Searching for a connection between the two‐electron redox behavior of Group‐14 elements and their possible use as platforms for the photoreductive elimination of chlorine, we have studied the photochemistry of [(
Searching for a connection between the two‐electron redox behavior of Group‐14 elements and their possible use as platforms for the photoreductive elimination of chlorine, we have studied the photochemistry of [(
- Award ID(s):
- 1856453
- NSF-PAR ID:
- 10307671
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 60
- Issue:
- 41
- ISSN:
- 1433-7851
- Page Range / eLocation ID:
- p. 22352-22358
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract o ‐(Ph2P)C6H4)2GeIVCl2]PtIICl2and [(o ‐(Ph2P)C6H4)2ClGeIII]PtIIICl3, two newly isolated isomeric complexes. These studies show that, in the presence of a chlorine trap, both isomers convert cleanly into the platinum germyl complex [(o ‐(Ph2P)C6H4)2ClGeIII]PtICl with quantum yields of 1.7 % and 3.2 % for the GeIV–PtIIand GeIII–PtIIIisomers, respectively. Conversion of the GeIV–PtIIisomer into the platinum germyl complex is a rare example of a light‐induced transition‐metal/main‐group‐element bond‐forming process. Finally, transient‐absorption‐spectroscopy studies carried out on the GeIII–PtIIIisomer point to a ligand arene–Cl.charge‐transfer complex as an intermediate. -
more » « less
Abstract Binuclear alkyne manganese carbonyls of the type (RC≡CR')Mn2(CO)
n (R and R'=methyl or dimethylamino;n =8, 7, 6) and their isomers related to the experimentally known (MeC2NEt2)Mn2(CO)n (n =8, 7) structures have been investigated by density functional theory. The alkyne ligand remains intact in the only low energy (Me2N)2C2Mn2(CO)8isomer, which has a central Mn2C2tetrahedrane unit and is otherwise analogous to the well‐known (alkyne)Co2(CO)6derivatives except for one more CO group per metal atom. The low‐energy structures of the unsaturated (Me2N)2C2Mn2(CO)n (n =7, 6) systems include isomers in which the nitrogen atom of one of the dimethylamino groups as well as the C≡C triple bond of the alkyne is coordinated to the central Mn2unit. In other low‐energy (Me2N)2C2Mn2(CO)n (n =7, 6) isomers the alkyne C≡C triple bond has broken completely to form two separate bridging dimethylaminocarbyne Me2NC ligands analogous to the experimentally known iron carbonyl complex (Et2NC)2Fe2(CO)6. The (alkyne)Mn2(CO)n (n =8, 7, 6) systems of the alkynes MeC≡CMe and Me2NC≡CMe with methyl substituents have significantly more complicated potential surfaces. In these systems the lowest energy isomers have bridging ligands derived from the alkyne in which one or two hydrogen atoms have migrated from a methyl group to one or both of the alkyne carbon atoms. These bridging ligands include allene, manganallyl, and vinylcarbene ligands, the first two of which have been realized experimentally in research by Adams and coworkers. Theoretical studies suggest that the mechanism for the conversion of the simple alkyne octacarbonyl (MeC2NMe2)Mn2(CO)8to the dimethylaminomanganaallyl complex Mn2(CO)7[μ‐η4‐C3H3Me2] involves decarbonylation to the heptacarbonyl and the hexacarbonyl complexes. Subsequent hydrogen migrations then occur through intermediates with C−H−Mn agostic interactions to give the final product. Eight transition states for this mechanistic sequence have been identified with activation energies of ∼20 kcal/mol for the first hydrogen migration and ∼14 kcal/mol for the second hydrogen migration. -
more » « less
Abstract The hitherto elusive monobridged Ge(
