Heterobimetallic gold-osmium and gold-ruthenium hydrido complexes. X-ray crystal and molecular structures of [Au2Os(H)3(PPh3)5]PF6 and [AuRu(H)2(CO)(PPh3)4]PF6

Abstract

Several new heterobimetallic hydrides containing gold have been synthesized. [Au2Os(H)3(PPh3)5]PF6 (1) was made by the reaction of AuPPh3NQ3 and Os(H)4(PPh3)3 with CH2C12 as solvent. [Au2Ru(H)3(PPh3)5]PF6 (2) was synthesized in an analogous manner from AuPPh3NQ3 and Ru(H)4(PPh3)3 with toluene as solvent. [AuRu(H)2(CO)(PPh3)4]PF6 (3) and its osmium analogue, [AuOs(H)2(CO)(PPh3)4]PF6 (4), and [AuOs(H)2(CO)2(PPh3)3]PF6 (5) and its ruthenium analogue, [AuRu(H)2(CO)2(PPh3)3]PF6 (6), were prepared by the reaction of AuPPh3N03 with M(H)2(CO)(PPh3)3 (M = Ru, Os) and M(H)2(CO)2(PPh3)2 ( = Ru, Os), respectively, with CH2C12 as solvent. Compounds 1 and 3 were characterized by single-crystal X-ray diffraction in the solid state [l-3CH2Cl2.2Et20, monoclinic P2¡/n, a = 13.64 (2) A, b = 40.89 (2) k,c= 17.53 (1) A, ß = 102.54 (9)°, = -116 °C, Z = 4,R = 0.051 for 10 180 observations; 3-2CH2Cl2, triclinic PI, a = 15.404 (3) A, b = 19.461 (8) A, c = 13.868 (7) k, a = 98.86 (4)°, ß -105.68 (3)°, y = 87.73 (2)°, T = 22 °C, Z = 2, R = 0.051 for 9648 observations] and by 31P and NMR spectroscopy in solution. The structure of complex 1 consists of two Au(PPh3) units bonded to an Os(PPh3)3 moiety forming a slightly distorted trigonal-bipyramidal geometry with no Au-Au bond (4.28 A). The hydride ligands were not directly observed by X-ray diffraction in 1; however, spectroscopic evidence indicates the presence of one hydride bridging each of the Au-Os bonds on the outside edges of the Au2Os triangle and a third hydride briding one of the Au-Os bonds on the inside edge of the Au2Os triangle. Supporting evidence for the characterization of complex 1 in the solid state was obtained with the use of CP MAS 31P NMR spectroscopy. In the X-ray diffraction analysis of complex 3 one of the hydride ligands was directly observed bridging the Au-Ru bond. Spectroscopic evidence supports the formulation of 3 as a bis(g-hydrido) species. The average Au-Os and Au-Ru distances in 1 and 3 are 2.703 (0) and 2.786 (1) A, respectively, and the Ru-H and Au-H separations in 3 are 1.78 (4) and 1.61 (4) A, respectively. Compounds 2 and 4-6 were also determined to have bridging hydrides by NMR and IR spectroscopy. Preliminary results indicate that the gold adduct [AuRu(H)2(CO)(PPh3)4]PF6 (3) has a significantly higher rate of catalytic activity than its parent complex, Ru(H)2(CO)(PPh3)3, for the isomerization of 1-hexene to cis-and trans-2-hexene in CH2C12 at 25 °C and 1 atm of N2.

The Reagent [K(18-crown-6)][RuH(PPh3)2(η5-7,8-C2B9H11)] as a Precursor to New Ruthenacarborane Complexes

“…In the gold complex 8a (Figure ) there is no exopolyhedral B−H⇀Au bond supplementing the Ru( μ -H)Au linkage [Ru−Au 2.7205(8) Å, Ru−H(001) 1.79(6) Å, Au−H(001) 1.37(5) Å]. These distances compare well with those found in the cation [RuAu( μ -H) 2 (CO)(PPh 3 ) 4 ] + [Ru−Au 2.786(1) Å, Ru−H 1.78(4) Å, Au−H 1.61(4) Å] . The absence of an agostic B−H⇀Au interaction in 8a and the presence of the B−H⇀Cu linkage in 7a can be related to the relative differences in the energies of the unoccupied frontier orbitals in the fragments M(PPh 3 ) (M = Cu or Au).…”

Chemical catalysis by colloids and clusters

“…While the origin of the enhancement by gold (but not by copper) is not known, these results strongly support catalysis by intact clusters.226 Other mixed-metal ruthenium-gold clusters catalyze olefin isomerization as well. 321 A mixed-metal Ni-Ru cluster, CpNiRu3(n-H)3(CO)9, selectively catalyzes hydrogenation and isomerization of double bonds. The presence of both metals is important in the catalysis, indicating cluster catalysis.…”

Hydride Transfer to Gold: Yes or No? Exploring the Unexpected Versatility of Au⋅⋅⋅H−M Bonding in Heterobimetallic Dihydrides

“…This strategy has been extended to other transition metals such as Nb, [25] Ru, [26] Os. [27] More recent studies revealed that these species might turn into interesting catalytic systems; for example, Crimmin reported that heterobimetallic copper-gold hydrides can hydroborate CO2 in the presence of pinacolborane in high selectivity to give formate derivatives. [28] From a mechanistic point of view, Au-H-M moieties can be seen as a situation where the hydride transfer is arrested in an intermediate stage.…”