647012-10-0Relevant articles and documents
Alkene Metatheses in Transition Metal Coordination Spheres: Effect of Ring Size and Substitution on the Efficiencies of Macrocyclizations that Join Trans Positions of Square-Planar Platinum Complexes
Bauer, Eike B.,Hampel, Frank,Gladysz
, p. 5567 - 5580 (2008/10/09)
Reactions of KPPh2 and Br(CH2)nCH=CH 2 give the phosphines PPh2(CH2) nCH=CH2 (n = a, 4; b, 6; c, 8; d, 9; 95-41%), which are combined with the platinum tetrahydrothiophene complex [Pt(μ-Cl)(C 6F5)(S(CH2CH2-)2)] 2 to give trans-(Cl)(C6F5)Pt(PPh 2(CH2)nCH=CH2)2 (3a-d, 71-54%). When treated with Grubbs' catalyst, ring-closing alkene metatheses occur to give 13- to 23-membered macrocycles with trans-spanning diphosphine ligands (96-85%, including some dimeric or oligomeric byproducts). The mixtures of C=C isomers are hydrogenated (1 atm, 10% Pd/C) to give trans-(Cl)(C 6F5)Pt(PPh2(CH2) 2n+2PPh2) (6a-d), which are isolated in 72-50% yields. Comparable results are obtained with (1) the second-generation dihydroimidazolylidene Grubbs' catalyst and (2) a series of compounds derived from the dimethylated phosphine Ph2P(CH2) 2C(CH3)2(CH2)3CH=CH 2, in turn prepared by sequential reactions of BrCH 2CH2C(CH3)2CH2CH 2Br with BrMgCH2CH=CH2/Li2CuCl 4 and KPPh2. The crystal structures of 6a-d are analyzed, but no special features that would promote intramolecular macrocyclizations are noted. A reaction of [Pt(μ-Cl)(C6F5)(S(CH 2CH2-)2)]2 and the diphosphine Ph2P(CH2)14PPh2 leads to a multitude of products and little 6b (15%).
