A highly emissive inorganic hexamolybdenum cluster complex as a handy precursor for the preparation of new luminescent materials.

The synthesis and characterisation of a new, highly luminescent inorganic cluster complex, (Bu4N)2[Mo6I8(NO3)6], are described. The complex possesses labile nitrato ligands and is therefore a useful precursor for the design of new luminescent materials. To exemplify this, functionalised polystyrene beads have been utilised as "polymeric ligands" to immobilise the molybdenum cluster complex.

Unexpected ligand substitutions in the cluster core {Re6Se8}: synthesis and structure of the novel cluster compound Cs11(H3O)[Re6Se4(O)4Cl6]3.4H2O.

The compound Cs11(H3O)[Re6Se4(O)4Cl6]3.4H2O containing a novel cluster core {Re6Se4(O)4} with ordered ligands, where the 4 positions of one face of a Se4(O)4 cube are occupied exclusively by Se atoms and 4 O atoms lie in the opposite face was synthesized via the interaction of solid Re6Se8Br2 with molten KOH.

[[Cu(en)(2)](2)Re(4)Te(4)(CN)(12)].5H(2)O and [[Cu(en)(2)](2)Re(6)Te(8)(CN)(6)].5H(2)O: bonding of a transition-metal complex to a rhenium chalcocyanide cluster.

The use of a cyano group of a transition-metal cluster complex to bond to another transition-metal complex has been realized in the syntheses of [[Cu(en)(2)](2)Re(4)Te(4)(CN)(12)].5H(2)O (1) and [[Cu(en)(2)](2)Re(6)Te(8)(CN)(6)].5H(2)O (2), (en = ethylenediamine). These compounds have been synthesized by the reaction of an aqueous solution of K(4)[Re(4)Te(4)(CN)(12)].5H(2)O (for 1) or K(4)[Re(6)Te(8)(CN)(6)] (for 2) with an ammonia solution of Cu(en)(2)Cl(2). In each compound, two Cu(en)(2) groups are bonded to the Re cluster through Cu-N(cyanide) bonds. In compound 1, which contains a tetrahedral cluster core, the Cu(en)(2) groups are necessarily bonded to cis cyano groups; in compound 2, which has an octahedral cluster core, they are bonded to trans cyano groups. Compound 1 crystallizes in the monoclinic space group C2/c with four formulas in unit cell of dimensions a = 18.9077(10), b = 15.4841(8), c = 14.4483(8) A, beta = 95.124(1) degrees, and V = 4213.1(4) A(3) (T = 153 K); compound 2 crystallizes in the triclinic space group P1 with one formula in a unit cell of dimensions a = 9.4906(3), b = 10.6529(4), c = 12. 6252(5) A, alpha = 113.599(1) degrees, beta = 103.404(1) degrees, gamma = 92.659(1) degrees, and V = 1123.87(7) A(3) (T = 153 K).

Study of glycosylation with N-trichloroacetyl-D-glucosamine derivatives in the syntheses of the spacer-armed pentasaccharides sialyl lacto-N-neotetraose and sialyl lacto-N-tetraose, their fragments, and analogues.

The syntheses of 2-aminoethyl glycosides of the pentasaccharides Neu5Ac-alpha(2-->3)-Gal-beta(1-->4)-GlcNAc-beta(1-->3)-Gal-beta(1-->4)-Glc and Neu5Ac-alpha(2-->3)-Gal-beta(1-->3)-GlcNAc-beta(1-->3)-Gal-beta(1-->4)-Glc, their asialo di-, tri-, and tetrasaccharide fragments, and analogues included a systematic study of glycosylation with variously protected mono- and disaccharide donors derived from N-trichloroacetyl-D-glucosamine of galactose, lactose, and lactosamine glycosyl acceptors bearing benzoyl protection around the OH group to be glycosylated. Despite the low reactivity of these acceptors, stereospecificity and good to excellent yields were obtained with NIS-TfOH-activated thioglycoside donors of such type, or with AgOTf-activated glycosyl bromides, while other promotors, as well as a trichloroacetimidate donor, were less effective, and a beta-acetate donor was inactive. In NIS-TfOH-promoted glycosylation with the thioglycosides, the use of TfOH in catalytic amount led to rapid formation of the corresponding oxazoline, but the quantity of TfOH necessary for further efficient coupling with an acceptor depended on the reactivity of the donor, varying from 0.07 equiv for a 3,6-di-O-benzylated monosaccharide derivative to 2.1 equiv for a peracetylated disaccharide one. In the glycosylation products, the N-trichloroacetyl group was easily converted into N-acetyl by alkaline hydrolysis followed by N-acetylation.

Synthesis, Structure, and Properties of Molybdenum and Tungsten Cyano Complexes with Cuboidal M(4)(&mgr;(3)-E)(4) (M = Mo, W; E = S, Se, Te) Cores.

Four new tungsten and molybdenum cyano complexes of formula KCs(5)[W(4)S(4)(CN)(12)].CH(3)OH.2H(2)O (1), K(6)[W(4)Se(4)(CN)(12)].6H(2)O (2), K(6)[W(4)Te(4)(CN)(12)].5H(2)O (3), and K(7)[Mo(4)Te(4)(CN)(12)].12H(2)O (5) have been prepared by high-temperature 430-450 degrees C reaction of the polymeric chain compounds {W(3)S(7)Br(4)}(x)(), {W(3)Se(7)Br(4)}(x)(), {Mo(3)Te(7)I(4)}(x)() and solid-state WTe(2) with KCN, and crystallization from aqueous solutions. In addition Cs(6)[Mo(4)Te(4)(CN)(12)].2H(2)O (4) has been prepared by oxidation of 5 with bromine water. The molecular structures have been investigated by X-ray crystallography. Mixed-valence (3.5) compounds 1-4 are diamagnetic. Mixed-valence (3.25) compound 5 is paramagnetic (&mgr; = 2.03 &mgr;(B) at 77 K). In addition to the structural data for these complexes IR and UV-vis spectroscopy have been used to characterize the complexes. Cyclic-voltammetry data have shown that M(4)E(4)(n)()(+) (M = Mo, W; E = S, Se, Te) cubes are capable of existing in three oxidation states ranging from the most oxidized (n = 6; 10 electrons) to the most reduced electron-precise (n = 4; 12 electrons). The (77)Se, (125)Te, and (183)W NMR spectra of the cubes (1-3) demonstrate unambiguously the unaltered environments of the W and E atoms in aqueous solution.