Ingo Krossing

Donorfreie und donorhaltige supersilylalkalimetalle tBu3SiM1: Synthesen, charakterisierung, strukturen ☆

Supersilyl alk. metals (alkali supersilanides) tBu3SiM without or with donors (Do) like ethers, amines, arom. hydrocarbons are easily obtained by the action of alk. metals M on supersilyl halides tBu3SiX above room temp. in alkanes or donor-solvents like THF, benzene: tBu3SiX + 2M -> tBu3SiM + MX; tBu3SiM + nDo -> tBu3SiM(Do). Ethers as donors can be exchanged by stronger donors like PMDTA, 18-crown-6, cryptand-222. In particular the following extremely water and air sensitive compds. are prepd.: yellow tBu3SiLi (as to x-ray structure anal. dimeric with Si...Li...Si contacts), orange yellow tBu3SiNa (as to x-ray structure anal. dimeric with Si...Na...Si contacts), light-yellow tBu3SiK (as to its insoly. in alkanes polymeric), tBu3SiM (M = Rb, Cs; insol. in alkanes), light-yellow to colorless tBu3SiLi(THF)2 (probably monomeric), light-yellow tBu3SiNa(THF)2 (as to x-ray structure anal. dimeric with CH3...Na contacts), light-yellow tBu3SiNa(OBu2)2 (probably analogously structured as the THF adduct), yellow tBu3SiK(THF)n (loses THF; stable only in THF), light-yellow tBu3SiNa(PMDTA) (as to x-ray structure anal. monomeric), orange-red tBu3SiK(Benzene)3 (as to x-ray structure anal. monomeric), orange-yellow tBu3SiNa(18-C-6) (unstable as to its tendency to deprotonate 18-crown-6), tBu3SiM(C222) (M = Na, K; not isolable as to its tendency to deprotonate cryptand-222). Because of the high tendency of the anionic part tBu3Si- of the compds. mentioned for delivering electrons, the supersilyl alk. metals act as strong bases which deprotonate even weak bases such as THF or benzene under formation of supersilane tBu3SiH. Over and above that, they work as good nucleophiles and reducing agents which for example react with Me3SiX under formation of trimethylsilylsupersilane Me3Si-SitBu3 and with Ag+NO3- under formation of superdisilane tBu3Si-SitBu3. As the supersilyl alk. metals may even be oxidized by supersilyl halides in alkanes at 100 Deg by way of tBu3SiM + tBu3SiX -> tBu3Si. + MX + tBu3Si., and tBu3Si. + RH -> tBu3SiH + R., and 2tBu3Si..dblarw.(tBu3Si)2, the formation of tBu3SiM from tBu3SiI and K, Rb, Cs at elevated temps. in satd. hydrocarbons is accompanied by the formation of supersilane, superdisilane and secondary products of R.. [on SciFinder (R)]

The Aluminum–Nitrogen Bond in Monomeric Bis(amino)alanes: A Systematic Experimental Study of Bis(tetramethylpiperidino)alanes and Quantum Mechanical Calculations on the Model System (H2N)2AlY

Reactions of metalated nucleophiles M(I)Y [Y = OR, SR, NR2, PR2, AsR2, CR3, Si(SiMe3)3, R = organyl, H] with bis(2,2,6,6-tetramethylpiperidino)aluminum halides [tmp2AlX, (X = Cl, Br, I)] offer facile access to a variety of bis(amino)alanes of the type tmp2AlY. As indicated by 27Al-NMR spectroscopy, mass spectrometry, and x-ray crystal structure detns., all of these compds. are monomeric in the solid state, in soln., and in the gas phase. Even Al-E single bonds (E = Si, P, As etc.) that are not commonly encountered are stabilized by the supporting tmp fragments. The results of a systematic anal. of the bonding parameters detd. for the tmp2AlY compds., combined with a quantum mech. study on model compds. (H2N)2AlY, not only reveal the presence of a highly polar Al-N bond, but at the same time rule out AlN-pp(p) bonding, in contrast to the situation in the analogous tmp2BY compds. The Al-N bond length depends on the acidic character of the protic species HY: the shorter d(Al-N), the less basic is Y. [on SciFinder (R)]

