Azadigermiridines by Addition of Diazomethane or Trimethylsilyldiazomethane to a Digermene¹

Tetrakis(2,4,6-triisopropylphenyl)digermene (2), prepared by treatment of germanium bis(trimethylsilyl)amide with 2,4,6-triisopropylphenyllithium, reacts with diazomethane or trimethylsilyldiazomethane in a [2+1] fashion to furnish the N-methyleneamino-substituted azadigermiridines 7 and 8, respectively. The dissociation equilibrium between 2 and bis(triisopropylphenyl)germylene has been confirmed by the trapping reaction with a 1,2-quinone, from which the 1,3-dioxa-2-germaindan 10 was isolated. The structures of 2, 7, 8, and 10 were determined by X-ray crystallography. The sterically congested digermene 2 has a short Ge−Ge double-bond length of 2.213(1) Å

Tetraarylstannagermene: A Molecule with a GeSn Double Bond¹

The reaction of the Grignard compound RMgBr, R = 2,4,6-iPr3C6H2, with GeCl2·(dioxane) and SnCl2 furnishes the stannagermene R2GeSnR2 (4) with a short Ge−Sn double bond length of 2.5065(5) Å. Treatment of 4 with dry oxygen at low temperature yields a 3,4-germastannadioxetane with a stretched O−O bond length

Acetylene-Linked Bis(germaethenes): The First Molecules with Conjugated Germanium−Carbon Double Bonds¹

In solution, the digermene Ar2GeGeAr2 (Ar = 2-tBu-4,5,6-Me3C6H) partly dissociates into two molecules of the germylene Ar2Ge:. The reaction of this digermene with some 1,3-diynes (RC⋮C−)2 leads to the formation of the acetylene-linked bis(germaethenes) Ar2GeC(R)C⋮C(R)CGeAr2 (R = n-C4H9 (6a), C6H5 (6b)). The conjugation between the two GeC units is reflected by the positions of the UV/vis absorptions at longest wavelengths of 518 (6a) and 595 (6b) nm. An X-ray structure analysis of 6a reveals a nearly linear C4 skeleton and short GeC bond lengths of 1.819(2) Å

Azadigermiridines by Addition of Diazomethane or Trimethylsilyldiazomethane to a Digermene¹

Tetrakis(2,4,6-triisopropylphenyl)digermene (2), prepared by treatment of germanium bis(trimethylsilyl)amide with 2,4,6-triisopropylphenyllithium, reacts with diazomethane or trimethylsilyldiazomethane in a [2+1] fashion to furnish the N-methyleneamino-substituted azadigermiridines 7 and 8, respectively. The dissociation equilibrium between 2 and bis(triisopropylphenyl)germylene has been confirmed by the trapping reaction with a 1,2-quinone, from which the 1,3-dioxa-2-germaindan 10 was isolated. The structures of 2, 7, 8, and 10 were determined by X-ray crystallography. The sterically congested digermene 2 has a short Ge−Ge double-bond length of 2.213(1) Å

Silylene and Germylene Additions to 1,3-Diynes: Bis(silacyclopropenes) versus Germaethenes Formation, a DFT Study

The addition of silylenes and germylenes to triple-bond systems has been investigated with density functional theory methods. The experimentally observed formation of bis(silacyclopropenes) upon reaction of silylenes with 1,3-diynes is explained in terms of their much higher thermodynamic stability compared to the alternative acetylene-linked bis(silaethenes). For the germanium counterparts, the energetic difference is calculated to be much smaller and is reversed for the addition to 1,3-diacetylene in the case of very bulky germylenes (Ge(2-t-Bu-Ph)2). Silylenes add to triple bonds in a concerted reaction; no intermediate π complex nor transition state has been located, which is also true for most germylenes. Again, only for sterically demanding germylenes could these stationary points be found with a barrier between intermediate and TS of 1.7 kJ/mol. Generally, the additions of silylenes and germylenes to triple-bond systems take place in an electrophilic manner and appear to have the same mechanism

Addition Reactions of Maleic Anhydride to a Disilene and a Tetrasilabuta-1,3-diene: Formation of Bi- and Tetracyclic Compounds^1,2

