- Award ID(s):
- 1855328
- NSF-PAR ID:
- 10149398
- Date Published:
- Journal Name:
- Chemical Science
- Volume:
- 11
- Issue:
- 7
- ISSN:
- 2041-6520
- Page Range / eLocation ID:
- 2006 to 2014
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The investigation of the coordination chemistry of rare-earth metal complexes with cyanide ligands led to the isolation and crystallographic characterization of the Ln III cyanotriphenylborate complexes dichlorido(cyanotriphenylborato-κ N )tetrakis(tetrahydrofuran-κ O )lanthanide(III), [ Ln Cl 2 (C 19 H 15 BN)(C 4 H 8 O) 4 ] [lanthanide ( Ln ) = dysprosium (Dy) and yttrium Y)] from reactions of LnCl 3 , KCN, and NaBPh 4 . Attempts to independently synthesize the tetraethylammonium salt of (NCBPh 3 ) − from BPh 3 and [NEt 4 ][CN] in THF yielded crystals of the phenyl-substituted cyclic borate, tetraethylazanium 2,2,4,6-tetraphenyl-1,3,5,2λ 4 ,4,6-trioxatriborinan-2-ide, C 8 H 20 N + ·C 24 H 20 B 3 O 3 − or [NEt 4 ][B 3 (μ-O) 3 (C 6 H 5 ) 4 ]. The mechanochemical reaction of BPh 3 and [NEt 4 ][CN] without solvent produced crystals of tetraethylazanium cyanodiphenyl-λ 4 -boranyl diphenylborinate, C 8 H 20 N + ·C 25 H 20 B 2 NO − or [NEt 4 ][NCBPh 2 (μ-O)BPh 2 ]. Reaction of BPh 3 and KCN in THF in the presence of 2.2.2-cryptand (crypt) led to a crystal of bis[(2.2.2-cryptand)potassium] 2,2,4,6-tetraphenyl-1,3,5,2λ 4 ,4,6-trioxatriborinan-2-ide cyanomethyldiphenylborate tetrahydrofuran disolvate, 2C 18 H 36 KN 2 O 6 + ·C 24 H 20 B 3 O 3 − ·C 14 H 13 BN − ·2C 4 H 8 O or [K(crypt)] 2 [B 3 (μ-O) 3 (C 6 H 5 ) 4 ][NCBPh 2 Me]·2THF. The [NCBPh 2 (μ-O)BPh 2 ] 1− and (NCBPh 2 Me) 1− anions have not been structurally characterized previously. The structure of 1-Y was refined as a two-component twin with occupancy factors 0.513 (1) and 0.487 (1). In 4 , one solvent molecule was disordered and included using multiple components with partial site-occupancy factors.more » « less
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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 reduction potentials (reported vs. Fc + /Fc) for a series of Cp′ 3 Ln complexes (Cp′ = C 5 H 4 SiMe 3 , Ln = lanthanide) were determined via electrochemistry in THF with [ n Bu 4 N][BPh 4 ] as the supporting electrolyte. The Ln( iii )/Ln( ii ) reduction potentials for Ln = Eu, Yb, Sm, and Tm (−1.07 to −2.83 V) follow the expected trend for stability of 4f 7 , 4f 14 , 4f 6 , and 4f 13 Ln( ii ) ions, respectively. The reduction potentials for Ln = Pr, Nd, Gd, Tb, Dy, Ho, Er, and Lu, that form 4f n 5d 1 Ln( ii ) ions ( n = 2–14), fall in a narrow range of −2.95 V to −3.14 V. Only cathodic events were observed for La and Ce at −3.36 V and −3.43 V, respectively. The reduction potentials of the Ln( ii ) compounds [K(2.2.2-cryptand)][Cp′ 3 Ln] (Ln = Pr, Sm, Eu) match those of the Cp′ 3 Ln complexes. The reduction potentials of nine (C 5 Me 4 H) 3 Ln complexes were also studied and found to be 0.05–0.24 V more negative than those of the Cp′ 3 Ln compounds.more » « less
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null (Ed.)N , N ′-Di- tert -butylcarbodiimide, Me 3 CN=C=NCMe 3 , undergoes reductive cleavage in the presence of the Gd II complex, [K(18-crown-6) 2 ][Gd II (N R 2 ) 3 ] ( R = SiMe 3 ), to form a new type of ligand, the tert -butylcyanamide anion, (Me 3 CNCN) − . This new ligand can bind metals with one or two donor atoms as demonstrated by the isolation of a single crystal containing potassium salts of both end-on and side-on bound tert -butylcyanamide anions, (Me 3 CNCN) − . The crystal contains [K(18-crown-6)(H 2 O)][NCNCMe 3 - kN ], in which one ( t BuNCN) − anion is coordinated end-on to potassium ligated by 18-crown-6 and water, as well as [K(18-crown-6)][η 2 -NCNCMe 3 ], in which an 18-crown-6 potassium is coordinated side-on to the terminal N—C linkage. This single crystal also contains one equivalent of 1,3-di- tert -butyl urea, (C 9 H 20 N 2 O), which is involved in hydrogen bonding that may stabilize the whole assembly, namely, aqua( tert -butylcyanamidato)(1,4,7,10,13,16-hexaoxacyclooctadecane)potassium(I)–( tert -butylcyanamidato)(1,4,7,10,13,16-hexaoxacyclooctadecane)potassium(I)– N , N ′-di- tert -butylcarbodiimide (1/1/1) [K(C 5 H 9 N 2 )(C 12 H 24 O 6 )]·[K(C 5 H 9 N 2 )(C 12 H 24 O 6 )(H 2 O)]·C 9 H 20 N 2 .more » « less
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Abstract Antiaromaticity, as introduced in 1965, usually refers to monocyclic systems with 4
n π electrons. This concept was extended to all‐metal molecules after the observation of Li3Al4−in the gas phase. However, the solid‐phase counterparts have not been documented to date. Herein, we describe a series of all‐metal antiaromatic anions, [Ln(η 4‐Sb4)3]3−(Ln=La, Y, Ho, Er, Lu), which were isolated as the K([2.2.2]crypt) salts and identified by single‐crystal X‐ray diffraction. Based on the results obtained from the chemical bonding analysis, multicenter indices, and the electron‐counting rule, we conclude that the core [Ln(η 4‐Sb4)3]3−fragment of the crystal has three locally π‐antiaromatic Sb4fragments. This complex represents the first locally π‐antiaromatic all‐metal system in the solid state, which is stabilized by interactions of the three π‐antiaromatic units with the central metal atom.