Scott S. D. Brown

The heteronuclear cluster chemistry of the group 1B metals. Part 4. Synthesis, structures, and dynamic behaviour of group 1B metal–ruthenium cluster compounds containing sulphur ligands. X-Ray crystal structures of [M2Ru3(µ3-S)(µ-Ph2PCH2PPh2)(CO)9](M = Cu or Au)

Treatment of a tetrahydrofuran solution of the salt K2[Ru3(µ3-S)(CO)9] with the complex [MX(PPh3)](M =Cu or Au, X =Cl; M = Ag, X = I), in the presence of TIPF6, affords a mixture of cluster compounds, [MRu3(µ-H)(µ3-S)(CO)9(PPh3)][for M = Cu (2), Ag (3), or Au (4)], [MRu3(µ-H)-(µ3-S)(CO)8(PPh3)2][for M = Cu (5) or Ag (6)], and [M2Ru3(µ3-S)(CO)9(PPh3)2][for M = Cu (8), Ag (9), or Au (10)]. In addition, the pentanuclear clusters [M2Ru3(µ3-S)(µ-Ph2PCH2PPh2)-(CO)9][M = Cu (12) or Au (13)] can be synthesized from the reaction between K2[Ru3(µ3-S)-(CO)9] and [M2(µ-Ph2PCH2PPh2)Cl2], using TIPF6. Infrared and n.m.r. spectroscopic data imply that the tetranuclear copper- or silver-containing species (2), (3), (5), and (6) all adopt the same ‘butterfly’ MRu3 metal-core geometry as that previously established for the Au cluster (4) and that the pentanuclear Cu and Ag species (8) and (9) exhibit the same trigonal-bipyramidal M2Ru3 framework as that determined for the Au cluster (10). However, X-ray diffraction studies on the bidentate phosphine-containing pentanuclear Cu2Ru3 species (12) and its Au2Ru3 analogue (13) reveal two different metal-corestructures. The Cu cluster (12) has a trigonal-bipyramidal metal skeleton [Cu–Cu 2.515(3), Cu–Ru 2.552(2)–2.794(2), Ru–Ru 2.814(2)–2.856(2)A], with one of the two phosphine-bridged Cu atoms occupying an equatorial site and the other an axial site. The S atom caps the Ru3 face of the trigonal-bipyramidal unit. In the Au species (13), the metal framework structure is intermediate between a trigonal bipyramid and a square-based pyramid [Au–Au 2.802(1), Au–Ru 2.742(l)–2.836(1), Ru–Ru 2.773(2)–2.968(2)A]. Variable-temperature n.m.r. studies show that, at ambient temperature in solution, the coinage metals in each of the pentanuclear clusters (8)–(10), (12), and (13) are exchanging between the two distinct sites in the cluster skeleton, the PPh3 groups in the copper–ruthenium species (2) and the silver–ruthenium species (3), (6), and (9) are undergoing intermolecular exchange between clusters, and the CO ligands in all of the clusters exhibit dynamic behaviour involving intramolecular site-exchange.

The heteronuclear cluster chemistry of the group 1B metals. Part 9. Stereochemical non-rigidity of the metal skeletons of cluster compounds in solution. 109Ag-{1H} INEPT nuclear magnetic resonance studies on [Ag2Ru4(µ3-H)2{µ-Ph2P(CH2)nPPh2}(CO)12](n= 1, 2, or 4) and X-ray crystal structure of [Ag2Ru4(µ3-H)2(µ-Ph2PCH2PPh2)(CO)12]

A combination of spectroscopic data and an X-ray diffraction study on [Ag2Ru4(µ3-H)2(µ-Ph2PCH2PPh2)(CO)12][Ag–Ag 2.756(6), Ag–Ru 2.820(6)–3.151(6), Ru–Ru 2.775(7)—2.998(6)A] shows that the clusters [Ag2Ru4(µ3-H)2{µ-Ph2P(CH2)nPPh2}(CO)12](n= 1–6) all adopt a capped trigonal-bipyramidal metal core geometry. However, although there are two distinct silver sites in the ground-state structures, ambient temperature 109Ag-{1H} INEPT n.m.r. spectra of the clusters in which n= 1, 2, or 4 show a single averaged silver resonance in each case. These studies provide the first direct evidence for stereochemical non-rigidity of the metal skeletons of Group 1B metal heteronuclear clusters in solution. In addition, values of 1J(107,109Ag107,109Ag) have been measured for the first time. The results of 31P-{109Ag} and 109Ag INEPT and DEPT n.m.r. studies on [AgRu4(µ3-H)3(CO)12(PPh3)] are also reported.

