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Reactivity of a P–H Functionalized Al/P‐Based Frustrated Lewis Pair – Hydrophosphination versus Classic Adduct Formation
Author(s) -
Uhl Werner,
Keweloh Lukas,
Hepp Alexander,
Stegemann Frank,
Layh Marcus,
Bergander Klaus
Publication year - 2017
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201700340
Subject(s) - chemistry , adduct , frustrated lewis pair , lewis acids and bases , reactivity (psychology) , stereochemistry , medicinal chemistry , moiety , diastereomer , hydrogen bond , molecule , catalysis , organic chemistry , medicine , alternative medicine , pathology
The P–H functionalized Al/P‐based frustrated Lewis pair (FLP) Mes(H)P–C[Al{CH(SiMe 3 ) 2 } 2 ]=C(H)– t Bu ( 3 ) has the typical functionality of FLPs with Lewis acidic and basic centers in a single molecule and is able to transfer the P bound H atom to activated substrates. Nevertheless, 3 reacted with NH 3 only by adduct formation with the N atom coordinated to Al ( 5 ). The relatively low basicity of the P atom prevented the formation of a hydrogen bridge between P and Al. Similarly, benzil and 3 afforded a simple adduct ( 6 ) with only one C=O group bonded to P and Al. The second C=O group and the P–H moiety were unaffected. 6 has two stereogenic centers, and the resulting diastereomers were identified by crystal structure determinations. Migration of the P bound H atom was only observed for substrates containing basic N atoms. Nitriles gave heterocyclic iminophosphine adducts ( 7 ) in which the N–H groups were coordinated to the Al atoms. An isocyanate and two isothiocyanates afforded adducts via Al– X and P–C bond formation ( X = O, S), and phosphaurea derivatives ( 8a to 8c ) resulted from H shift to the exocyclic N atoms. A carbodiimide reacted with 3 by the formation of a phosphaguanidine ( 8d ) with the imine N atom coordinated to Al. The latter reactions proceed under mild conditions and represent formally the hydrophosphination of unsaturated substrates.