Metallierung von Triisopropylsilylarsan durch Bis(tetrahydrofuran)calcium‐bis[tris(trimethylsilylmethyl)zinkat]

Metalation of Triisopropylsilylarsane with Bis(tetrahydrofuran)calcium‐bis[tris(trimethylsilylmethyl)zincate] The transmetalation of bis(trimethylsilylmethyl)zinc with distilled calcium in THF yields bis(tetrahydrofuran)calcium bis[tris‐(trimethylsilylmethyl)zincate] ( 1 ). The trialkylzincate anion appears as a bidentate ligand with Ca‐C‐Zn three‐center‐bonds. The CaC bond lengths show values of 265.5(2) and 271.7(2) pm. The metalation of triisopropylsilylarsane gives tetrakis(tetrahydrofuran)calcium [1, 3‐bis(triisopropylsilylarsanyl)‐2, 4‐bis(triisopropylsilyl)‐1, 3‐dizinca‐2, 4‐diarsacyclobutane‐2, 4‐diide] ( 2 ). The central moiety is a sligthly distorted trigonal As₂CaZn₂ bipyramid with the arsenic atoms in apical positions. The mean Ca‐As bond lengths lie with a mean value of 291.4 pm in the charakteristic region for calcium bis‐(arsanides).     

Strontium- und Barium-bis[N,N′ -bis(trimethylsilyl)benzamidinate] aus der Additionsreaktion der Erdalkalimetall-bis[bis(trimethylsilyl)amide] mit Benzonitril

Strontium and Barium Bis[N,N′-bis(trimethylsilyl)benzamidinates] from the Addition Reaction of the Alkaline Earth Metal Bis[bis(trimethylsilyl)amides] and Benzonitrile The reaction of strontium bis[bis trimethylsilyl)amide] with benzonitrile yields strontium bis[N,N′- bis(trimethylsilyl)benzamidinate] · 2THF, which crystallizes in the orthorhombic space group Pbcn (a = 1845.4(3); b = 131 1,3(2); c = 1838,(3) pm; Z = 4). During the similar reaction of barium bis[bis(trimethylsilyl)amide] with benzonitrile the benzonitrile adduct barium bis[N,N′-bis(trimethylsilyl)benzamidinate] · 2 THF · benzonitrile is formed. After the addition of diphenylacetylene to the strontium di(benzamidinate) in diglyme a clathrate of the composition strontium bis[N,N′-bis(trimethylsilyl)benzamidinate] · diglyme · diphenylacetylene could be isolated; the spectroscopic data as well as the X-ray structure (monoclinic, C2/c, a = 1492.2(2); b = 1539.1(2); c = 2337.8(3)pm; Z = 4) confirm the isolated appearance of the acetylene molecule without interaction to the metal center in solution and in the solid state, respectively.     

Synthesis and molecular structures of phenylamides of magnesium, calcium, strontium, and barium--from molecular to polymeric structures

Several preparative procedures for the synthesis of the THF complexes of the alkaline earth metal bis(phenylamides) of Mg (1), Ca (2), Sr (3), and Ba (4) are presented such as metalation of aniline with strontium and barium, metathesis reactions of MI2 with KN(H)Ph, and metalation of aniline with arylcalcium compounds or dialkylmagnesium. The THF content of these compounds is rather low and an increasing aggregation is observed with the size of the metal atom. Thus, tetrameric [(THF)2Ca{mu-N(H)Ph}2]4 (2) and polymeric [(THF)2Sr{mu-N(H)Ph}2]infinity and {[(THF)2Ba{mu-N(H)Ph}2]2[(THF)Ba{mu-N(H)Ph}2]2}infinity show six-coordinate metal atoms with increasing interactions to the pi systems of the phenyl groups with increasing the radius of the alkaline earth metal atom.     

