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Treatment of [Cl.sub.2]Si[(NH-t-Bu).sub.2] (6a) with t-BuN[H.sub.2] in boiling toluene yields trisamino(chloro)silane ClSi[(NH-t-Bu).sub.3] (7); formation of the tetraaminosilane Si[(NH-t-Bu).sub.4] is not observed. The reaction of Si[Cl.sub.4] with 4 equiv, of LiNHR produces the corresponding tetraaminosilanes Si[(NHR).sub.4] (2a, R = i-Pr; 2b, R = t-Bu; 2c, R = p-tol) in good yields. When the sterically demanding adamantyl derivative LiHNAd is employed, only disubstitution occurs to form [Cl.sub.2]Si[(NHAd).sub.2] (6b). Oxidation of the dimeric imidosilicates [{[Li.sub.3][Si[(NR).sub.3](NHR)].THF}.sub.2] (3a, R = i-Pr; 3b, R = t-Bu) with 1 mol of iodine produces the persistent radicals [[Li.sub.2] [Si[(NR).sub.3](NHR)] x Lil x 3THF}, which, on the basis of EPR spectra, exist as Si[N.sub.3][Li.sub.3]I cubes in solution. The spirocyclic tetraimidosilicate monoanion radical [{[[(THF).sub.2]Li[(μ-Nnaph).sub.2]Si[(μ-Nnaph).sub.2] Li[(THF).sub.2]]}.sup.-.] (10) is formed upon oxidation of the tetralithiated species {[Li.sub.4] [Si[(Nnaph).sub.4]].4[Et.sub.2]0} (1) and {[[Li(12-crown-4)].sub.2][([Et.sub.2]O).sub.2]Li[(μ-Nnaph).sub.2] Si[(μ-Nnaph).sub.2]Li[([Et.sub.2]O).sub.2]]} (8) with iodine. The spectroscopic characterization of hexa(amino)disiloxane [(t-BuNH).sub.3]SiOSi[(NH-t-Bu)l.sub.3] (14) formed from the reaction of [Cl.sub.3]SiOSi[Cl.sub.3] with 6 equiv. of LiNH-t-Bu is discussed. Key words: imido ligands, silicate, radicals, EPR spectra, lithium. Le traitement du [Cl.sub.2]Si[(NH-t-Bu).sub.2] (6a) par de la t-BuN [H.sub.2] dans du toluene bouillant conduit a la formation de trisamino(chloro)silane, ClSi[(NH-t-Bu).sub.3] (7); on n'a pas observe de formation du tetraaminosilane, Si[(NH-t-Bu).sub.4]. La reaction du Si[Cl.sub.4] avec quatre Equivalents de LiNHR conduit a la formation des tetraaminosilanes correspondants, Si[(NHR).sub.4] (2a, R = i-Pt; 2b, R = t-Bu; 2c, R = p-tol), avec de bons rendements. Lorsqu'on effectue la reaction avec le LiHNAd, un derive de l'adamantane dont les contraintes steriques sont plus grandes, on ne se produit qu'une disubstitution conduisant a la formation du [Cl.sub.2]Si[(NHAd).sub.2] (6b). L'oxydation des imidosilicates dimeres [{[Li.sub.3][Si[(NR).sub.3](NHR) x THF}.sub.2] (3a, R = i-Pr; 3b, R = t-Bu) avec une mole d'iode conduit a la formation des radicaux persistants {[Li.sub.2][Si[(NR).sub.3]-(NHR) x LiI x THF}.sup..] qui, sur la base de leurs spectres RPE, existeraient en solution sous la forme de cubes de Si[N.sub.3][Li.sub.3]I. L'oxydation par de l'iode des especes tetralithiees {[Li.sub.4][[SiNnaph).sub.4]] x 4[Et.sub.2]O} (1) et {Li[[12-couronne-4].sub.2][([Et.sub.2]O).sub.2]Li[(μ-Nnaph).sub.2] Si(μ-Nnaph).sub.2]Li[([Et.sub.2]O).sub.2]]} (8) conduit a la formation du radical monoanion tetraimidosilicate spirocyclique [{[[(THF).sub.2]Li[(μ-Nnaph).sub.2]Si[(μ-Nnaph).sub.2]Li [(THF).sub.2]]}.sup.-.] (10). On discute de la caracterisation spectroscopique de l'hexa(amino)disiloxane [(t-BuNH).sub.3]SiOSi[(NH-t-Bu).sub.3] (14) qui se forme par reaction du [Cl.sub.3]SiOSi[Cl.sub.3] avec six Equivalents de LiNH-t-Bu. Mots cles: ligands imido, silicate, radicaux, spectre RPE, lithium. [Traduit par la Redaction], Introduction An ongoing area of research in main group chemistry is the synthesis and characterization of imido [[NR].sup.2-] (R = alkyl, aryl) analogues of common p-block oxoanions such as sulfate [...]

