Electron-Deficient Early−Late Heterobimetallic Sulfido Clusters. Unusual Reactivities of Ti2Ru2S4 Cubane-Type Clusters with Four Cyclopentadienyl Coligands

Treatment of [Cp 2 Ti(SH) 2 ] ( 1; Cp = η 5 -C 5 H 5 ) with [(Cp*Ru) 4 (μ 3 -Cl) 4 ] ( 2; Cp* = η 5 -C 5 Me 5 ) in a Ti:Ru ratio of 1:1 afforded the hydrosulfido-bridged titanium−ruthenium heterobimetallic complex [Cp 2 Ti(μ 2 -SH) 2 RuClCp*] ( 3 ). Complex 3 reacted with an excess of triethylamine to give the early−late heterobimetallic cubane-type sulfido cluster [(CpTi) 2 (Cp*Ru) 2 (μ 3 -S) 4 ] ( 4 ), with a loss of HCl and cyclopentadiene. An X-ray diffraction study and extended Hückel molecular orbital calculations for the 60e - cluster 4 demonstrated that 4 has four Ru→Ti dative bonds and a weak Ti−Ti interaction. The reaction of 4 with 3 equiv of [Cp 2 Fe][PF 6 ] afforded the dicationic cubane-type cluster [(CpTi) 2 (Cp*Ru) 2 (μ 3 -S) 4 ][PF 6 ] 2 ( 5 ), which contains an additional Ru−Ru bond. In contrast, oxidation of 4 with an excess of HCl at room temperature resulted in the formation of the neutral dichloride cluster [(CpTiCl 2 )(CpTi)(Cp*Ru) 2 (μ 3 -S) 4 ] ( 6 ). Clusters 5 and 6 were converted into each other by treatment with chloride or hexafluorophosphate anion. Furthermore, substitution of one of the cyclopentadienyl ligands in 6 by a chloride anion took place in boiling 1,2-dichloroethane to give the trichloride cluster [(TiCl 3 )(CpTi)(Cp*Ru) 2 (μ 3 -S) 4 ] ( 7 ). The detailed structures of these oxidized cubane-type clusters 5 ·2DMF, 6 ·CH 2 Cl 2, and 7 ·CH 2 Cl 2 as well as the hydrosulfido-bridged dinuclear complex 3 have also been determined by X-ray crystallography. The Ti 2 Ru 2 S 4 cubane-type cores in 5 − 7 differ considerably in structure from each other, depending upon the ancillary ligands bound to the Ti atoms, although they have a Ru−Ru bond and two Ru→Ti dative bonds in common.