1338777-83-5Relevant articles and documents
New nickel(ii) and iron(ii) helicates and tetrahedra derived from expanded quaterpyridines
Glasson, Christopher R. K.,Meehan, George V.,Motti, Cherie A.,Clegg, Jack K.,Turner, Peter,Jensen, Paul,Lindoy, Leonard F.
, p. 10481 - 10490 (2011/11/13)
As an extension of prior studies involving the linear quaterpyridine ligand, 5,5″′-dimethyl-2,2′:5′,5″:2″, 2″′-quaterpyridine 1, the synthesis of the related expanded quaterpyridine derivatives 2 and 3 incorporating dimethoxy-substituted 1,4-phenylene and tetramethoxy-substituted 4,4′-biphenylene bridges between pairs of 2,2′-bipyridyl groups has been carried out via double-Suzuki coupling reactions between 5-bromo-5′-methyl-2′- bipyridine and the appropriate di-pinacol-diboronic esters using microwave heating. Reaction of 2 and 3 with selected Fe(ii) or Ni(ii) salts yields a mixture of both [M2L3]4+ triple helicates and [M4L6]8+ tetrahedra, in particular cases the ratio of the products formed was shown to be dependent on the reaction conditions; the respective products are all sufficiently inert to allow their chromatographic separation and isolation. Longer reaction times and higher concentrations were found to favour tetrahedron formation. The X-ray structures of solvated [Ni2(2)3](PF6)4, [(PF6) ? Fe4(2)6](PF6) 7, [Fe4(3)6](PF6)8 and [Ni4(3)6](PF6)8 have been determined, while the structure of the parent Fe(ii) cage in the series, [(PF6) ? Fe4(1)6](PF6) 7, was reported previously. The internal volumes of the Fe(ii) tetrahedral cages have been calculated and increase from 102 A3 for [Fe4(1)6]8+ to 227 A3 for [Fe4(2)6]8+ to 417 A3 for [Fe4(3)6]8+ and to an impressive 839 A3 for [Ni4(3)6]8+. The corresponding void volume in the triple helicate [Ni2(2) 3]4+ is 29 A3.