Synthesis and characterisation of the hexanuclear ruthenium diphosphine clusters [Ru6C(CO)15{μ-Ph2P(CH2  )nPPh2}] (n = 1–4); crystal structures where n = 1–3

Abstract

Treatment of a hexane solution of the complex [Ru 6 C(CO) 17 ] and 1 equivalent of the organodiphosphine ligands Ph 2 P(CH 2 ) n PPh 2 (n = 1-3) produced the series of derivatives [Ru 6 C(CO) 15 {µ-Ph 2 P(CH 2 ) n PPh 2 }] 1-3, respectively, in ca. 74-94% yield. These clusters have been characterised by IR and NMR spectroscopy and in the solid state by X-ray analyses. The three related compounds all adopt a similar octahedral metal core geometry with the bidentate diphosphine ligand bridging one Ru᎐Ru edge of the metal polyhedron. Reaction of [Ru 6 C(CO) 17 ] with 1,4-bis(diphenylphosphine)butane, Ph 2 P(CH 2 ) 4 PPh 2 , yielded two products which differ in the mode of bonding of the disphospine ligand, the major product [Ru 6 C(CO) 16 -{Ph 2 P(CH 2 ) 4 PPh 2 -P}] 4a in ca. 74% yield and the minor product [Ru 6 C(CO) 15 {µ-Ph 2 P(CH 2 ) 4 PPh 2 }] 4b in ca. 10% yield.The chemistry of binuclear metal complexes containing chelating diphosphine ligands is now well established. 1-3 In recent years bridging phosphine groups have been used in metal cluster chemistry because of their ability to maintain the integrity of the metal core intact during chemical reactions and to act as templates for the synthesis of metal-metal bonds by bridgeassisted reactions. 4-6 From these studies it has been found that in the solid state the diphosphine groups adopt a variety of bonding modes on the cluster surface including monodentate, chelating, edge-bridging and even an example of the ligand spanning the base of a square pyramid. 7-10It has been well established that direct substitution of carbonyl ligands in [Ru 6 C(CO) 17 ] by monodentate phosphines is possible under mild conditions 11,12 but similar studies with diphosphines are still relatively rare. 11,13 This work reports the results of the reactions of a series of disphosphines Ph 2 P(CH 2 ) n -PPh 2 [dppm (n = 1), dppe (n = 2), dppp (n = 3), dppb (n = 4)] with the hexanuclear cluster [Ru 6 C(CO) 17 ] which produce the cluster series [Ru 6 C(CO) 15 {Ph 2 P(CH 2 ) n PPh 2 }] (n = 1 1, 2 2, 3 3 or 4 4). Full crystal structure analyses of 1,* 2 and 3 have been made. These compounds enable a comparison of the structural variations that arise from lengthening the organic backbone in the diphosphine ligand. Reaction of [Ru 6 C(CO) 17 ] with dppb also gives the compounds [Ru 6 C(CO) 16 {Ph 2 P(CH 2 ) 4 PPh 2 }] 4a and [Ru 6 C(CO) 15 {Ph 2 P(CH 2 ) 4 PPh 2 }] 4b for which NMR studies indicate that in the major product (4a) the diphosphine ligand adopts an unusual P-pendant bonding mode, whilst in the minor product (4b) it adopts the more common P 2 PЈ-edgebriding configuration.

Chelate and Bridge Diphosphine Isomerization: Triosmium and Triruthenium Clusters Containing 1,1‘-Bis(diphenylphosphino)ferrocene (dppf)

“…In the past two decades, there has been considerable advances in the synthesis and reactivity of transition metal complexes bearing diphosphine ligands due to their potential applicability to effect organic transformations, their ability to act as templates for the synthesis of metal−metal bonds by bridge-assisted reactions, − and their widespread application in homogeneous catalysis. − When metal bound, diphosphines can coordinate in monodentate, chelating, or bridging modes, and interconversions between these often result from slight changes in the ligand backbone or in co-ligands bound to the metal center(s) …”

Ligand substitutions in Ru–Pt clusters: isolation of compounds with unusual geometries

“…These were formulated as [ (dppm)] 15 was identified on the basis of its IR, mass and NMR spectra, by comparison with data from the literature. 15 Crystals of [Ru 6 C(CO) 15 (dppm)] 15 suitable for X-ray structure determination were obtained, and the unit cell parameters also fitted with the literature data. 15 The cluster [Ru 6 C(CO) 15 (dppm)] had been shown to display an octahedral cluster core, 15 in accord with the PSEPT rules for the 86 electron count of 15.…”

“…15 Crystals of [Ru 6 C(CO) 15 (dppm)] 15 suitable for X-ray structure determination were obtained, and the unit cell parameters also fitted with the literature data. 15 The cluster [Ru 6 C(CO) 15 (dppm)] had been shown to display an octahedral cluster core, 15 in accord with the PSEPT rules for the 86 electron count of 15. The second product, by order of elution, was [Ru 6 C(CO) 13 (dppm) 2 ] 19.…”

“…Two CO ligands are bridging Ru"apical"-Ru"equatorial" edges, on opposite sides of the octahedron. The octahedron is unchanged when compared to The third product, [Ru 6 C(CO) 15 Pt 2 (dppm)] 20, was only characterised by IR spectroscopy and mass spectrometry, due to the very low yield in which it was isolated. Its IR spectrum displayed bands attributable to terminal CO ligands only.…”

Immobilisation of ruthenium cluster catalysts via novel derivatisations of ArgoGel resinsElectronic supplementary information (ESI) available: footnotes to the text. See http://www.rsc.org/suppdata/cc/b1/b106336g/

“…In the case of [Ru 6 C(CO) 17 ] the stronger bidentate coordination is expected. 9 Diphenylphosphine was treated with paraformaldehyde according to a literature procedure 10 and the phosphido-Mannich intermediate thus formed was added to ArgoGel amine to give the supported phosphine ligand 6 (Scheme 2). The peaks in the 31 P NMR spectrum at d 226 and 227 indicated formation of the supported phosphine ligand.…”