A new family of phosphido-bridged dinuclear ruthenium carbonyl complexes: synthesis of [Ru-2(CO)(6){mu-P(C(CH)(3)O)(2)}(mu-eta(1),eta(2)-C(CH)(3)O)] and its reactivity towards terminal alkynes

Thermal reaction of [Ru-3(CO)(12)] with tri(2-furyl) phosphine affords the dinuclear phosphido-bridged complex [Ru-2 (CO)(6) {mu -P(C(CH)(3)O)(2)}(mu- eta (1),eta (2)-C(CH)(3)O)] 1a in good yield via cleavage of Ru-Ru and P-C( furyl) bonds in the starting compounds and a small amount of the disubstitu tion product [Ru-3(CO)(10){P(C(CH)(3)O)(3)}(2)] 1b. The X-ray structural an alysis of 1a shows that it contains a dissociated furyl fragment bonded to the Ru-2 unit in a mu-eta (1),eta (2) coordination mode through one and one bond. This represents the rst structurally characterised example of such a furyl-bonded dinuclear organometallic complex. Complex 1a readily reacts w ith two equivalents of terminal alkynes HC=CR [R = Ph, p-C6H4Me, p-C6H4NO2, (C4H2S) C=CH or (C4H2S)(2)C=CH] by an interesting head-to-tail ynyl coupli ng with a furan group to form a series of phosphido-bridged diruthenium com pounds containing a novel furyl-substituted C-4 hydrocarbyl chain of stoich iometry [Ru-2(CO)(4) {mu -P(C(CH)(3)O)(2)}{mu-eta (1),eta (1)(,)eta (2),eta (3)-RCC(H)C(R)C(H)C( CH)(3)O}] [R = Ph 2, p-C6H4 Me 3, p-C6H4NO2 4, (C4H2S ) C=CH 5 or (C4H2S)(2)C=CH 6] in moderate to good yields, all of which have been characterised by spectroscopic and crystallographic methods. Assignme nts of the proton NMR spectra have been made with the aid of a 2-D H-1-H-1 COSY technique. On reaction with the thienyl-linked diyne ligands, only one free C=CH group is involved in the coupling sequence while the other termi nal alkyne functionality remains intact. All these new dinuclear complexes are electron precise with 34 cluster valence electrons.