H)(µ-1,µ-3-C6H4)Re2(CO)8(µ-H), 3. Reaction of 1 with naphthalene yielded two doubly CH activated isomers, Re2(CO)8(µ-H)(µ-η2-1,2-µ-η2-3,4-C10H6)Re2(CO)8(µ-H), 4, 41% yield, and Re2(CO)8(µ-H)(µ-η2-1,2-µ-η2-5,6-C10H6)Re2(CO)8(µ-H), 5, via the mono CH activated intermediate Re2(CO)8(µ-η2-C10H7)(µ-H), 2. Compound 4 contains two Re2(CO)8(µ-H) groups on one C6 ring formed by CH activations at the 2- and 4-positions. Compound 5 contains two Re2(CO)8(µ-H) groups; one formed by CH activation at the 2-position on one C6 ring and the other formed by CH activation at the 6-position (or centrosymmetrically related 2'-position) on the second C6 ring. The Re2(CO)8(µ-H) groups are coordinated to the C6 rings by binuclear σ + π coordination to two adjacent carbon atoms in the rings. Compound 1 reacts with anthracene to yield the mono-CH activated compound Re2(CO)8(µ-η2-1,2-C14H9)(µ-H), 6, and two doubly CH activated compounds, Re2(CO)8(µ-H)(µ-η2-1,2-µ-η2-3,4-C14H8)Re2(CO)8(µ-H), 7, and Re2(CO)8(µ-H)(µ-η2-1,2-µ-η2-5,6-C14H8)Re2(CO)8(µ-H), 8. Compounds 7 and 8 are isomers that are structurally similar to 4 and 5. Compounds 7 and 8 can also be obtained in good yields from the reaction of 6 with 1. In the presence of a 5/1 ratio of 1/anthracene, a small amount (5% yield) of the tetra-substituted anthracene product [Re2(CO)8(µ-H)]4(µ-η2-1,2-µ-η2-3,4-µ-η2-5,6-µ-η2-7,8-C14H6), 9, was formed. Compound 9 contains four σ + π coordinated Re2(CO)8(µ-H) groups formed by oxidative additions of the CH bonds of anthracene to the Re2(CO)8 groups at the 2, 4, 6, and 8 positions of the three ring system. Molecular orbital calculations have been performed for all new compounds in order to develop an understanding of the bonding of the ring systems to the Re2(CO)8(µ-H) groups. All new compounds were characterized by single-crystal X-ray diffraction analyses.

Correction: Multiple cluster CH activations and transformations of furan by triosmium carbonyl complexes.

Correction for 'Multiple cluster CH activations and transformations of furan by triosmium carbonyl complexes' by Richard D. Adams et al., Chem. Commun., 2018, 54, 3464-3467.

Multiple C-H Bond Activations and Ring-Opening C-S Bond Cleavage of Thiophene by Dirhenium Carbonyl Complexes.

The reaction of Re2(CO)8(µ-C6H5)(µ-H) (1) with thiophene in CH2Cl2 at 40 °C yielded the new compound Re2(CO)8(µ-η2-SC4H3)(µ-H) (2), which contains a bridging σ-π-coordinated thienyl ligand formed by the activation of the C-H bond at the 2 position of the thiophene. Compound 2 exhibits dynamical activity on the NMR time scale involving rearrangements of the bridging thienyl ligand. The reaction of compound 2 with a second 1 equiv of 1 at 45 °C yielded the doubly metalated product [Re2(CO)8(µ-H)]2(µ-η2-2,3-µ-η2-4,5-C4H2S) (3), formed by the activation of the C-H bond at the 5 position of the thienyl ligand in 2. Heating 3 in a hexane solvent to reflux transformed it into the ring-opened compound Re(CO)4[µ-η5-η2-SCC(H)C(H)C(H)][Re(CO)3][Re2(CO)8(µ-H)] (4) by the loss of one CO ligand. Compound 4 contains a doubly metalated 1-thiapentadienyl ligand formed by the cleavage of one of the C-S bonds. When heated to reflux (125 °C) in an octane solvent in the presence of H2O, the new compound Re(CO)4[η5-µ-η2-SC(H)C(H)C(H)C(H)]Re(CO)3 (5) was obtained by cleavage of the Re2(CO)8(µ-H) group from 4 with formation of the known coproduct [Re(CO)3(µ3-OH)]4. All new products were characterized by single-crystal X-ray diffraction analyses.

Formation of N, N-Dimethylacrylamide by a Multicenter Hydrocarbamoylation of C2H2 with N, N-Dimethylformamide Activated by Ru5(µ5-C)(CO)15.

