A Dimeric NHC-Silicon Monotelluride: Synthesis, Isomerization, and Reactivity.

The reaction of the NHC-disilicon(0) complex [(IAr )Si=Si(IAr )] (1, IAr =:C{N(Ar)C(H)}2 , Ar=2,6-iPr2 C6 H3 ) with two equiv of elemental Te in toluene at room temperature for three days afforded a mixture of the first dimeric NHC-silicon monotelluride [(IAr )Si=Te]2 (2) and its isomeric complex [(IAr )Si(µ-Te)Si(IAr )=Te] (3). When the same reaction was performed for ten days, only 3 was isolated from the reaction mixture. Compound 1 reacted with four equiv of elemental Te in toluene for four weeks, which proceeded through the formation of 2, 3 and the NHC-disilicon tritelluride complex [{(IAr )Si(=Te)}2 Te] (5-Te), to form the dimeric NHC-silicon ditelluride [(IAr )Si(=Te)(µ-Te)]2 (4). The reactions are in line with theoretical mechanistic studies for the formation of 4. Compound 3 reacted with one equiv of elemental sulfur in toluene to form the first NHC-disilicon sulfur ditelluride complex [{(IAr )Si(=Te)}2 S] (5-S).

Trapping a Silicon(I) Radical with Carbenes: A Cationic cAAC-Silicon(I) Radical and an NHC-Parent-Silyliumylidene Cation.

The trapping of a silicon(I) radical with N-heterocyclic carbenes is described. The reaction of the cyclic (alkyl)(amino) carbene [cAACMe ] (cAACMe =:C(CMe2 )2 (CH2 )NAr, Ar=2,6-iPr2 C6 H3 ) with H2 SiI2 in a 3:1 molar ratio in DME afforded a mixture of the separated ion pair [(cAACMe )2 Si:. ]+ I- (1), which features a cationic cAAC-silicon(I) radical, and [cAACMe -H]+ I- . In addition, the reaction of the NHC-iodosilicon(I) dimer [IAr (I)Si:]2 (IAr =:C{N(Ar)CH}2 ) with 4 equiv of IMe (:C{N(Me)CMe}2 ), which proceeded through the formation of a silicon(I) radical intermediate, afforded [(IMe )2 SiH]+ I- (2) comprising the first NHC-parent-silyliumylidene cation. Its further reaction with fluorobenzene afforded the CAr -H bond activation product [1-F-2-IMe -C6 H4 ]+ I- (3). The isolation of 2 and 3 confirmed the reaction mechanism for the formation of 1. Compounds 1-3 were analyzed by EPR and NMR spectroscopy, DFT calculations, and X-ray crystallography.

Synthesis of a Bent 2-Silaallene with a Perturbed Electronic Structure from a Cyclic Alkyl(amino) Carbene-Diiodosilylene.

The cyclic alkyl(amino) carbene (cAAC) 1 reacted with SiI4 in toluene, affording the cAAC-silicon tetraiodide complex [(cAACMe)SiI4] (2, cAACMe = :C(CH2)(CMe2)2NAr, Ar = 2,6-iPr2C6H3). It further reacted with two equivalents of KC8 in toluene at room temperature to afford the first cAAC-diiodosilylene [(cAACMe)SiI2] (3). DFT calculations show that the Ccarbene-Si bond in 3 is formed by the donation of the lone pair of electrons on the Ccarbene atom to the SiI2 moiety, while the π-back-bonding of the lone pair of electrons on the Si atom to the Ccarbene atom is negligible. The presence of the lone pair of electrons on the silicon atom in 3 is also evidenced by its reaction with N3SiMe3 to form the cAAC-silaimine complex [(cAACMe)Si(NSiMe3)I2] (4). Compound 3 reacted with IiPrMe (:C{N(iPr)CMe}2) in n-hexane to form the NHC-cAAC-silyliumylidene iodide [cAACMe(SiI)IiPrMe]I (5), which was then reacted with two equivalents of KC8 in toluene to furnish [cAACMeSi(IiPrMe)] (6). The experimental and theoretical studies suggest that 6 can be described as a bent silaallene with a perturbed electronic structure, which can be attributed to the different donor-acceptor properties of cAACMe and IiPrMe. Compounds 3-6 were elucidated by NMR spectroscopy, X-ray crystallography, and theoretical studies.

Reactivity Study of a Pyridyl-1-azaallylgermanium(I) Dimer: Synthesis of Heavier Ether and Ester Analogues of Germanium.

The reactivity study of a pyridyl-1-azaallylgermanium(I) dimer LGe-GeL [1; L = N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)] with different stoichiometric ratios of elemental selenium and tellurium is described. The reactions of 1 with 1 equiv of selenium and tellurium afforded the first examples of heavier ether analogues of germanium, bis(germylene) selenide and telluride LGe(µ-E)GeL [E = Se (2) and Te (3)], respectively. Meanwhile, the reactions of 1 with 2 equiv of selenium and tellurium gave the heavier ester analogues LGe═E(µ-E)GeL [E = Se (4) and (5)]. All compounds have been characterized by X-ray crystallography and multinuclear NMR spectroscopy.

Synthesis and characterization of an octanuclear copper(I) methanediide cluster.

The reaction of [K{CH((i)Pr2P=S)2(C9H6N-2)}]n (1) with one equivalent of CuCl in THF afforded a rare octanuclear copper(I) methanediide cluster (3). The structure of compound 3 as determined by X-ray crystallography was found to have eight copper atoms that form a Gyrobifastigium (J26).

Synthesis of hetero-binuclear complexes from bisgermavinylidene.

Bisgermavinylidene [(Me3SiN═PPh2)2C═Ge→Ge═C(PPh2═NSiMe3)2] (1) has been used as a source of unstable germavinylidene for the synthesis of a series of heterobinuclear complexes. The reaction of 1 with stoichiometric amounts of transition metal chlorides MCl2 (M = Mn, Fe) yielded [(Me3SiN═PPh2)2(GeCl)CMn(µ-Cl)]2 (2) and [(Me3SiN═PPh2)2(GeCl)CFeCl] (3), respectively. Treatment of 1 with Me3SiN3 gave the [2 + 3] cycloaddition product [(Me3SiN═PPh2)2CGeN(SiMe3)N═N] (4). While similar reaction of 1 with ((n)Bu)3SnN3 ((n)Bu = n-butyl) and water-borane adduct H2O → B(C6F5)3 afforded the 1,2-addition products [(Me3SiN═PPh2){((n)Bu)3Sn}CPPh2NSiMe3GeN3] (5) and [HC(PPh2═NSiMe3)2Ge(OH)B(C6F5)3] (6), respectively. The results suggested that the germanium-carbon bond in germavinylidene is capable of forming addition reaction products. The X-ray structures of 2-6 have been determined.

Synthesis and structural characterization of a tin analogue of allene.

The reaction of [MgC(PPh(2)═S)(2)(THF)](2) (1; THF = tetrahydrofuran) with 1 equiv of SnCl(4) in THF afforded a novel tin analogue of allene [Sn{C(PPh(2)═S)(2)}(2)] (2). The structure of compound 2 has been characterized by X-ray crystallography and NMR spectroscopy.