High-resolution 31P-{1H} nuclear magnetic resonance studies of Group IB metal heteronuclear cluster compounds in the solid state

Abstract High-resolution 31 P-{ 1 H} NMR spectra of a series of crystalline mixed-metal cluster compounds containing M(PR 3 ) (M = Cu, Ag, or Au; R = alkyl or aryl) fragments have been recorded using magic angle sample spinning. The solid-state spectra are compared with those measured for the same compounds in solution and the values of the chemical shifts and, for the silver-containing species, the magnitudes of J ( 107,109 AgP) av , are generally very similar. The solid-state NMR spectra suggest that the dynamic processes involving hydrido ligand site-exchange or intermolecular exchange of PR 3 ligands between clusters, which have been previously observed at ambient temperature in solution for some of the clusters studied, do not occur or are not sufficiently rapid to be detected when the same compounds are in the crystalline state. In addition, the intramolecular metal core rearrangements, which all of the bimetallic clusters containing inequivalent M(PR 3 ) fragments undergo at ambient temperature in solution, are also not observed by solid-state NMR spectroscopy in the crystalline compounds. For some of the clusters of this latter class, the solid-state spectra can provide useful structural information about the ground-state metal framework geometries which it is impossible to obtain from solution studies, even at low temperatures.

The heteronuclear cluster chemistry of the Group 1B metals. Part 13. Synthesis and structural characterization of the bimetallic hexanuclear Group 1B metal cluster compounds [M2Ru4(µ-CO)3(CO)10(PPh3)2](M = Cu, Ag, or Au). X-Ray structure analyses of [M2Ru4(µ-CO)3(CO)10(PPh3)2](M = Cu or Ag)

Treatment of the salt [N(PPh3)2]2[Ru4(CO)13]·thf (thf = tetrahydrofuran) with 2 equivalents of the complex [M(NCMe)4]PF6(M = Cu or Ag) at –30 °C, followed by the addition of 2 equivalents of PPh3, affords the mixed-metal cluster compounds [M2Ru4(µ-CO)3(CO)10(PPh3)2][M = Cu (1) or Ag (2)] in ca. 35–40% yield. The analogous gold-containing species, [Au2Ru4(µ-CO)3(CO)10(PPh3)2](3), was obtained in ca. 65% yield by treating a dichloromethane solution of [N(PPh3)2]2[Ru4(CO)13]·thf with a dichloromethane solution containing 2 equivalents of the complex [AuCl(PPh3)] at –30 °C, in the presence of TIPF6. Single-crystal X-ray diffraction studies on (1) and (2) show that both clusters exhibit similar capped trigonal-bipyramidal metal frameworks, consisting of a tetrahedron of ruthenium atoms with two Ru3 faces capped by M(PPh3)(M = Cu or Ag) units [Cu–Ru 2.608(2)–2.848(2), Ru–Ru 2.771(2)–2.981(2)A for (1); Ag–Ru 2.806(1)–2.977(1), Ru–Ru 2.797(1)–3.074(1)A for (2)]. Spectroscopic data suggest that the gold-containing cluster (3) also adopts a similar metal core structure. The skeletal geometries of clusters (1)–(3) are in marked contrast to the capped trigonal-bipyramidal skeletal geometries previously characterized in the solid state for the very closely related dihydrido clusters [M2Ru4H2(CO)12(PPh3)2](M = Cu, Ag, or Au), in which the Group 1B metals are in close contact. Thus, the formal replacement of two hydrido ligands in the latter clusters by the sterically more demanding CO group in (1)–(3) causes a fundamental change in the positions that the M(PPh3)(M = Cu, Ag, or Au) units adopt on the ruthenium tetrahedra of these species.