Homoleptic alkaline earth metal bis(trifluoromethanesulfonyl)imide complex compounds obtained from an ionic liquid

The first homoleptic alkaline earth bis(trifluoromethanesulfonyl)imide (Tf2N) complexes [mppyr]2[Ca(Tf2N)4], [mppyr]2[Sr(Tf2N)4], and [mppyr][Ba(Tf2N)3] were crystallized from a solution of the respective alkaline earth bis(trifluoromethanesulfonyl)imide and the ionic liquid [mppyr][Tf2N] (mppyr = 1,1-N-methyl-N-propylpyrrolidinium). In the calcium and strontium compounds, the alkaline earth metal (AE) is coordinated by four bidentately chelating Tf2N ligands to form isolated (distorted) square antiprismatic [AE(Tf2N)4]2- complexes which are separated by N-methyl-N-propylpyrrolidinium cations. In contrast, the barium compound, [mppyr][Ba(Tf2N)3], forms an extended structure. Here the alkaline earth cation is surrounded by six oxygen atoms belonging to three Tf2N- anions which coordinate in a bidentate chelating fashion. Three further oxygen atoms of the same ligands are linking the Ba2+ cations to infinite (infinity)(1)[Ba(Tf2N)3] chains.     

Synthese,Struktur und Hydrolyse von Tetrakis(tetrahydropyran)strontium-bis[bis(dimethylisopropylsilyl)phosphanid]

Synthesis, Structures, and Hydrolysis of Tetrakis(tetrahydropyran)strontium Bis[bis(dimethylisopropylsilyl)phosphanide] The metalation of bis(dimethylisopropylsilyl)phosphane in tetrahydropyran with strontium bis[bis(trimethylsilyl)amide] yields almost quantitatively tetrakis(tetrahydropyran)strontium bis[bis(dimethylisopropylsilyl)phosphanide], which crystallizes in the monoclinic space group C2/c (a = 2340.71(1), b = 1028.74(1), c = 2186.02(1) pm, β = 91.03(1)°, Z = 4, wR₂ = 0.0759). The phosphanide ligands are in trans-positions and the P–Sr–P bond angle is found to be 168.5°. Partial hydrolysis of this compound leads to the formation of bis(dimethylsilylisopropylsilyl)phosphane and Sr₄O[P(SiMePr)₂]₆ with a central oxygen atom surrounded tetrahedrally by four alkaline earth metal atoms (monoclinic, space group C2/c, C2/c, a = 2265.83(6), b = 1702.11(5), c = 2462.46(9) pm, β = 91.34(1)°, Z = 4, wR₂ = 0.1057). The edges of the strontium tetrahedron are bridged by phosphanide ligands. The metal atoms are coordinated trigonal planarily by three phosphanide groups.     

Kristallstrukturen und spektroskopische Eigenschaften von 2λ3‐Phospha‐1, 3‐dionaten und 1, 3‐Dionaten des Calciums ‐ ein Vergleich am Beispiel der 1, 3‐Diphenyl‐ und 1, 3‐Di(tert‐butyl)‐Derivate

Crystal Structures and Spectroscopic Properties of 2λ³‐Phospha‐1, 3‐dionates and 1, 3‐Dionates of Calcium ‐ Comparative Studies on the 1, 3‐Diphenyl and 1, 3‐Di(tert‐butyl) Derivatives A hydrogen‐metal exchange between dibenzoylphosphane and calcium carbide in tetrahydrofuran (THF) followed by addition of the ligand 1, 3, 5‐trimethyl‐1, 3, 5‐triazinane (TMTA) furnishes the binuclear complex bis[(tmta‐N, N′, N″)calcium bis(dibenzoylphosphanide)] ( 1a ) co‐crystallizing with benzene. Similarly, reaction of bis(2, 2‐dimethylpropionyl)phosphane with bis(thf‐O)calcium bis[bis(trimethylsilyl)amide] in 1, 2‐dimethoxyethane (DME) gives bis(dme‐O, O′)calcium bis[bis(2, 2‐dimethylpropionyl)phosphanide] ( 1b ) in high yield. The carbon analogues 1, 3‐diphenylpropane‐1, 3‐dione (dibenzoylmethane) or 2, 2, 6, 6‐tetramethylheptane‐3, 5‐dione (dipivaloylmethane) and bis(thf‐O)calcium bis[tris(trimethylsilylmethyl)zincate] in DME afford bis(dme‐O, O′)calcium bis(dibenzoylmethanide) ( 2a ) and the binuclear complex (μ‐dme‐O, O′)bis[(dme‐O, O′)calcium bis(dipivaloylmethanide)] ( 2b ), respectively. Dialkylzinc formed during the metalation reaction shows no reactivity towards the 1, 3‐dionates 2a and 2b . Finally, from the reaction of the unsymmetrically substituted ligand 2‐(methoxycarbonyl)cyclopentanone and bis(thf‐O)calcium bis[bis(trimethylsilyl)amide] in toluene, the trinuclear complex 3 is obtained, co‐crystallizing with THF. The β‐ketoester anion bridges solely via the cyclopentanone unit.     