New platinasiloxanes were synthesized and their reactivity was studied. Oxidative addition of [(HSi[Me.sub.2]).sub.2]O to Pt[(P[Et.sub.3]).sub.3] led to dehydrogenation and quantitative formation of the four-membered platinacyclosiloxane [[(P[Et.sub.3]).sub.2]Pt([(Si[Me.sub.2]).sub.2]O)] which was characterized by X-ray diffraction. This complex was stable towards non-polar substrates and aerobic conditions, but reacted readily with electrophiles and Lewis acids. Reaction with MeI resulted in ring opening, while MeOTf gave an oxonium complex, with retention of the platinacycle structure. A complex resulting from B[F.sub.3] coordination to the ring oxygen atom was also obtained. An unprecedented open-chain diplatinasiloxane containing the Pt-Si-O-Si-O-Si-Pt fragment was formed by oxidative addition of H-Si[Me.sub.2]-O-Si[Me.sub.2]-O-Si[Me.sub.2]-H to Pt(P[Et.sub.3]).sub.3] and it was characterized by X-ray diffraction. Key words: cyclosiloxane, metallacycle, platinum silyl, Lewis base, oxidative addition. On a realise la synthese de nouveaux platinasiloxanes et on en a etudie la reactivite. L'addition oxydante du [(HSi[Me.sub.2]).sub.2]O] a du Pt[(P[Et.sub.3]).sub.3] conduit a une deshydrogenation et a la formation quantitative du platinacyclosiloxane a quatre chainons [[(P[Et.sub.3]).sub.2]Pt([(Si[Me.sub.2]).sub.2]O)] qui a ete caracterise par diffraction des rayons X. Ce complexe est stable vis-a-vis des substrats non polaires et des conditions aerobiques, mais il reagit facilement avec les electrophiles et les acides de Lewis. Sa reaction avec du MeI conduit a une ouverture de cycle, alors que sa reaction avec du MeOTf conduit a la formation d'un complexe d'oxonium, avec retention de la structure platinacyclique. Un complexe resultant de la coordination du B[F.sub.3] a l'atome d'oxygene du cycle a aussi ete obtenu. L'addition oxydante de H-Si[Me.sub.2]-O-Si[Me.sub.2]-O-Si[Me.sub.2]H a du Pt[(P[Et.sub.3]).sub.3] conduit d'un diplatinasiloxane a chaine ouverte contenant le fragment Pt-Si-O-Si-O-Si-Pt inconnu jusqu' a maintenant et qui a ete caracterise par diffraction des rayons X. Mots cles : cyclosiloxane, metallacyclique, silyle platine, base de Lewis, addition oxydante. [Traduit par la Redaction]