Hydrocarbamoylation of C2H2 by N, N-dimethylformamide (DMF) to N, N-dimethylacrylamide was effected by a series of cluster-opening reactions with Ru5(µ5-C)(CO)15 (1). The reaction of 1 with DMF yielded the new complexes Ru5(µ5-C)(CO)14(µ-η2-O═CNMe2)(µ-H) (2) and a minor coproduct Ru5(µ5-C)(CO)13(HNMe2)(µ-η2-O═CNMe2)(µ-H) (3) by a cluster-opening activation of the formyl C-H bond of DMF. Compound 3 was obtained from 2 by a further reaction with DMF. Compound 3 reacted with C2H2 (1 atm, 70 °C) to yield Ru5(µ5-C)(CO)13(µ-η3-O═CNMe2CHCH)(µ-H) (4) by the addition and coupling of C2H2 to the bridging dimethylformamido ligand. Compound 4 contains a σ-π-coordinated, dimethylformamido-substituted vinyl ligand that bridges a Ru-Ru edge of an open Ru5C cluster. The formamido group is also coordinated to one of the metal atoms. The addition of CO (1 atm, 25 °C) to 4 yielded the CO adduct Ru5(µ5-C)(CO)14(η2-O═CNMe2CH═CH)(µ-H) (5) containing a chelating dimethylacrylamido ligand, which released dimethylacrylamide by the reductive elimination of a C-H bond upon a further addition of CO (400 psi, 125 °C) with the re-formation of 1. All of the products were characterized by single-crystal X-ray diffraction analyses.

Multiple cluster CH activations and transformations of furan by triosmium carbonyl complexes.

Reaction of Os3(CO)10(NCMe)2 with the triosmium furyne complex Os3(CO)9(µ3,η2-C4H2O)(µ-H)2, 1 yielded the bis-triosmium complex 2 containing a bridging furyenyl ligand by CH activation at the uncoordinated C-C double bond. Heating 2 led to additional CH activation with formation of the first furdiyne C4O ligand in the complex Os3(CO)9(µ-H)2(µ3-η2-2,3-µ3-η2-4,5-C4O)Os3(CO)9(µ-H)2, 3. The furdiyne ligand in 3 was subsequently ring-opened and decarbonylated to yield products 4 and 5 containing novel bridging C3 ligands. Complex 2 also undergoes ring opening to yield an intermediate Os3(CO)9(µ-H)(µ3-η2-µ-η2-CH-C-CH-C[double bond, length as m-dash]O)Os3(CO)10(µ-H), 6 which was also decarbonylated thermally to yield 4 and 5. All products were characterized by a combination of IR, NMR, mass spec and single-crystal X-ray diffraction analyses.

Multiple aromatic C-H bond activations by a dirhenium carbonyl complex.

Multiple aromatic CH activations by a dirhenium complex have provided meta-related dimetallated arene rings in the complexes Re2(CO)8(µ-H)(µ-η2-1,2-µ-η2-3,4-C14H8)Re2(CO)8(µ-H), 3 and Re2(CO)8(µ-H)(µ-η1-1,µ-η1-3-C6H4)Re2(CO)8(µ-H), 4. Both products were characterized structurally by single crystal X-ray diffraction and DFT molecular orbital analyses.

Synthesis and Reactivity of Electronically Unsaturated Dirhenium Carbonyl Compounds Containing Bridging Gold-Carbene Groups.

The electronically unsaturated compounds Re2(CO)8[µ-Au(NHC)](µ-Ph), 1, and Re2(CO)8[µ-Au(NHC)]2, 2, were obtained from the reaction of Re2(CO)8[µ-η2-C(H)═C(H)Bun](µ-H) with MeAu(NHC), NHC = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene. Compound 1 was converted to the new compound Re2(CO)8[µ-Au(NHC)](µ-H), 3, by reaction with H2. Addition of CO to 3 yielded the new compound Re2(CO)9[Au(NHC)](µ-H), 4, which contains a terminally coordinated Au(NHC) group on one of the rhenium atoms, and the hydrido ligand was shifted to bridge the Re-Au bond. The mechanism of the formation of 4 was established by DFT computational analyses. Compound 3 also reacted with C2H2 by an addition with insertion into the Re-H bonds to yield the compound Re2(CO)8[µ-Au(NHC)](µ-C2H3), 5, which contains a σ-π coordinated, bridging C2H3 ligand. The stereochemistry of the insertion was found to proceed preferentially with a cis- (syn-) stereochemistry. Compound 1 reacted with HCl to yield Re2(CO)8[µ-Ph](µ-H), 6, and ClAu(NHC) by selective removal of the bridging Au(NHC) group. All new compounds were characterized by single-crystal X-ray diffraction analyses.

Opening of Carborane Cages by Metal Cluster Complexes: The Reaction of a Thiolate-Substituted Carborane with Triosmium Carbonyl Cluster Complexes.

