A known trinuclear structure was used to design the heterobimetallic mixed‐valent, mixed‐ligand molecule [CoII(hfac)3−Na−CoIII(acac)3] (
A known trinuclear structure was used to design the heterobimetallic mixed‐valent, mixed‐ligand molecule [CoII(hfac)3−Na−CoIII(acac)3] (
- NSF-PAR ID:
- 10158063
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 59
- Issue:
- 24
- ISSN:
- 1433-7851
- Page Range / eLocation ID:
- p. 9624-9630
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract 1 ). This was used as a template structure to develop heterotrimetallic molecules [CoII(hfac)3−Na−FeIII(acac)3] (2 ) and [NiII(hfac)3−Na−CoIII(acac)3] (3 ) via isovalent site‐specific substitution at either of the cobalt positions. Diffraction methods, synchrotron resonant diffraction, and multiple‐wavelength anomalous diffraction were applied beyond simple structural investigation to provide an unambiguous assignment of the positions and oxidation states for the periodic table neighbors in the heterometallic assemblies. Molecules of2 and3 are true heterotrimetallic rather than a statistical mixture of two heterobimetallic counterparts. Trinuclear platform1 exhibits flexibility in accommodating a variety of di‐ and trivalent metals, which can be further utilized in the design of molecular precursors for the NaMM′O4functional oxide materials. -
An unusual heterobimetallic volatile compound [Pb2Co5(acac)14] was synthesized by the gas phase/solid-state technique. The preparation can be readily scaled up using the solution approach. X-ray powder diffraction, ICP-OES analysis, and DART mass spectrometry were engaged to confirm the composition and purity of heterobimetallic complex. The composition is unique among the large family of lead(tin): transition metal = 2:1, 1:1, and 1:2 β-diketonates compounds that are mostly represented by coordination polymers. The molecular structure of the complex was elucidated by synchrotron single crystal X-ray diffraction to reveal the unique heptanuclear moiety {Co(acac)2[Pb(acac)2-Co(acac)2-Co(acac)2]2} built upon bridging interactions of acetylacetonate oxygens to neighboring metal centers that bring their coordination numbers to six. The appearance of unique heptanuclear assembly can be attributed to the fact that the [Co(acac)2] units feature both cis- and trans-bis-bridging modes, making the polynuclear moiety rather flexible. This type of octahedral coordination is relatively unique among known lead(tin)-3d transition metal β-diketonates. Due to the high-volatility, [Pb2Co5(acac)14] can be potentially applied as a MOCVD precursor for the low-temperature preparation of lead-containing functional materials.
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Abstract Exploration of the reduction chemistry of the 2,2’‐bipyridine (bipy) lanthanide metallocene complexes Cp*2LnCl(bipy) and Cp*2Ln(bipy) (Cp* = C5Me5) resulted in the isolation of a series of complexes with unusual composition and structure including complexes with a single Cp* ligand, multiple azide ligands, and bipy ligands with close parallel orientations. These results not only reveal new structural types, but they also show the diverse chemistry displayed by this redox‐active platform. Treatment of Cp*2NdCl(bipy) with excess KC8resulted in the formation of the mono‐Cp* Nd(III) complex, [K(crypt)]2[Cp*Nd(bipy)2],
