Octahedral Ru(II) amido complexes TpRu(L)(L')(NHR) (Tp = hydridotris(pyrazolyl)borate; L = L' = P(OMe)3 or PMe3 or L = CO and L' = PPh3; R = H,Ph, or tBu): synthesis,characterization, and reactions with weakly acidic C-H bonds

The octahedral Ru(II) amine complexes [TpRu(L)(L')(NH(2)R)][OTf] (L = L' = PMe(3), P(OMe)(3) or L = CO and L' = PPh(3); R = H or (t)Bu) have been synthesized and characterized. Deprotonation of the amine complexes [TpRu(L)(L')(NH(3))][OTf] or [TpRu(PMe(3))(2)(NH(2)(t)Bu)][OTf] yields the Ru(II) amido complexes TpRu(L)(L')(NH(2)) and TpRu(PMe(3))(2)(NH(t)Bu). Reactions of the parent amido complexes or TpRu(PMe(3))(2)(NH(t)Bu) with phenylacetylene at room temperature result in immediate deprotonation to form ruthenium-amine/phenylacetylide ion pairs, and heating a benzene solution of the [TpRu(PMe(3))(2)(NH(2)(t)Bu)][PhC(2)] ion pair results in the formation of the Ru(II) phenylacetylide complex TpRu(PMe(3))(2)(C[triple bond]CPh) in >90% yield. The observation that [TpRu(PMe(3))(2)(NH(2)(t)Bu)][PhC(2)] converts to the Ru(II) acetylide with good yield while heating the ion pairs [TpRu(L)(L')(NH(3))][PhC(2)] yields multiple products is attributed to reluctant dissociation of ammonia compared with the (t)butylamine ligand (i.e., different rates for acetylide/amine exchange). These results are consistent with ligand exchange reactions of Ru(II) amine complexes [TpRu(PMe(3))(2)(NH(2)R)][OTf] (R = H or (t)Bu) with acetonitrile. The previously reported phenyl amido complexes TpRuL(2)(NHPh) [L = PMe(3) or P(OMe)(3)] react with 10 equiv of phenylacetylene at elevated temperature to produce Ru(II) acetylide complexes TpRuL(2)(C[triple bond]CPh) in quantitative yields. Kinetic studies indicate that the reaction of TpRu(PMe(3))(2)(NHPh) with phenylacetylene occurs via a pathway that involves TpRu(PMe(3))(2)(OTf) or [TpRu(PMe(3))(2)(NH(2)Ph)][OTf] as catalyst. Reactions of 1,4-cyclohexadiene with the Ru(II) amido complexes TpRu(L)(L')(NH(2)) (L = L' = PMe(3) or L = CO and L' = PPh(3)) or TpRu(PMe(3))(2)(NH(t)Bu) at elevated temperatures result in the formation of benzene and Ru hydride complexes. TpRu(PMe(3))(2)(H), [Tp(PMe(3))(2)Ru[double bond]C[double bond]C(H)Ph][OTf], [Tp(PMe(3))(2)Ru=C(CH(2)Ph)[N(H)Ph]][OTf], and [TpRu(PMe(3))(3)][OTf] have been independently prepared and characterized. Results from solid-state X-ray diffraction studies of the complexes [TpRu(CO)(PPh(3))(NH(3))][OTf], [TpRu(PMe(3))(2)(NH(3))][OTf], and TpRu(CO)(PPh(3))(C[triple bond]CPh) are reported.     

Structural variations of potassium aryloxides

A series of potassium aryloxides (KOAr) were isolated from the reaction of a potassium amide (KN(SiMe(3))(2)) and the desired substituted phenoxide (oMP, 2-methyl; oPP, 2-iso-propyl; oBP, 2-tert-butyl; DMP, 2,6-di-methyl; DIP, 2,6-di-iso-propyl; DBP, 2,6-di-tert-butyl) in tetrahydrofuran (THF) or pyridine (py) as the following: [([K(mu(4)-oMP)(THF)][K(mu(3)-oMP)])(5)]( infinity ) (1), [[K(6)(eta(6),mu(3)-oMP)(4)(eta(6),mu(4)-oMP)(2)(py)(4)].[K(6)(eta(6),mu(3)-oMP)(6)(eta(6)-py)(4)]]( infinity ) (2), [K(mu(3)-oPP)](4)(THF)(3) (3), [K(4)(eta(6),mu(3)-oPP)(2)(mu(3)-oPP)(2)(py)(3)]( infinity ) (4), [K(mu(3)-oBP)(THF)](6) (5), [K(6)(eta(6),mu(3)-oBP)(2)(mu(3)-oBP)(4)(py)(4)]( infinity ) (6), [K(3)(eta(6),mu(3)-DMP)(2)(mu-DMP)(THF)]( infinity ) (7), [[K(eta(6),mu-DMP)(py)](2)]( infinity ) (8), [K(eta(6),mu-DIP)]( infinity ) (9), [K(eta(6),mu-DBP)]( infinity ) (10). Further exploration of the aryl interactions led to the investigation of the diphenylethoxide (DPE) derivative which was isolated as [K(mu(3)-DPE)(THF)](4) (11) or [K(mu(3)-DPE)(py)](4).py(2) (12) depending on the solvent used. In general, the less sterically demanding ligands (oMP, oPP, oBP, and DMP) were solvated polymeric species; however, increasing the steric bulk (DIP and DBP) led to unsolvated polymers and not discrete molecules. For most of this novel family of compounds, the K atoms were pi-bound to the aryl rings of the neighboring phenoxide derivatives to fill their coordination sites. The synthesss and characterization of these compounds are described in detail.     

