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Alkenyl‐Alkynylgermanes Functionalised by Lewis Acids: Intramolecular Aluminium– and Gallium–Alkyne Interactions and Potential Ge–C Bond Activation
Author(s) -
Uhl Werner,
Pelties Stefan,
Rohling Martina,
Tannert Jens
Publication year - 2014
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201402132
Subject(s) - chemistry , intramolecular force , gallium , alkyne , isomerization , lewis acids and bases , medicinal chemistry , aluminium , frustrated lewis pair , hydride , metal , triple bond , stereochemistry , double bond , crystallography , polymer chemistry , catalysis , organic chemistry
Treatment of various diethynylgermanes, (R 1 ) 2 Ge(C≡C–R 2 ) 2 (R 1 = C 6 H 5 , CH 3 ; R 1 –R 1 = C 6 H 4 –C 6 H 4 ; R 2 = CH 3 , CMe 3 , n Bu, C 6 H 5 ), with equimolar quantities of di( tert ‐butyl)aluminium or ‐gallium hydride, R 2 E–H (E = Al, Ga), afforded mixed alkenyl‐alkynylgermanes, (R 1 ) 2 Ge(C≡C–R 2 )[C{E(CMe 3 ) 2 }=C(H)–R 2 ], by reduction of one of their C≡C triple bonds. The alkenyl groups have a cis arrangement of H and Al or Ga atoms across the C=C double bonds, which reflects the kinetically favoured situation. The cis / trans isomerisation is probably prevented from yielding thermodynamically favoured trans isomers; this is a result of an intramolecular bonding interaction between the α‐carbon atoms of the remaining ethynyl groups and the coordinatively unsaturated metal atoms. The higher Lewis acidity of Al compared to Ga results in relatively short Al ··· C(ethynyl) contacts (>231.2 pm) and a concomitant lengthening of the Ge–C bonds.