Alkali Metal and Alkaline Earth Metal Complexes with the Bis(borane‐diphenylphosphanyl)amido Ligand – Synthesis,Structures, and Catalysis for Ring‐Opening Polymerization of ϵ‐Caprolactone

The syntheses of lithium and alkaline earth metal complexes with the bis(borane‐diphenylphosphanyl)amido ligand ( 1 ‐ H ) of molecular formulas [{κ²‐N(PPh₂(BH₃))₂}Li(THF)₂] ( 2 ) and [{κ³‐N(PPh₂(BH₃))₂}₂M(THF)₂] [(M = Ca ( 3 ), Sr ( 4 ), Ba ( 5 )] are reported. The lithium complex 2 was obtained by treatment of bis(borane‐diphenylphosphanyl)amine ( 1 ‐ H ) with lithium bis(trimethylsilyl)amide in a 1:1 molar ratio via the silylamine elimination method. The corresponding homoleptic alkaline earth metal complexes 3 – 5 were prepared by two synthetic routes – first, the treatment of metal bis(trimethylsilyl)amide and protio ligand 1 ‐ H via the elimination of silylamine, and second, through salt metathesis reaction involving respective metal diiodides and lithium salt 2 . The molecular structures of lithium complex 2 and barium complex 5 were established by single‐crystal X‐ray diffraction analysis. In the solid‐state structure of 2 , the lithium ion is ligated by amido nitrogen atoms and hydrogen atoms of the BH₃ group in κ²‐coordination of the ligand 1 resulting in a distorted tetrahedral geometry around the lithium ion. However, in complex 5 , κ³‐coordination of the ligand 1 was observed, and the barium ion adopted a distorted octahedral arrangement. The metal complex 5 was tested as catalyst for the ring opening polymerization of ?‐caprolactone. High activity for the barium complex 5 towards ring opening polymerization (ROP) of ?‐caprolactone with a narrow polydispersity index was observed. Additionally, first‐principle calculations to investigate the structure and coordination properties of alkaline earth metal complexes 3 – 5 as a comparative study between the experimental and theoretical findings were described.     

Reaktion von Bis(methylzink)‐1,2‐dipyridyl‐1,2‐bis(tert‐butyldimethylsilylamido)ethan mit Triisopropylsilylphosphan und ‐arsan

Reaction of Bis(methylzinc)‐1,2‐dipyridyl‐1,2‐bis(tert‐butyldimethylsilylamido)ethane with Triisopropylsilylphosphane and ‐arsane The reaction of bis(methylzinc)‐1,2‐dipyridyl‐1,2‐bis(tert‐butyldimethylsilylamido)ethane ( 1 ) with triisopropylsilylphosphane gives the three‐nuclear complex [1,2‐dipyridyl‐1,2‐bis(tert‐butyldimethylsilylamido)ethane]trizinc‐bis(μ‐triisopropylsilylphosphanediide) ( 2 ). Two zinc atoms show the coordination number of four whereas the third metal center is located between the two phosphorus atoms with a bent P–Zn–P‐moiety. The reaction of 1 with triisopropylsilylarsane proceeds analoguesly, however, we were not able to isolate analytically pure [1,2‐dipyridyl‐1,2‐bis(tert‐butyldimethylsilylamido)ethane]trizinc‐bis(μ‐triisopropylsilylarsanediide) ( 3 ).     

Synthese und Molekülstruktur von Barium-bis[N,N′-bis(trimethylsilyl)benzamidinat] · DME · THF

Synthesis and Molecular Structure of Barium Bis[N,N′-bis(trimethylsilyl)benzamidinate] ° DME ° THF Barium bis[N,N′-bis(trimethylsilyl)benzamidinate] · thf · dme crystallizes in the monoclinic space group P2₁/n with a = 1 122.0(2), b = 2 190.7(4), c = 1 840.2(3) pm, β = 98.04(1)° and Z = 4 containing a metal center in a distorted monocapped trigonal prismatic surrounding. The barium dibenzamidinate moiety is sent with an angle of 120°, although this leads to different Ba? N distances of 273 and 282 pm originating from the interligand repulsion of the trimethylsilyl groups and the dme substituent. The 1,3-diazaallyl fragment with C? N bond lengths of 132 pm shows a delocalisation of the anionic charge.     

