3H‐Phosphaallenes Revisited: Facile Synthesis by Hydroalumination of Alkynylphosphines and β‐Elimination, Stability and Trapping of Transient Species by Coordination to Transition Metal Atoms. Issue 18 (1st March 2019)

• Record Type: Journal Article
• Authors: Klöcker, Hans; Tendyck, Jonas C.; Keweloh, Lukas; Hepp, Alexander; Uhl, Werner
• Is Part Of: Chemistry. Volume 25:Issue 18(2019)
• Page Start: 4793
• Page End: 4807
• Publication Date: 2019-03-01
• Subjects: alkynylphosphines -- coordination compounds -- frustrated Lewis pairs -- hydroalumination -- phosphaallenes; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201806334
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: A facile method for the efficient synthesis of 3H‐phosphaallenes, R−P=C=C(H)−R′, is presented, which comprises treatment of dialkynylphosphines with dialkylaluminium hydrides (hydroalumination) and elimination of aluminium alkynides from intermediate alkenyl‐alkynylphosphines. The stability of the phosphaallenes depends on steric shielding by the substituents at phosphorus (aryl or CH(SiMe3 )2 groups). Only supermesityl compounds are persistent at room temperature in solution. This simple method starting with easily accessible dialkynylphosphines and commercially available aluminium hydrides (HAlEt2, HAl i Bu2 ) allows the generation of transient species, which were trapped by coordination to transition metals. The η 1 ‐coordination via a P−W bond was observed for tungsten, while the side‐on coordination via the P=C bond resulted with platinum. Decomposition of the mesityl derivative yielded an unprecedented product, which may be formed by 1, 3‐H shift to the P atom, hydrophosphination of the P=C bond of a second phosphaallene and formation of a P−P bond. Abstract : Break through : 3H‐Phosphaallenes form a fascinating class of compounds with respect to bonding and reactivity. Hydroalumination of dialkynylphosphines and elimination of aluminium alkynides represent a new method for the efficient generation of various persistent and transient derivatives including alkyl compounds in a multigram scale. Side‐on coordination of platinum atoms and a new decomposition pathway are reported.