| 17140238 |
Foucault HM, Bryce DL, Fogg DE: A chelate-stabilized ruthenium (sigma-pyrrolato) complex: resolving ambiguities in nuclearity and coordination geometry through 1H PGSE and 31P solid-state NMR studies. Inorg Chem. 2006 Dec 11;45(25):10293-9.
Reaction of RuCl2 (PPh3) 3 with LiNN' (NN' = 2-[(2,6-diisopropylphenyl) imino] pyrrolide) affords a single product, with the empirical formula RuCl [(2,6-iPr2C6H3) N=CHC4H3N](PPh3) 2. We identify this species as a sigma-pyrrolato complex, [Ru (NN')(PPh3) 2] 2 (mu-Cl) 2 (3b), rather than mononuclear RuCl (NN')(PPh3) 2 (3a), on the basis of detailed 1D and 2D NMR characterization in solution and in the solid state. Retention of the chelating, sigma-bound iminopyrrolato unit within 3b, despite the presence of labile (dative) chloride and PPh3 donors, indicates that the chelate effect is sufficient to inhibit sigma --> pi isomerization of 3b to a piano-stool, pi-pyrrolato structure. 2D COSY, SECSY, and J-resolved solid-state 31P NMR experiments confirm that the PPh3 ligands on each metal center are magnetically and crystallographically inequivalent, and 31P CP/MAS NMR experiments reveal the largest 99Ru-31P spin-spin coupling constant (1J (99Ru,31P) = 244 +/- 20 Hz) yet measured. Finally, 31P dipolar-chemical shift spectroscopy is applied to determine benchmark phosphorus chemical shift tensors for phosphine ligands in hexacoordinate ruthenium complexes. |
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