Synthesis and nonlinear optical properties of carbonylrhenium bromide complexes with conjugated pyridines

Carbonylrhenium bromide complexes with conjugated pyridines fac-Br(OC)3ReL2 (L = FcCH:CH-p-C5H4N (Fc = ferrocenyl), FcCH:CHC(Me):CHCH:CHCH:C(Me)CH:CH-p-C5H4N, 1,1Fc(CH:CH-p-C5H4N)2 p-Me2NC6H4CH:CHCH:CH-p-C5H4N (I), and p-Me2NC6H4CH:CHC(Me):CHCH:CHCH:C(Me)CH:CH-p-C5H4N) and cis-Br(OC)4ReL (L = FcCH:CH-p-C5H4N (II) and p-Me2NC6H4CH:CHCH:CH-p-C5H4N) were synthesized. The structures of I (monoclinic, C2/c, a = 18.3826(1), b = 15.1048(1), c = 28.5866(1) .ANG., b = 92.848(1) Deg, V = 7927.71(7) .ANG.3, Z = 8, rc = 1.636 g/cm3, m(MoKa) = 4.317 mm-1, F(000) = 3848, 7804 independent reflections, 480 refined parameters, R1 = 0.0726, wR2 = 0.1723) and II (rhombohedral, R.hivin.3, a = 30.357(4), c = 12.398(2) .ANG., V = 9895(2) .ANG.3, Z = 18, rc = 2.016 g/cm3, m(MoKa) = 8.003 mm-1, F(000) = 5688, 2930 independent reflections, 262 refined parameters, R1 = 0.0578, wR2 = 0.1048) were detd. by x-ray diffraction anal. Compd. I exhibits a remarkable quadratic hyperpolarizability. [on SciFinder (R)]

Lithium and sodium alkoxy- and aryloxyhydridoaluminates in solution and in the solid state

The reactions of lithium and sodium aluminum hydride with alcs. and phenols in ether solvents were studied as a route to mono-, di- and triorganyloxyhydridoaluminates MAlH4-n(OR)n. However, the stability of these compds. towards disproportionation is strongly dependent on the steric demand of the org. group and the solvent. This process gives MAlH4 and more highly substituted organyloxyalumohydrides, as shown by 27Al NMR spectroscopy. The crystal structures of nine organyloxyhydridoaluminates were detd. by x-ray structure anal. Both Al-H-M and Al-O-M bridges were found for the coordination of the cation M (Li or Na). The species LiAlH3(OR) was stable only for R = 2,6-tBu2C6H3; it is dimeric in the solid state. Four stable solvated compds. MAlH2(OR)2 were obtained for M = Li, R = tBu2MeC (M = Li, Na), 2,6-tBu2C6H3 and M = Na, R = CPh3, all of which are mol. complexes in the solid state. Reductive ring opening of THF occurs for MAlH2(OC6H3tBu2-2,6)2 (M = Li, Na). Triorganyloxyhydridoaluminates are the most stable compds. in this series. For M = Li, R = tBu2MeC, CPh3, 2,6-iPr2C6H3 and M = Na, R = CPh3, crystal structures were detd. Depending on the bulk of the group R, both M-H-Al and M-O-Al bridges (smaller R groups) are obsd. [on SciFinder (R)]

Bis(tetramethylpiperidino)aluminum halide adducts tmp2AlX.Do and tetrahaloaluminates of tricoordinated aluminum cations [tmp2Al(Do)]AlX4