2,3,4,5‐Tetraethylpentela‐cyclo‐pentadienide (2,3,4,5‐Tetraethylpentolide) der Erdalkalimetalle Magnesium,Calcium, Strontium und Barium

2,3,4,5‐Tetraethylpentela‐cyclo‐pentadienides (2,3,4,5‐Tetraethylpentolides) of the Alkaline Earth Metals Magnesium, Calcium, Strontium, and Barium The reaction of bis(cyclopentadienyl)‐1‐zircona‐2,3,4,5‐tetraethyl‐cyclo‐penta‐2,4‐diene with ECl₃ (E = P, As, Sb) yields 1‐chloro‐tetraethylphosphole ( 1 ), ‐arsole ( 2 ) und ‐stibole ( 3 ). The reduction of these pentoles gives in a first step the corresponding octaethyldiphospholyle ( 4 ), ‐diarsolyle ( 5 ) and ‐distibolyle ( 6 ). Further reduction of these dipentolyles with magnesium and calcium leads in the presence of the corresponding dihalides to the formation of magnesium chlorid (2,3,4,5‐tetraethylphospholide) ( 7 ), ‐arsolide) ( 8 ) and ‐stibolide) ( 9 ) and calcium chlorid (2,3,4,5‐tetraethylphospholide) ( 10 ), ‐arsolide) ( 11 ) and ‐stibolide) ( 12 ), respectively. In the absence of alkaline earth metal dihalides no reaction is observed. For the larger metals strontium and barium the reduction of the dipentolyles succeeds in THF also without the addition of halides and the 1,1′‐dipentela‐octaethylstrontocene [E = P ( 13 ), As ( 14 ), Sb ( 15 )] as well as ‐barocene [E = P ( 16 ), As ( 17 ), Sb ( 18 )] are isolated halogen‐free. The strontocene crystallizes as a THF adduct whereas the barocene precipitates coligand‐free but with a chain structure. The molecular structures of 7 , 10 , and 16 are discussed.     

Synthese von substituierten Calcium-bis(disilylamiden) mittels der Transmetallierung von Zinn(II)- und Zinn(IV)-amiden

Synthesis of Substituted Calcium-bis(disilylamides) by Transmetalation of Tin(II) and Tin(IV) Amides Stannylenes as well as stannanes with substituted disilylamino groups are valuable synthons for the synthesis of alkaline earth metal bis(disilylamides) via the transmetallation reaction. Whereas bis[2,2,5,5-tetramethyl-2,5-disilaaza-cyclo-pentyl]stannylene 1 is a suitable reagent for this type of reaction, bis[trimethylsilyl-tris(trimethylsilyl)silylamino]stannylene 2 (monoclinic, P2₁/c, a = 1492.6(2), b = 1705.2(2), c = 1865.3(3) pm, β = 109.03(2)º, Z = 4) is not only attacked at the Sn? N-bond but also the N? Si-bond is cleaved by calcium metal. Similar light sensitivity as for 2 is observed for the mercury bis[trimethylsilyl-tris(trimethylsilyl)silylamide] 3 , the homolytic M? N-bond cleavage leads to the formation of the trimethylsilyl-tris(trimethylsilyl)silylamino radical (g = 2.00485; a(N) = 16.2 G). The calcium tin exchange reaction of 1 in THF yields tris(tetrahydrofuran-O)calcium-bis[2,2,5,5-tetramethyl-2,5-disilaaza-cyclo-pentanide] 4 (monoclinic, P2₁/n, a = 1060.9(2), b = 1919.3(5), c = 1686.0(3) pm, β = 90.30(2)º, Z = 4). The stannanes Me_n-4Sn[N(SiMe₃)₂]_n with n = 1 or 2 are also valuable materials for the synthesis of bis(tetrahydrofuran-O)calcium-bis[bis(trimethylsilyl)amide].     

