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New Reactivity Patterns in 3H‐Phosphaallene Chemistry [Aryl‐P=C=C(H)‐ t Bu]: Hydroboration of the C=C Bond, Deprotonation and Trimerisation
Author(s) -
Tendyck Jonas C.,
Hepp Alexander,
Würthwein ErnstUlrich,
Uhl Werner
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202002506
Subject(s) - chemistry , hydroboration , borane , deprotonation , reactivity (psychology) , aryl , molecule , stereochemistry , crystallography , medicinal chemistry , double bond , catalysis , polymer chemistry , organic chemistry , medicine , ion , alkyl , alternative medicine , pathology
3H‐Phosphaallenes, R−P=C=C(H)C−R’ ( 3 ), are accessible in a multigram scale on a new and facile route and show a fascinating chemical reactivity. BH 3 (SMe 2 ) and 3 a (R=Mes*, R’= t Bu) afforded by hydroboration of the C=C bonds of two phosphaallene molecules an unprecedented borane ( 7 ) with the B atom bound to two P=C double bonds. This compound represents a new FLP based on a B and two P atoms. The increased Lewis acidity of the B atom led to a different reaction course upon treatment of 3 a with H 2 B‐C 6 F 5 (SMe 2 ). Hydroboration of a C=C bond of a first phosphaallene is followed in a typical FLP reaction by the coordination of a second phosphaallene molecule via B−C and P−B bond formation to yield a BP 2 C 2 heterocycle ( 8 ). Its B−P bond is short and the B‐bound P atom has a planar surrounding. Treatment of 3 a with t BuLi resulted in deprotonation of the β‐C atom of the phosphaallene ( 9 ). The Li atom is bound to the P atom as demonstrated by crystal structure determination, quantum chemical calculations and reactions with HCl, Cl‐SiMe 3 or Cl‐P t Bu 2 . The thermally unstable phosphaallene Ph−P=C=C(H)‐ t Bu gave a unique trimeric secondary product by P−P, P−C and C−C bond formation. It contains a P 2 C 4 heterocycle and was isolated as a W(CO) 4 complex with two P atoms coordinated to W ( 15 ).