Upon treatment with Lewis bases Do (Do = pyridine bases or THF), the Lewis acids tmp2AlX (X = Cl, Br, I) are converted exclusively to the monoadducts tmp2AlX.Do. Crystal and mol. structure of these monoadducts were detd. The Al-X bonds of these addn. compds. are considerably elongated, indicating a tendency towards the formation of ionic species [tmp2Al(Do)]X. Due to the steric requirements of the bulky tmp ligands, addn. of an excess of the Lewis base does not force these compds. to form tetracoordinated Al cations [tmp2Al(Do)2]+ or pentacoordinated adducts tmp2AlX.Do2. Attempts to prep. ionic representatives by reaction of tmp2AlX.Do with qateq complexes of comparatively low nucleophilicity [MY = NaBP4, AgBPh4, LiB(C6F5)4, AgBF4, AgOtos] result in phenylation products (e.g. tmp2AlPh and BPh3.py) or tetracoordinated addn. compds. tmp2AlY.Do (Y = anion). However, addn. of 1 equiv. of AlX3 (X = Br, I) initiates halide abstraction with formation of the ionic [tmp2Al(Do)]AlX4 species, as indicated by 27Al-NMR data and cond. measurements. Solid [tmp2Al(py)]AlI4 decomps. readily into tmpAlI2 and tmpAlI2.py. Addn. of non-polar aliph. solvents to solns. of [tmp2Al(Do)]AlX4 leads to slow decompn. into tmp2AlX and AlX3.Do. This also occurs in polar donor solvents, where compds. AlX3.Do are favored due to the formation of penta- or hexacoordinated species AlX3.Do.Solvn (n = 1, 2). Semiempirical AM1 calcns. reveal the gas-phase stability of the tricoordinated bis(tmp)aluminum cation in the salt [tmp2AlPy]AlCl4 as the only representative in a series of calcd. Al cations [(R2N)2A1Py]AlCl4 (R2N = Me2N, Et2N, iPr2N, tmp). According to these calcns., the stability of a given cation increases when tetrachloroaluminate is replaced by tetraiodoaluminate. Ab initio calcns. were performed on 2 cations [(H2N)2Al(Do)]+ (Do = NH3, py) and indicate very short Al-N bond lengths owing to ionic bonding contributions. [on SciFinder (R)]

Tetramethylpiperidine-alane adducts tmpH.AlX3 (X = Cl, Br, I) and tmpH.AlH2Cl. Synthesis, solution behavior, and x-ray crystal structures

2,2,6,6-Tetramethylpiperidine (tmpH) reacts smoothly with AlX3 (X = Cl, Br, I) and AlH2Cl.2THF to give the addn. compds. tmpH.AlX3 (X = Cl, Br, I) and tmpH.AlH2Cl, resp. These adducts of the secondary amine tmpH are stable and do not undergo intramol. elimination of HX or H2 with formation of the aminoalanes tmpAlX2 or tmpAl(H)Cl. In the solid state, tmpH.AlX3 (X = Cl, Br, I) and tmpH.AlH2Cl are tetracoordinated mol. adducts. While this is also true for solns. of tmpH.AlX3 (X = Br, I) and tmpH.AlH2Cl, the compd. tmpH.AlCl3 dissolves in CH2Cl2 as the salt [tmpAlCl3]-tmpH2 and the adduct tmpH.Al2Cl6, as is evident from its NMR spectra and from cond. measurements. This behavior is supported by a semiempirical AM1 calcn. [on SciFinder (R)]

Über einige Aluminiumbromid-Ether-Addukte: Strukturen in Lösung und im festen Zustand / Aluminium Bromide Ether Adducts: Structures in Solution and in the Solid State

Monoglyme forms a molecular 1:1 adduct with AlBr3 which dissociates into the ions AlBr2(DME)2+ and AlBr4- in DME, CH2Br2 and CDCl3 as solvents. A hexacoordinated Al center is present in the solid adduct AlBr3·diglyme. The oxygen and bromine atoms are arranged in a meriodional configuration as shown by X-ray crystallography. However, in solution dissociation occurs into AlBr2(diglym)2+ and AlBr4-. Not unexpectedly, AlBr3 forms the adduct AlBr3·2THF with tetrahydrofuran. The dioxane adduct AlBr3·diox is polymeric in the solid state and has a chain structure with pentacoordinated trigonal-bipyramidal Al centers. The Br atoms are arranged in a slightly distorted trigonal plane. In solution, the presence of tetracoordinated Al is indicated by 27AI NMR spectroscopy. AlBr3 cleaves one of the C-O bonds of 12-crown-4 leading to the dimer of ω-bromo-tetra(ethyleneoxy)aluminium dibromide. This dimer contains pentacoordinated Al centers as proven by X-ray structure analysis. In contrast, the adduct of AlBr3 with 15-crown-5 is most likely an ionic compound, and is best described as [AlBr2(15-crown-5)]AlBr4 based on 27Al NMR and IR data.

