| Abstract
| - Protonation of the classical trihydride [(triphos)RhH3] (2) at 210 K in either THF or CH2Cl2 by either HBF4·OMe2or CF3SO2OH gives the nonclassical η2-H2 complex [(triphos)Rh(η2-H2)H2]+ (1) [triphos = MeC(CH2PPh2)3].Complex 1 is thermally unstable and highly fluxional in solution. In THF above 230 K, 1 transforms into thesolvento dihydride complex [(triphos)Rh(η1-THF-d8)H2]+ (5) that, at room temperature, quickly converts to thestable dimer trans-[{(triphos)RhH}2(μ-H)2]2+ (trans-6). In CH2Cl2, 1 is stable up to 240 K. Above this temperature,the η2-H2 complex begins to convert into a mixture of trans- and cis-6, which, in turn, transform into the bridging-chloride dimers trans- and cis-[{(triphos)RhH}2(μ-Cl)2]2+ at room temperature. Complex 1 contains a fast-spinningH2 ligand with a T1min of 38.9 ms in CD2Cl2 (220 K, 400 MHz). An NMR analysis of the bis-deuterated isotopomer[(triphos)RhH2D2]+ (1-d2) did not provide a J(HD) value. At 190 K, the perdeuterated isotopomers [(triphos)RhD3] (2-d3) and 1-d4 show T1min values of 16.5 and 32.6 ms (76.753 MHz), respectively, for the rapidly exchangingdeuterides. An analogous 2-fold elongation of T1min is also observed on going from [(triphos)IrD3] to [(triphos)Ir(η2-D2)D2]+. A rationale for the elongation of T1min in nonclassical polyhydrides is proposed on the basis ofboth the results obtained and recent literature reports.
- Protonation of the classical trihydride [(triphos)RhH3] (2) at 210 K in either THF or CH2Cl2 by HBF4·OMe2 gives the nonclassical η2-H2 complex [(triphos)Rh(η2-H2)H2]+ (1) [triphos = MeC(CH2PPh2)3]. No J(HD) value is observed for the bis-deuterated isotopomer [(triphos)RhH2D2]+ (1-d2) because of both the high fluxionality and the fast relaxation rate of deuterium. At 190 K, the perdeuterated isotopomers [(triphos)RhD3] (2-d3) and [(triphos)Rh(η2-D2)D2]+ (1-d4) show T1min values of 16.5 and 32.6 ms (76.753 MHz), respectively, for the rapidly exchanging deuterides, respectively. An analogous 2-fold elongation of T1min is also observed on going from [(triphos)IrD3] to [(triphos)Ir(η2-D2)D2]+ deuterides, respectively. A rationale for the elongation of T1min in nonclassical polyhydrides is proposed on the basis of the results obtained as well as recent literature reports.
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