ChemInform Abstract The thermal title reaction gives the bis(phosphido)-bridged Mo2 complex (III) (space group P1, Z=2) containing a Mo-Mo double bond. Further decarbonylation leads to the µ-carbonyl derivative (IV) ( P21/n, Z=4) with a Mo-Mo triple bond. Protonation of (III) occurs across the Mo-Mo bond to give the µ-hydrido derivative (V). Oxidation of (III) results in the formation of the trans and cis isomers (VIIa) (P1, Z=2) and (VIIb); the same oxidation products are obtained similarly from (IV) in 1.9 and 52% yield.

A series of 1,3,4-benzotriazepine-based CCK(2) antagonists have been devised by consideration of the structural features that govern CCK receptor affinity and the receptor subtype selectivity of 1,4-benzodiazepine-based CCK(2) antagonists. In contrast to the latter compounds, these novel 1,3,4-benzotriazepines are achiral, yet they display similar affinity for CCK(2) receptors to the earlier molecules and are highly selective over CCK(1) receptors.

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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.