1 , as well as [K(crypt)][Cp*2NdCl2],2 , and the previously reported [K(crypt)][Cp*2Nd(bipy)]. A mono‐Cp* Lu(III) complex, Cp*Lu(bipy)2,3 , was also found in an attempt to make Cp*2Lu(bipy) from LuCl3, 2 equiv. of KCp*, bipy, and K/KI. Surprisingly, the (bipy)1−ligands in neighboring molecules in the structure of3 are oriented in a parallel fashion with intermolecular C⋅⋅⋅C distances of 3.289(4) Å, which are shorter than the sum of van der Waals radii of two carbon atoms, 3.4 Å. Another product with one Cp* ligand per lanthanide was isolated from the reaction of [K(crypt)][Cp*2Eu(bipy)] with azobenzene, which afforded the dimeric Eu(II) complex, [K(crypt)]2[Cp*Eu(THF)(PhNNPh)]2,4 . Attempts to make4 from the reaction between Cp*2Eu(THF)2and a reduced azobenzene anion generated instead the mixed‐valent Eu(III)/Eu(II) complex, [K(crypt)][Cp*Eu(THF)(PhNNPh)]2,5 , which allows direct comparison with the bimetallic Eu(II) complex4 . Mono‐Cp* complexes of Yb(III) are obtained from reactions of the Yb(II) complex, [K(crypt)][Cp*2Yb(bipy)], with trimethylsilylazide, which afforded the tetra‐azido [K(crypt)]2[Cp*Yb(N3)4],6 , or the di‐azido complex [K(crypt)]2[Cp*Yb(N3)2(bipy)],7 a , depending on the reaction stoichiometry. A mono‐Cp* Yb(III) complex is also isolated from reaction of [K(crypt)][Cp*2Yb(bipy)] with elemental sulfur which forms the mixed polysulfido Yb(III) complex [K(crypt)]2[Cp*Yb(S4)(S5)],8 a . In contrast to these reactions that form mono‐Cp* products, reduction of Cp*2Yb(bipy) with 1 equiv. of KC8in the presence of 18‐crown‐6 resulted in the complete loss of Cp* ligands and the formation of [K(18‐c‐6)(THF)][Yb(bipy)4],9 . The (bipy)1−ligands of9 are arranged in a parallel orientation, as observed in the structure of3 , except in this case this interaction is intramolecular and involves pairs of ligands bound to the same Yb atom. Attempts to reduce further the Sm(II) (bipy)1−complex, Cp*2Sm(bipy) with 2 equiv. of KC8in the presence of excess 18‐crown‐6 led to the isolation of a Sm(III) salt of (bipy)2−with an inverse sandwich Cp* counter‐cation and a co‐crystallized K(18‐c‐6)Cp* unit, [K2(18‐c‐6)2Cp*]2[Cp*2Sm(bipy)]2 ⋅ [K(18‐c‐6)Cp*],10 . -
The crystal structures of two intermediates, 4-amino-3,5-difluorobenzonitrile, C7H4F2N2(
I ), and ethyl 4-amino-3,5-difluorobenzoate, C9H9F2NO2(II ), along with a visible-light-responsive azobenzene derivative, diethyl 4,4′-(diazene-1,2-diyl)bis(3,5-difluorobenzoate), C18H14F4N2O4(III ), obtained by four-step synthetic procedure, were studied using single-crystal X-ray diffraction. The molecules ofI andII demonstrate the quinoid character of phenyl rings accompanied by the distortion of bond angles related to the presence of fluorine substituents in the 3 and 5 (ortho ) positions. In the crystals ofI andII , the molecules are connected by N—H...N, N—H...F and N—H...O hydrogen bonds, C—H...F short contacts, and π-stacking interactions. In crystal ofIII , only stacking interactions between the molecules are found. -
Abstract Visible‐light capture activates a thermodynamically inert CoIII−CF3bond for direct C−H trifluoromethylation of arenes and heteroarenes. New trifluoromethylcobalt(III) complexes supported by a redox‐active [OCO] pincer ligand were prepared. Coordinating solvents, such as MeCN, afford green, quasi‐octahedral [(SOCO)CoIII(CF3)(MeCN)2] (
2 ), but in non‐coordinating solvents the complex is red, square pyramidal [(SOCO)CoIII(CF3)(MeCN)] (3 ). Both are thermally stable, and2 is stable in light. But exposure of3 to low‐energy light results in facile homolysis of the CoIII−CF3bond, releasing.CF3radical, which is efficiently trapped by TEMPO.or (hetero)arenes. The homolytic aromatic substitution reactions do not require a sacrificial or substrate‐derived oxidant because the CoIIby‐product of CoIII−CF3homolysis produces H2. The photophysical properties of2 and3 provide a rationale for the disparate light stability.