The crystal structures of (MesSi),Si.THF (a = b = 12.310(1) A, c = 17.308(2) A, tetragonal, space group P4/ncc (No. 130), Z = 4), [(Me3Si)&i][(Me3Si)3SiLi(THF)3]~ (a = b = 15.146(8) A, c = 21.338(10) A, trigonal, space groupP3cl (No. 165), Z = 2), (Me3Si)3SiLi(THF)3 (a = b = 31.342(4) A, c = 22.000(6) A, rhombohedral, space groupR3c (No. 161), Z = 24), and (Me3Si)3SiSi(SiMe3)3aTHF (a = 11.360(3) A, b = 17.131(6) A, c = 18.952(6) A, 0 = 91.21(3)', monoclinic, space group P21/c (No. 14), Z = 4), have been determined by low-temperature X-ray analysis. Whereas the small S i S i S i angle in (tris(trimethylsily1)silyl)lithium of 102.1 O supports the ionic character of the Si-Li bond, there must be at least some covalent contribution leading to a *J[%,7Li] coupling constant of 38.6 Hz. A modified preparation for (Me3si)~siLi(THF)~ is reported giving the pure product rather than the cocrystallization product [(Me3Si)4Si] [(Me3Si)3SiLi(THF)3]2, where the starting material is still present in the ratio 1:2. The pure product is far more reactive than the cocrystallized material and is as pyrophoric as 'BuLi powder.

In guten Ausbeuten ist das erste Disilagermiran 1 aus (Me 3 Si) 3 SiLi(thf) 3 und GeCl 2 zugänglich. Hergestellt wurde auch die Germyllithium‐Verbindung 2 , deren Anion, das höhere Homologe zur Si‐Vorstufe von 1 , sich als wichtiger Baustein für eine Vielzahl gemisch ter dreigliedriger Ringsysteme aus schwereren Elementen der Gruppe 14 erweisen könnte. magnified image

Abstract Acylic silylated phosphazenes of the type HN(PR2NSiMe3)2 (1) react quantitatively with molecules MMe3 (M = Al, Ga, In) under ring formation and CH4 evolution. The ring compounds N(PPh2NSiMe3)2AlMe2 (2 a) and N(PPh2NSiMe3)2InMe2 (4 a) have been investiga­ ted by X-ray structure determination. 2a and 4a crystallize in the space groups P 1̄ and P 31, respectively; they show different conformations regarding the cyclohexane framework. NMR spectroscopy of the nuclei in the chelating phosphazene ligand indicates decreasing Lewis acidity of the metal containing fragments in the series AlMe2 ≥ GaMe2 > InMe2.

The title compound is obtained from the reaction of (Me3Si)3SiLi(thf)3 with CuBr in n-hexane and structurally characterised by X-ray diffraction; in [Cu2R2BrLi(thf)3], R = Si(SiMe3)3 one silyl ligand is bridging a very short Cu-Cu bond, resulting in a three-centre two-electron bond, while the second is terminally bound to copper; the other copper atom is linked to a lithium atom via a Cu...Br...Li bridge.

Eine SiCu2‐Drei‐Zentren‐Zwei‐Elektronen‐Bindung mit kurzem Cu‐Cu‐Abstand ist das herausragende Merkmal des im Titel erwähnten Lithiumsilylcuprats Li(thf)4‐1, der ersten röntgenographisch charakterisierten Verbindung dieses Typs (Bild rechts ohne SiMe3‐Substituenten). Die Struktur des Aluminats entspricht einem eingefrorenen Intermediat aus der Umsetzung (Me3Si)3SiLi + AlCl3. Beide Verbindungen sind extrem thermolabil. magnified image

The title compound is obtained from the reaction of (Me3Si)3SiLi(thf)3 with CuBr in n-hexane and structurally characterised by X-ray diffraction; in [Cu2R2BrLi(thf)3], R = Si(SiMe3)3 one silyl ligand is bridging a very short Cu–Cu bond, resulting in a three-centre two-electron bond, while the second is terminally bound to copper; the other copper atom is linked to a lithium atom via a Cu ⋯ Br ⋯ Li bridge.

The synthesis and crystal structure of 1,3-di-tert-butyl-4,4-dimethyl-2-pentafluorophenyl-1,3,4,2-diazastannoboracyclobutane are reported.

Synthesis and Structure of CpAlCl2 Compounds with Sterically Demanding Substituents (Cp = Me5C5, EtMe4C5)[1]The compounds Cp*AlCl2 (3) (Cp* = Me5C5) and Cp′AlCl2 (4) (Cp′ = EtMe4C5) have been prepared by the reaction of Cp*SiMe3 (1) and Cp′SiMe3 (2) with AlCl3. The single‐crystal X‐ray structures of 3 and 4 are reported.

2,5-Bisdimethylamino-2,5-dihydrobenzo[b]-1,2,5-thiadiborole (2) has been obtained from the diiodine-derivative by reaction with dimethyl-aminotrimethylsilane. Reaction of 2 or 2,5-bisdimethylamino-1′,2′-dimethyl-2,5-dihydrobenzo[b]-thiadiborole with di-tert-butyl-, tertbutyl-trimethylsilyl- and bistrimethylsilyl-sulfurdiimide yields the 2,7,3,6-tetrahydrobenzo[b]-1,2,7,3,6-thiadiazadiborepines (3a-3e). 1H, 11B, 13C NMR, MS and analytical data and results of analysis are given. For 3a the X-ray structure is reported.

Ein zentraler drachenförmiger AM2Li‐Ring, in dem das Li‐Atom die beiden an das Al‐Atom gebundenen hydridischen Wasserstoffatomeverbrückt, liegt in einem der Intermediate der Umsetzung von HN(SiMe3)2 mit LiAIH4 vor. Die Bindungswinkel zeigen, daß Verbindung 1 relativ gespannt ist. Dennoch dissoziiert 1 in Lösung nicht: Im 7Li‐NMR‐Spektrum bei niedriger Temperatur wird eine 1J(Li,H)‐Kopplung beobachtet.magnified image

Twofold Borylation of Benzene Derivatives with (Diisoalkylamino)boradiyl UnitsThe reaction of subvalent boron species generated by the defluorination of difluoro(diorganylamino)borane with Na/K alloy in the presence of 1,4‐disubstituted benzene derivatives leads to products which contain two (diorganylamino)boradiyl units and two remaining double bonds which are located on the substituted C atoms. Compounds 5 to 8 exhibit structures based on a 2,8‐diborabicyclo[3,2,1]octa‐3,6‐diene skeleton while 9 shows a skeleton with a 1,3a,4,6a‐tetrahydroborolo[3,2‐b]borole structure. The latter structure corresponds to that of 1 obtained in the same reaction with benzene. The compounds are characterized by elemental analyses and spectroscopically [MS, NMR (1H, 11B, 13C, 15N, 19F, 29Si)]. X‐ray structure analyses are presented for 1, 6, 7, 8, and 9.