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The synthesis, electrochemistry, and magnetism of two novel dimeric, [Fe.sup.3}-containing tungstogermanates is reported. Both polyanions exhibit diamagnetic ground states with a small amount of paramagnetic impurity and have common simultaneous reduction of all of their [Fe.sup.3} centers.

A single-crystal X-ray diffraction, IR and elemental analysis are used to synthesize and characterize four new lanthanide-substituted polyoxotung-states. It is indicated that the [P.sub.8][W.sub.48] anion are occupied by lacunary polytungstate cations.

The synthesis, crystal structure, and solid-state characterization of three different compounds obtained from the reaction of [(CH3).sub.2]SnCl2 with [Na.sub.2]Mo[O.sub.4] in an aqueous medium in different pH ranges are reported. All the compounds show hybrid organic-inorganic extended assemblies based on molybdate anions linked by [(CH3).sub.2][Sn.sub.2+] organometallic moieties to give 2- or 3-dimensional lattices.

The benzene-Ru(II)-supported dilacunary decatungstosilicate [{Ru(C6H6)(H2O)}{RU(C6H6)}(gamma-SiW10(O36)).sup.4-] (1)and the isostructural decatungstogermanate [{Ru(C5H5)(H2O)}{RU(C6H6)}(gamma-SiW10(O36)).sup.4-] (2) are synthesized and characterized by multinuclear solution NMR, IR, elemental analysis, and electrochemistry. A ligand substitution reaction was observed upon addition of dimethyl sulfoxide (dmso) to 1,2, or [Ru(C6H6)Cl2.sub.2], which facilitates substantially the oxidation of the Ru center.

Research has been conducted on the ammonium salt of the 1:1 complex Ce(III). The preparation and characterization of this salt via elemental analysis, vibrational and NMR spectroscopy, cyclic voltammetry and single-crystal X-ray analysis are described.

The heteropolyanions (Bi2W22O74(OH)2)12- and (X2W20M2O70(H2O)6)(14-2n)- (X = Sb3+, Bi3+; M(super n+) = Fe3+, Co2+, Zn2+) were synthesized as alkali metal and ammonium salts, respectively. They were characterized by elemental analysis, infrared spectroscopy and X-ray crystallography. These tungsto bismutates and antimonates have one common characteristic: the trivacant beta-B-XW9O33 Keggin fragment as the structural building unit.

The nitroxyl free radical 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) forms adducts that show strong magnetic interactions, and can be isolated from organic solvents. Isolation of a TEMPO adduct of Fe(hfac)(sub2) failed and the formed mixtures contained colorless and red crystalline solids. X-ray analysis identified the organic salt 2,2,6,6-tetramethylpiperidinium trifluoracetate and a novel Fe(super3+) dimer.

Nitrones can exhibit a variety of activities as ligands. A bidentate pyridyl nitrone can form complex salts with divalent manganese, cobalt, nickel and iron and a neutral complex with divalent copper. A monodentate nitrone, on the other hand, yields a diiron complex when it interacts with iron and crystalline dimers when it interacts with divalent manganese, cobalt or nickel.

A beta hydrogen in nitroxides destabilizes the compound because of disproportionation. This instability can be remedied by complexing the nitroxide with manganese, nickel or cobalt to yield a stable crystal. Antiferromagnetic coupling is observed with magnetic susceptibility studies of manganese and nickel complexes. The applications of these findings in spin trapping experiments are presented.

Study of the stereochemistry of dioxygen complexes of group 6 transition elements reveals that oxo and peroxo ligands occupy mutually cis positions in the oxidation state to interact with metal orbitals. Oxomonoperoxo complexes and oxodiperoxo complexes are analogous to cis-dioxo and fac-trioxo species, respectively. The O(super 2-)(sub 2) ligand is a pi-donor.

The reaction between ([C.sub.6][H.sub.5])Sn[Cl.sub.3] and [Na.sub.10][A-[alpha]-Ge[W.sub.9][O.sub.34] in water was performed to obtain the monomeric, trisubstituted keggin species, [[[{([C.sub.6][H.sub5])Sn(OH)}.sub.3]([A-[alpha]-Ge[W.sub.9][O.sub.34])].sup.4-]. The products constitute the first organotin derivative of a trilacunary keggin tungstogermanate which are closely associated in the solid state through (Sn)O-H...[O.sub.t] hydrogen bonds reinforced by weak C-H...[O.sub.t] contacts to form 2-dimensional or 1-dimensional arrangements.

The synthesis and structural characterization of the two polyanions, [[([alpha]-[Ti.sub.3]P[W.sub.9][O.sub.38]).sub.3](P[O.sub.4])](18-) and [[([alpha]-[Ti.sub.3]Si[W.sub.9][O.sub.37]OH).sub.3](Ti[O.sub.3][([OH.sub.2]).sub.3])](17-) as the first examples of trimeric Ti-containing polytungstates are reported. Both the complexes are composed of three ([Ti.sub.3]X[W.sub.9][O.sub.37]) units (X = P or Si) linked via three Ti-O-Ti bridges and a capping group, which is either tetrahedral P[O.sub.4] or octahedral Ti[O.sub.6].

The synthesis and characterization of peroxo-zirconium containing 30-tungstosilicate [[[M.sub.6][([O.sub.2]).sub.6][(OH).sub.6][([gamma]-Si[W.sub.10][O.sub.36]).sub.3]].sup.18-] (M = Zr, Hf) is described. The simple, one-pot synthesis of these two polyanions that involves dropwise addition of aqueous hydrogen peroxide can be used to incorporate peroxo groups into a large variety of transition metal and lanthanide containing polyoxometalates (POMs).

