Ion-Bearing Propellers:  Alkali Metal Complexes of Tris(2-alkoxyphenyl)amine Ionophores

Abstract

NMR spectroscopic studies reveal that binding of Na(+) by tris(2-methoxyphenyl)amine (3) brings two of these tripod ethers together about the metal ion; the related double-tripod-ether ionophore 1,2-bis[2-(bis(2-methoxyphenyl)amino)phenoxy]ethane (4), in which two triarylamines are covalently attached, binds LiI, LiBPh(4), NaI, NaBPh(4), and KB(4-ClPh)(4). Dynamic NMR puts lower limits on binding free energies of 4 for Na(+) (71.8 kJ mol(-)(1)) and K(+) (66.8 kJ mol(-)(1)) ions. X-ray studies of 3(2).NaBPh(4), 4.NaBPh(4), 4.NaB(4-ClPh)(4), and 4.KB(4-ClPh)(4).CH(3)NO(2) show eight-coordinate M(+) ions bound between crystallographically independent, homochiral triarylamine tripod ethers in structures reminiscent of alkali metal [2.2.2] cryptates. Complexes crystallize as follows: 3(2).NaBPh(4), monoclinic, P2(1)/c, Z = 4, a = 10.701(3) Å, b = 37.593(3) Å, c = 13.774(2) Å, and beta = 98.24(2) degrees; 4.NaBPh(4), triclinic, P&onemacr;, Z = 2, a = 12.157(1) Å, b = 14.811(1) Å, c = 15.860(2) Å, alpha = 105.400(8) degrees, beta = 91.594(9) degrees, and gamma = 95.354(8) degrees; 4.NaB(4-ClPh)(4), monoclinic, P2(1)/n, Z = 4, a = 13.652(5) Å, b = 18.75(1) Å, c = 22.805(5) Å, and beta = 92.21(5) degrees; 4.KB(4-ClPh)(4).CH(3)NO(2), monoclinic, Pn, Z = 2, a = 13.663(4) Å, b = 12.228(3) Å, c = 18.712(8) Å, and beta = 91.45(3) degrees. They show variable N-M-N angles; 3(2).NaBPh(4) is surprisingly bent ( angleN-Na-N = 154.5 degrees ), while the 4.M(+) complexes are normal: nearly linear for Na(+) ( angleN-Na-N = 178.6, 178.1 degrees ) and again bent with the larger K(+) ( angleN-K-N = 164.5 degrees ). Finally, free 4 is structurally similar to 3; it crystallizes in the triclinic space group P&onemacr;, with Z = 2, a = 8.068(1) Å, b = 14.599(2) Å, c = 16.475(3) Å, alpha = 115.43(1) degrees, beta = 92.51(1) degrees, and gamma = 90.40(1) degrees.

Chapter 19. The co-ordination chemistry of open-chain polydentate ligands

“…R = 1 -methyl-4,5diphenyl-2-imidazolyl HLZ6' all R = 2-C5H4NMe-6 HL2" all R = 2-CsH4N studied. The cation [Fe'12Fe1112(L260)2(p-F)2(OH),(H20)z]2 is a class II mixed-valence compIex containing two dinudear {Fe2(LZ6')) fragments linked by fluoride bridges.454 The cation [ C O " ' , ( L ~~~~~-P ~O P O , X H , O ) O I Z + undergoes very rapid hydrolysis of the co-ordinated phenylphosphate bridge.455 The anion [RU"'(L~'~)(~-02CR),]has strong antiferromagnetic coupling (J = -400crn-') and undergoes two metal-centred reductions separated by 600 mV.456 Detailed 'H NMR spectroscopic studies on [Ni2(L263)(NCMe)4]4+ were performed to beIp understand the NMR spectra of Ni-based metal lop rote in^.^^' In [ C U , ( L ~~~) ( N C M ~) , ] ~+the Cu" centres are magnetically Whereas the podand ligands L264 and L265 are heptadentate N,O, donors to l a n t h a n i d e ~, 4 ~~+ ~~ [Pb(L'")] is four-co-ordinate (two co-ordinated bidentate arms) to leave a space in the co-ordination sphere for the stereochemically active lone pair.461 Solution NMR spectroscopic studies were performed on Na + complexes with various mixed ether/amine ligands, such as tetradentate N(C,H,OMe-2), and octadentate L266 462. Thecomplex [CO'~C~"(L~~~)(H,O)J-~H,O consists of ferrimagnetic chains which are antiferromagnetically ordered; reversible loss of the two waters of crystaIlisation changes the structure to one in which the ferrimagnetic chains become ferromagnetically ordered.463 In [M(Lz68)Jz-(M = Cu or Ni) the metal ions occupy the central tetradentate cavity; these are building blocks for magnetic polymers which may be formed by co-ordination of additional metal ions at the external 0,O-chelating sites.464 The structures, magnetic properties and eIectronic spectra of Cu" and vanadyl complexes of highly delocalised salen derivatives such as L269 (and numerous smaller tridentate and tetradentate analogues) were Deprotonatioo of the peripheral imidazole groups in dinuclear [CU,(H,L~'~)]~+ results in assembly of the polymer [(CU(L"~)),] via binding of the now bridging imidazoles to axial Cu" sites; very N HsLza X = C(0)H; Y = CI H3L265 X = Y = H occurs.466 Dinuclear Cu" and Nil' complexes of LZ7' form discotic r n e s ~p h a s e s .…”