The scandium complex bearing both methylidene and phosphinidene ligands, (LSc)2(μ2-CH2)(μ2-PDIPP) (L = MeC(NDIPP)CHC(NDIPP)Me−, DIPP = 2,6-( i Pr)2C6H3) (2), has been synthesized, and its ...reactivity has been investigated. Reaction of scandium methyl phosphide LSc(Me){P(H)DIPP} with 1 equiv of scandium dimethyl complex LScMe2 in toluene at 60 °C provided complex 2 in good yield, and the structure of complex 2 was determined by single-crystal X-ray diffraction. Complex 2 easily undergoes nucleophilic addition reactions with CO2, CS2, benzonitrile, and tert-butyl isocyanide. In the above reactions, the unsaturated substrates insert into the Sc–C(methylidene) bond to give some interesting dianionic ligands while the Sc–P(phosphinidene) bond remains untouched. The bonding situation of complex 2 was analyzed using DFT methods, indicating a more covalent bond between the scandium ion and the phosphinidene ligand than between the scandium ion and the methylidene ligand.
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The reactions of rare-earth metal benzyl complexes supported by silicon-bridged boratabenzene fluorenyl ligands with PhSiH
in toluene gave the corresponding dinuclear hydrides {μ-Me
Si(C
H
)(C
H
BNEt
...)}Ln(μ-H)(THF)
(3-Ln; Ln = La, Nd, Gd), wherein the rare-earth metal ions are linked by both silicon-bridged boratabenzene fluorenyl ligands and hydrido ligands. The reactivity of these hydrides toward unsaturated substrates was studied. Among these, alkynides {μ-Me
Si(C
H
)(C
H
BNEt
)}Ln(μ-CCPh)
(4-Ln; Ln = La, Nd) were obtained via the σ-bond metathesis reaction, when 3-Ln (Ln = La, Nd) was treated with phenylacetylene. While reacting with 3-hexyne, the mono-addition product {μ-Me
Si(C
H
)(C
H
BNEt
)}Ln
(μ-H)μ-C(Et)double bond, length as m-dashC(H)Et (5-Ln; Ln = La, Nd) was formed. Further investigations on the reactivity of 3-La displayed that benzonitrile and tert-butyl isonitrile readily inserted into the La-H bonds, affording an azomethine complex {μ-Me
Si(C
H
)(C
H
BNEt
)}La{μ-Ndouble bond, length as m-dashC(H)Ph}
(6-La) and an N-tert-butylformimidoyl complex {μ-Me
Si(C
H
)(C
H
BNEt
)}La{μ,η
-C(H)double bond, length as m-dashN
Bu}
(7-La), respectively. The reaction with N,N'-diisopropylcarbodiimide at room temperature or at 75 °C gave a dimeric complex {μ-Me
Si(C
H
)(C
H
BNEt
)}La
(μ-H)μ-N(
Pr)CHN(
Pr) (8-La) or a monomeric complex Me
Si(C
H
)(C
H
BNEt
)LaN(
Pr)CHN(
Pr) (9-La), respectively.
Abstract
M=E/M≡E multiple bonds (M = transition metal, E = main group element) are of significant fundamental scientific importance and have widespread applications. Expanding the ranges of M and E ...represents grand challenges for synthetic chemists and will bring new horizons for the chemistry. There have been reports of M=E/M≡E multiple bonds for the majority of the transition metals, and even some actinide metals. In stark contrast, as the largest subgroup in the periodic table, rare-earth metals (Ln) were scarcely involved in Ln=E/Ln≡E multiple bonds. Until recently, there were a few examples of rare-earth monometallic alkylidene, imido and oxo complexes, featuring Ln=C/N/O bonds. What are in absence are rare-earth monometallic phosphinidene complexes with Ln=P bonds. Herein, we report synthesis and structure of rare-earth monometallic phosphinidene complexes, namely scandium phosphinophosphinidene complexes. Reactivity of scandium phosphinophosphinidene complexes is also mapped out, and appears to be easily tuned by the supporting ligand.