Silicon-bridged thiophene oligomers have been prepared via the reactions of lithiated (3,4-ethylenedioxy)thiophene (EDOT) (1) or 2,2'-bis-(3,4-ethylenedioxy)thiophene (biEDOT) (2) with dichlorodimethylsilane to afford bis-(2,3-dihydro-thieno[3,4-b][l,4]dioxin-5-yl)-dimethylsilane (3) and dimethyl-bis-(2,3,2',3'-tetrahydro-[5,5']bi[thieno[3,4-b] [1,4]dioxinyl]-7-yl)silane (4). Products 3 and 4 were characterized and show good stability in organic solvent and in air. The electropolymerization of these monomers affords stable and highly conducting polymers. The conductivity was found to be 25 and 60 S/cm for Poly3 and Poly4, respectively. Characterization data for the polymers suggested that the resulting materials have a backbone identical to p(EDOT), which formed through cleavage of the silicon-carbon (Si--C) bonds during electropolymerization. Key words: polythiophenes, EDOT, silicon, electropolymerization, Si--C bond cleavage, conductivity.

Hydrogen-terminated porous silicon (pSi-H) films were fabricated through electrochemical anodization of crystalline silicon in hydrofluoric-acid-based solutions. The pSi-H surface was chemically functionalized by thermal reaction with undecylenic acid to produce an organic monolayer covalently attached to the silicon surface through Si--C bonds and bearing an acid terminal group. Bovine serum albumin (BSA) was adsorbed onto such surface-modified pSi structures. The resulting surfaces were characterized using scanning electron microscopy (SEM), reflection FT-IR spectroscopy, and ellipsometry. SEM showed that the porous films were damaged and partially lifted off the silicon substrate after a prolonged BSA adsorption. Ellipsometry analysis revealed that the BSA penetrated ~1.3 [micro]m into the porous structure. The film damage is likely a result of BSA anchoring itself tightly through strong electrostatic interaction with the acid-covered Si sidewalls. A change in surface tension during BSA film formation then causes the pSi layer to buckle and lift off the underlying Si substrate. FT-IR results from the undecylenic-acid-modified pSi surfaces before and after BSA adsorption showed the presence of strong characteristic amide I, II, and III vibrational bands after BSA adsorption. The surface properties of the pSi matrix and its interactions with BSA are examined in this study. Key words: ellipsometry, porous silicon, protein adsorption, surface passivation.

[Si.sup.+][(C[O.sub.2]).sub.n] and [Si.sup.+][(C[O.sub.2]).sup.n] Ar ion-molecule complexes were produced by laser vaporization in a pulsed supersonic expansion. The ions were mass-selected in a reflection time-of-flight spectrometer and studied with infrared photodissociation spectroscopy near the asymmetric stretch vibration of C[O.sub.2]. [Si.sup.+][(C[O.sub.2]).sub.n] clusters fragment by the loss of C[O.sub.2] whereas [Si.sup.+][(C[O.sub.2]).sub.n]Ar complexes fragment by the loss of argon. All clusters have resonances near the C[O.sub.2] asymmetric stretch, but with shifts in frequency that are size dependent. The patterns seen in the small clusters are consistent with electrostatic bonding, while the larger systems provide evidence for an intracluster reaction forming oxide-carbonyl species. Density functional theory was employed to examine the structures of these clusters, and their calculated vibrational frequencies were compared to the measured values. Ligand assembly in [Si.sup.+][(C[O.sub.2]).sub.n] complexes is dominated by the presence of the occupied 3p valence orbital of the silicon cation. Key words: ion-molecule complexes, infrared spectroscopy, photodissociation, density functional theory.

The line profiles of dense cores in infrared-dark clouds indicate the presence of young stellar objects (YSOs)+ but the youth of the YSOs and the large distances to the clouds make it difficult to distinguish the outflows that normally accompany star formation from turbulence within the cloud. We report here the first unambiguous identification of a bipolar outflow from a young stellar object (YSO) in an infrared-dark cloud, using observations of SiO to distinguish the relatively small amounts of gas in the outflow from the rest of the ambient cloud. Key words: infrared-dark clouds, star formation, bipolar outflows, SiO, G81.56+0.10.