Thermal transformations of tris(2-thienyl)phosphine (PTh3) at low-valent ruthenium cluster centers : Part I. Carbon-hydrogen, carbon-phosphorus and carbon-sulfur bond activation yielding Ru3(CO)8L{μ-Th2P(C4H2S)}(μ-H) (L = CO, PTh3), Ru3(CO)7(μ-PTh2)2(μ3-η2-C4H2S), Ru4(CO)9(μ-CO)2(μ4-η2-C4H2S)(μ4-PTh) and Ru5(CO)11(μ-PTh2)(μ4-η4-C4H3)(μ4-S)

• Reaction of Ru3(CO)12 with tris(2-thienyl)phosphine (PTh3) in CH2Cl2 at room temperature or in THF in the presence of a catalytic amount of Na[Ph2CO] furnishes the carbonyl substitution products Ru3(CO)11(PTh3) (1), Ru3(CO)10(PTh3)2 (2), and Ru3(CO)9(PTh3)3 (3). Heating 1 in toluene affords the cyclometalated cluster Ru3(CO)9{μ-Th2P(C4H2S)}(μ-H) (4) resulting from carbonyl loss and carbon-hydrogen bond activation, and both 4 and the substituted derivative Ru3(CO)8{μ-Th2P(C4H2S)}(PTh3)(μ-H) (5) resulted from the direct reaction of Ru3(CO)12 and PTh3 at 110 °C in toluene. Interestingly, thermolysis of 2 in benzene at 80 °C affords 5 together with phosphido-bridged Ru3(CO)7(μ-PTh2)2(μ3-η2-C4H2S) (6) resulting from both phosphorus-carbon and carbon-hydrogen bond activation of coordinated PTh3 ligand(s). Cluster 6 is the only product of the thermolysis of 2 in toluene. Heating cyclometalated 4 with Ru3(CO)12 in toluene at 110 °C yielded the tetranuclear phosphinidine cluster, Ru4(CO)9(μ-CO)2(μ4-η2-C4H2S)(μ4-PTh) (7), resulting from carbon-phosphorus bond scission, together with the pentaruthenium sulfide cluster, Ru5(CO)11(μ-PTh2)(μ4-η4-C4H3)(μ4-S) (8), in which sulfur is extruded from a thiophene ring. All the new compounds were characterized by elemental analysis, mass spectrometry, IR and NMR spectroscopy, and by single crystal X-ray diffraction analysis in case of clusters 4, 6, 7, and 8. Cluster 4 consists of a triangular ruthenium framework containing a μ3-Th2P(C4H2S) ligand, while 6 consists of a ruthenium triangle containing η2-μ3-thiophyne ligand and two edge-bridging PTh2 ligands. Cluster 7 exhibits a distorted square arrangement of ruthenium atoms that are capped on one side by a μ4-phosphinidene ligand and on the other by a 4e donating μ4-η2-C4H2S ligand. The structure of 8 represents a rare example of a pentaruthenium wing-tip bridged-butterfly skeleton capped by μ4-S and μ4-η4-C4H3 ligands. The compounds 4, 6, 7, and 8 have been examined by density functional theory (DFT), and the lowest energy structure computed coincides with the X-ray diffraction structure. The hemilabile nature of the activated thienyl ligand in 4 and 6 has also been computationally investigated.

Ämnesord

NATURVETENSKAP  -- Kemi -- Oorganisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Inorganic Chemistry (hsv//eng)

Nyckelord

C-P, C-H, and C-S bond scission

DFT

Functionalized phosphine

Ruthenium cluster

Thienyl

X-ray diffraction

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