Transition metal complexes containing the S(NtBu)4(2-) tetraimidosulfate dianion.

Three novel metal complexes [(acac)2Cu2(NtBu)4S] (), [Li(thf)4]2[I4Cd2(NtBu)4S] () and [(thf)2Li{(SiMe3)2N}Zn(NtBu)4S] () are prepared from the intended transmetalation of the dilithium complex of N,N',N'',N'''-tetrakis(tert-butyl)tetraimidosulfate [(thf)4Li2(NtBu)4S] (). The two lithium cations are replaced by either the cationic (acac)Cu(ii) moiety, the neutral I2Cd(ii) residue or only a single lithium cation is substituted by the cationic (Me3Si)2NZn(ii) fragment. The complexes show two main results: first the S(NtBu)4(2-) tetrahedron can serve as a ligand to transition metals from the soft Cu(ii) to the harder Zn(ii) at opposite sides and second the S-N bond distances vary only marginally in response to the various metals and the four distances constantly sum up to 6.38(2) Å. Hence the electropositive sulfur atom responds by internal shift to the metal-polarized negative charge at the outside of the S(NR)4(2-) tetrahedron.

Oxidative addition versus substitution reactions of group 14 dialkylamino metalylenes with pentafluoropyridine.

Dialkylamino compounds of group 14 elements (Si, Ge, Sn) in the +2 oxidation state supported by benzamidinate ligands were synthesized and treated with pentafluoropyridine. Two different modes of reactivity were observed, depending on the metal atom and the basicity of the substituent at the metal. Pentafluoropyridine undergoes oxidative addition reaction at the Si(II) and Ge(II) atoms whereas at the Sn(II) atom substitution of the NMe(2) group by the para fluorine of pentafluoropyridine occurs. The C-F bond activation by the lone pair of germanium is the first report of this kind. The Sn(II) fluoride obtained has an elongated Sn-F bond length and can be used as a good fluorinating agent. The compounds were characterized by multinuclear NMR spectroscopy, mass spectrometry, elemental analysis, and X-ray structural analysis. Single crystal X-ray structural analysis of the tin fluoride shows an asymmetric dimer with weak [Formula: see text] interactions.

Synthesis of tetrasubstituted alkenes through a palladium-catalyzed domino carbopalladation/C-H-activation reaction.

Helical tetrasubstituted alkenes (7) were obtained in a highly efficient way through a palladium-catalyzed domino-carbopalladation/CH-activation reaction of propargylic alcohols 6 in good to excellent yields. Electron-withdrawing- and electron-donating substituents can be introduced onto the upper and lower aromatic rings. The substrates (6) for the domino process were synthesized by addition of the lithiated alkyne (20) to various aldehydes (19); moreover, the substrates were accessible enantioselectively (in 95% ee) by reduction of the corresponding ketone using the Noyori procedure.

Elegant approach to spacer arranged silagermylene and bis(germylene) compounds.

Herein we report on the reactions of the stable LSiCl (1) and LGeCl (2) [L = PhC(NtBu)(2)] with L(1)Ge, [L(1) = CH{(C[double bond, length as m-dash]CH(2))(CMe)(2,6-iPr(2)C(6)H(3)N)(2)}] (3) to yield 1-sila-5-germylene (4) and a 1,5-bis(germylene) (5). The reactions proceed through the 1,4 nucleophilic addition of the M-Cl (M = Si or Ge) to 3 without any modification of the oxidation state although the change of the oxidation state is thermodynamically more favorable. Compounds 4 and 5 were investigated by single crystal X-ray structural analyses, multi-nuclear NMR spectroscopy, and micro-analysis. Treatment of L(1)AlMe·thf (6) with 1 resulted in the formation of the 1-sila-5-aluminium complex (7). The complex contains a Si(II) and an Al(III) atom in the molecule. All reported reactions proceed without changing the oxidation states at the metal centers.

Pentafluoropyridine as a fluorinating reagent for preparing a hydrocarbon soluble ß-diketiminatolead(II) monofluoride.

A well-designed method for the preparation of a ß-diketiminatolead(II) monofluoride has been developed using LPbNMe(2) (L = [CH{C(Me)(2,6-iPr(2)C(6)H(3)N)}(2)]) and pentafluoropyridine (C(5)F(5)N). The resulting LPbF was used for the synthesis of amidinatosilicon(II) monofluoride. Moreover the activation of a ketone was observed when the LPbF was treated with PhCOCF(3).

A stable silicon(II) monohydride.

A stable silicon(II) monohydride is accomplished through a covalent shared interaction of the silylene lone-pair and a sp(3)-hybridized boron atom of the Lewis acidic BH(3). Experimental charge density investigations reveal a central positively charged silicon atom bound to a negatively charged hydrogen atom. The positively charged H-Si-BH(3) moiety is coordinated by the lone-pairs of electrons of the benzamidinate ligand. This coordination is reinforced by a transannular Si1···C1 privileged exchange channel.

Reaction of ß-diketiminate tin(II) dimethylamide LSnNMe2 [L = HC(CMeNAr)2; Ar = 2,6-iPr2C6H3] with ketones and alkynes.

