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The synthesis of (CN)Pt^II(acac) complexes (CN = benzo[h]quinoline, 8-methylquinoline) and their oxidation with PhI(OAc)2 are reported as a model system for palladium-catalyzed C−H bond functionalization. Dimeric Pt^III−Pt^III complexes containing a bridging acetate ligand are obtained in HOAc, and monomeric Pt^IV complexes incorporating alkoxide and acetate ligands are obtained in MeOH, EtOH, and iPrOH. The implications of these results for the mechanism of analogous Pd-catalyzed reactions is discussed.

Rice hull ash RHA silica 80–98 wt. amorphous, >25 m2g−1silica, 2–20 porous amorphous C can be depolymerized in aqueous alcohol with NR48OH R Me, CH2CH2OH under ambient conditions with the selective formation of octasilicate anions, NR48OSiO1.58. Dissolution kinetics were studied as a function of base and water concentration and temperature. Dissolution rates were determined by conversion of the octaanion to HMe2OSiO1.58, OHS. Activation energies for dissolution were 5 ± 1 kcal mol−1, much lower than for typical base-promoted silica dissolution. Furthermore, dissolution was not catalytic in base as found for other base-promoted silica dissolution reactions. Reaction rates were dependent on ammonium base and water concentrations and temperature. Dissolution was optimal at approximately one equivalent of NR48OH and three equivalents of water for choline hydroxide and five equivalents of water for NMe48OH. A single crystal study of the octacholine Me3NCH2CH2OH8derivative indicates that the compound crystallizes with three equivalents of water per SiO1.5suggesting that the rate limiting step in the dissolution process may be formation of the octaanion which is in accord with theoretical Ea’s calculated for the condensation of polyhydroxyl siloxanes. Octasilicate anions offer access to novel polyfunctional silsesquioxane platforms with each functional group occupying a single octant in Cartesian space. These platforms offer potential as precursors to dendrimers and hyperbranched polymers, and as nanobuilding blocks for the formation of nanocomposites. Furthermore, choline is structurally similar to: 1 -N,N,N-trimethyl-γ-hydroxy-lysine, 2 the oligomeric N-methylpropylamine components found in silafins, and 3 possibly the hydroxyamino acid units found in sponge filament proteins; all of which are thought to play a role in silica accretion, transport and deposition in diatoms and sponges. Thus, the octasilicate structure may reflect the structures of species involved in silica transport andor deposition in biosilicification processes.

1,2-Dihydro-2-phenyl-1,2-azaborine (6a) has been prepared by a multistep synthesis from the readily available 2,2-dibutyl-2,5-dihydro-1-trimethylsilyl-1H-1,2-azastannole (7). Deprotonation of 6a affords 1-phenyl-1,2-azaboratabenzene 1a, which on reaction with [Cp*RuCl]4 gives the sandwich compound 5. 5 has been shown to function as a nucleophilic catalyst for the acylation of benzyl alcohol by phenylethylketene.

Two general methods have been developed for the synthesis of alkali metal salts of 2-substituted-1,2-oxaborolides (6). 2-Phenyl-1,2-oxaborolide (6b) has been converted to RuCp* complex 11b and to Mn(CO)3 complex 12b, in which the metals are η⁵-bound to the ligand.

The reaction of (Et3P)2Pd(μ-S)Ge[N(SiMe3)2]2 (2) with paraformaldehyde under photolytic conditions results in the insertion of formaldehyde into the Pd−Ge bond, with bond cleavage, to give (Et3P)2Pd(μ-S)(μCH2O)Ge[N(SiMe3)2]2 (3). Subsequent addition of CO to 3 results in migratory insertion into the Pd−C bond, followed by rapid reductive elimination to regenerate the Pd⁰ metal center and give a unique five-membered organic heterocycle, Ge[N(SiMe3)2]2SC(O)CH2O (6). The X-ray crystal structure of the dppe (dppe = bis(diphenylphosphino)ethane) derivative of 3, (dppe)Pd(μ-S)(μCH2O)Ge[N(SiMe3)2]2 (4), is reported.

The sequential reaction of 9-fluorenyllithium and CpNa with (ⁱPr)2NBCl2 followed by the sequential treatment with LDA and ZrCl4 afforded [(η⁵-C13H8)BN(ⁱPr)2(η⁵-C5H4)ZrCl2 (2e). The structure of 2e was determined by X-ray diffraction, which shows that the molecule has Cs symmetry. On activation by excess methylaluminoxane (MAO) 2e was converted to an active catalyst for polymerization of ethylene and propylene. The polypropylene is syndiotactic (81% rr triads).