The facile and reversible addition of the Si–H bond of phenylsilane to the ScN bond of the scandium terminal imido complex LScNDIPP(DMAP) (1; L MeC(N(DIPP))CHC(Me)(NCH2CH2NMe)−, DIPP = 2,6- i ...Pr2C6H3) is reported. The reaction gives the scandium anilido hydride LSc(H)(N(DIPP)(SiH2Ph)) (2), and a labeling experiment shows a rapid σ-bond metathesis between Sc–H of the formed scandium anilido hydride and Si–H of phenylsilane during the reaction. 2 was trapped by an insertion reaction with diphenylcarbodiimide, giving the stable scandium anilido amidinate LSc(N(DIPP)(SiH2Ph))(κ2(N,N′)-PhNCHNPh) (3). Furthermore, the scandium terminal imido complex can efficiently catalyze the hydrosilylation of N-benzylidenepropan-1-amine. The reaction was completed within 2 h at 50 °C with 5 mol % of catalyst loading and highly selectively produced the monoaminosilane.
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High amylose maize flour (HAMF), normal maize flour (NMF), extruded normal maize flour (ENMF) and extruded high amylose maize flour (EHAMF) were employed to analyze the effects of the extrusion ...process on their physicochemical properties and in vitro digestion. The disruption degree of NMF and HAMF under extrusion followed the degree of gelatinization order. HAMF and EHAMF had higher onset temperature, peak temperature and conclusion temperature but lower melting enthalpies in comparison with NMF and ENMF. Extrusion treatment decreased viscosity and transformed A-type and B-type starch in NMF and HAMF into B + V-type. The solubility of all samples and swelling power of NMF and HAMF showed an increase, while swelling power of extruded maize flour decreased with increasing temperature. HAMF and EHAMF had a higher content of resistant starch but a lower content of slowly digestible starch and rapidly digestible starch than NMF and ENMF.
•The greater DG of extruded maize flour, the greater disruption level.•Extrusion decreases the viscosity of NMF and HAMF.•The SP of NMF and HAMF increases, while extruded flours decrease.•EHAMF retains higher RS than NMF under the same extrusion condition.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
We examine the transfer of graphene grown by chemical vapor deposition (CVD) with polymer scaffolds of poly(methyl methacrylate) (PMMA), poly(lactic acid) (PLA), poly(phthalaldehyde) (PPA), and ...poly(bisphenol A carbonate) (PC). We find that optimally reactive PC scaffolds provide the cleanest graphene transfers without any annealing, after extensive comparison with optical microscopy, x-ray photoelectron spectroscopy, atomic force microscopy, and scanning tunneling microscopy. Comparatively, films transferred with PLA, PPA, PMMA PC, and PMMA have a two-fold higher roughness and a five-fold higher chemical doping. Using PC scaffolds, we demonstrate the clean transfer of CVD multilayer graphene, fluorinated graphene, and hexagonal boron nitride. Our annealing free, PC transfers enable the use of atomically-clean nanomaterials in biomolecule encapsulation and flexible electronic applications.
A silicon-bridged boratabenzene fluorenyl ligand Me2Si(C13H8)(C5H4BNEt2)2– (L 2–) was designed and synthesized. By employment of this ligand, two divalent rare-earth metal complexes ...Me2Si(C13H8)(C5H4BNEt2)Ln(THF)2 (Ln = Sm (1), Yb (2)) were obtained from salt metathesis of K2Me2Si(C13H8)(C5H4BNEt2) (K 2 L) with LnI2(THF)2 in THF. Complex 2 undergoes redox reaction with cyclooctatetraene to give a trivalent Yb complex (C8H8)Yb2μ-{Me2Si(C13H8)(C5H4BNEt2)}2 (3), accompanied with oxidative coupling of two fluorenyl groups. A series of chloro-bridged trimeric trivalent rare-earth metal complexes Li(THF)42{Me2Si(C13H8)(C5H4BNEt2)Ln(μ-Cl)Li(THF)3}3(μ-Cl)3(μ3-Cl)2 (Ln = Nd (4), Sm (5), and Gd (6)) were synthesized by reactions of Li2Me2Si(C13H8)(C5H4BNEt2) (Li 2 L) with LnCl3 in THF. Treatment of K2Me2Si(C13H8)(C5H4BNEt2) (K 2 L) with LnI3(THF) n gave the monomeric complexes Me2Si(C13H8)(C5H4BNEt2)LnI(THF) (Ln = La (7), Nd (8), Sm (9), and Gd (10)). These iodides were subsequently reacted with KCH2C6H4-o-NMe2 to afford THF coordinated benzyl complexes Me2Si(C13H8)(C5H4BNEt2)Ln(CH2C6H4-o-NMe2)(THF) (Ln = La (11), Nd (12), and Gd (13a)) and non-THF coordinated complex Me2Si(C13H8)(C5H4BNEt2)Gd(CH2C6H4-o-NMe2) (13b).