The reactions of stable ß-diketiminate tin(II) dimethylamide LSnNMe2 [L = HC(CMeNAr)2; Ar = 2,6-iPr2C6H3] (1) with ketones and activated terminal alkynes are described. 1 reacts with 2-benzoylpyridine and 2,2,2-trifluoroacetophenone to give the tin(II)-alkoxides LSnOCPh(2-Py)NMe2 (2) and LSnOCPh(CF3)NMe2 (3), respectively, by nucleophilic addition of the dimethylamido group to the carbonyl moiety. Furthermore, the reaction of 1 with terminal alkynes (HCCCO2R, R = Me, Et) forms tin(II)-alkynyl LSnCCCO2R (R= Me, (4); R = Et, (5)) compounds under elimination of Me2NH rather than undergoing a nucleophilic addition reaction at the carbon­carbon triple bond. Compounds 2-5 were characterized by microanalysis and multinuclear NMR spectroscopy. Moreover, 2 and 5 could be crystallized and their constitutions were confirmed by X-ray structural analysis. 2 and 5 are monomers in the solid state and the metal atom shows a distorted trigonal-pyramidal coordination sphere.

Dehydrogenation of LGeH by a Lewis N-heterocyclic carbene borane pair under the formation of L'Ge and its reactions with B(C(6)F(5))(3) and trimethylsilyl diazomethane: an unprecedented rearrangement of a diazocompound to an isonitrile.

Herein we report the dehydrogenation of LGeH (1) [L = CH{(CMe)(2,6-iPr(2)C(6)H(3)N)}(2)] by a frustrated Lewis NHC borane pair under the formation of an imidazolium borate salt (2) and the heterocyclic germylene L'Ge (3) [L' = CH{(C horizontal lineCH(2))(CMe)(2,6-iPr(2)C(6)H(3)N)(2)}]. The reaction of 3 with B(C(6)F(5))(3) in toluene results in the formation of a zwitterion containing a germylene moiety, [B(C(6)F(5))(3)L''Ge] (4) [L'' = CH{(CCH(2))(CMe)(2,6-iPr(2)C(6)H(3)N)(2)}]. Subsequent treatment of 4 with 1 equiv of 1,3-di-tert-butylimidazol-2-ylidene (NHC) gives B(C(6)F(5))(3)L'''Ge (5) [L''' = CH{(C horizontal lineCH(2))(CCH(2)B(C(6)F(5))(3))(2,6-iPr(2)C(6)H(3)N)(2)}] under formation of the imidazolium cation. Moreover compound 3 reacts with trimethylsilyl diazomethane (N(2)CHSiMe(3)) to form the diazogermylene LGeC(N(2))SiMe(3) (6) under C-H bond cleavage. Compound 6 slowly rearranges to the isonitriletrimethylsilyl germanium(II) amide LGeN(SiMe(3))NC (6a). All compounds were characterized by microanalysis and multinuclear NMR spectroscopy. Compounds 4, 6, and 6a were unequivocally identified by single crystal X-ray structure analysis.

Cleavage of a N-H bond of ammonia at room temperature by a germylene.

The reaction of LGeCl [1; L = CH{(CMe)(2,6-(i)Pr(2)C(6)H(3)N)}(2)] with 1,3-di-tert-butylimidazol-2-ylidene results in the formation of the germylene L'Ge [2; L' = CH{(C=CH(2))(CMe)(2,6-(i)Pr(2)C(6)H(3)N)(2)}]. 2 reacts with ammonia under N-H cleavage to give LGeNH(2) (3). This type of reaction can also be used to activate primary amines. 3 is characterized by microanalysis, multinuclear NMR spectroscopy, and X-ray structural analysis. The single-crystal X-ray structural analysis indicates 3 to be a monomer, and the germanium atom shows a trigonal-pyramidal environment with a stereochemically active lone pair.

A germanium(II) hydride as an effective reagent for hydrogermylation reactions.

Herein we report on the reactivity of the stable germanium(II) hydride LGeH (L = CH{(CMe)(2,6-iPr(2)C(6)H(3)N)}(2)) (2), which contains a low-valent germanium atom. 2 is prepared from the corresponding germanium(II) chloride LGeCl (1) using H(3)Al x NMe(3) or K[HB(iBu)(3)] in toluene. The reaction of 2 with carbon dioxide in toluene at room temperature affords a germanium(II) ester of formic acid, LGe-O-C(O)H (3), which is formed by insertion of the carbon dioxide into the germylene hydrogen bond. 2 also reacts with alkynes at room temperature to give the first germanium(II)-substituted alkenes (4, 5, and 6). These two reaction types have in common the fact that the hydrogen and germylene from LGeH are transferred to an unsaturated bond: the carbon-oxygen double bond (C=O) in the former case and the carbon-carbon triple bond (C[triple bond]C) in the latter. Moreover, the reaction of 2 with elemental sulfur in toluene at room temperature leads to the germanium dithiocarboxylic acid analogue LGe(S)SH (7). Compound 7 is formed by the unprecedented insertion of elemental sulfur into the germylene hydrogen bond and oxidative addition of elemental sulfur to the germanium(II) atom. This leads to the formal conversion of the GeH hydride to a SH proton. Compounds 3-7 were investigated by microanalysis, multinuclear NMR spectroscopy, and single-crystal X-ray structural analyses.