Effect of the Positioning of Metal Centers on a Cavitand in the Ruthenium-Catalyzed <i>N</i>-Alkylation of Amines
Two bis-ruthenium(II) complexes, namely <i>N</i>,<i>N′</i>-{5,17-diamino-4(24),6(10),12(16),18(22)-tetramethylenedioxy-2,8,14,20-tetrapentylresorcin[4]arene}-bis-[dichloro-(<i>p</i>-cymene)-ruthenium(II)] (<b>1</b>) and <i>N</i>,<i>N′...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-02-01
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| Series: | Molecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1420-3049/30/4/951 |
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| Summary: | Two bis-ruthenium(II) complexes, namely <i>N</i>,<i>N′</i>-{5,17-diamino-4(24),6(10),12(16),18(22)-tetramethylenedioxy-2,8,14,20-tetrapentylresorcin[4]arene}-bis-[dichloro-(<i>p</i>-cymene)-ruthenium(II)] (<b>1</b>) and <i>N</i>,<i>N′</i>-{5,11-diamino-4(24),6(10),12(16), 18(22)-tetramethylenedioxy-2,8,14,20-tetrapentylresorcin[4]arene}-bis-[dichloro-(<i>p</i>-cymene)-ruthenium(II)] (<b>2</b>) were synthesized and tested as catalysts in the <i>N</i>-alkylation of primary amines with arylmethyl alcohol using the green “hydrogen borrowing” methodology. The catalytic results were compared with those obtained when the <i>N</i>-{5-amino-4(24),6(10),12(16),18(22)-tetramethylenedioxy-2,8,14,20-tetrapentyl-resorcin[4]arene}-[dichloro-(<i>p</i>-cymene)-ruthenium(II)] (<b>3</b>) complex was employed as catalyst. The rate of the <i>N</i>-alkylation of aniline with benzyl alcohol increased in the order <b>3</b> < <b>1</b> ≪ <b>2</b>, which highlights the importance of the relative positioning of the two metal centers on the upper rim of the resorcin[4]arene. Theoretical investigations suggest that the grafting of the two “RuCl<sub>2</sub>(<i>p</i>-cymene)NH<sub>2</sub>” moieties on two distal aromatic rings of the cavitand allows a cooperative effect between a ruthenium atom and the coordinated amine of the second metal center. |
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| ISSN: | 1420-3049 |