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We analyze the optical, chemical, and electrical properties of chemical vapor deposition (CVD) grown hexagonal boron nitride (h-BN) using the precursor ammonia-borane (H3N–BH3) as a function of Ar/H2 ...background pressure (P TOT). Films grown at P TOT ≤ 2.0 Torr are uniform in thickness, highly crystalline, and consist solely of h-BN. At larger P TOT, with constant precursor flow, the growth rate increases, but the resulting h-BN is more amorphous, disordered, and sp3-bonded. We attribute these changes in h-BN grown at high pressure to incomplete thermolysis of the H3N–BH3 precursor from a passivated Cu catalyst. A similar increase in h-BN growth rate and amorphization is observed even at low P TOT if the H3N–BH3 partial pressure is initially greater than the background pressure P TOT at the beginning of growth. h-BN growth using the H3N–BH3 precursor reproducibly can give large-area, crystalline h-BN thin films, provided that the total pressure is under 2.0 Torr and the precursor flux is well-controlled.
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Substoichiometric molybdenum oxide ceramics have aroused widespread interest owing to their promising optical and electrical performance. In this work, the thermal stability and decomposition ...mechanism of Mo
O
and Mo
O
at 700-1000 °C and 700-1100 °C were investigated, respectively. Based on this information, MoO
(2 < x < 3) bulk ceramics were prepared by spark plasma sintering (SPS). The results show that Mo
O
is stable up to 790 °C in an argon atmosphere. As the temperature rises, it decomposes into Mo
O
. Mo
O
can exist stably at 830 °C, beyond which it will convert to MoO
. The MoO
ceramic bulks with four different components (MoO
, MoO
, MoO
and MoO
) were successfully sintered by SPS, and their relative density was greater than 96.4% as measured by the Archimedes principle. The reflectivity of MoO
ceramic bulk is low and only 6.3% when the composition is MoO
. The resistivity increases from 10
to 10
Ωcm with the increase in the O/Mo atomic ratio x. In general, the thermal stability information provides a theoretical basis for the processing of MoO
materials, such as the sintering of the MoO
target. The optical and electrical properties show that MoO
is a low-reflective conductive oxide material with great photoelectric application value.
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A series of magnesium, zinc, and calcium monoalkyl or monoamide complexes containing tridentate nitrogen ligands, CH
3C(2,6-(
i
Pr)
2C
6H
3N)CHC(CH
3) (NCH
2CH
2–D) (D
=
NMe
2, N((CH
2CH
2)
2CH
2)), ...have been synthesized, and six of which were characterized by single-crystal X-ray diffraction. The X-ray diffraction results show that the metal complexes are all solvent-free monomers and the pendant arm D bonds to the metal ion. These metal complexes are highly active for the ring-opening polymerization of
rac-lactide and give preference for heterotactic polylactide.
A series of magnesium, zinc, and calcium monoalkyl or monoamide complexes containing tridentate nitrogen ligands, CH
3C(2,6-(
i
Pr)
2C
6H
3N)CHC(CH
3) (NCH
2CH
2–D) (D = NMe
2, N((CH
2CH
2)
2CH
2)), have been synthesized, and six of which were characterized by single-crystal X-ray diffraction. The X-ray diffraction results show that the metal complexes are all solvent-free monomers and the pendant arm D bonds to the metal ion. These metal complexes are highly active for the ring-opening polymerization of
rac-lactide and give preference for heterotactic polylactide.
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