The reaction of hexakis(2,4,6-triisopropylphenyl)tetrasilabutadiene with maleic anhydride (3) furnishes the 2,9-dioxa-5,6,7,8-tetrasilatetracyclodecan-3-one derivative 4, presumably by a sequence of two consecutive [2 + 2] cycloadditions. Tetrakis(2,4,6-triisopropylphenyl)disilene reacts with 3 to afford the bicyclic 1,2-dihydrofuro[3,2-d][1,2,3]oxadisilol-5(6H)-one derivative 5 via a formal [2 + 3] cycloaddition and a 1,2-hydrogen shift. The structures of 4 and 5 were determined by X-ray crystallography

Reaction Modes of a Tetragermabutadiene: Cycloadditions versus Ge−Ge Bond Cleavages¹

Treatment of hexakis(2,4,6-triisopropylphenyl)tetragermabuta-1,3-diene (2) with selenium in the presence of Et3P furnishes a selenatetragermacyclopentene derivative with an endocyclic Ge−Ge double bond. With small amounts of water 2 reacts to afford an oxatetragermacyclopentane, analogous to THF. The reaction of 2 with Et3PTe proceeds by cleavage of all Ge−Ge bonds to yield a 1,2,4,5-tetratellura-3,6-digermacyclohexane derivative together with small amounts of the “double-decker” compound R4Ge4Te6, R = 2,4,6-iPr3C6H2, and a telluradigermirane. In the reaction of 2 with 2-methoxyphenyl isocyanide one Ge−Ge double bond is cleaved to give the 4(1H)-trigermatimine ring system with an endocyclic Ge−Ge double bond and the known tetrakis(2,4,6-triisopropylphenyl)digermene (10). All new compounds were characterized by X-ray crystallography. Redetermination of the structure of 10 revealed two independent molecules with GeGe bond lengths of 2.2894(6) and 2.2635(14) Å, respectively

Silylene and Disilene Additions to an Octa-1,3,5,7-tetrayne: Formation of a C−C-Linked Quatersilirene^1,2

Tetra-tert-butyldisilene and di-tert-butylsilylene (1), generated by photolysis of hexa-tert-butylcyclotrisilane, react with 1,8-di-tert-butylocta-1,3,5,7-tetrayne to furnish a C−C-linked bis(disilacyclobutene) derivative with terminal alkynyl groups 7 and a quatersilirene 8 by addition of 1 to all C−C triple bonds. Upon prolonged irradiation, 8 rearranges partly to the 2,5-disilabicyclo[2.2.0]hexa-1(6),3-diene with terminal silirene groups 9. The structures of 7, 8, and 9 were determined by X-ray crystallography

Hexaarylcyclotriplumbane: A Molecule with a Homonuclear Ring System of Lead

The reaction of lead(II) bromide with RMgBr, R = 2,4,6-Et3C6H2, furnishes black crystals of hexakis(2,4,6-triethylphenyl)cyclotriplumbane (1) as the first molecule with a homonuclear lead ring. 1 adopts a skewed structure with highly stretched Pb−Pb bond lengths of 3.185 Å (average), which indicate that the three-membered ring is formed by weak interactions of 3 singlet plumbylene molecules

Addition Reactions of Maleic Anhydride to a Disilene and a Tetrasilabuta-1,3-diene: Formation of Bi- and Tetracyclic Compounds^1,2

The reaction of hexakis(2,4,6-triisopropylphenyl)tetrasilabutadiene with maleic anhydride (3) furnishes the 2,9-dioxa-5,6,7,8-tetrasilatetracyclodecan-3-one derivative 4, presumably by a sequence of two consecutive [2 + 2] cycloadditions. Tetrakis(2,4,6-triisopropylphenyl)disilene reacts with 3 to afford the bicyclic 1,2-dihydrofuro[3,2-d][1,2,3]oxadisilol-5(6H)-one derivative 5 via a formal [2 + 3] cycloaddition and a 1,2-hydrogen shift. The structures of 4 and 5 were determined by X-ray crystallography