Parallel synthesis of unsymmetrically substituted tetraphenyl porphyrins on Wang resin

A method for synthesizing combinatorial libraries of unsymmetrically substituted tetra-meso-phenyl porphyrins on polystyrene based resin is described. Attachment of 5,15-dibromo-10-(4-hydroxyphenyl)-20-(4-nitrophenyl)porphyrin onto brominated Wang resin gave a convenient scaffold for the synthesis of photoactive porphyrin libraries with three points for generating diversity. An array of nine TPP derivatives was prepared by sequential Suzuki coupling/nitro-reduction and acylation protocols.     

Chiroptical switching polyguanidine synthesized by helix-sense-selective polymerization using [(R)-3,3'-dibromo-2,2'-binaphthoxy](di-tert-butoxy)titanium(IV) catalyst

A series of chiral binaphthyl titanium alkoxide complexes were synthesized. Among them, chiral titanium complex [(R)-3,3'-dibromo-2,2'-binaphthoxy](di-tert-butoxy)titanium(IV) (R-3) exists as a crystallographic C2 dimer in the solid state but a monomer in solution at room temperature. Application of R-3 in the helix-sense-selective polymerization of achiral carbodiimide, N-(1-anthryl)-N'-octadecylcarbodiimide (1), yielded a well-defined regioregular, stereoregular poly[N-(1-anthryl)-N'-octadecylguanidine] (poly-1b) with a relatively narrow polymer dispersity index of 2.7. Full racemization of poly-1b at +80 degrees C in toluene requires more than 100 h. Interestingly, poly-1b was found to undergo fast reversible chiroptical switching at +38.5 degrees C in toluene. Furthermore, at room temperature, poly-1b shows a positively signed Cotton effect in toluene, but negative ones in THF and chloroform, respectively. The chiroptical switching takes place around the toluene content of 90% (vol) in the mixed toluene/THF solvents. This is the first example of chiroptical switching phenomenon occurring in a helical polymer possessing no chiral moieties in the polymer chains. We believe this reversible chiroptical switching phenomenon occurs by reorientation of anthracene rings relative to the chain director.     

NMR elucidation of some pentacycloundecane derived ligands

The complete NMR elucidation of four pentacycloundecane (PCU) derived ligands is reported. 2D NMR techniques are used to overcome the problem of major overlapping of methine signals on the cage skeleton. One of the cage ligands is chiral and the ¹³C NMR signals of the leucinol side “arms” to the cage appear to be split into two or more peaks indicating either impurities or conformational differences. Impurities were ruled out and the only logical explanation for this unusual observation appears to be conformational effects due to different positions of the two relative bulky side chains or “arms”. The rigid cage skeleton is known for through space deshielding of signals in close proximity to oxygen atoms attached to the cage skeleton. The leucinol side chains in closer proximity to the cage ether bridge would experience a larger shielding effect causing those carbon atoms to be shifted upfield with respect to the corresponding atoms in other conformations. The intrinsic chiral nature of the cage could also play a role in this case to perhaps enhance the observed effect. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

(Zr6B)Cl11-xI2+x] (0< or = x < or = 6): a new mixed-halide structure with zigzag cains of clusters in multiply twinned crystals

The new [(Zr6B)Cl11-xI2+x] phase (with 0 < or = x < or = 6) is obtained from reactions of ZrI4, ZrCl4, and elemental Zr and B for 2-4 weeks in sealed Ta tubing at 800-850 degrees C. Single crystals of [(Zr6B)Cl6.44(7)I6.56] have been characterized by X-ray diffraction at room temperature (orthorhombic Pbcn, Z = 4, a = 12.365(2) A, b = 15.485(3) A, c = 13.405(2) A). This structure contains zigzag chains of boron-centered (Zr6B) octahedra that are interconnected by Cl(i-i) halides. Further three-dimensional connectivity is achieved by I(a-a-a) bridges. The noncluster interconnecting two-bonded X(i) sites are occupied statistically by a mixture of Cl and I. For each site both positions were resolved. This structure forms within a phase width of 0 < or = x < or = 6 at temperatures between 800 and 850 degrees C. Crystals of this phase appear to be always multiply twinned.