While the 1 : 1 reaction of 3 with an N-heterocyclic carbene ({(Me)CN(i-Pr)} 2 C:) in THF resulted in ligand-substituted product 4, the corresponding 1 : 2 reaction (in the presence of H 2 O) gives the first structurally characterized germanium tris(dithiolene)dianion 5 as the major product and the “naked” dithiolene radical 6˙ as a minor by-product. The structure and bonding of 4 and 5 were probed by experimental and theoretical methods. Our study suggests that carbene-mediated partial hydrolysis may represent a new method to access tris(dithiolene) complexes of main-group elements.
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Lewis base-complexed magnesium dithiolenes
The first magnesium-based dithiolene, 2 , was prepared by reaction of the lithium dithiolene radical, 1˙ , with 2-mesitylmagnesium bromide. Reaction of 2 with N-heterocyclic carbenes (in toluene) gave a carbene-stabilized magnesium monodithiolene complex, 3 . Complex 3 , in turn, is readily converted to a THF-solvated magnesium bis-dithiolene dianion, 4 , via partial hydrolysis in polar solvents ( i.e. , THF/CH 3 CN). Compounds 2 , 3 and 4 have been spectroscopically and structurally characterized and probed by DFT computations.
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- NSF-PAR ID:
- 10118807
- Date Published:
- Journal Name:
- Chemical Communications
- Volume:
- 55
- Issue:
- 56
- ISSN:
- 1359-7345
- Page Range / eLocation ID:
- 8087 to 8089
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract The 1 : 2 reaction of the imidazole‐based dithiolate (
2 ) with GeCl2 • dioxane in THF/TMEDA gives3 , a TMEDA‐complexed dithiolene‐based germylene. Compound3 is converted to monothiolate‐complexed (5 ) and N‐heterocyclic carbene‐complexed (7 ) germanium(II) dithiolene complexes via Lewis base ligand exchange. A bis‐dithiolene‐based germylene (8 ), involving a 3c–4e S‐Ge‐S bond, has also been synthesized through controlled hydrolysis of7 . The bonding nature of3 ,5 , and8 was investigated by both experimental and theoretical methods. -
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Abstract Whereas low‐temperature (−78 °C) reaction of the lithium dithiolene radical
1 .with boron bromide gives the dibromoboron dithiolene radical2 ., the parallel reaction of1 .with (C6H11)2BCl (0 °C) affords the dicyclohexylboron dithiolene radical3 .. Radicals2 .and3 .were characterized by single‐crystal X‐ray diffraction, UV/Vis, and EPR spectroscopy. The nature of these radicals was also probed computationally. Under mild conditions,3 .undergoes unexpected thiourea‐mediated B−C bond activation to give zwitterion4 , which may be regarded as an anionic dithiolene‐modified carbene complex of the sulfenyl cation RS+(R=cyclohexyl). -
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Abstract Whereas low‐temperature (−78 °C) reaction of the lithium dithiolene radical
1 .with boron bromide gives the dibromoboron dithiolene radical2 ., the parallel reaction of1 .with (C6H11)2BCl (0 °C) affords the dicyclohexylboron dithiolene radical3 .. Radicals2 .and3 .were characterized by single‐crystal X‐ray diffraction, UV/Vis, and EPR spectroscopy. The nature of these radicals was also probed computationally. Under mild conditions,3 .undergoes unexpected thiourea‐mediated B−C bond activation to give zwitterion4 , which may be regarded as an anionic dithiolene‐modified carbene complex of the sulfenyl cation RS+(R=cyclohexyl). -
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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 .
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/C9CC03427G
