The reaction of 9,10-dibromo-9,10-dihydro-9,10-diboraanthracene (9,10-dibromo-DBA, 3) with two equivalents of 9-lithio-2,6- or 9-lithio-2,7-di-tert-butylanthracene gave the corresponding 9,10-dianthryl-DBAs featuring two (4) or four (5) inward-pointing tert-butyl groups. Compound 4 exists as two atropisomers, 4 and 4', due to hindered rotation about the exocyclic B-C bonds. X-ray crystallography of 5 suggests that the overall interactions between facing tert-butyl groups are attractive rather than repulsive. Even in solution, 4/4' and 5 are stable toward air and moisture for several hours. Treatment of 3 with 10-lithio-9-R-2,7-di-tert-butylanthracenes carrying phenyl (R=Ph), dimesitylboryl (R=Mes(2)B), or N,N-di(p-tolyl)amino (R=Tol(2)N) groups gave the corresponding 9,10-dianthryl-DBA derivatives 9-11 in moderate to good yields. In these molecules, all four solubilizing tert-butyl groups are outward pointing. The solid-state structures of 4, 5, 9, and 10 reveal twisted conformations about the exocyclic B-C bonds with dihedral angles of 70-90°. A significant electron-withdrawing character was proven for the Mes(2)B moiety, but no appreciable +M effect was evident for Tol(2)N. Compounds 5, 9, and 11 show two reversible DBA-centered reduction waves in the cyclic voltammogram. In the case of 10, a third reversible redox transition can be assigned to the Mes(2)B-anthryl substituents. The UV/Vis absorption spectrum of 5 is characterized by a very broad band at λ(max)=510 nm, attributable to a twisted intramolecular charge-transfer interaction from the anthryl donors to the DBA acceptor. The corresponding emission band shows pronounced positive solvatochromism (λ(em)=567 nm, C(6)H(12); 680 nm, CH(2)Cl(2)) in line with a highly polar excited state. The charge-transfer bands of 10 and 11, as well as the emission bands of 9 and 10, are redshifted relative to those of 5. The Tol(2)N derivative 11 is essentially nonfluorescent in solution, but emits bright wine-red light in the solid state.

The tetraphosphenediides M2[t-Bu3SiPPPPSi-t-Bu3] (M = Li, Na, K) were accessible by the reaction of P4 with the silanides M[Si-t-Bu3] (M = Li, Na, K), whereas M2[t-Bu3SiPPPPSi-t-Bu3] (M = Rb, Cs) were obtained from the reaction of RbCl and CsF with Na2[t-Bu3SiPPPPSi-t-Bu3]. 31P NMR experiments revealed that, in tetrahydrofuran, Na2[t-Bu3SiPPPPSi-t-Bu3] adopts a cis configuration. However, treatment of Na2[t-Bu3SiPPPPSi-t-Bu3] with 18-crown-6 led to the formation of [Na(18-crown-6)(thf)2]2[t-Bu3SiPPPPSi-t-Bu3] that possesses a trans configuration in the solid state. The ion-separated tetraphosphenediide [Na(18-crown-6)(thf)2]2[t-Bu3SiPPPPSi-t-Bu3] was analyzed using X-ray crystallography (monoclinic, space group P2(1)/n). The reaction of Na2[t-Bu3SiPPPPSi-t-Bu3] with BaI2 gave, conveniently, the corresponding barium derivative Ba[t-Bu3SiPPPPSi-t-Bu3]. However, addition of AuI to the tetraphosphenediide Na2[t-Bu3SiPPPPSi-t-Bu3] yielded 1,3-diiodo-2,4-disupersilyl-cyclotetraphosphane (monoclinic, space group C2/c), which is an isomer of disupersilylated diiodotetraphosphene. A further isomeric derivative of disupersilylated tetraphosphene, the 3,5-disupersilyl-2,2-di-tert-butyl-2-stanna-bicyclo[2.1.0(1,4)]pentaphosphane, which possesses a phosphanylcyclotriphosphane structure, was obtained by the reaction of Na2[t-Bu3SiPPPPSi-t-Bu3] with t-Bu2SnCl2. Calculations revealed that the acyclic cis and trans isomers of the dianions [HPPPPH]2- and [H3SiPPPPSiH3]2- are thermodynamically more stable than the cyclic isomers with a phosphanylcyclotriphosphane or a cyclotetraphosphane structure. However, the neutral cyclic isomers of H4P4 and H2(H3Si)2P4 represent more stable structures than the cis- and trans-tetraphosphenes H2P-P=P-PH2 and (H3Si)HP-P=P-PH(SiH3), respectively. In addition, the molecular orbitals (MOs) of the silylated cis- and trans-tetraphosphene dianions of [H3SiPPPPSiH3]2-, which are comparable with those of the ion-separated supersilylated tetraphosphenediide [t-Bu3SiPPPPSi-t-Bu3]2-, show the highest occupied antibonding pi*MO (HOMO). The HOMO is represented by the (p(z)-p(z)+p(z)-p(z)) pi* MO.