Super‐Bulky Penta‐arylcyclopentadienyl Ligands: Isolation of the Full Range of Half‐Sandwich Heavy Alkaline‐Earth Metal Hydrides

Hydrogenolysis of the half‐sandwich penta‐arylcyclopentadienyl‐supported heavy alkaline‐earth‐metal alkyl complexes (Cp^Ar)Ae[CH(SiMe₃)₂](S) (Cp^Ar=C₅Ar₅, Ar=3,5‐ⁱPr₂‐C₆H_3; S=THF or DABCO) in hexane afforded the calcium, strontium, and barium metal–hydride complexes as the same dimers [(Cp^Ar)Ae(μ‐H)(S)]₂ (Ae=Ca, S=THF, 2‐Ca ; Ae=Sr, Ba, S=DABCO, 4‐Ae ), which were characterized by NMR spectroscopy and single‐crystal X‐ray analysis. 2‐Ca , 4‐Sr , and 4‐Ba catalyzed alkene hydrogenation under mild conditions (30 °C, 6 atm, 5 mol % cat.), with the activity increasing with the metal size. A variety of activated alkenes including tri‐ and tetra‐substituted olefins, semi‐activated alkene (Me₃SiCH=CH₂), and unactivated terminal alkene (1‐hexene) were evaluated.     

Synthese eines hexanuklearen Calcium–Phosphor‐Käfigs über heteroleptische Calcium‐amid‐phosphanid‐Vorstufen

Synthesis of a Hexanuclear Calcium–Phosphorus‐Cage The metalation of tri(tert‐butyl)silylphosphane with calcium bis[bis(trimethylsilyl)amide] yields the dimer {(Me₃Si)₂N–Ca(THF)[μ‐P(H)Si^tBu₃]}₂ ( 1 ). In THF monomerization occurs and dismutation reactions lead to the homoleptic compounds, namely (THF)₂Ca[N(SiMe₃)₂]₂ and (THF)₄Ca[P(H)Si^tBu₃]₂. In toluene, 1 undergoes dismutation reactions, bis(tetrahydrofuran)calcium bis[bis(trimethylsilyl)amide] is regained and [(Me₃Si)₂N–Ca(THF)]₂Ca[P(H)Si^tBu₃]₄ ( 2 ) precipitates. At raised temperatures, 2 undergoes a homometallic metalation with the loss of two equivalents of HN(SiMe₃)₂ and dimerizes. The thus formed cage compound (THF)₂Ca₆[PSi^tBu₃]₄[P(H)Si^tBu₃]₄ ( 3 ) with a central Ca₄P₄ heterocubane moiety crystallizes upon cooling of the toluene solution. The molecular structures of 2 and 3 were determined.     

Rare earth metal bis(amide) complexes bearing amidinate ancillary ligands: synthesis, characterization, and performance as catalyst precursors for cis-1,4 selective polymerization of isoprene

A family of rare earth metal bis(amide) complexes bearing monoanionic amidinate [RC(N-2,6-Me(2)C(6)H(3))(2)](-) (R = cyclohexyl (Cy), phenyl (Ph)) as ancillary ligands were synthesized and characterized. One-pot salt metathesis reaction of anhydrous LnCl(3) with one equivalent of amidinate lithium [RC(N-2,6-Me(2)C(6)H(3))(2)]Li, following the introduction of two equivalents of NaN(SiMe(3))(2) in THF at room temperature afforded the neutral and unsolvated mono(amidinate) rare earth metal bis(amide) complexes [RC(N-2,6-Me(2)C(6)H(3))(2)]Y[N(SiMe(3))(2)](2) (R = Cy (1); R = Ph (2)), and the "ate" mono(amidinate) rare earth metal bis(amide) complex [CyC(N-2,6-Me(2)C(6)H(3))(2)]Lu[N(SiMe(3))(2)](2)(μ-Cl)Li(THF)(3) (3) in 61-72% isolated yields. These complexes were characterized by elemental analysis, NMR spectroscopy, FT-IR spectroscopy, and X-ray single crystal diffraction. Single crystal structural determination revealed that the central metal in complexes 1 and 2 adopts a distorted tetrahedral geometry, and in complex 3 forms a distorted trigonal bipyramidal geometry. In the presence of AlMe(3), and in combination with one equimolar amount of [Ph(3)C][B(C(6)F(5))(4)], complexes 1 and 2 showed high activity towards isoprene polymerization to give high molecular weight polyisoprene (M(n) > 10(4)) with good cis-1,4 selectivity (>90%).     

Molekül- und Kristallstruktur von Magnesium-bis[bis(trimethylsilyl)phosphanid] · DME

Molecular and Crystal Structure of Magnesium Bis[bis(trimethylsilyl)phosphide] · DME Magnesium bis[bis(trimethylsilyl)phosphide] crystallizes in the tetragonal space group I4 c2 with a = 1652.9(2); c = 2282.6(5) pm and Z = 8. The magnesium atom is distorted tetrahedrally surrounded by two oxygen and two phosphorus atoms with Mg? P- and Mg? O-bond lengths of 248.7(2) and 204.7(5) pm, respectively. The phosphorus atom displays a trigonal pyramidal coordination.     

