160226-72-2Relevant academic research and scientific papers
Hydride complexes of ruthenium and related metals: Preparation and structures of Cp(PMe3)2RuH and [Cp(PMe3)2RuH2]BF4
Lemke, Frederick R.,Brammer, Lee
, p. 3980 - 3987 (1995)
The reaction of Cp(PMe3)2RuCl with either KOMe in MeOH or LiAlH4 in Et2O produces the hydride Cp(PMe3)2RuH (1) in high yield. Protonation of 1 with HX quantitatively generates the dihydrides [Cp(PMe3)2RuH2]X (X = Cl (2), BF4 (3), 6[3,5-(CF3)2C6H3]4 (4)). The spectroscopic data on 3 indicate a classical dihydride configuration with no evidence for a dihydrogen tautomer. The pKa of 3 in CH2Cl2 is 13.9, and the contribution of the ancillary ligands to the pKa value is discussed. X-ray crystal structures of hydride 1 and dihydride 3 have been determined. Hydride 1 exhibits a three-legged piano stool geometry, while the cation of 3 exhibits a four-legged piano stool geometry, consistent with the classical dihydride configuration. A comparison of the structures of 1 and 3 with related d6 Cp′L2-MH, d1 Cp′L2MH2, and d6 Cp′L2M(η2-H2) complexes (Cp′ = η5-C5H5) η5-C5Me5, η5-C5H5Me) reveals several general structural trends. First, the angle between the Cp′ plane and the ML2 plane lies in the range 59-79° (mean 67.6(13)°) for d6 Cp′L2MH complexes but is in the range 86-90° (mean 87.6(4)°) for d4 Cp′L2MH2 complexes and has a mean value of 56.1(8)° for known d6 Cp′L2M(η2-H2) complexes. Second, the angle between the M-H vector and the normal to the ML2 plane is generally less than 10° (mean 7.9(12)°) for the d6 Cp′L2MH complexes, while in d4 Cp′L2MH2 complexes the M-H vector is shifted toward the ML2 plane, increasing this angle by ca. 20° (mean 30.0(20)°). The corresponding angle in d6 Cp′L2M-(η2-H2) complexes has a mean value of 15.5(18)°. Third, the L-M-L′ angles in d6 Cp′L2MH complexes (range 84-101°, mean 93.0(19)°) are typically smaller that the corresponding angles in d4 Cp′L2MH2 complexes (range 101-111°, mean 107.2(10)°).
