Preparation and Structural Characterization of Three Types of Homo- and Heterotrinuclear Boron Complexes: Salen{[B-O-B][O2BOH]}, Salen{[B-O-B][O2BPh]}, and Salen{[B-O-B][O2<
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- 作者：Gabriela Vargas ; Irá ; n Herná ; ndez ; Herbert Hö ; pfl ; Marí ; a-Eugenia Ochoa ; Dolores Castillo ; Norberto Farfá ; n ; Rosa Santillan ; and Elizabeth Gó ; mez
- 刊名：Inorganic Chemistry
- 出版年：2004
- 出版时间：December 27, 2004
- 年：2004
- 卷：43
- 期：26
- 页码：8490 - 8500
- 全文大小：319K
- 年卷期：v.43,no.26(December 27, 2004)
- ISSN：1520-510X
文摘
Three types of homo- and heterotrinuclear boron complexes have been obtained in moderate to good yields fromreactions of salen-type ligands with boric acid and combinations of boric acid with phenylboronic and phenylphosphonicacid. The products are air-stable and have relatively high melting points (>290 
C) but are poorly soluble or insolublein common organic solvents. They have been characterized as far as possible by elemental analysis, massspectrometry, IR, 1H, 11B, and 31P NMR spectroscopy, and X-ray crystallography. Furthermore, theoretical calculationshave been performed for representative examples to permit a complete comparison of the different structure types.A detailed analysis of the molecular structures showed that the complexes are constructed around a central B3O3or B2PO3 ring. The salen ligands are attached to two boron atoms of these rings, which have therefore tetrahedralcoordination geometries. The complexes contain seven- and eight-membered heterocycles of the B2CnON2 (n =2, 3) type with chair or twisted-chair and boat-chair or chair-chair conformations, respectively. In the homotrinuclearcomplexes one of the three boron atoms is three-coordinate and can therefore still act as Lewis acid, thus makingthese products interesting for catalytic applications, e.g. in asymmetric synthesis. Depending on the substitutentsattached to the boron atoms, these complexes show a relationship with either trimetaboric acid, boroxine, or thetetraborate dianion found in Borax.
C) but are poorly soluble or insolublein common organic solvents. They have been characterized as far as possible by elemental analysis, massspectrometry, IR, 1H, 11B, and 31P NMR spectroscopy, and X-ray crystallography. Furthermore, theoretical calculationshave been performed for representative examples to permit a complete comparison of the different structure types.A detailed analysis of the molecular structures showed that the complexes are constructed around a central B3O3or B2PO3 ring. The salen ligands are attached to two boron atoms of these rings, which have therefore tetrahedralcoordination geometries. The complexes contain seven- and eight-membered heterocycles of the B2CnON2 (n =2, 3) type with chair or twisted-chair and boat-chair or chair-chair conformations, respectively. In the homotrinuclearcomplexes one of the three boron atoms is three-coordinate and can therefore still act as Lewis acid, thus makingthese products interesting for catalytic applications, e.g. in asymmetric synthesis. Depending on the substitutentsattached to the boron atoms, these complexes show a relationship with either trimetaboric acid, boroxine, or thetetraborate dianion found in Borax.