名称:
XPS Investigations of (1,4,7-trimethyl-1,4,7-triazacyclononane)RhMe3 and [1,1,1-tris((dimethylphosphino)methyl)ethane]RhMe3 and Their Rh−C Cleavage Derivatives. Comparison of Hard- and Soft-Ligated Rhodium Organometallics
摘要:
The new molecules P(3)RhMe(3-n)(OTf)(n) are reported (n = 0-2; P-3 = MeC(CH(2)PMe(2))(3); OTf = OS(O)(2)CF3). The known fac-(Me(3)P)(3)RhMe(3) was converted to mer-(Me(3)P)(3)RhMe(3-n)Cl(n). (n = 1, 2) by cleavage with HCl in ether. X-ray photoelectron spectra (XPS) of these were recorded, and all except the P(3)RhMe(3-n)Cl(n) series afforded clean spectra. XPS were also obtained for the known CnRhMe(3-n)X(n) (n = 0-2; X = Cl, Br, OTf; Cn = 1,4,7-trimethyl-1,4,7-triazacyclononane), CnRhX(3) (X = Cl, Br), CnRhMe(OH)(OTf), and [CnRhMe(2)(CO)]OTf. An X-ray crystal structure of P(3)RhMe(3) is reported, and the geometry at the metal is compared among P(3)RhMe(3), (Me(3)P)(3)RhMe(3), and CnRhMe(3). Core binding energies (BEs) for the series L(3)RhMe(3-n)X(n) (L(3) = Cn, P-3) change linearly with n for a given L(3) and X. For CnRhMe(3-n)X(n), replacement of methyl by chloride or bromide gives similar Delta BE values (similar to 0.7 eV), while triflate-for-methyl substitution gives a much larger Delta BE (1.2 eV). Triflate-for-methyl substitution in P(3)RhMe(3-n)(OTf)(n), however, causes a Delta BE of only 0.8 eV. Thus, the Rh(3d(5/2)) core binding energies in these complexes change less in triflate-for-methyl substitutions when the P-3 ancillary ligand is present than in the presence of Cn; apparently P-3 compensates for changes in electron density at the rhodium center more effectively than does Cn, presumably as a result of the greater polarizability of phosphorus (softer) compared to nitrogen (harder). The XPS trends for these series effectively mean that P-3 makes Rh-III a softer metal and Cn makes Rh-III a harder metal.