Deprotonation reaction of α‐amino acid N‐carboxyanhydride at 4‐CH position by yttrium tris[bis(trimethylsilyl)amide]

Reaction of yttrium tris[bis(trimethylsilyl)amide] [(TMSN)₃Y] with equivalent L ‐alanine N‐carboxyanhydride (ALA NCA) yields yttrium α‐isocyanato carboxylate ( II ), yttrium ketenyl carbamate ( III ), and hexamethyldisilazane ( V ). The products indicate that 4‐CH group of ALA NCA monomer is deprotonated in addition to 3‐NH group, which has been neglected in NCA chemistry for decades. This result proves the acidity of 4‐CH in NCA and provides the first direct evidence for racemization phenomenon of NCA in strong base in microscopic aspect. Rare earth tris[bis(trimethylsilyl)amide] (TMSN)₃Ln (Ln = Sc, Y, La, Dy, and Lu) compounds are high efficient catalysts for ring‐opening polymerizations of NCAs. Polypeptides can be produced in quantitative yields with narrow molecular weight distributions below 1.3, and block copolypeptides can be facilely prepared by sequential addition method. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Role of donor and secondary interactions in the structures and thermal properties of alkaline-earth and rare-earth metal pyrazolates

The addition of neutral coligands to reduce the aggregation and improve the volatility of potential heavy alkaline-earth metal chemical vapor deposition (CVD) precursors has typically resulted in liberation of the coligand upon heating. A new series of dinuclear alkaline-earth and rare-earth metal pyrazolates, bis[bis(3,5-di-tert-butylpyrazolato)(tetrahydrofuran)calcium] (1), bis[bis(3,5-di-tert-butylpyrazolato)(tetrahydrofuran)strontium] (2), and bis[bis(3,5-di-tert-butylpyrazolato)bis(tetrahydrofuran)barium] (3), have been obtained from our previous donor-free oligonuclear complexes [{M(3,5-tBu2pz)2}n] (5, M = Ca, n = 3; 6, M = Sr, n = 4; 7, M = Ba, n = 6) by treatment with tetrahydrofuran (THF). Compounds 1-3, as well as the europium analogue bis[bis(3,5-di-tert-butylpyrazolato)(tetrahydrofuran)europium(II)] (4), can also be prepared by direct reaction of the metals and pyrazole in THF and anhydrous liquid ammonia. Recrystallization from hexane led to single crystals of 2-4, while the powder diffraction pattern of 1 revealed it to be isostructural with the previously published bis[bis(3,5-di-tert-butylpyrazolato)(tetrahydrofuran)ytterbium(II)] (8), providing important insight into differences and similarities between the two groups of metals. Detailed structural analysis of the compounds reveals secondary interactions including pi-bonding and agostic interactions, which are considered essential in stabilizing the metal complexes. The direct comparison of structural features and thermal properties (as evaluated by thermogravimetric analysis and sublimation studies) of the donor-free oligonuclear and the donor-containing dinuclear species offers a better understanding of the role of donors and secondary interactions.     

Synthesis and structural characterization of alkaline-earth-metal bis(amido)silane and lithium oxobis(aminolato)silane complexes

Several of alkaline-earth-metal complexes [(η(2):η(2):μ(N):μ(N)-Li)(+)](2)[{η(2)-Me(2)Si(DippN)(2)}(2)Mg](2-) (4), [η(2)(N,N)-Me(2)Si(DippN)(2)Ca·3THF] (5), [η(2)(N,N)-Me(2)Si(DippN)(2)Sr·THF] (6), and [η(2)(N,N)-Me(2)Si(DippN)(2)Ba·4THF] (7) of a bulky bis(amido)silane ligand were readily prepared by the metathesis reaction of alkali-metal bis(amido)silane [Me(2)Si(DippNLi)(2)] (Dipp = 2,6-i-Pr(2)C(6)H(3)) and alkaline-earth-metal halides MX(2) (M = Mg, X = Br; M = Ca, Sr, Ba, X = I). Alternatively, compounds 5-7 were synthesized either by transamination of M[N(SiMe(3))(2)](2)·2THF (M = Ca, Sr, Ba) and [Me(2)Si(DippNH)(2)] or by transmetalation of Sn[N(SiMe(3))(2)](2), [Me(2)Si(DippNH)(2)], and metallic calcium, strontium, and barium in situ. The metathesis reaction of dilithium bis(amido)silane [Me(2)Si(DippNLi)(2)] and magnesium bromide in the presence of oxygen afforded, however, an unusual lithium oxo polyhedral complex {[(DippN(Me(2)Si)(2))(μ-O)(Me(2)Si)](2)(μ-Br)(2)[(μ(3)-Li)·THF](4)(μ(4)-O)(4)(μ(3)-Li)(2)} (8) with a square-basket-shaped core Li(6)Br(2)O(4) bearing a bis(aminolato)silane ligand. All complexes were characterized using (1)H, (13)C, and (7)Li NMR and IR spectroscopy, in addition to X-ray crystallography.     