The di- and trinuclear ferrocene species Li[Fc-BPh(2)-Fc] (Li[]) and Li(2)[Fc-BPh(2)-fc-BPh(2)-Fc] (Li(2)[]) have been investigated with regard to their electrochemical properties and the degree of intervalence charge-transfer after partial oxidation. Li[] shows two distinct one-electron redox waves for its chemically equivalent ferrocenyl substituents in the cyclic voltammogram (E(1/2) = -0.38 V, -0.64 V; vs. FcH/FcH(+)). The corresponding values of Li(2)[] are E(1/2) = -0.45 V (two-electron process) and -1.18 V. All these redox events are reversible at r. t. on the time scale of cyclic voltammetry. X-ray crystallography on the mixed-valent Fe(II)(2)Fe(III) complex Li(12-c-4)(2)[] reveals the centroid-centroid distance between the cyclopentadienyl rings of each of the terminal ferrocenyl substituents (3.329 A) to be significantly smaller than in the central 1,1'-ferrocenediyl fragment (3.420 A). This points towards a charge-localized structure (on the time scale of X-ray crystallography) with the central iron atom being in the Fe(III) state. Mössbauer spectroscopic measurements on Li(12-c-4)(2)[] lend further support to this interpretation. Spectroelectrochemical measurements on Li[] and Li(2)[] in the wavelength range between 300-2800 nm do not show bands interpretable as intervalence charge-transfer absorptions for the mixed-valent states. All data accumulated so far lead to the conclusion that electronic interaction between the individual Fe atoms in Li[] and Li(2)[] occurs via a through-space pathway and/or is electrostatic in nature.

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A one-pot synthesis of the tetrasilatetrahedrane (tBu 3 Si) 4 Si 4 was achieved by the reaction of HSiCl 3 and Na[SitBu 3 ]. In this reaction the silane tBu 3 SiH was obtained along with (tBu 3 Si) 4 Si 4 and tBu 3 SiSitBu 3 . The tetrasilatetrahedrane (tBu 3 Si) 4 Si 4 was also obtained via a one-pot approach by treatment of Cl 3 SiSiCl 3 or Cl 3 SiSiCl 2 SiCl 3 with Na-[SitBu 3 ]. In the reaction of HSiCl 3 with Na[SitBu 3 ], two molecules of the tetrasilatetrahedrane (tBu 3 Si) 4 Si 4 crystallize together with one molecule of tBu 3 SiSitBu 3 and one molecule of benzene. Single crystals suitable for X-ray diffraction composed of one molecule of (tBu 3 Si) 4 Si 4 and two molecules of benzene were obtained by recrystallization from benzene.

The caesium triphosphenide Cs[tBu3SiPPPSitBu3] was accessible from the reaction of CsF with the sodium triphosphenide Na[tBu3SiPPPSitBu3] in tetrahydrofuran at room temperature. In contrast to the preparation of tetrahydrofuran-solvated silanides M[SitBu3] (M = Li, Na, K), our efforts to synthesize the caesium silanide Cs[SitBu3] as a tetrahydrofuran complex failed. When tBu3SiBr was treated with an excess of caesium metal in tetrahydrofuran at room temperature, the caesium enolate Cs[OCH=CH2] and the supersilane tBu3SiH formed rather than the silanide Cs[SitBu3]. X-Ray quality crystals of the enolate Cs[OCH=CH2] (orthorhombic, Pnma) were obtained from tetrahydrofuran at ambient temperature. In contrast to the structures of its homologues M[tBu3SiPPPSitBu3] (M = Na, K), the caesium triphosphenide Cs[tBu3SiPPPSitBu3] features a polymer in the solid state (orthorhombic, Cmcm).