Herein we report the CH insertion of a stable germylene, Ge[CH(SiMe3)2]2, into the α-CH bonds of the acetyl-containing ketones acetone, butanone, and cyclopropyl methyl ketone. This CH insertion reaction requires the presence of MgCl2, yet the reaction can be successfully carried out in hydrocarbon, aromatic, and ethereal solvents. In the absence of MgCl2, these acetyl-containing ketones do not undergo CH insertion but instead undergo an OH insertion to give a germyl vinyl ether. A number of other ketones, including the acetyl-containing pinacolone, have been observed to only undergo insertion into the OH bond even in the presence of MgCl2.

Ge[CH(SiMe3)2]2 (1) and Ge[N(SiMe3)2]2 (2) react with anthraquinone and naphthoquinone in a 2:1 ratio to form five-membered rings with the carbonyl oxygens and the ortho carbons of the adjacent aromatic ring. The reaction with 1,4-diacetylbenzene proceeds in a similar fashion with 1; however no reaction is observed with 2. Compounds 1 and 2 react with 1,2-diacetylbenzene to yield a novel bicyclo species. In a previous report describing equilibria between 1 and phenones, it appeared that 2 did not undergo reaction to generate the five-membered ring with the accompanying formation of a conjugated triene. However, these quinone results indicate that an equilibrium can exist between 2 and a phenone moiety. In the reaction with quinones, a second equivalent of germylene effectively traps the conjugated triene by undergoing a 1,4-addition reaction. Unlike the initial triene formation, this second insertion is irreversible.

The reaction of 1,1-dibutyl-1-stannacyclohexa-2,5-diene (8) with 1,2-bis(dichloroboryl)benzene 9 affords exchange product 10, which on deprotonation followed by reaction with ZrCl4 gives the very labile o-phenylene-bridged bis(1-boratabenzene)zirconium dicholoride 6. A similar reaction sequence from 8 and 1,1-bis(dichloroboryl)-2-methyl-1-propene 11 affords the 1,1-isobutenyl-bridged bis(1-boratabenzene)zirconium dichloride 7. The X-ray structure of 7 is described.

The synthesis and characterization of several co-oligomers, 5,5‘-bis(4,4‘-dialkyl-2,2‘-bithiazol-5-yl)-(3,4,3‘,4‘-bis(ethylenedioxy)-2,2‘-dithienyl) (AT2A), 5,5‘-bis(3,4-ethylenedioxythien-2-yl)-4,4‘-dibutyl-2,2‘-bithiazole (TBT), and 5,5‘-bis(3,4,3‘,4‘-bis(ethylenedioxy)-2,2‘-dithien-5-yl)-4,4‘-dibutyl-2,2‘-bithiazole (T2BT2) are described. The solid-state structure of AT2A features π-stacking with a short intermolecular distance of 3.5 Å. In thin films, the π-stacks are parallel to the film substrate as determined by X-ray diffraction. The UV−vis spectra of AT2A films show features that are ascribed to the effects of π-stacking. In addition, all these co-oligomers, composed of donor−acceptor moieties, show lowered optical band gaps, mainly because of the low oxidation potential imparted by incorporation of the 3,4-ethylenedioxythiophene (EDOT) moiety. Cyclic voltammetry indicates that these co-oligomers can be either p-doped or n-doped, and the spectroelectrochemical measurements show that the AT2A films are stable upon cycling the oxidation state. All these features make these materials promising for use in electronic devices, e.g., organic thin film transistors.

The synthesis of three novel Pd germylene complexes is reported. (Ph3P)2PdGe[N(SiMe3)2]2 (1) was synthesized by ligand substitution of (Ph3P)4Pd, whereas (Et3P)PdGe[N(SiMe3)2]2 (2) and {dppePdGe[N(SiMe3)2]2}2 (3b) (dppe = (diphenylphosphino)ethane) were synthesized by photolytic reduction of their corresponding phosphine oxalato complexes followed by addition of the germylene ligand. In solution, 3b exists in equilibrium with the monomeric dppePdGe[N(SiMe3)2]2 (3a). The germylene ligand of 2 was found to be 1 order of magnitude more labile than the analogous Pt system and 2 orders of magnitude less labile than the analogous Ni system. The reactivity of these new palladium germylenes toward O2 is described.