The structure of an organic-inorganic tungstoborate reveals presence of an organostannoxane hexamer. This hexamer moiety stabilizes the tungstoborate structure.

A combination of single-crystal X-ray diffraction, as well as the thermogravimetric analysis is used to study the synthesis and structure of the monolanthanide-containing silicotungstates [[Ln[([[beta].sub.2]-Si[W.sub.11][O.sub.39]).sub.2]].sup.13-] (Ln = La, Ce, Sm, Eu, Gd, Tb, Yb, Lu). The results prove the importance of the solvent medium in the stabilization of the compounds, as the polyanion fragments can be stabilized by lanthanide centers in solution.

The synthesis and crystal structure of the first dimethyltin-containing isopolytungstate, [{[[C[H.sub.3]].sub.2]Sn}].sub.2]([[W.sub.6][O.sub.22])].sup.4-], which is obtained from the reaction of [Na.sub.2]W[O.sub.4] and [(C[H.sub.3]).sub.2]Sn[Cl.sub.2] in water, is described. The selective crystallization of [{[[C[H.sub.3]].sub.2]Sn}].sub.2]([[W.sub.6][O.sub.22])].sup.4-] with guanidinium cations has resulted in solid-state one-dimensional assembly [[C[(N[H.sub.2]).sub.3]].sub.4][[{[(C[H.sub.3]).sub.2]Sn}.sub.2]([W.sub.6][O.sub.22])].2[H.sub.2])O via distorted trigonal-bipyramidal cis-[(C[H.sub.3]).sub.2]Sn[O.sub.3] moieties.

The dilacunary decatungstogermanate, {[gamma]-Ge[W.sub.10][O.sub.36]}[.sup.8-] is synthesized and structurally characterized in solution and in the solid state. Polyanion {[gamma]-Ge[W.sub.10][O.sub.36]}[.sup.8-] represents a novel lacunary polyoxometalate, giving rise to a multitude of derivatives by reaction with transition metals, lanthanides and other electrophiles.

The trimeric Zr6-containing silicotungstate [Zr6O2(OH)4(H2O)3(beta-SiW10O37)3](super 14-) and the dimeric Zr6-containing silicotungstate [Zr4O2(OH)2(H2O)4(beta-SiW10O37)2](super 10-) are synthesized and structurally characterized. Both polyanions are chiral and [Zr6O2(OH)4(H2O)3(beta-SiW10O37)3](super 14-) contains more zirconium centers than any other known polyoxometalate.

The organometallic Ru(II)-supported trilacunary heteropolytungstates [RuC(sub 6)H(sub 6))(sub 2)XW(sub 9)O(sub 34)](super 6-) (X=Si, Ge) are synthesized and characterized by NMR, UV-vis and X-ray analysis. The novel polyanion structure consists of two (RuC(sub 6)H(sub 6)) units linked to a trilacunary (XW(sub 9)O(sub 34)) Keggin fragment via Ru-O(W) and Ru-O(X) bonds resulting in an assembly with C(sub s) symmetry.

Structures of 1:2 complexes of Ce(III) with lacunary (W17) derivatives of [H(sub 4)XW(sub 18)O(sub 62)](super 7-) confirm the Wells-Dawson framework with a tungsten vacancy in the cap position adjacent to the phosphate group. Bond valence calculations show that the four protons are attached to internal oxygen atoms that define the vacant tetrahedron.

The new niobate and tantalate derivatives are easily prepared in good yield in acqueous solution, starting with [M(CO)3(CH3CN)(sub 3)](super +1) or under hydrothermal conditions starting with [(M(CO)5Br]. The compositions and structures of the new complexes are established by elemental analysis, by infrared and (super 17)O NMR spectroscopy and by single-crystal X-ray diffraction of five salts.

Three novel dimetric silicotungstates [(SiM(sub 2)W(sub 9)O(sub 34)(H(sub 2)O)](sub 2)](super 12-) (M = Mn(super 2+), Cu(super 2+), Zn(super 2+) have been synthesized. As revealed by single-crystal X-ray diffraction, the polyanions have a sandwich-type structure and they represent the second type of silicotungstates containing four transition metal ions.

The synthesis and structural characterization of two novel, tris(phenyltin)antimony(III) and tetrakis(phenyltin)arsenic(III) heteropolyanions, derived from the lacunary anions [alpha-SbW9O33](super 9-) and [alpha-AsW9O33](super 9-) are reported. The elemental analyses, multinuclear NMR spectroscopy of the complexes are fully consistent with the solid-state structures revealed by X-ray crystallography.

New functionalized tungstorhodates with Rh-C bonds are formed in good yield in aqueous solution from acetate, rhodium(III) and heteropolytungstate, the first-ever such process in rhodium chemistry. The complexes were produced by the hydrothermal reaction of an equimolar mixture of rhodium(III) chloride and K(sub 7)PW(sub 11)O(sub 39) oor K(sub 8)SiW(sub 11)O(sub 39) in an acetate buffer at 120 degrees C. A terminal functional group which can be further derivatized is found in the new heteropolyanions.

Hydrothermal reaction of lacunary ((PO4)W11O35)7- with rhodium acetate dimer was found to produce the unique dirhodium-substituted Keggin anion, ((PO4)W11O35(Rh2(OAc)2))5- (1). An X-ray structure determination of the guanidinium salt of the dimethyl sulfoxide derivative of 1 confirmed the structure deduced from proton and tungsten NMR spectroscopy. Oxidation of 1 to an unstable Rh(super II,III) derivative and synthesis of other polytungstate analogs was found to be possible. The tetrabutylammoniun salt of 1 showed modest catalytic reactivity for cyclopropanation.