Polythiophene was functionalized with redox-active ferrocenylborane pendent groups. A postpolymerization modification procedure was applied, in which silylated polythiophene was reacted with BBr 3 to give a polymer with pendent BBr 2 groups. The dibromoboryl functionalities were then further elaborated by first treating the intermediate with FcSnMe 3 to introduce the ferrocenyl moieties and then with an arylcopper derivative ArCu (Ar = 2,4,6-trimethylphenyl (Mes), 2,4,6-triisopropylphenyl (Tip)) to sterically stabilize the boron centers. Using similar methods, two quaterthiophene derivatives were also prepared. The number-average molecular weight (M n ) of the polymers was determined by gel permeation chromatography (GPC) relative to narrow PS standards to range from 9400 to 14 600 Da. The polymer structure was further confirmed by MALDI-TOF mass spectrometry and by multinuclear NMR spectroscopy. H,H-NOESY spectroscopy and single crystal X-ray diffraction experiments on the quaterthiophene derivatives were used to gain insight into the conformation of the oligomers and polymers in solution and the solid state. The electronic structure of the oligo-and polythiophenes was studied in detail by UV-vis spectroscopy and electrochemical measurements.

The reaction of the tridentate [N,O,N] (pyrazol-1-yl)borate ligand [Ph(pz)B(μ-O)(μ-pz)B(pz)Ph] -([L 1 ] -) with [Cp*RuCl] 4 and [(p-cym)RuCl 2 ] 2 gives the Ru II complexes [Cp*Ru(L 1 )] and [(p-cym)-Ru(L 1 )]Cl, respectively (pz = pyrazolyl, Cp* = pentamethylcyclopentadienyl, p-cym = p-cymene). In order to avoid degradation of the [(p-cym)Ru(L 1 )] þ complex in solution, its Clcounterion has been exchanged for PF 6-, [B(C 6 F 5 ) 4 ] -, tosylate, and triflate. When the reaction between [L 1 ]and [(p-cym)Ru-Cl 2 ] 2 is carried out in the presence of 4 equiv of TlPF 6 , the dinuclear pyrazolyl-bridged complex [(p-cym)-Ru(μ-Cl)(μ-pz) 2 Ru(p-cym)]PF 6 and the mononuclear speciesIn a targeted synthesis, the lithium salt of the novel ligand [L 2 ] 2was prepared from 2 equiv of Lipz and 2,4,6-Ph 3 B 3 O 3 and successfully transformed into [(p-cym)Ru(L 2 )].[Cp*Ru(L 1 )], [(p-cym)Ru(L 1 )]PF 6 , and [(p-cym)Ru(L 2 )] have been characterized by NMR spectroscopy, X-ray crystallography, and (spectro)electrochemistry. One-electron oxidation of [Cp*Ru(L 1 )] by electrochemical or chemical ([Cp 2 Fe]PF 6 ) means leads to the Ru III species [Cp*Ru(L 1 )]PF 6 , which has been isolated and fully characterized (E 1/2 (Ru II /Ru III ) = -0.39 V; CH 2 Cl 2 , vs FcH/FcH þ ). A comparison of the solid-state structures of [Cp*Ru(L 1 )] and [Cp*Ru(L 1 )]PF 6 reveals that oxidation of the ruthenium center results in a lengthening of the average Ru-Cp* distances and a shortening of all Ru-L 1 bond lengths. According to the X-ray data, the angle strain within [(p-cym)Ru(L 1 )]PF 6 is higher than in [(p-cym)Ru(L 2 )], which could account for the fact that [L 1 ]is apparently less stable than [L 2 ] 2-.