María L. Buil

From tetrahydroborate- to aminoborylvinylidene-osmium complexes via alkynyl-aminoboryl intermediates

The tetrahydroborate OsH(η(2)-H(2)BH(2))(CO)(P(i)Pr(3))(2) (1) reacts with aniline and p-toluidine to give the aminoboryl derivatives [chemical structure: see text] (R = H (2), CH(3) (3)) and four H(2) molecules. Treatment of 2 and 3 with phenylacetylene gives Os{B(NHC(6)H(4)R)(2)}(C≡CPh)(CO)(P(i)Pr(3))(2) (R = H (4), CH(3) (5)), which react with HBF(4) to afford the amino(fluoro)boryl species Os{BF(NHC(6)H(4)R)}(C≡CPh)(CO)(P(i)Pr(3))(2) (R = H (6), CH(3) (7)). In contrast to HBF(4), the addition of acetic acid to 4 and 5 induces the release of phenylacetylene and the formation of the six-coordinate derivatives Os{B(NHC(6)H(4)R)(2)}(κ(2)-O(2)CCH(3))(CO)(P(i)Pr(3))(2) (R = H (8), CH(3) (9)). The coordination number six for 4 and 5 can be also achieved by addition of CO. Under this gas Os{B(NHC(6)H(4)R)(2)}(C≡CPh)(CO)(2)(P(i)Pr(3))(2) (R = H (10), CH(3) (11)) are formed. In toluene, these alkynyl-aminoboryl compounds evolve into the aminoborylvinylidenes Os{═C═C(Ph)B(NHC(6)H(4)R)(2)}(CO)(2)(P(i)Pr(3))(2) (R = H (12), CH(3) (13)) via a unimolecular 1,3-boryl migration from the metal to the C(β) atom of the alkynyl ligand. Similarly to 4 and 5, complexes 6 and 7 coordinate CO to give Os{BF(NHC(6)H(4)R)}(C≡CPh)(CO)(2)(P(i)Pr(3))(2) (R = H (15), CH(3) (16)), which evolve to Os{═C═C(Ph)BF(NHC(6)H(4)R)}(CO)(2)(P(i)Pr(3))(2) (R = H (17), CH(3) (18)).

Perfluoro-tagged rhodium and ruthenium nanoparticles immobilized on silica gel as highly active catalysts for hydrogenation of arenes under mild conditions

Perfluoro-tagged rhodium and ruthenium nanoparticles have been stabilized on highly fluorinated hybrid organic–inorganic silica gel. The method for preparation of these nanoparticles is highly reproducible and the new materials were robust, recoverable and active catalysts for arene hydrogenation under very mild conditions.

An Entry to Stable Mixed Phosphine–Osmium–NHC Polyhydrides

An entry to mixed phosphine-osmium-NHC polyhydride complexes is described, starting from the five-coordinate hydrido-alkylidyne compounds [OsHCl(≡CPh)(IPr)(PR3)]OTf (IPr = 1,3-bis(2,6-disopropylphenyl)imidazolylidene; OTf = CF3SO3; PR3 = P(i)Pr3 (1), PPh3 (2)). The experimental procedure involves the borylation of the Os-C triple bond of 1 and 2 with NaBH4 and the subsequent alcoholysis of the borylation products OsH2Cl(η(2)-H-BCH2Ph)(IPr)(PR3) (PR3 = P(i)Pr3 (3), PPh3 (4)) or OsH2(η(2):η(2):H2BCH2Ph)(IPr)(P(i)Pr3) (5). Stirring of 3 in 2-propanol affords the five coordinate chloride-trihydride OsH3Cl(IPr)(P(i)Pr3)2 (6), which reacts with NaBH4 to give OsH3(κ(2)-H2BH2)(IPr)(P(i)Pr3) (7). This trihydride-tetrahydrideborate derivative and its PPh3 counterpart OsH3(κ(2)-H2BH2)(IPr)(PPh3) (8) can be also obtained in a one-pot procedure, starting from 1 and 2 and using methanol at -60 °C instead of 2-propanol as alcoholysis agent. The bonding situation in 7 and 8, analyzed by DFT calculations using AIM and NBO methods, resembles that found in B2H6 and contrasts with the bonding situation in the bis-σ-borane derivative 5. Stirring of 7 and 8 in 2-propanol leads to the corresponding d(2)-hexahydride derivatives OsH6(IPr)(PR3) (PR3 = P(i)Pr3 (9), PPh3 (10)), which reduce the C≡N triple bond of benzonitrile and promote the subsequent chelate-assisted ortho-CH bond activation of the resulting phenylmethanimine, to form the trihydride compounds OsH3{κ(2)-N,C-(NH═CH-C6H4)}(IPr)(PR3)2 (PR3 = P(i)Pr3 (11), PPh3 (12)), containing a stabilized orthometalated aldimine.

