16 research outputs found
Dynamic, reversible oxidative addition of highly polar bonds to a transition metal
The combination of Pt0 complexes and indium trihalides leads to compounds that form equilibria in solution between their In-X oxidative addition (OA) products (PtII indyl complexes) and their metal-only Lewis pair (MOLP) isomers (LnPt→InX3). The position of the equilibria can be altered reversibly by changing the solvent, while the equilibria can be reversibly and irreversibly driven towards the MOLP products by addition of further donor ligands. The results mark the first observation of an equilibrium between MOLP and OA isomers, as well as the most polar bond ever observed to undergo reversible oxidative addition to a metal complex. In addition, we present the first structural characterization of MOLP and oxidative addition isomers of the same compound. The relative energies of the MOLP and OA isomers were calculated by DFT methods, and the possibility of solvent-mediated isomerization is discussed
Nucleophilic Substitution at a Coordinatively Saturated Five-Membered NHC∙Haloborane Centre
In this paper, we have used a saturated five-membered N-Heterocyclic carbene (5SIDipp = 1,3-bis-(2,6-diisopropylphenyl)imidazolin-2-ylidine) for the synthesis of SNHC-haloboranes adducts and their further nucleophilic substitutions to put unusual functional groups at the central boron atom. The reaction of 5-SIDipp with RBCl2 yields Lewis-base adducts, 5-SIDipp·RBCl2 [R = H (1), Ph (2)]. The hydrolysis of 1 gives the NHC stabilized boric acid, 5-SIDipp·B(OH)3 (3), selectively. Replacement of chlorine atoms from 1 and 2 with one equivalent of AgOTf led to the formation of 5-SIDipp·HBCl(OTf) (4) and 5-SIDipp·PhBCl(OTf) (5a), where all the substituents on the boron atoms are different. The addition of two equivalents of AgNO3 to 2 leads to the formation of rare di-nitro substituted 5-SIDipp·BPh(NO3)2 (6). Further, the reaction of 5-SIDipp with B(C6F5)3 in tetrahydrofuran and diethyl ether shows a frustrated Lewis pair type small molecule activated products, 7 and 8
Synthesis and Structure of [{PhC(NtBu)2}2Ge2(μ-S)2Cl2] and a Germanium Dithiocarboxylate Analogue
Sen SS, Ghadwal R, Kratzert D, Stern D, Roesky HW, Stalke D. Synthesis and Structure of [{PhC(NtBu)2}2Ge2(μ-S)2Cl2] and a Germanium Dithiocarboxylate Analogue. Organometallics. 2011;30(5):1030-1033
End-on nitrogen insertion of a diazo compound into a germanium (II) hydrogen bond and a comparable reaction with diethyl azodicarboxylate
A happy ending: The germanium(II) hydride [LGeH], where L=[HC{(CMe)(2,6-iPr2C6H3N)}2], reacts with a diazoalkane to form the hydrazone derivative (see picture). The reaction proceeds through the unprecedented end-on nitrogen insertion of the diazo compound
A Remarkable End-On Activation of Diazoalkane and Cleavage of Both C–Cl Bonds of Dichloromethane with a Silylene to a Single Product with Five-Coordinate Silicon Atoms
The 1:1 reaction of benzamidinato-stabilized chlorosilylene
PhC(N<i>t</i>Bu)<sub>2</sub>SiCl (<b>1</b>) with CH(SiMe<sub>3</sub>)N<sub>2</sub> resulted in the formation of colorless [PhC(N<i>t</i>Bu)<sub>2</sub>Si(Cl){N<sub>2</sub>CH(SiMe<sub>3</sub>)}]<sub>2</sub> (<b>2</b>), which consists of a four-membered Si<sub>2</sub>N<sub>2</sub> ring. Surprisingly, N<sub>2</sub> elimination
from the diazoalkane did not occur, but rather an end-on activation
of the nitrogen was observed. For the mechanism, we propose the formation of a silaimine
complex <b>A</b> as an intermediate, which is formed during
the reaction and dimerized under [2 + 2] cycloaddition to <b>2</b>. In contrast, treatment of <b>1</b> with dichloromethane afforded
a 2:1 product, [{PhC(N<i>t</i>Bu)<sub>2</sub>Si(Cl<sub>2</sub>)}<sub>2</sub>CH<sub>2</sub>] (<b>3</b>), which is obviously
formed by oxidative addition under cleavage of both C–Cl bonds
and formation of two Si–Cl and two Si–C bonds. Both
silicon atoms in <b>3</b> are five-coordinate. Compounds <b>2</b> and <b>3</b> were characterized by single-crystal
X-ray studies, multinuclear NMR spectroscopy, and EI-mass spectrometry
A Remarkable End-On Activation of Diazoalkane and Cleavage of Both C–Cl Bonds of Dichloromethane with a Silylene to a Single Product with Five-Coordinate Silicon Atoms
