Germylene Ge Research Articles

Insertion Behavior of Dialkylgermylene Ge(FluTMS)2 in Different E-X σ Bonds (E = Au, Si, Ge, Sn) and Its Relevance for Germanium Cluster Formation.

We present the insertion behavior of the alkyl-substituted germylene Ge(FluTMS)2 in different E-X σ bonds (E = Au, Si, Ge, Sn), first with the isolation of the germylgold complex (FluTMS)2Ge(Cl)AuPPh3. Afterward, the oxidative addition of GeCl4 to Ge(FluTMS)2 gives the digermane (FluTMS)2Ge(Cl)GeCl3, followed by a reductive elimination of GeCl2 and the formation of the oxidation product (FluTMS)2GeCl2. A comparable behavior is observed, with the homologues ECl4 (E = Si, Sn) stopping at different steps of the reaction. The formation of the germylgermylene (FluTMS)2Ge(Cl)GeCl starting from Ge(FluTMS)2 and GeCl2·dioxane is also spectroscopically observable, followed by ligand rearrangements to the tetramer [FluTMSGeCl]4. Adding a phosphine as the Lewis base has a direct influence on the stability and structure of (FluTMS)2Ge(Cl)GeCl, leading to the formation of FluTMSGeCl·PEt3 as a stable product. Subsequent investigations of Ge(FluTMS)2 with a metastable Ge(I)Br solution show that at a ratio of 6:1 GeBr/Ge(FluTMS)2 the alkyl-substituted germylene no longer acts as a redox-active agent but as a cluster building block. This link and the involvement of a germylene in insertion reactions give an indication of how the construction or expansion of Ge cluster species can operate.

A Phosphanyl Phosphagermene and its Reactivity.

Reaction of a nucleophilic germylene Ge[CH(SiMe3)2]2 with the phosphanyl phosphaketene [{(H2C)(NDipp)}2P]PCO induces decarbonylation to form a phosphanyl phosphagermene [{(H2C)(NDipp)}2P]P=Ge[CH(SiMe3)2]2 (1; Dipp=2,6-diisopropyl-phenyl). Addition of CO2 or MeCN to 1 results in [3+2]-cycloaddition reactions to afford five-membered heterocycles. This mode of reactivity is reminiscent of that observed for frustrated Lewis pairs, with the pendant phosphanyl group acting as a base and the germanium center as a Lewis acid. Contrastingly, 1,2-addition across the P=Ge bond was observed when using ammonia, small primary amines (NH2 nP), or metal complexes (e. g. Au(PPh3)Cl and ZnEt2). These latter reactions allow for the one-step synthesis of metal phosphide complexes.

A neutral germanium-centred hard and soft lewis superacid and its unique reactivity towards hydrosilanes.

The germanium-centred Lewis superacid Ge(pinF)2 (1) was isolated as acetonitrile mono-adduct 1·MeCN and thoroughly characterized by NMR spectroscopy, X-ray crystallography and quantum chemical calculations. Ion abstraction and NMR experiments revealed the hard as well as soft Lewis superacidic nature of 1·MeCN. The title compound readily activates hydrosilanes such as Et3SiH, which is not feasible for its harder silicon homologue 2·MeCN, and even reacts with Et3SiF. The strongly coordinating acetonitrile could be abstracted by B(C6F5), giving the donor-free Ge(pinF)2 (1) and Si(pinF)2 (2) which are Lewis superacids. Unlike 1·MeCN, the donor-free 1 efficiently catalyses hydrosilylation of α-methylstyrene by Et3SiH. For this process, an inverse temperature dependence was observed, i.e. a complete conversion was achieved rapidly when the reaction was cooled to -35 °C, but the reaction stopped at elevated temperatures. Mechanistic investigations, including stoichiometric experiments and quantum chemical calculations, outlined the formation of germylene Ge(pinF) (3), which acts as the active catalyst. The germylene is formed by reductive elimination of the silylated pinacol from the hydrogermane intermediate, which is obtained by the initial reaction of 1 with Et3SiH. The inverse temperature dependence of the catalytic reaction could be explained by low entropy associated with the complexation of two cooperating germylenes and the substrates. With this example we introduce an in situ generated Lewis acidic germylene complex for catalytic hydrosilylation of olefins and again exemplify the great potential of main-group-element-based complexes in catalysis.