Transmetalation of tin-bearing cyclic imidates gave 2-azaallyllithiums that underwent [π6s + π4s] cycloadditions with cycloheptatriene to produce tricyclic adducts, which may be useful as analogs of cocaine. The peri- and stereoselectivity of this process are discussed.

1,2-Dihydro-1,2-azaborines (1c, 1d, and 1e) have been prepared by the reaction of the corresponding 2,3-dihydro-1H-1,2-azaborol-3-yllithium reagents (1c, 1d, and 1e). The reaction of 1e with Py3Mo(CO)3 and BF3·OEt2 affords Mo(CO)3 complex 5e, while the reaction of 1c with Cr(CH3CN)3(CO)3 affords Cr(CO)3 complex 6c. X-ray structures of 5e and 6c show that the metals are η⁶-bound to the 1,2-dihydro-1,2-azaborine rings.

1-Arsanaphthalene (3) and 2-trimethylsilyl-1-arsanaphthalene (4) have been prepared from the corresponding 1,4-dihydro-1,1-dimethyl-1-stannanaphthalenes 7 and 17, respectively, via an exchange reaction with AsCl3 followed by dehydrohalogenation by DBU. Both 3 and 4 are in mobile equilibrium with their head-to-head Diels−Alder dimers. The reaction of 4 with Mo(CO)3(Py)3 and BF3·OEt2 affords Mo(CO)3 complex 5. The crystal structure of 5 shows that the Mo(CO)3 group is η⁶-bound to the C5As ring of the arsanaphthalene.

The reaction of 1-chloro-1-boracyclohexadiene (12) with N,N‘-dimethyl-N,N‘-bis(trimethylsilyl)ethylene-1,2-diamine followed by LDA afforded the dilithium salt of N,N‘-bis(1-boratabenzene)-N,N‘-dimethylethylene-1,2-diamine (14). The reaction of 14 with ZrCl4 afforded the boron-bridged dimethylethylenediamino bis(boratabenzene) zirconium dichloride complex 8, while reaction of 14 with FeCl2 afforded the corresponding dimethylethylenediamino-bridged iron(II) complex 9. The structures of 8 and 9 were determined by X-ray diffraction. In each case the boratabenzene units are bridged by an approximately C2-symmetric dimethylethylenediamino bridge which makes 8 and 9 chiral. A barrier to interconversion of the enantiomeric conformers of 8 was determined by 2D ¹H NOESY as 21.2 ± 0.2 kcal/mol, while the corresponding barrier of 9 was determined from variable-temperature ¹³C NMR spectroscopy to be 16.9 ± 0.5 kcal/mol. Both barriers involve rotation about the exocyclic B−N π-bonds. Comparison has been made with the corresponding bridged cyclopentadienyl complexes 10 and 11.

The syntheses of the 1,4-bis-5-(4,4‘-dialkyl-2,2‘-bithiazole)-1,3-butadiynes, ABDs, (6a−c) are reported. The crystal and molecular structure of the butyl derivative was determined by single-crystal X-ray diffraction. The BBD (the 4,4‘-di-n-butyl ABD) molecules are properly aligned in the solid state for topotactic 1,4-polymerization to occur, but these materials do not undergo such polymerization under a variety of conditions. The lack of topotactic polymerization is attributed to the rigidity of the aromatic groups directly bonded to the butadiyne. These compounds do polymerize in the molten state to give soluble polymers that are characterized by UV−vis, FT-IR, and NMR spectroscopies and cyclic voltammetry. Molecular modeling was also used to explore some representative conformation space. These data suggest that the polymerization occurs primarily via 1,2-addition, but some 1,4-addition also occurs.

A new transition metal germylene complex, (Ph3P)2NiGe[2,4,6-(CF3)3C6H2]2 (2), has been synthesized and structurally characterized. The metrical parameters of complex 2 are compared and contrasted with the previously synthesized complexes (Ph3P)2NiGe[N(SiMe3)2]2 (3) and (Et3P)2PtGe[N(SiMe3)2]2 (1). Nonlocal BP86 density functional calculations support the presence of Ni−Ge d−p π bonding in complexes 2 and 3.