μ ‐H)GeH (X1A′) molecule was prepared in the gas phase by bimolecular reaction of atomic germanium with germane (GeH4). Electronic structure calculations revealed that this reaction commenced on the triplet surface with the formation of a van der Waals complex, followed by insertion of germanium into a germanium‐hydrogen bond over a submerged barrier to form the triplet digermanylidene intermediate (HGeGeH3); the latter underwent intersystem crossing from the triplet to the singlet surface. On the singlet surface, HGeGeH3predominantly isomerized through two successive hydrogen shifts prior to unimolecular decomposition to Ge(μ ‐H)GeH isomer, which is in equilibrium with the vinylidene‐type (H2GeGe) and dibridged (Ge(μ ‐H2)Ge) isomers. This reaction leads to the formation of cyclic dinuclear germanium molecules, which do not exist on the isovalent C2H2surface, thus deepening our understanding of the role of nonadiabatic reaction dynamics in preparing nonclassical, hydrogen‐bridged isomers carrying main group XIV elements. -
Although N-heterocyclic carbenes (NHCs) have been known as ligands for organometallic complexes since the 1960s, these carbenes did not attract considerable attention until Arduengo et al. reported the isolation of a metal-free imidazol-2-ylidene in 1991. In 2001 Crabtree et al. reported a few complexes featuring an NHC isomer, namely an imidazol-5-ylidene, also termed abnormal NHC (aNHCs). In 2009, it was shown that providing to protect the C-2 position of an imidazolium salt, the deprotonation occurred at the C-5 position, affording imidazol-5-ylidenes that could be isolated. Over the last ten years, stable aNHCs have been used for designing a range of catalysts employing Pd( ii ), Cu( i ), Ni( ii ), Fe(0), Zn( ii ), Ag( i ), and Au( i / iii ) metal based precursors. These catalysts were utilized for different organic transformations such as the Suzuki–Miyaura cross-coupling reaction, C–H bond activation, dehydrogenative coupling, Huisgen 1,3-dipolar cycloaddition (click reaction), hydroheteroarylation, hydrosilylation reaction and migratory insertion of carbenes. Main-group metal complexes were also synthesized, including K( i ), Al( iii ), Zn( ii ), Sn( ii ), Ge( ii ), and Si( ii / iv ). Among them, K( i ), Al( iii ), and Zn( ii ) complexes were used for the polymerization of caprolactone and rac -lactide at room temperature. In addition, based on the superior nucleophilicity of aNHCs, relative to that of their nNHCs isomers, they were used for small molecules activation, such as carbon dioxide (CO 2 ), nitrous oxide (N 2 O), tetrahydrofuran (THF), tetrahydrothiophene and 9-borabicyclo[3.3.1]nonane (9BBN). aNHCs have also been shown to be efficient metal-free catalysts for ring opening polymerization of different cyclic esters at room temperature; they are among the most active metal-free catalysts for ε-caprolactone polymerization. Recently, aNHCs successfully accomplished the metal-free catalytic formylation of amides using CO 2 and the catalytic reduction of carbon dioxide, including atmospheric CO 2 , into methanol, under ambient conditions. Although other transition metal complexes featuring aNHCs as ligand have been prepared and used in catalysis, this review article summarize the results obtained with the isolated aNHCs.more » « less
-
The title compound, [PtCl 2 (C 26 H 22 P 2 )]·2CHCl 3 (I), is the third monoclinic polymorph of this platinum(II) complex involving the bidentate ligand cis -1,2-bis(diphenylphosphanyl)ethylene ( cis -dppe) [for the others, see: Oberhauser et al. (1998 a ). Inorg. Chim. Acta , 274 , 143–154, and Oberhauser et al. (1995). Inorg. Chim. Acta , 238 , 35–43]. The structure of compound (I) was solved in the space group P 2 1 / c , with one complex molecule in the asymmetric unit along with two solvate chloroform molecules. The Pt II atom is ligated by two P and two Cl atoms in the equatorial plane and has a perfect square-planar coordination sphere. In the crystal, the complex molecule is linked to the chloroform solvate molecules by C—H...Cl hydrogen bonds and face-on C—Cl...π interactions. There are also weak offset π–π interactions present [intercentroid distances are 3.770 (6) and 4.096 (6) Å], linking the molecules to form supramolecular sheets that lie in the bc plane.more » « less
