3053-60-9Relevant academic research and scientific papers
Alkene metatheses in transition metal coordination spheres: Dimacrocyclizations that join trans positions of square-planar platinum complexes to give topologically novel diphosphine ligands
Shima, Takanori,Bauer, Eike B.,Hampel, Frank,Gladysz
, p. 1012 - 1028 (2007/10/03)
The alkene-containing phosphines PPh((CH2)nCH=CH 2)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)(C6F 5)(S(CH2CH2-)2)]2 (12) to give the square-planar adducts trans-(Cl)(C6F5) Pt(PPh((CH2)nCH=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)Pt(PPh(CH2) 14P(CH2)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)(C6F 5)Pt(PPh(CH2)14)2 (16e) is independently prepared by (i) protecting 4e as a borane adduct, H 3B·PPh((CH2)6CH=CH2) 2, (ii) cyclization with 2 and hydrogenation to give H 3B·PPh(CH2)14, (iii) deprotection and reaction with 12. The sample derived from lie 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(PPh(CH2) 2CH=CH(CH2)2)2 (86%), as confirmed by a crystal structure of the hydrogenation product. Although lib does not yield tractable products, 11c gives syn-(E,E)-trans-(Cl)(C6F 5)Pt(PPh(CH2)4CH=CH(CH2) 4P(CH2)4CH=CH(CH2)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).
