Ternary CuInSe(2) nanowires were synthesized for the first time by the solution-liquid-solid (SLS) mechanism. Here, both metal-organic multiple- and single-source molecular precursors were thermally decomposed in the presence of molten metal nanoparticles and coordinating ligands. The nature of the precursor-multiple- compared to single-source (wherein Cu-Se-In bonds are effectively preformed)-as well as the choice of coordinating ligands, reaction temperature, and reactant order-of-addition strongly affected the morphology and composition of the reaction product obtained. Crystalline, straight, and nearly stoichiometric CuInSe(2) nanowires were most readily achieved using the single-source precursor; however, careful tuning of reaction conditions could also be used to obtain high-quality nanowires from multiple-source precursor systems. The CuInSe(2) nanowires are strong light absorbers from the near-infrared through the visible and ultraviolet spectral regions and, thereby, comprise new soluble and processable "building blocks" for applications in solar-light harvesting.

This report describes the solid state structures of a series of divinylzinc complexes, one of which represents the only structurally characterized zinc(II) π-complex. Vinylzinc reagents, Zn[C(Me) =CH 2 ] 2 (1) and Zn[C(H)=CMe 2 ] 2 (2), have been synthesized and isolated as white crystalline solids in 66% and 72% yield, respectively. Each compound exhibits an infinite polymeric architecture in the solid state via a series of zinc-π (1) and zinc-σ-bonded (2)

Heterobimetallic Lewis acids M 3(THF) n (BINOLate) 3Ln [M = Li, Na, K; Ln = lanthanide(III)] are exceptionally useful asymmetric catalysts that exhibit high levels of enantioselectivity across a wide range of reactions. Despite their prominence, important questions remain regarding the nature of the catalyst-substrate interactions and, therefore, the mechanism of catalyst operation. Reported herein are the isolation and structural characterization of 7- and 8-coordinate heterobimetallic complexes Li 3(THF) 4(BINOLate) 3Ln(THF) [Ln = La, Pr, and Eu], Li 3(py) 5(BINOLate) 3Ln(py) [Ln = Eu and Yb], and Li 3(py) 5(BINOLate) 3La(py) 2 [py = pyridine]. Solution binding studies of cyclohexenone, DMF, and pyridine with Li 3(THF) n (BINOLate) 3Ln [Ln = Eu, Pr, and Yb] and Li 3(DMEDA) 3(BINOLate) 3Ln [Ln = La and Eu; DMEDA = N, N'-dimethylethylene diamine] demonstrate binding of these Lewis basic substrate analogues to the lanthanide center. The paramagnetic europium, ytterbium, and praseodymium complexes Li 3(THF) n (BINOLate) 3Ln induce relatively large lanthanide-induced shifts on substrate analogues that ranged from 0.5 to 4.3 ppm in the (1)H NMR spectrum. X-ray structure analysis and NMR studies of Li 3(DMEDA) 3(BINOLate) 3Ln [Ln = Lu, Eu, La, and the transition metal analogue Y] reveal selective binding of DMEDA to the lithium centers. Upon coordination of DMEDA, six new stereogenic nitrogen centers are formed with perfect diastereoselectivity in the solid state, and only a single diastereomer is observed in solution. The lithium-bound DMEDA ligands are not displaced by cyclohexenone, DMF, or THF on the NMR time scale. Use of the DMEDA adduct Li 3(DMEDA) 3(BINOLate) 3La in three catalytic asymmetric reactions led to enantioselectivities similar to those obtained with Shibasaki's Li 3(THF) n (BINOLate) 3La complex. Also reported is a unique dimeric [Li 6(en) 7(BINOLate) 6Eu 2][mu-eta (1),eta (1)-en] structure [en = ethylenediamine]. On the basis of these studies, it is hypothesized that the lanthanide in Shibasaki's Li 3(THF) n (BINOLate) 3Ln complexes cannot bind bidentate substrates in a chelating fashion. A hypothesis is also presented to explain why the lanthanide catalyst, Li 3(THF) n (BINOLate) 3La, is often the most enantioselective of the Li 3(THF) n (BINOLate) 3Ln derivatives.

Shibasaki's REMB catalysts (REMB; RE = Sc, Y, La-Lu; M = Li, Na, K; B = 1,1'-bi-2-naphtholate; RE/M/B = 1/3/3) are among the most enantioselective asymmetric catalysts across a broad range of mechanistically diverse reactions. However, their widespread use has been hampered by the challenges associated with their synthesis and manipulation. We report here the self-assembly of novel hydrogen-bonded rare earth metal BINOLate complexes that serve as bench-stable precatalysts for Shibasaki's REMB catalysts. Incorporation of hydrogen-bonded guanidinium cations in the secondary coordination sphere leads to unique properties, most notably, improved stability toward moisture in solution and in the solid state. We have exploited these properties to develop straightforward, high-yielding, and scalable open-air syntheses that provide rapid access to crystalline, nonhygroscopic complexes from inexpensive hydrated RE starting materials. These compounds can be used as precatalysts for Shibasaki's REMB frameworks, where we have demonstrated that our system performs with comparable or improved levels of stereoselectivity in several mechanistically diverse reactions including Michael additions, aza-Michael additions, and direct Aldol reactions.

[reaction: see text] We report the catalytic asymmetric allylation of ketones under highly concentrated reaction conditions with a catalyst generated from titanium tetraisopropoxide and BINOL (1:2 ratio) in the presence of isopropanol. This catalyst promotes the addition of tetraallylstannane to a variety of ketones to produce tertiary homoallylic alcohols in excellent yield (80-99%) with high enantioselectivities (79-95%). The resulting homoallylic alcohols can also be epoxidized in situ using tert-butyl hydroperoxide (TBHP) to afford cyclic epoxy alcohols in high yield (84-87%).

