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: Alkene metatheses in transition metal coordination spheres: dimacrocyclizations that join trans positions of square-planar platinum complexes to give topologically novel diphosphine ligands. Author: Shima T, Bauer EB, Hampel F, Gladysz JA. Journal: Dalton Trans; 2004 Apr 07; (7):1012-28. PubMed ID: 15252680. Abstract: The alkene-containing phosphines PPh((CH2)(n)CH=CH2)2)2 are prepared from PPhH(2), n-BuLi, and the corresponding bromoalkenes (1:2:2), and combined with the platinum tetrahydrothiophene complex [Pt(mu-Cl)(C(6)F(5))(S(CH2CH2(-))2)]2 to give the square-planar adducts trans-(Cl)(C(6)F(5))Pt(PPh((CH2)(n)CH=CH2)2)2 (11, 93-73%; n=a, 2; b, 3; c, 4; d, 5; e, 6; f, 8). Ring-closing metatheses with Grubbs' catalyst (2) are studied. With, two isomers of trans-(Cl)(C6F5)[formula: see text](14)Ph)(15e) are isolated after hydrogenation. Both form via dimacrocyclization between the trans-phosphine ligands, but differ in the dispositions of the PPh rings (syn, 31%; anti, 7%). The alternative intraligand metathesis product trans-(Cl)(C6F5)[formula: see text](14)Ph)2 (16e) is independently prepared by (i) protecting 4e as a borane adduct, H(3)B.PPh((CH(2))(6)CH=CH2)2, (ii) cyclization with 2 and hydrogenation to give H(3)B[formula: see text] (14), (iii) deprotection and reaction with 12. The sample derived from 11e contains < or = 2% 16e; mass spectra suggest that the other products are dimers or oligomers. The structures of syn-15e, anti-15e and 16e are verified crystallographically, and the macrocycle conformations analyzed. As expected from the (CH(2))(n) segment length, 11a undergoes intraligand metathesis to give (Z,Z)-trans-(Cl)(C6F5)Pt[formula: see text]CH2)2)2 (86%), as confirmed by a crystal structure of the hydrogenation product. Although 11b does not yield tractable products, 11c gives syn-(E,E)-trans-(Cl)(C6F5[formula:see text](21%). This structure, and that of the hydrogenation product (syn-15c; 95%), are verified crystallographically. Analogous sequences with 11d,f give syn-15d (5 and 14% overall).[Abstract] [Full Text] [Related] [New Search]