Gold-197 Mössbauer spectra of some gold–ruthenium cluster compounds

The 197Au Mossbauer spectra of nine cluster compounds containing AuL (L = PPh3 or ½Ph2PCH2PPh2) and Ru(CO)3 groups are reported. In three cases, separate signals are resolved for non-equivalent Au(PPh3) groups within the cluster. Relative intensities of the two sub-spectra are correlated with estimates of the recoil-free fractions of the two types of atom. For the whole series, the isomer shift and quadrupole splitting become smaller as the number of contacts between the gold atoms and their neighbours increases, and the parameters correlate well with the average Au–Ru bond lengths.

The synthesis and structural characterization of the mixed-metal cluster compounds [M2Ru4(μ-CO)3(CO)10(PPh3)2] (M=Cu, Ag, Au): X-ray crystal structures of [M2Ru4(μ-CO)3(CO)10(PPh3)2] (M=Cu, Ag)

Abstract The novel mixed-metal cluster compounds [M 2 Ru 4 (μ-CO) 3 (CO) 10 (PPh 3 ) 2 ] (M  Cu, Ag or Au) have been synthesized from [N(PPh 3 ) 2 ] 2 [Ru 4 (CO) 13 ]·THF. Single-crystal X-ray diffraction studies on the copper- and silver-ruthenium clusters reveal that they adopt metal core structures consisting of a Ru 4 tetrahedron with M(PPh 3 ) (M  Cu or Ag) groups capping two Ru 3 faces, in marked contrast to the capped trigonal bipyramidal skeletal geometries exhibited by the very closely related species [M 2 Ru 4 H 2 (CO) 12 (PPh 3 ) 2 ] (M  Cu, Ag or Au), in which the two coinage metals are in close contact.

109 Ag{1H} INEPT n.m.r. studies on the silver heteronuclear cluster compounds [Ag2Ru4(µ3-H)2{µ-Ph2P(CH2)nPPh2}(CO)12](n= 1, 2, or 4). Direct evidence for intramolecular metal core rearrangements in solution and the first measurement of 1J(107,109Ag107,109Ag)

Resonances from the silver atoms in the mixed-metal cluster compounds [Ag2Ru4(µ3-H)2{µ-Ph2P(CH2)nPPh2}(CO)12](n= 1, 2, or 4) have been detected using 109Ag{1H} INEPT n.m.r. spectroscopy; this technique provides the first direct evidence that, in solution at ambient temperature, group 1B metal heteronuclear clusters undergo an intramolecular fluxional process involving a rearrangement of their metal skeletons and values of 1J(107,109Ag107,109Ag) have been measured for the first time.

Detection of non-equivalent gold sites in mixed-metal cluster compounds by Mössbauer spectroscopy

The first 197Au Mossbauer data for mixed-metal cluster compounds are reported; structurally non-equivalent gold atoms bearing the same exo-ligands can be distinguished in gold–ruthenium clusters.

Pericyclynosilanes: synthesis of a new class of cyclic organosilicon compounds

The pericyclynosilanes, systematically known as cyclopoly(silapropynylenes), (R2SiCC)n(where R = Me or Ph, n 5) have been synthesised, in high yield, by the reaction of the dilithium derivatives of diorganodiethynylsilanes with the corresponding diorganodichlorosilanes, and the dodecamethyl (n= 6) and dodecaphenyl (n= 6) derivatives have been isolated and fully characterised; when the organic substituents present in the diorganodiethynylsilane differ from those of the diorganodichlorosilane, a redistribution reaction is observed, leading to a product in which the organosilicon units are randomly distributed.

The synthesis and dynamic behaviour of copper- and silver-ruthenium cluster compounds containing the asymmetric bidentate ligands Ph2As(CH2)nPPh2 (n = 1 or 2)

Abstract The novel mixed-metal cluster compounds [M 2 Ru 4 (μ 3 -Ph 2 As(CH 2 ) n -PPh 2 }(CO) 12 ] (M = Cu or Ag; n = 1 or 2) have been synthesized in good yield (ca. 65–70%0. Variable temperature 1 H and 31 P-{ 1 H} NMR spectroscopic studies demonstrate that two distinct structural isomers exist in solution at low temperature for both copper-ruthenium clusters and that each of these pairs of isomer undergoes interconversion at ambient temperature by a fluxional process involving an intramolecular metal core rearrangement.