These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Construction of titanasiloxanes by incorporation of silanols to the metal oxide model [(Ti(eta 5-C5Me5)(mu-O))3(mu3-CR)]: DFT elucidation of the reaction mechanism.
    Author: Carbó JJ, González-del Moral O, Martín A, Mena M, Poblet JM, Santamaría C.
    Journal: Chemistry; 2008; 14(26):7930-8. PubMed ID: 18613160.
    Abstract:
    A family of novel titanasiloxanes containing the structural unit ([Ti(eta 5-C5Me5)O]3) were synthesized by hydron-transfer processes involving reactions with equimolecular amounts of mu3-alkylidyne derivatives [(Ti(eta 5-C5Me5)(mu-O))(3)(mu3-CR)] (R=H (1), Me (2)) and monosilanols, R3'Si(OH), silanediols, R2'Si(OH)2, and the silanetriol tBuSi(OH)3. Treatment of 1 and 2 with triorganosilanols (R'=Ph, iPr) in hexane affords the new metallasiloxane derivatives [(Ti(eta 5-C5Me5)(mu-O))(3)(mu-CHR)(OSiR3')] (R=H, R'=Ph (3), iPr (4); R=Me, R'=Ph (5), iPr (6)). Analogous reactions with silanediols, (R'=Ph, iPr), give the cyclic titanasiloxanes [(Ti(eta 5-C5Me5)(mu-O))(3)(mu-O2SiR'2)(R)] (R=Me, R'=Ph (7), iPr (8); R=Et, R'=Ph (9), iPr (10)). Utilization of tBuSi(OH)3 with 1 or 2 at room temperature produces the intermediate complexes [(Ti(eta 5-C5Me5) (mu-O))(3)(mu-O2Si(OH)tBu)(R)] (R=Me (11), Et(12)). Further heating of solutions of 11 or 12 affords the same compound with an adamantanoid structure, [(Ti(eta 5-C5Me5)(mu-O))3(mu-O3SitBu)] (13) and methane or ethane elimination, respectively. The X-ray crystal structures of 3, 4, 6, 8, 10, 12, and 13 have been determined. To gain an insight into the mechanism of these reactions, DFT calculations have been performed on the incorporation of monosilanols to the model complex [(Ti(eta 5-C5H5)(mu-O))3(mu3-CMe)] (2 H). The proposed mechanism consists of three steps: 1) hydron transfer from the silanol to one of the oxygen atoms of the Ti3O3 ring, forming a titanasiloxane; 2) intramolecular hydron migration to the alkylidyne moiety; and 3) a mu-alkylidene ligand rotation to give the final product.
    [Abstract] [Full Text] [Related] [New Search]