Synthese von Magnesium-bis[N,N′-bis(trimethylsilyl)benzamidinat] als Bis(THF)- und Benzonitril-Addukt

Synthesis of Magnesium Bis[N,N′ -bis(trimethylsilyl)benzamidinate] as both Bis(THF) and Benzonitrile Adduct Magnesium bis[bis(trimethylsilyl)amide] 1 , reacts with benzonitrile in toluene at room temperature to yield magnesium bis[N,N′-bis(trimethylsilyl)benzamidinate]-benzonitrile(1/1) 2 . Addition of THF leads to a quantitative substitution of the benzonitrile ligand by two THF molecules. The performance of the addition reaction in THF yields magnesium bis[N,N′-bis(trimethylsilyl)benzamidinate] · THF(1/2) 3 . The upper benzonitrile complex 2 , crystallizes in the orthorhombic space group Pbcn with {a = 1383.2(2); b = 2589.1(4); c = 1133.7(1) pm; Z = 4}. The magnesium atom is coordinated distorted trigonal-bipyramidal, where the benzonitrile ligand lies within the equatorial plane. The axial bound nitrogen atom of the benzamidinate substitution shows with a value of 213 pm a slightly longer bond distance to the metal center than the one in the equatorial plane (210 pm). The steric strain within the benzamidinate ligand leads to an elongation of the silicon atoms out of the 1,3-diazaallylic moiety under an enlargement of the C? N? Si angle to 131°.     

Synthese,Eigenschaften und Struktur von Amin-Addukten der Lithium-tris[bis(trimethylsilyl)methyl]zinkate

Synthesis, Properties, and Structure of the Amine Adducts of Lithium Tris[bis(trimethylsilyl)methyl]zincates . Bis[bis(trimethylsilyl)methyl]zinc and the aliphatic amine 1,3,5-trimethyl-1,3,5-triazinane (tmta) yield in n-pentane the 1:1 adduct, the tmta molecule bonds as an unidentate ligand to the zinc atom. Bis[bis(trimethylsilyl)methyl]zinc · tmta crystallizes in the triclinic space group P1 with {a = 897.7(3); b = 1 114.4(4); c = 1 627.6(6) pm; α = 90.52(1); β = 103.26(1); γ = 102.09(1)°; Z = 2}. The central C₂ZnN moiety displays a nearly T-shaped configuration with a CZnC angle of 157° and Zn? C bond lengths of 199 pm. The Zn? N distances of 239 pm are remarkably long and resemble the loose coordination of this amine; a nearly complete dissociation of this complex is also observed in benzene. The addition of aliphatic amines such as tmta or tmeda to an equimolar etheral solution of lithium bis(trimethylsilyl)methanide and bis[bis(trimethylsilyl)methyl]zinc leads to the formation of the amine adducts of lithium tris[bis(trimethylsilyl)methyl]zincate. Lithium tris[bis(trimethylsilyl)methyl]zincate · tmeda · 2 Et₂O crystallizes in the orthorhombic space group Pbca with {a = 1 920.2(4); b = 2 243.7(5); c = 2 390.9(5) pm; Z = 8}. In the solid state solvent separated ions are observed; the lithium cation is distorted tetrahedrally surrounded by the two nitrogen atoms of the tmeda ligand and the oxygen atoms of both the diethylether molecules. The zinc atom is trigonal planar coordinated; the long Zn? C bonds with a value of 209 pm can be attributed to the steric and electrostatic repulsion of the three carbanionic bis(trimethylsilyl)methyl substituents.