The 1:1 reaction of benzamidinato-stabilized chlorosilylene
PhC(N<i>t</i>Bu)<sub>2</sub>SiCl (<b>1</b>) with CH(SiMe<sub>3</sub>)N<sub>2</sub> resulted in the formation of colorless [PhC(N<i>t</i>Bu)<sub>2</sub>Si(Cl){N<sub>2</sub>CH(SiMe<sub>3</sub>)}]<sub>2</sub> (<b>2</b>), which consists of a four-membered Si<sub>2</sub>N<sub>2</sub> ring. Surprisingly, N<sub>2</sub> elimination
from the diazoalkane did not occur, but rather an end-on activation
of the nitrogen was observed. For the mechanism, we propose the formation of a silaimine
complex <b>A</b> as an intermediate, which is formed during
the reaction and dimerized under [2 + 2] cycloaddition to <b>2</b>. In contrast, treatment of <b>1</b> with dichloromethane afforded
a 2:1 product, [{PhC(N<i>t</i>Bu)<sub>2</sub>Si(Cl<sub>2</sub>)}<sub>2</sub>CH<sub>2</sub>] (<b>3</b>), which is obviously
formed by oxidative addition under cleavage of both C–Cl bonds
and formation of two Si–Cl and two Si–C bonds. Both
silicon atoms in <b>3</b> are five-coordinate. Compounds <b>2</b> and <b>3</b> were characterized by single-crystal
X-ray studies, multinuclear NMR spectroscopy, and EI-mass spectrometry
Access to Silicon(II)– and Germanium(II)–Indium Compounds
Despite
the remarkable ability of N-heterocyclic silylene to act
as a Lewis base and form stable Lewis adducts with group 13 elements
such as boron, aluminum, and gallium, there has been no such comparable
investigation with indium and the realization of a stable silylene–indium
complex has still remained elusive. Similarly, a germylene–indium
complex is also presently unknown. We describe herein the reactions
of [PhC(N<i>t</i>Bu)<sub>2</sub>SiN(SiMe<sub>3</sub>)<sub>2</sub>] (<b>1</b>) and [PhC(N<i>t</i>Bu)<sub>2</sub>GeN(SiMe<sub>3</sub>)<sub>2</sub>] (<b>4</b>) with InCl<sub>3</sub> and InBr<sub>3</sub> that have resulted in the first silylene–indium
complexes, [PhC(N<i>t</i>Bu)<sub>2</sub>Si{N(SiMe<sub>3</sub>)<sub>2</sub>}→InCl<sub>3</sub>] (<b>2</b>) and [PhC(N<i>t</i>Bu)<sub>2</sub>Si{N(SiMe<sub>3</sub>)<sub>2</sub>}→InBr<sub>3</sub>] (<b>3</b>), as well as the first germylene–indium
complexes, [PhC(N<i>t</i>Bu)<sub>2</sub>Ge{N(SiMe<sub>3</sub>)<sub>2</sub>}→InCl<sub>3</sub>] (<b>5</b>) and [PhC(N<i>t</i>Bu)<sub>2</sub>Ge{N(SiMe<sub>3</sub>)<sub>2</sub>}→InBr<sub>3</sub>] (<b>6</b>). The solid-state structures of all species
have been validated by single-crystal X-ray diffraction studies. Note
that <b>5</b> and <b>6</b> are the first structurally
characterized organometallic compounds that feature a Ge–In
single bond (apart from the compounds in Zintl phases). Theoretical
calculations reveal that the Si(II)→In bonds in <b>2</b> and <b>3</b> and the Ge(II)→In bonds in <b>5</b> and <b>6</b> are dative bonds
Stable Silaimines with Three- and Four-Coordinate Silicon Atoms
Samuel PP, Azhakar R, Ghadwal R, et al. Stable Silaimines with Three- and Four-Coordinate Silicon Atoms. Inorganic Chemistry. 2012;51(20):11049-11054.The reactions of silylenes with organic azides are quite diverse, depending on the substituents of the silylene center and on the nature of the azide employed. Elusive silaimine with three-coordinate silicon atom L1SiN(2,6-Triip2-C6H3) (5) {L1 = CH[(C═CH2)(CMe)(2,6-iPr2C6H3N)2] and Triip = 2,4,6-triisopropylphenyl} was synthesized by treatment of the silylene L1Si (1) with a sterically demanding 2,6-bis(2,4,6-triisopropylphenyl)phenyl azide (2,6-Triip2C6H3N3). The reaction of Lewis base-stabilized dichlorosilylene L2SiCl2 (2) {L2 = 1,3-bis(2,6-iPr2C6H3)imidazol-2-ylidene} with Ph3SiN3 afforded four-coordinate silaimine L2(Cl2)SiNSiPh3 (6). Treatment of 2,6-Triip2C6H3N3 with L3SiCl (3) (L3 = PhC(NtBu)2) yielded silaimine L3(Cl)SiN(2,6-Triip2-C6H3) (7) possessing a four-coordinate silicon atom. The reactions of L3SiN(SiMe3)2 (4) with adamantyl and trimethylsilyl azide furnished silaimine compounds with a four-coordinate silicon atom L3(N(Ad)SiMe3)SiN(SiMe3) (8) (Ad = adamantyl) and L3(N(SiMe3)2)SiN(SiMe3) (9). Compound 8 was formed by migration of one of the SiMe3 groups. Compounds 5–9 are stable under inert atmosphere and were characterized by elemental analysis, NMR spectroscopy, and single-crystal X-ray studies