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Issue 7, 2004
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Alkene metatheses in transition metal coordination spheres: dimacrocyclizations that join trans positions of square-planar platinum complexes to give topologically novel diphosphine ligands

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Abstract

The alkene-containing phosphines PPh((CH2)nCH[double bond, length as m-dash]CH2)2)2 (4) are prepared from PPhH2, n-BuLi, and the corresponding bromoalkenes (1 ∶ 2 ∶ 2), and combined with the platinum tetrahydrothiophene complex [Pt(μ-Cl)(C6F5)(S(CH2CH2–)2)]2 (12) to give the square-planar adducts trans-(Cl)(C6F5)Pt(PPh((CH2)nCH[double bond, length as m-dash]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 11e, two isomers of trans-(Cl)(C6F5)[lower bond 1 start]Pt([upper bond 1 start]PPh(CH2)14P[lower bond 1 end](C[upper bond 1 end]H2)14Ph) (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)Pt([upper bond 1 start]PPh(C[upper bond 1 end]H2)14)2 (16e) is independently prepared by (i) protecting 4e as a borane adduct, H3B·PPh((CH2)6CH[double bond, length as m-dash]CH2)2, (ii) cyclization with 2 and hydrogenation to give H3[upper bond 1 start]PPh(C[upper bond 1 end]H2)14, (iii) deprotection and reaction with 12. The sample derived from 11e contains ≤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 (CH2)n segment length, 11a undergoes intraligand metathesis to give (Z,Z)-trans-(Cl)(C6F5)Pt([upper bond 1 start]PPh(CH2)2CH[double bond, length as m-dash]CH(C[upper bond 1 end]H2)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)[lower bond 1 start]Pt([upper bond 1 start]PPh(CH2)4CH[double bond, length as m-dash]CH(CH2)4P[lower bond 1 end](CH2)4CH[double bond, length as m-dash]CH(C[upper bond 1 end]H2)4Ph) (21%). This structure, and that of the hydrogenation product (syn-15c; 95%), are verified crystallographically. Analogous sequences with 11d,f give syn-15d,f (5 and 14% overall).

Graphical abstract: Alkene metatheses in transition metal coordination spheres: dimacrocyclizations that join trans positions of square-planar platinum complexes to give topologically novel diphosphine ligands

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Publication details

The article was received on 06 Jan 2004, accepted on 11 Feb 2004 and first published on 24 Feb 2004


Article type: Paper
DOI: 10.1039/B400156G
Dalton Trans., 2004, 1012-1028

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    Alkene metatheses in transition metal coordination spheres: dimacrocyclizations that join trans positions of square-planar platinum complexes to give topologically novel diphosphine ligands

    T. Shima, E. B. Bauer, F. Hampel and J. A. Gladysz, Dalton Trans., 2004, 1012
    DOI: 10.1039/B400156G

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