Md. Arzu Miah

Reactivity of triruthenium thiophyne and furyne clusters: competitive S–C and P–C bond cleavage reactions and the generation of highly unsymmetrical alkyne ligands

The synthesis and reactivity of the thiophyne and furyne clusters [Ru3(CO)7(mu-dppm)(mu3-eta2-C4H2E)(mu-P(C4H3E)2)(mu-H)] (E = S, O) is reported. Addition of P(C4H3E)3 to [Ru3(CO)10(mu-dppm)] (1) at room temperature in the presence of Me3NO gives simple substitution products [Ru3(CO)9(mu-dppm)(P(C4H3E)3)] (E = S, 2; E = O, 3). Mild thermolysis in the presence of further Me3NO affords the thiophyne and furyne complexes [Ru3(CO)7(mu-dppm)(mu3-eta2-C4H2E)(mu-P(C4H3E)2)(mu-H)] (E = S, 4; E = O, 6) resulting from both carbon-hydrogen and carbon-phosphorus bond activation. In each the C4H2E (E = S, O) ligand donates 4-electrons to the cluster and the rings are tilted with respect to the mu-dppm and the phosphido-bridged open triruthenium unit. Heating 4 at 80 degrees C leads to the formation of the ring-opened cluster [Ru3(CO)5(mu-CO)(mu-dppm)(mu3-eta3-SC4H3)(mu-P(C4H3S)2)] (5) resulting from carbon-sulfur bond scission and carbon-hydrogen bond formation and containing a ring-opened mu3-eta3-1-thia-1,3-butadiene ligand. In contrast, a similar thermolysis of 3 affords the phosphinidene cluster [Ru3(CO)7(mu-dppm)(mu3-eta2-C4H2O)(mu3-P(C4H3O))] (7) resulting from a second phosphorus-carbon bond cleavage and (presumably) elimination of furan. Treatment of 4 and 6 with PPh3 affords the simple phosphine-substituted products [Ru3(CO)6(PPh3)(mu-dppm)(mu3-eta2-C4H2E)(mu-P(C4H3E)2)(mu-H)] (E = S, 8; E = O, 9). Both thiophyne and furyne clusters 4 and 6 readily react with hydrogen bromide to give [Ru3(CO)6Br(mu-Br)(mu-dppm)(mu3-eta2-eta1-C4H2E)(mu-P(C4H3E)2)(mu-H)] (E = S, 10; E = O, 11) containing both terminal and bridging bromides. Here the alkynes bind in a highly unsymmetrical manner with one carbon acting as a bridging alkylidene and the second as a terminally bonded Fisher carbene. As far as we are aware, this binding mode has only previously been noted in ynamine complexes or those with metals in different oxidation states. The crystal structures of seven of these new triruthenium clusters have been carried out, allowing a detailed analysis of the relative orientations of coordinated ligands.

Reinvestigation of the reaction of [Ru3(CO)12] with 2-mercaptobenzothiazole: X-ray structure of [(μ-H)2Ru3 (μ-η2-C7H4NS2)(μ3-η2-C7H4NS2)(CO)7]

Treatment of Ru3(CO)12 with 2-mercaptobenzothiazole at 68°C gave the known compound [(μ-H)Ru3(μ3-η2-C7H4NS2)(CO)9] 1 and the new compound [(μ-H)2Ru3(μ-η2-C7H4NS2) (μ3-η2-C7H4NS2)(CO)7] 2 in 15 and 10% yields respectively. Compound 2 has been characterized by elemental analysis, infrared, 1H NMR and mass spectroscopic data together with single crystal X-ray crystallography. It crystallizes in the monoclinic space group C2/c with a = 31.662(6), b = 14.577(3), c = 11.602(2) Å, β = 104.15(3)°, Z = 8, and V = 5192.4(2) Å3. The compound consists of a Ru3 triangle with three different Ru-Ru bond lengths [2.75264, 2.79084, 2.97604 Å] and the two 2-mercaptobenzothiazole ligands are differently attached to the metal atoms. Compound 2 is also obtained by the reaction of 1 with excess 2-mercaptobenzothiazole at 68°C.