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Two Different Structural Motifs Observed for Dimeric Dialkylaluminum and Dialkylgallium Alkynides [R 2 E‐C≡C‐C 6 H 5 ] 2
Author(s) -
Uhl Werner,
Breher Frank,
Haddadpour Sima,
Koch Rainer,
Matar Madhat
Publication year - 2004
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.200400150
Subject(s) - triple bond , chemistry , molecule , gallium , steric effects , crystallography , lithium (medication) , alkyne , group 2 organometallic chemistry , quantum chemical , stereochemistry , double bond , polymer chemistry , organic chemistry , medicine , endocrinology , catalysis
The dialkylaluminum and dialkylgallium alkynides [R 2 E‐C≡C‐R′] 2 (R = Me, CMe 3 ; E = Al, Ga; R′ = Ph) containing C≡C triple bonds attached to their central aluminum or gallium atoms are easily obtained by the reactions of dialkylelement chlorides with lithium alkynides or by treatment of the corresponding alkyne R‐C≡C‐H with dialkylaluminum or dialkylgallium hydrides. The first reaction is favored by the precipitation of LiCl, the second one by the formation of elemental hydrogen. All products form dimers in which the carbanionic carbon atoms of the alkynido groups adopt bridging positions, but, interestingly, different types of molecular structures were observed depending on the steric demand of the substituents terminally attached to the aluminum or gallium atoms. The small methyl substituents gave structures in which the aluminum or gallium atoms seemed to be side‐on coordinated by the C≡C triple bonds of almost linear E‐C≡C groups. In contrast, the more bulky tert ‐butyl groups forced an arrangement in which the C≡C triple bonds were perpendicular to the E‐E axis of the molecules. Different bonding modes result, which were analyzed by quantum‐chemical calculations.