Square-Planar Alkylidyne–Osmium and Five-Coordinate Alkylidene–Osmium Complexes: Controlling the Transformation from Hydride-Alkylidyne to Alkylidene

Square-planar alkylidyne and five-coordinate alkylidene mixed (i)Pr3P-Os-IPr (IPr = 1,3-bis(diisopropylphenyl)imidazolylidene) complexes have been discovered and characterized, and their formation has been rationalized. The cationic five-coordinate hydride-alkylidyne compounds [OsHX(≡CPh)(IPr)(P(i)Pr3)]OTf (X = Cl (1), F (4); OTf = CF3SO3) undergo deprotonation with KO(t)Bu to afford the trans-halide-alkylidyne square-planar derivatives OsX(≡CPh)(IPr)(P(i)Pr3) (X = Cl (2), F (5)). Oxidative addition of the C(sp)-H bond of phenylacetylene and methyl propiolate along the Cl-Os-CPh axis of 2 with the hydrogen atom directed to the alkylidyne leads to alkynyl-cis-hydride-alkylidyne intermediates, which rapidly evolve into the five-coordinate alkylidene complexes Os(C≡CR)Cl(═CHPh)(IPr)(P(i)Pr3) (R = Ph (6), CO2Me (7)) as a consequence of the migration of the hydride from the metal center to the Cα atom of the alkylidyne. Oxidative addition of the C(sp)-H bond of methyl propiolate along the X-Os-CPh axis of 2 and 5 with the hydrogen atom directed to the halide gives the alkynyl-trans-hydride-alkylidyne derivatives OsH(C≡CCO2Me)X(≡CPh)(IPr)(P(i)Pr3) (X = Cl (8), F (9)). Complex 8 evolves into 7. However, complex 9 containing the stronger π-donor fluoride is stable. The oxidative addition of HCl to 2 selectively yields the cis-hydride-alkylidyne compound OsHCl2(≡CPh)(IPr)(P(i)Pr3) (10), which is also stable.

Reactions of OsH2(η2−CH2=CHEt)(CO)(PiPr3)2 with unsaturated organic molecules

The 1-butene ligand of the dihydrido complex OsH2(η2-CH2=CHEt)(CO)(PiPr3)2 (1) can be readily displaced by cyclopentadiene to yield OsH2(η2-C5H6)(CO)(PiPr3)2 (2). Complex 1 selectively hydrogenates the carbon−carbon triple bond of 2-methyl-1-hexen-3-yne to give the methylhexadiene derivative Os{η4-CH2=C(CH3)(CH=CHCH2CH3}(CO)(PiPr3)2 (3). Treatment of 1 with phenylacetylene in a 1:10 molar ratio leads to the diphenylbutenynyl complex Os(C2Ph){η3-C(C≡CPh)=CHPh}(CO)(PiPr3)2 (5a) containing the carbonyl ligand trans disposed to the carbon−carbon triple bond of the butenynyl unit. In benzene-d6 at 60°C, 5a affords a new isomer 5b, where the carbonyl group is disposed trans to the OsC= carbon atom of the diphenylbutenynyl ligand. Isomer 5a reacts with HBF4 · H2O to give Os(CH2Ph)(FBF3)(CO)2(PiPr3)2 (6), which by reaction with NaCl yields Os(CH2Ph)Cl(CO)2(PiPr3)2 (7). The reactions of 1 with dicyclohexyl-carbodiimide, phenylisocyanate, phenylisothiocyanate and methylisothiocyanate lead to the corresponding insertion products OsH{κ2-N(Cy)CHN(Cy)}(CO)(PiPr3)2 (8), OsH {κ2-N(Ph)CHO}(CO)(PiPr3)2 (9) OsH{κ2-N(Ph)CHS}(CO)(PiPr3)2 (10) and OsH{κ2-N(CH3)CHS}(CO)(PiPr3)2 (11). Complex 1 also reacts with benzophenone imine, in this case the reaction product is Download full-size image (Co)(PiPr3)2 (12). The protonation of 12 with HBF4 · OEt2 gives the five-coordinate complex [OsH(CO)(NH=CPh2)(PiPr3)2]BF4 (13). which by reaction with carbon monoxide and trimethylphosphite affords [OsH(CO)2(NH=CPh2)(PiPr3)2]BF4 (14) and [OsH(CO)(NH=CPh2){P(OMe)3}PiPr3)2]BF4 (15), respectively.

Synthesis and characterization of (PPr3i)2(CO)HRu(µ-H)- (µ-OMe)Ir(cod): an unusual example of a heterometallic complex containing a mixed hydrido–alkoxide bridge

The complex (PPr3i)2(CO)HRu(µ-H)(µ-OMe)Ir(cod) (cod=cycloocta-1,5-diene) was obtained by treatment of RuH2(CO)(PHPh2)(PPr3i)2 with [Ir(µ-OMe)(cod)]2. The structure of this heterodinuclear compound has been determined by X-ray diffraction analysis. The molecule is dinuclear and consists of a distorted square-planar coordination around iridium and a distorted octahedral coordination around ruthenium connected through a mixed hydrido–methoxy bridge. The Ru–Ir separation is 2.8635(5) A.