Synthesis and characterisation of mono-acetylide and unsymmetrical bis-acetylide complexes of ruthenium and osmium:: X-ray structure determinations on [(dppe)2Ru(Cl)(CC-C6H4-p-NO2)], [(dppe)2Ru(Cl)(CC-C6H3-o-CH3-p-NO2)] and [(dppm)2Os(CC-C6H4-p-CH3)(CC-C6H4-p-NO2)]

The synthesis of a series of metal mono-acetylides trans-[(dppe)(2)Ru(Cl)(C=C-R)] (R = C6H4-p-C6H5, C6H4-p-CH3, C6H4-p-NO2, C6H3-o-CH3-p-NO2, dppe = Ph2PCH2CH2PPh2), and unsymmetrical metal bis-acetylides trans-[(dppm)(2)M(C=C-R)(C=C-R)]; (M = Ru, Os; R = C6H4-p-NO2, R' = C6H5, C6H4-p-CH3; R = C6H5, R' = C6H4-p-CH3) using a variety of sigma-acetylide coupling reactions is reported. Three compounds have been structurally characterised, including the unsymmetrical trans[(dppm)(2)Os(C=C-R)(C=C-R')] (R = C6H4-p-CH3, R' = C6H4-p-NO2] which shows the 'rigid-rod' nature of the acetylide-metalacetylide linkage. The electrochemistry of symmetrical and unsymmetrical Ru(II) complexes demonstrates the role of the acetylide and the auxiliary ligands in determining the ease of oxidation at the metal centre whilst W-vis spectral changes illustrate the influence of electron-withdrawing and -donating ligands. (C) 1999 Elsevier Science S.A. All rights reserved.