91030-50-1Relevant academic research and scientific papers
Assessment of the T1 Criterion for Distinguishing between Classical and Nonclassical Transition-Metal Hydrides: Hydride Relaxation Rates in Tris(triarylphosphine)osmium Tetrahydrides and Related Polyhydrides
Desrosiers, Peter J.,Cai, Lisheng,Lin, Zerong,Richards, Rosalie,Halpern, Jack
, p. 4173 - 4184 (2007/10/02)
[OsH4(PTol3)2] (1, Tol = ρ-tolyl) and a series of related isotopomers [OsHxD4-x{P(Tol-o-d2)3}3] (x = 1, 2, 3, and 4) were prepared and hydride spin-lattice relaxation times, 7, determined as a function of temperature for each one. From these measurements the contributions to the relaxation rates of the hydride ligands from the other hydrides and from the ortho protons of the triarylphosphine ligands were determined to be 62% and 33%, respectively. Taking account of these, as well as of the contributions from the phosphorus nuclei (2%) and osmium nucleus (-1 (T1 (min) = 238 ms at 500 MHz) agrees to within 3% with the measured one, 4.29 s-1. Similar calculations were performed on 33 other classical hydrides for which the relaxation rates at 500 MHz ranged from 1.67 to 9.09 s-1M (T1min) at 500 MHz from 670 to 110 ms). For the majority of these, the calculated and observed relaxation rates agree to within 10%, with contributions from dipole-dipole interactions with nuclei other than metal-coordinated protons accounting for more than 60% of the observed relaxation rates. Such contributions, typically, have been neglected in previous interpretations of T1(min). For nonclassical hydrides, i.e. those containing η2-H2 ligands, agreement between observed and calculated relaxation rates was less satisfactory. Even in such cases dipole-dipole interactions with nuclei other than metal-coordinated protons account for up to 25% of the observed relaxation rates emphasizing that, in general, such interactions cannot be ignored. There is an overlap between the range of T1(min) values found for classical and nonclassical polyhydrides. For several polyhydrides of undetermined structure, such as [OsH5(PTol3)3]+, [RuH4(PCy3)3], and [RuH6(PCy3)2] (including some that had previously been assigned nonclassical structures on the basis of the T1 criterion ), T1 (min) is shown to be consistent with both classical and nonclassical structures.
COMPLEXES OF RHENIUM AND OSMIUM POLYHYDRIDES WITH METALLIC LEWIS ACIDS: X-RAY CRYSTAL STRUCTURE OF i2)2>2>
Connelly, Neil G.,Howard, Judith A.K.,Spencer, John L.,Woodley, Pamela K.
, p. 2003 - 2010 (2007/10/02)
Bis(di-isopropylphenylphosphine)heptahydridorhenium(VII) (1) reacts with AgPF6, AgI, CuI, and HgCl2 to give the heterometallic complexes i2)2>2> (2) and i2)2>> (3); i2)2>> (4); i2)2>> (5); and i2)2>> (6) respectively, without loss of hydrogen.Similarly, i2)2> reacts with HgCl2 to give i2)2>>.Complex formation is accompanied by only subtle changes in the hydride (1)H n.m.r. shifts ( ( Z = 2), with lattice parameters a = 13.188(6), b = 16.014(6), c = 14.827(6) Angstroem, α = 112.47(3), β = 101.03(3), and γ = 90.65(3)deg.The structure was solved and refined to R = 0.048 (R' = 0.047) for 4 452 reflections having 2Θ 50 deg (Mo-KαX-radiation) collected at 200 K.The complex cation comprises a silver atom and two Re(PPhPri2)2 fragments arranged linearly (Re-Ag-Re 172deg, mean Re-Ag 2.873 Angstroem ).No evidence of the hydride ligands was found from the diffraction study.
