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Menezesite, ideally [Ba.sub.2]Mg[Zr.sub.4]([Ba[Nb.sub.12][O.sub.42]) *12[H.sub.2]O, occurs as a rug mineral in the contact zone between dolomite carbonatite and 'jacupirangite' (=a pyroxenite) at the Jacupiranga mine, in Cajati county, Sao Paulo state, Brazil, associated with dolomite, calcite, magnetite, clinohumite, phlogopite, ancylite-(Ce), strontianite, pyrite, and tochilinite. This is also the type locality for quintinite-2H. The mineral forms rhombododecahedra up to 1 mm, isolated or in aggregates. Menezesite is transparent and displays a vitreous luster; it is reddish brown with a white streak. It is non-fluorescent. Mohs hardness is about 4. Calculated density derived from the empirical formula is 4.181 g/[cm.sup.3]. It is isotropic, [n.sub.means]> 1.93(1) (white light); [n.sub.calc] = 2.034. Menezesite exhibits weak anomalous birefringence. The empirical formula is [([Ba.sub.147][K.sub.0.53][Ca.sub.0.31][Ce.sub.0.17] [Nd.sub.0.10][Na.sub.0.06][La.sub.0.02]).sub.[SIGMA]2.66] [([Mg.sub.0.94][Mn.sub.0.23][Fe.sub.0.3] [Al.sub.0.03]).sub.[SIGMA]1.43]([[Zr.sub.2.75] [Ti.sub.0.96][Th.sub.0.29).sub.[SIGMA]4.00 [[([Ba.sub.0.72][Th.sub.0.26][U.sub.0.02]).sub.[SIGMA]1.00] [([Nb.sub.9.23][Ti.sub.2.29][Ta.sub.0.36] [Si.sub.0.12]).sub.[SIGMA]12.00][O.sub.42]*12[H.sub.2]O. The mineral is cubic, space group Im [bar.3] (204), a = 13.017(1) [Angstrom], V = 2206(1) [[Angstrom].sup.3] Z = 2. Menezesite is isostructural with the synthetic compound [Mg.sub.7][Mg[W.sub.12][O.sub.42]][(OH).sub.4]*8[H.sub.2]O. The mineral was named in honor of Luiz Alberto Dias Menezes Filho (born 1950), mining engineer, mineral collector and merchant. Both the description and the name were approved by the CNMMN-IMA (Nomenclature Proposal 2005-023). Menezesite is the first natural heteropolyniobate. Heteropolyanions have been employed in a range of applications that include virus-binding inorganic drugs (including the AIDs virus), homogeneous and heterogeneous catalysts, electro-optic and electrochromic materials, metal and protein binding, and as building blocks for nanostructuring of materials. Keywords: Menezesite, new mineral, polyoxometalates, heteropolyniobate, heteropolyanions, crystal structure, chemical composition, Jacupiranga mine, Cajati, Brazil

Matioliite, ideally NaMg[Al.sub.5][(P[O.sub.4]).sub.4][(OH).sub.6] x 2[H.sub.2]O, occurs as a secondary hydrothermal mineral in the Gentil mine granite pegmatite, Mendes Pimentel Co., Minas Gerais, Brazil. Some crystals are zoned to more Fe-rich compositions with an [Fe.sup.2+]:Mg ratio of approximately 1:1, corresponding to an intermediate member of the burangaite-matioliite solid-solution series. Matioliite is intimately associated with fluorapatite, crandallite, and zoned gormanite-souzalite cystals. The mineral forms prismatic to tabular crystals, up to 1 mm long. Matioliite is transparent and displays a vitreous luster; it is blue to colorless with a white streak. It is non-fluorescent. Mohs hardness is about 5. Calculated density is 2.948 g/[cm.sup.3]. Matioliite is biaxial negative, [[eta].sub.[alpha]] = 1.597(2), [[eta].sub.[beta]] = 1.627(2), [[eta].sub.[gamma]] = 1.632(1) (white light), 2V (meas.) = 43(2)[degrees], 2V (calc.) = 44[degrees], dispersion r > v, orientation X = b, Z ^ c = 6[degrees]. Pleochroism is Y > X > Z, X = light blue to colorless, Y = blue, Z = colorless. The empirical formula is [([Na.sub.0.94][Ca.sub.0.01]).sub.[summation]0.95 [([Mg.sub.0.88][Fe.sup.2+.sub.0.11][Mn.sub.0.01].sub.[summation]1.00] [([Al.sub.4.84][Fe.sup.3+.sub.0.13]).sub.[summation]4.97] [(P[O.sub.4]).sub.4.03][(OH).sub.5.76] x 2[H.sub.2]O. The mineral is monoclinic, space group C2/c, a = 25.075(1) [Angstrom], b = 5.0470(3) [Angstrom], c = 13.4370(7) [Angstrom], [beta] = 110.97(3)[degrees], V = 1587.9(4) [[Angstrom].sup.3], Z = 4. Crystal-structure determination was carried out and showed it is isostructural with burangaite, dufrenite, and natrodufrenite. Both the description and the name were approved by the CNMMN-IMA (Nomenclature Proposal 2005-011). The 'magnesium analog of burangaite' described from the Gold Quarry mine, Carlin-trend, Eureka County, Nevada; 'burangaite' from Hochgosch, Millstatter See-Rucken, Karnten, Austria; and 'burangaite' described from Corrego Pomarolli, Linopolis, Divino das Laranjeiras, Minas Gerais, Brazil, are probably matioliite. Keywords: Matioliite, new mineral, crystal structure, burangaite, chemical composition, Gentil mine, Mendes Pimentel, Brazil

