Crown ethers: sensors for ions and molecular scaffolds for materials and biological models.

First- and second-sphere coordination chemistry of alkali metal crown ether complexes

Cationic Aluminum Alkyl Complexes Incorporating Amidinate Ligands. Transition-Metal-Free Ethylene Polymerization Catalysts

Structural and Raman spectroscopic studies as complementary tools in elucidating the nature of the bonding in polyiodides and in donor-I2 adducts

1,8-Bis(tetramethylguanidino)naphthalene (TMGN, 1) is a new, readily accessible, and stable proton sponge with an experimental pKBH+ value of 25.1 in MeCN, which is nearly seven orders of magnitude higher in basicity than the classical proton sponge 1,8-bis(dimethylamino)-naphthalene (DMAN). Because of the sterically less crowded character of the proton-accepting sp2-nitrogen atoms, TMGN also has a higher kinetic basicity than DMAN, which is shown by time-resolved proton self-exchange reactions. TMGN is more resistant to hydrolysis and is a weaker nucleophile towards the alkylating agent EtI in comparison to the commercially available guanidine 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD). Crystal structures of the free base, of the mono- and bisprotonated base were determined. The dynamic behavior of all three species in solution was investigated by variable-temperature 1H NMR experiments. G values obtained by spectra simulation reveal a concerted mechanism of rotation about the C-N bonds of the protonated forms of TMGN.

1,8-Bis(tetramethylguanidino)naphthalene (TMGN): A New, Superbasic and Kinetically Active “Proton Sponge”

The reaction of HCl(g), H 2 O, and 18-crown-6 in toluene gives [H 3 O•18-crown-6] [Cl−H−Cl]•3.6 tol (tol=toluene), from which crystals of [H 3 O•18-crown-6] [Cl−H−Cl] are isolated: space group P2 1 /c. The liquid clathrate dissolves KCl, and upon standing, the solution affords crystals of [K•18-crown-6] [Cl−H−Cl]: space group P2 1 /c. In a similar fashion, the liquid clathrate dissolves MgCl 2 and yields [Mg•18-crown-6] [Cl−H−Cl]2: space group Pbca. The [Br−H−Br] − anion is produced by the reaction of HBr(g), H 2 O, and 18-crown-6 in toluene

Synthesis of salts of the hydrogen dichloride anion in aromatic solvents. 2. Syntheses and crystal structures of [K.cntdot.18-crown-6][Cl-H-Cl], [Mg.cntdot.18-crown-6][Cl-H-Cl]2, [H3O.cntdot.18-crown-6][Cl-H-Cl], and the related [H3O.cntdot.18-crown-6][Br-H-Br]

Synthesis and x-ray Structure of [H3O+.cntdot.18-crown-6][I7-]. A New Infinite Sawhorse Geometry for I7- Crystallized from a Liquid Clathrate Medium

The title compound was synthesized by the reaction of [H3O+·18-crown-6][Cl-H-Cl−]·38 C6H5Me with two equivalents of H2O Colorless crystals, which slowly deposited from the corresponding liquid clathrate, belong to the monoclinic space group P21/n witha=10648(6),b=9571(2),c=20801(6) A,β=9867(5)°, andD
c=124 g cm−3 forZ=4 Refinement based on 1609 observed reflections led to a finalR value of 0072 In the crystal structure the [H3O+·18-crown-6]+ cations are packed in layers separated by puckered sheets of [(H5O
 2
 +
 )(Cl−)2]−

Preparation and X-ray structure of [H3O+18-crown-6]-[(H5O 2 + )(Cl?)2], a compound containing both H3O+ and H5O 2 + crystallized from aromatic solution

Liquid clathrate media containing transition metal halocarbonyl anions; formation and crystal structures of [K+ · 18-crown-6][Cr(CO)5Cl], [H3O+ · 18-crown-6][W(CO)5Cl], [H3O+ · 18-crown-6][W(CO)4Cl3], and [H2O · bis-aza-18-crown-6 · (H+)2][W(CO)4Cl3]2

[H3O+·18-crown-6][Br−Br−Br−] crystallizes in the triclinic space group P 1 witha=6.105(1),b=8.658(1),c=11.072(1)A, α=71.35(1), β=77.58(1), γ=71.09(1)0, andDc=1.68 g cm−3 forZ=1. Refinement based on 1112 observed reflections led toR=0.044. The cation exhibits a planar oxonium ion bonded symmetrically to the 18-crown-6 (O(oxonium) resides 0.092 A out of the plane of the crown ether oxygen atoms). The anion also resides on a center of inversion with Br−Br=2.530(1)A.

Synthesis and X-ray structure of [H3O+·18-crown-6] [Br−Br−Br−]; a compound containing both H3O+ and a linear and symmetrical Br 3 t- ion crystallized from aromatic solution

Michael T. May

Papers

Synthesis of salts of the hydrogen dichloride anion in aromatic solvents. 2. Syntheses and crystal structures of [K.cntdot.18-crown-6][Cl-H-Cl], [Mg.cntdot.18-crown-6][Cl-H-Cl]2, [H3O.cntdot.18-crown-6][Cl-H-Cl], and the related [H3O.cntdot.18-crown-6][Br-H-Br]

Synthesis and x-ray Structure of [H3O+.cntdot.18-crown-6][I7-]. A New Infinite Sawhorse Geometry for I7- Crystallized from a Liquid Clathrate Medium

Preparation and X-ray structure of [H3O+18-crown-6]-[(H5O 2 + )(Cl?)2], a compound containing both H3O+ and H5O 2 + crystallized from aromatic solution

Liquid clathrate media containing transition metal halocarbonyl anions; formation and crystal structures of [K+ · 18-crown-6][Cr(CO)5Cl], [H3O+ · 18-crown-6][W(CO)5Cl], [H3O+ · 18-crown-6][W(CO)4Cl3], and [H2O · bis-aza-18-crown-6 · (H+)2][W(CO)4Cl3]2

Synthesis and X-ray structure of [H3O+·18-crown-6] [Br−Br−Br−]; a compound containing both H3O+ and a linear and symmetrical Br 3 t- ion crystallized from aromatic solution