Synthesis and Reactivity toward H2 of (畏5-C5Me5)Rh(III) Complexes with Bulky Aminopyridinate Ligands

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• 作者：Ana Zamorano ; Nuria Rend贸n ; Jos茅 E. V. Valpuesta ; Eleuterio 脕lvarez ; Ernesto Carmona
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：July 6, 2015
• 年：2015
• 卷：54
• 期：13
• 页码：6573-6581
• 全文大小：574K
• ISSN：1520-510X

文摘

Electrophilic, cationic Rh(III) complexes of composition [(畏<sup>5sup>-C<sub>5sub>Me<sub>5sub>)Rh(Ap)]<sup>+sup>, (1<sup>+sup>), were prepared by reaction of [(畏<sup>5sup>-C<sub>5sub>Me<sub>5sub>)RhCl<sub>2sub>]<sub>2sub> and LiAp (Ap = aminopyridinate ligand) followed by chloride abstraction with NaBAr<sub>Fsub> (BAr<sub>Fsub> = B[3,5-(CF<sub>3sub>)<sub>2sub>C<sub>6sub>H<sub>3sub>]<sub>4sub>). Reactions of cations 1<sup>+sup> with different Lewis bases (e.g., NH<sub>3sub>, 4-dimethylaminopyridine, or CNXyl) led in general to monoadducts 1路L<sup>+sup> (L = Lewis base; Xyl = 2,6-Me<sub>2sub>C<sub>6sub>H<sub>3sub>), but carbon monoxide provided carbonyl鈥揷arbamoyl complexes 1路(CO)<sub>2sub><sup>+sup> as a result of metal coordination and formal insertion of CO into the Rh鈥揘<sub>amidosub> bond of complexes 1<sup>+sup>. Arguably, the most relevant observation reported in this study stemmed from the reactions of complexes 1<sup>+sup> with H<sub>2sub>. <sup>1sup>H NMR analyses of the reactions demonstrated a H<sub>2sub>-catalyzed isomerization of the aminopyridinate ligand in cations 1<sup>+sup> from the ordinary 魏<sup>2sup>-N,N鈥?coordination to a very uncommon, formally tridentate 魏-N,畏<sup>3sup> pseudoallyl bonding mode (complexes 3<sup>+sup>) following benzylic C鈥揌 activation within the xylyl substituent of the pyridinic ring of the aminopyridinate ligand. The isomerization entailed in addition H鈥揌 and N鈥揌 bond activation and mimicked previous findings with the analogous iridium complexes. However, in dissimilarity with iridium, rhodium complexes 1<sup>+sup> reacted stoichiometrically at 20 掳C with excess H<sub>2sub>. The transformations resulted in the hydrogenation of the C<sub>5sub>Me<sub>5sub> and Ap ligands with concurrent reduction to Rh(I) and yielded complexes [(畏<sup>4sup>-C<sub>5sub>Me<sub>5sub>H)Rh(畏<sup>6sup>-ApH)]<sup>+sup>, (2<sup>+sup>), in which the pyridinic xylyl substituent is 畏<sup>6sup>-bonded to the rhodium(I) center. New compounds reported were characterized by microanalysis and NMR spectroscopy. Representative complexes were additionally investigated by X-ray crystallography.