Described are the synthesis and characterization of Ru(II) complexes of the type Ru[Cl.sub.2][L.sub.2](N-O), where [L.sub.2] is either 1,4-bis (diphenylphosphino)butane (dppb) or [(P[Ph.sub.3]).sub.2], and N-O represents chelated 2-benzoylpyridine (2-bzpy) or 2-acetylpyridine (2-acpy); the Ru presursors used were [Ru[Cl.sub.2][(dppb)].sub.2] ([mu]-dppb) or Ru[Cl.sub.2][(P[Ph.sub.3]).sub.3]. The crystal structure of cis-Ru[C1.sub.2](dppb)(2-bzpy) is presented, and three other Ru[Cl.sub.2][L.sub.2](N-O) complexes with cis-chlorines are isolated and characterized spectroscopically; of the trans-dichloro species, Ru[Cl.sub.2][(P[Ph.sub.3]).sub.2](N-O) complexes are isolated, while the corresponding dppb species are characterized in situ. In all cases, thermodynamically stable cis-complexes are formed from initially formed trans-species. Key words: ruthenium, phosphines, 2-benzoylpyridine, 2-acetylpyridine, X-ray structures.

Research has been conducted on the cyclization-elimination reactions. Results indicate that these reactions have been slower with zinc(II) than with cadmium(II) and that the complexes containing either cyclized or uncyclized ligands have been isolated.

The ruthenium(II) complex, [Ru[Cl.sub.2](NO)L] (I), (L = [[(2-py).sub.2]P[C.sub.2][H.sub.4]P[O.sub.2](2-py)]-) was obtained from recrystallization of Ru[Cl.sub.3]NO(d2pype) (d2pype = [(2-py).sub.2]P[C.sub.2][H.sub.4]P[(2-py).sub.2]) in the presence of HN[O.sub.3], crystallizing in the monoclinic space group [P2.sub.1] (no. 4), with a = 8.012(4) [Angstrom], b = 14.454(4) [Angstrom], c = 9.353(3) [Angstrom], [beta] = 105.77(3)[degrees], and Z = 2. Crystals of the DMSO solvate of the complex (II) were obtained from [(C[D.sub.3]).sub.2]SO solution, crystallizing in the monoclinic space group [P2.sub.1]/c (no.14) with a = 9.7080(2) [Angstrom], b = 22.2920(5) [Angstrom], c = 11.5230(3) [Angstrom], [beta] = 92.0450(10)[degrees], and Z = 4. In both complexes, the geometry about the ruthenium atom is a distorted octahedron mainly as a result of the tridentate [P,N,O]-bonding mode of L. The v (NO) bands at 1875 [cm.sup-1] in both complexes are consistent with the linear disposition of the NO group and the Ru atom as is observed in the X-ray crystal structure (Ru-N1-O1 angle = 178.5(4)[degrees]). Key words: pyridylphosphine, nitrosyl, ruthenium complex, X-ray structure.

A mixture of pyridoxalrhodanine, triethylphosphinegold(I) chloride and sodium methoxide in methanol has afforded the azacoumarin complex and it is characterized by X-ray diffractometry. The results have indicated that the complex has displayed in vitro antitumor activity than cisplatin against the cisplatin-resistant cell line A2780cis.

The synthesis of the new thiamine diphosphate derivative [SnMe2(HTDP)(H2O)]Cl.H2O, its structures in solid state and in water, and the results of the kinetic experiments are described. The resulting SnMe2-holoen-zyme retains a significant proportion of the catalytic activity of the native enzyme despite the methyl groups on the metal atom.