Amine olefin rhodium(I) complexes: pKa and NH bond strength.
Torsten Büttner, Frank Breher, Hansjörg Grützmacher
Index: Chem. Commun. (Camb.) 24 , 2820-2821, (2004)
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Abstract
A combination of the rigid bis(5H-dibenzo[a,d]cyclohepten-5-yl)amine (trop(2)NH) and 5-amino-5H-dibenzo[a,d]cycloheptene (tropNH(2)) ligand allowed the synthesis of the stable pentacoordinated 18 electron amine olefin rhodium(i) complex [Rh(trop(2)NH)(tropNH(2))]O(3)SCF(3)(); this complex can be cleanly deprotonated [pK(a)(DMSO) = 20.6(1)] to the corresponding amide [Rh(trop(2)N)(tropNH(2))](6) which is reversibly oxidised at -0.466 V (vs. Fc/Fc(+)). The coordinated NH bond strength in is estimated to be 379 +/- 10 kJ mol(-1).
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