The reaction of Os3(CO)10(NCMe)2 with closo-o-(1-SCH3)C2B10H11 has yielded the complex Os3(CO)9[µ3-η(3)-C2B10H9(SCH3)](µ-H)2, 1, by the loss of the two NCMe ligands and one CO ligand from the Os3 cluster and the coordination of the sulfur atom and the activation of two B-H bonds with transfer of the hydrogen atoms to the cluster. Reaction of 1 with a second equivalent of Os3(CO)10(NCMe)2 yielded the complex Os3(CO)9(µ-H)[(µ3-η(3)-1,4,5-µ3-η(3)-6,10,11-C2B10H8S(CH3)]Os3(CO)9(µ-H)2, 2, that contains two triosmium triangles attached to the same carborane cage. The carborane cage was opened by cleavage of two B-C bonds and one B-B bond. The B-H group that was pulled out of the cage became a triply bridging group on one of the Os3 triangles but remains bonded to the cage by two B-B bonds. When heated to 150 °C, 2 was transformed into the complex Os3(CO)9(µ-H)[(µ3-η(3)-µ3-η(3)-C2B10H7S(CH3)]Os3(CO)9(µ-H), 3, by the loss of two hydrogen atoms and a rearrangement that led to further opening of the carborane cage. Reaction of 1 with a second equivalent of closo-o-(1-SCH3)C2B10H11 has yielded the complex Os3(CO)6)(µ3-η(3)-C2B10H9-R-SCH3) (µ3-η(3)-C2B10H10-S-SCH3)(µ-H)3, 4a, containing two carborane cages coordinated to one Os3 cluster. Compound 4a was isomerized to the compound Os3(CO)6(µ3-η(3)-C2B10H9-R-SCH3)(µ3-η(3)-C2B10H10-R-SCH3)(µ-H)3, 4b, by an inversion of stereochemistry at one of the sulfur atoms by heating to 174 °C.

Cage Opening of a Carborane Ligand by Metal Cluster Complexes.

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 .

Binuclear Aromatic C-H Bond Activation at a Dirhenium Site.

The electronically unsaturated dirhenium complex [Re2(CO)8(µ-H)(µ-Ph)] (1) has been found to exhibit aromatic C-H activation upon reaction with N,N-diethylaniline, naphthalene, and even [D6]benzene to yield the compounds [Re2(CO)8(µ-H)(µ-η(1)-NEt2C6H4)] (2), [Re2(CO)8(µ-H)(µ-η(2)-1,2-C10H7)] (3), and [D6]-1, respectively, in good yields. The mechanism has been elucidated by using DFT computational analyses, and involves a binuclear C-H bond-activation process.

The Addition of Gold and Tin to Bismuth-Triiridium Carbonyl Complexes.

The reaction of Ir3(CO)9(µ3-Bi) with PhAu(NHC) (1), where NHC = 1,3-bis(2,6-diisopropylphenylimidazol-2-ylidene), has yielded the compound Ir3(CO)8(Ph)(µ3-Bi)[µ-Au(NHC)] (2) by the loss of one CO ligand and the oxidative addition of the Au-C (phenyl) bond of 1 to one of the iridium atoms. The Au(NHC) group bridges one of the Ir-Bi bonds of the cluster. On the basis of X-ray crystal structural analysis and molecular orbital and quantum theory of atoms in molecules calculations, the Au-Bi interaction was determined to be substantial and is comparable in character to the Ir-Bi and Ir-Ir bonds in this cluster. Compound 2 reacts with 2 equiv of HSnPh3 to yield the compound Ir3(CO)7(SnPh3)2(µ3-Bi)[µ-Au(NHC)](µ-H) (3), which contains two terminally coordinated SnPh3 ligands. Compound 3 reacts with H2O to yield the compound Ir3(µ3-Bi)(CO)7[µ-Ph2Sn(OH)SnPh2][µ-Au(NHC)] (4) by cleavage of a phenyl ring from each of the SnPh3 ligands and formation of a bridging OH group between the two tin atoms to form a chelating Ph2Sn(OH)SnPh2 ligand.

Host-guest behavior of a heavy-atom heterocycle Re4(CO)16(µ-SbPh2)2(µ-H)2 obtained from a palladium-assisted ring opening dimerization of Re2(CO)8(µ-SbPh2)(µ-H).

The heavy-atom heterocycle Pd[Re2(CO)8(µ-SbPh2)(µ-H)]2 (5) has been synthesized by the palladium-catalyzed ring-opening cyclodimerization of the three-membered heterocycle Re2(CO)8(µ-SbPh2)(µ-H) (3). The Pd atom occupies the center of the ring. The Pd atom in 5 can be removed reversibly to yield the palladium-free heterocycle [Re2(CO)8((µ-SbPh2)(µ-H)]2 (6).