Hydrogenation reactions catalyzed by HN(CH 2 CH 2 PR 2 ) 2 -ligated copper complexes
HN(CH 2 CH 2 PR 2 ) 2 -ligated copper borohydride complexes, ( R PN H P)Cu(BH 4 ) (R = i Pr, Cy, t Bu), which can be prepared from ( R PN H P)CuBr and NaBH 4 , are capable of catalyzing the hydrogenation of aldehydes in an alcoholic solvent. More active hydrogenation catalysts are ( R PN H P)CuBr mi...
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Veröffentlicht in: | Inorganic chemistry frontiers 2021-10, Vol.8 (21), p.4634-4649 |
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Hauptverfasser: | , , , |
Format: | Artikel |
Sprache: | eng |
Schlagworte: | |
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Zusammenfassung: | HN(CH
2
CH
2
PR
2
)
2
-ligated copper borohydride complexes, (
R
PN
H
P)Cu(BH
4
) (R =
i
Pr, Cy,
t
Bu), which can be prepared from (
R
PN
H
P)CuBr and NaBH
4
, are capable of catalyzing the hydrogenation of aldehydes in an alcoholic solvent. More active hydrogenation catalysts are (
R
PN
H
P)CuBr mixed with KO
t
Bu, allowing various aldehydes and ketones to be efficiently reduced to alcohols except those bearing a nitro,
N
-unprotected pyrrole, pyridine, or an ester group, or those prone to aldol condensation (
e.g.
, 1-heptanal). Modifying the catalyst structure by replacing the NH group in (
i
Pr
PN
H
P)CuBr with an NMe group results in an inferior catalyst but preserves some catalytic activity. The hexanuclear copper hydride cluster, (
i
Pr
PN
H
P)
3
Cu
6
H
6
, is also competent in catalyzing the hydrogenation of aldehydes such as benzaldehyde and
N
-methyl-2-pyrrolecarboxaldehyde, albeit accompanied by decomposition pathways. The catalytic performance can be enhanced through the addition of a strong base or
i
Pr
PN
H
P. The three catalytic systems likely share the same catalytically active species, which is proposed to be a mononuclear copper hydride (
R
PN
H
P)CuH with the NH group bound to copper. |
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ISSN: | 2052-1553 2052-1545 2052-1553 |
DOI: | 10.1039/D1QI00776A |