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Shibasaki's heterobimetallic complexes M 3 (THF) n (BINOLate) 3 Ln [M = Li, Na, K, Ln = lanthanide (III)] are among the most successful asymmetric Lewis acid catalysts. Why does M 3 (THF) n (BINOLate) 3 Ln readily bind substrates when M = Li but not when M = Na or K? Structural studies herein indicate Na-and K-C cation-π interactions and alkali metal radius may be more important than even lanthanide radius. Also reported is a novel polymeric [K 3 (THF) 2 (BINOLate) 3 Yb] n structure that provides the first evidence of interactions between M 3 (THF) n (BINOLate) 3 Ln complexes.Shibasaki's M 3 (THF) n (BINOLate) 3 Ln complexes (Figure 1) are among the most effective asymmetric Lewis acid catalysts known, exhibiting high enantioselectivities over a broad range of reactions. 1-3 Understanding how these heterobimetallic catalysts work, however, has proven challenging. 4-9 In particular, seemingly subtle alterations in the catalyst composition result in dramatic changes in selectivity. For example, in the nitro aldol reaction with M 3 (THF) n (BINOLate) 3 Ln, 94% ee was obtained when M = Li and 2% ee when M = Na. In contrast, the asymmetric Michael reaction gave 92% ee when M = Na and 29% ee for M = Li. 10 The first step in unraveling the factors that are responsible for these striking differences is understanding the impact of the alkali metal on substrate binding to the lanthanide centers.Reported herein are solution and solid state studies of M 3 (sol) n (BINOLate) 3 Ln complexes that illuminate dramatic differences in Ln binding ability when M = Li vs. Na and K. Also disclosed is an unprecedented helical polymer, [K 3 We recently demonstrated that DMF reversibly binds to paramagnetic lanthanides in Li 3 (THF) n (BINOLate) 3 Ln (Ln = Eu, Pr), exhibiting > 2 ppm lanthanide induced shift (LIS) in the formyl C-H resonance in the 1 H NMR spectrum. 8 Salvadori, on the other hand, reported 7 that Na 3 (THF) 6 (BINOLate) 3 Yb does not bind water in solution or the solid state, which was attributed to the small ionic radius of Yb (La = 1.17, Eu = 1.09, Yb = 1.01). This dichotomy prompted us to examine binding of the lithium analog, Li 3 (THF) n (BINOLate) 3 Yb, with DMF. In the presence of Li 3 (THF) n (BINOLate) 3 Yb, the formyl C-H shifted over 4 ppm, consistent with binding to Yb. Furthermore, crystallization of Li 3 (THF) n (BINOLate) 3 Yb from pyridine yielded 7-coordinate Li 3 (py) 5 (BINOLate) 3 Yb•py, the ORTEP of which is shown in Figure 2. We next examined binding of DMF to Na 3 (THF) 6 (BINOLate) 3 Ln [Ln = Yb, Eu] 11-13 and K 3 (THF) 6 (BINOLate) 3 Yb 14,7 under the same conditions. Surprisingly, no LISs (>0.1 ppm) were observed, indicating that binding to the lanthanide in the Na and K analogs is much less favorable than in the Li series.

This manuscript is dedicated to Prof. M. Shibasaki, whose creativity and insight has changed the way we think of asymmetric Lewis acid catalysis.Supporting information for this article is available on the WWW under http://asc.wiley-vch.de/home/.Abstract: Shibasakis heterobimetallic Lewis acids,Ln (M = Li, Na, K and Ln = lanthanide), are an exceptionally useful class of asymmetric catalysts that exhibit high levels of enantioselectivity across a wide range of reactions. In many instances, it is necessary to add water (and base) to achieve maximum enantioselectivity. We have investigated the reaction of water withand observed formation of a novel hydroxide-bridged dimer (M = Li) and tetramer (M = K). These compounds have been characterized, including Xray structure analysis. Under anhydrous conditions, only 6-coordinate monomericYb complexes were isolated and characterized by Xray crystallography. Isolation of the dimer 4 indicates that added water can react with this important class of bifunctional catalyst to give new products. C H T U N G T R E N N U N G (m-OH) 2 and tetramer K 4 A C H T U N G T R E N N U N G (THF) 9 A C H T U N G T R E N N U N G (BINOLate) 6 Yb 4 A C H T U N G T R E N N U N G (m 3 -OH)Keywords: additives; asymmetric catalysis; bridging hydroxide; heterobimetallic catalysts; lanthanides; Lewis acidsIn the early 1990s, Shibasaki and co-workers reported the synthesis and applications of a series of heterobimetallic Lewis acid catalysts, Figure 1, M = Li, Na, K and Ln = lanthanideA C H T U N G T R E N N U N G (III)] and their 7-coordinate hydrates[1-6] These bifunctional catalysts are exceptional in their ability to catalyze a broad range of asymmetric transformations, such as the Henry reaction, [1,7] conjugate additions, [4,5,[7][8][9][10] aldol condensations, [6,11] cyanoethoxycarbonylation of aldehydes, [12] and hydrophosphonylation of aldehydes and cyclic imines, [13,14] to name a few. Despite the widespread successful application of these heterobimetallic catalysts in asymmetric synthesis, their reaction mechanisms are not well understood, because their multifunctional nature complicates mechanistic studies.