137436-59-0Relevant academic research and scientific papers
Synthesis and the kinetic and thermodynamic acidity of η2-dihydrogen and dihydride complexes of the type [Ru(C5Me5)H2L2]+. X-ray crystal structure determination of the complex [Ru(C5Me5) (η2-H2) (PPh2CH2PPh2)]BF4
Jia, Guochen,Lough, Alan J.,Morris, Robert H.
, p. 161 - 171 (2008/10/08)
A series of Cp*RuH(L2) complexes were readily prepared by the reaction of NaOMe (excess) with Cp*RuCl(L2) (L2 = dppm, dppp, (PPh3)2, (PMePh2)2, (PMe2Ph)2, (PMe3)2). The chloro starting materials were prepared in situ by the reactions of Cp*RuCl2 with L2 in the presence of Zn. Protonation of complexes Cp*RuH(L2) gives dihydride complexes [Cp*Ru(H)2(L2)]+ or a mixture of dihydride complexes [Cp*Ru-(H)2(L2)]+ and η2-dihydrogen complexes [Cp*Ru(η2-H2)(L2)]+, depending on the phosphines around the ruthenium center. Protonation of Cp*RuH(dppp) or CpRuH(L2) at -60°C gives initially as the exclusive product the dihydrogen complexes [Cp*Ru(η2-H2)(dppp)]+ or [CpRu(η2-H2)(L2)++ when L2 = R2PCH2CH2PR2 and R = C6H5, p-C6H4OMe, p-C6H4CF3. When the reactant is Cp*RuH(dppm), then both [Cp*Ru-(H)2(dppm)]+ and [Cp*Ru(η2-H2)(dppm)]+ are produced. Concurrent reactions at -60°C involving protonation at the metal center and at the hydride might occur in this case. The two tautomers of [Cp*RuH2(dppm)]+ start to interconvert at temperatures above -40°C. Protonation of Cp*RuH(PMePh2)2 at -60°C gives the dihydride [Cp*Ru(H)2(PMePh2)2]+ as the only product detectable by NMR spectroscopy. The dihydrogen complexes are thought to have slowly rotating dihydrogen ligands with an H-H distance of 1.1 A? on the basis of T1 and 1J(H,D) measurements. Acid-base equilibria for the complexes [Cp*RuH2L2]+ indicate that they have a pKa range from 8.8 to 16.3. An increase in the basicity of phosphine, L, results in a large decrease in the acidity of the complexes [CpRu(H)2L2]+ and [Cp*Ru(H)2L2]+. The Ru-H bond energy varies by 5 kcal mol-1, depending on L, as indicated by a thermodynamic cycle utilizing electrochemical potentials of the monohydride complexes. A single-crystal X-ray diffraction study of [Cp*Ru(η2-H2)-(dppm)]BF4 shows that it crystallizes in the space group P21 with cell parameters a = 10.853 (2) A?, b = 15.125 (6) A?, c = 10.992 (2) A?, β = 113.48 (2)°, Z = 2, V = 1655 (2) A?3, R = 0.046, and Rw = 0.049.