Rearrangement of Bis(dimethylamino)bis(1-indenyl)diborane(4) into Bis(dimethylamino)bis(3-indenyl)diborane(4)

Indenyllithium reacts with dichlorobis(dimethylamino)diborane(4) with formation of bis(dimethylamino)bis(1-indenyl)-diborane(4) which rearranges on heating to the isomer bis(dimethylamino)bis(3-indenyl)diborane(4). The mixed isomer bis(dimethylamino)(1-indenyl)(3-indenyl)diborane(4) was obtained from indenyllithium and chlorobis(dimethylamino)(3-indenyl)diborane(4). Crystal data of 1,2-bis(dimethylamino)-1,2-bis(1-indenyl)diborane(4) (I): monoclinic, space group P21/c, a 15.8977(3), b 7.5756(1), c 16.8297(3) .ANG., b 93.323(1) Deg, Z = 4, rc = 1.116 g/cm3, m(MoKa) = 0.064 mm-1, F(000) = 728, 2781 obsd. reflections with I > 4s(I), R = 0.0789, wR2 = 0.1812; 1,2-bis(dimethylamino)-1-(1-indenyl)-2-(3-indenyl)diborane(4) (II): triclinic, space group P.hivin.1, a 8.8466(1), b 10.3594(2), c 11.1737(3) .ANG., a 77.403(1), b 85.428(1), g 83.222(1) Deg, Z = 4, rc = 1.140 g/cm3, m(MoKa) = 0.065 mm-1, F(000) = 364, 2640 obsd. reflections with I > 4s(I), R = 0.0474, wR2 = 0.1141. The main structural differences between the 2 isomers I and II are a slightly shorter B-B bond in II, as well as a stronger twist about the B-B bond (89,9 Deg vs. 67.4 Deg) and, as expected, a shorter B-C bond. There is, however, no significant B-C p bonding. [on SciFinder (R)]

Halbsandwich-Komplexe von (S)-1-Amino-2-(methoxymethyl)-pyrrolidin (SAMP)

The chloro-bridged complexes [Cp*MCl2]2 (Cp* = C5Me5, M = Ir, Rh), [(p-cymene)RuCl2]2, [(C6Me6)RuCl2]2, and [(Et3P)PdCl2]2 react with SAMP by cleavage of the chloro bridges to give the corresponding monomeric h1-SAMP complexes. The x-ray structural detns. of [cyclic] Cp*RhCl2NH2N(CH(CH2OMe)(CH2)3) and [cyclic] [(C6Me6)RuCl2NH2N(CH(CH2OMe)(CH2)3)] show coordination of the amino group in these complexes. From the chloro-bridged complexes, SAMP and sodium a-ketocarboxylates Schiff base N,O-chelate complexes were obtained. The structure of the [cyclic] [Cp*(Cl)IrO2CCMe2:N(NCH(CH2OMe)(CH2)3)] complex with coordination of the carboxylate-O and the imine-N atom was detd. by x-ray diffraction. [on SciFinder (R)]

Dimeric Di(tert-butyl)haloalanes and a Monomeric Di(tert-butyl)phosphino-di(tert-butyl)alane

The di(tert-butyl)aluminum halides, tBu2AlX (X = Br, I) have been prepared in yields ranging from 55 to 64% from AlX3 and LitBu in a 1 : 2 molar ratio in pentane. In the crystal these pyrophoric compounds are dimeric featuring Al-X-Al bridges. The reaction of AlCl3 with LitBu in diethyl ether produced a volatile solvate of composition tBu3Al-Cl-AltBu2(OEt2). Reaction of this species with AlCl3 at 120 ◦C yielded a separable mixture of tBu2AlCl and tBu2AlCl(OEt2). tBu2AlCl and tBu2GaCl react with tBu2PLi to produce the monomeric compounds tBu2E-PtBu2 (E = Al, Ga). The aluminum compound decomposes at 111 °C to give a mixture of the cis/trans-isomers of [tBu(H)Al- PtBu2]2 while at 200 °C only the trans-isomer is formed.