Interaction of germanium analogue of organic isonitrile with Cu(I) imide in side-on mode.

[NHC → GeN(Ar)Cu2NAr]2, the formal adduct of germanium analogue of organic isonitrile [GeNAr] with Cu(I) imide [(Cu2NAr)2] (Ar = 2,6-iPr2C6H3) was prepared from the N-heterocyclic carbene (NHC) stabilized acyclic germylene Ge[N(H)Ar]2 by reacting with two equivalents of nBuLi and CuCl(PPh3)3. As elucidated by X-ray crystal structural characterization, the two separated [GeNAr] moieties interacted with [(Cu2NAr)2] core in the side-on mode.

Reactivity of O,N-heterocyclic germylene and stannylene towards μ-dithio-bis(tricarbonyliron)

Abstract Synthesis and single-crystal X-ray diffraction study (SC-XRD) of the O,N-heterocyclic germylene Ge(PhAp) (1) containing chelate 4,6-di-tert-butyl-N-phenyl-o-amidophenolate ligand (PhApH2, where Ap – o-amidophenolate) are reported. Germylene 1 demonstrates a monomeric structure in contrast to earlier known related stannylene Sn(PhAp) (2) existing as a dimer. Diverse weak intermolecular interactions (Ge…Ge, CH…π(chelate) and Ge…π(arene)) were detected in the crystal packing of germylene 1. Hirshfeld surface analysis has been performed to evaluate such interactions. Reactivity of compounds 1 and 2 towards dithiodiiron hexacarbonyl has been examined. Low-valent germanium(II) and tin(II) centers are readily inserted into S-S bond of dithiodiiron hexacarbonyl with the formation of Fe4(µ4-ES4)(CO)12 (E: Ge(3); Sn(4)) and bis-ligand complexes of tetravalent metals E(PhAp)2. The resulting germanium(IV) and tin(IV) bis-o-amidophenolates were isolated as six-coordinated pyridine adducts E(PhAp)2(Py)2 (E: Ge(5); Sn(6)). All complexes were characterized by SC-XRD.

A Nickel Complex Containing a Pyramidalized, Ambiphilic Pincer Germylene Ligand.

Reaction of N-heterocyclic carbene (NHC)-stabilized PGeP-type germylene Ge{o-(PiPr2 )C6 H4 }2 ⋅Me IiPr (1) (Me IiPr=1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) with Ni(cod)2 gave pincer germylene complex Ni[Ge{o-(PiPr2 )C6 H4 }2 ](Me IiPr) (2), in which the Ge center of 2 is significantly pyramidalized. Theoretical calculation on 2 predicted the ambiphilicity of the germanium center, which was confirmed by reactivity studies. Thus, complex 2 reacted with both Lewis base Me IMe (Me IMe=1,3,4,5-tetramethylimidazol-2-ylidene) and Lewis acid BH3 ⋅SMe2 at the germanium center to afford the adducts Ni[Ge{o-(PiPr2 )C6 H4 }2 ⋅Me IMe](Me IiPr) (3) and Ni[Ge{o-(PiPr2 )C6 H4 }2 ⋅BH3 ](Me IiPr) (4), respectively. Furthermore, the former was slowly converted to dinuclear complex Ni2 [Ge{o-(PiPr2 )C6 H4 }2 ]2 (Me IMe)2 (5) at room temperature. Complex 5 can be regarded as a dimer of the Me IMe analog of 2 with a Ni-Ge-Ge-Ni linkage.

A Germylene Supported by Two 2-Pyrrolylphosphane Groups as Precursor to PGeP Pincer Square-Planar Group 10 Metal(II) and T-Shaped Gold(I) Complexes.

An efficient synthesis of 2-di-tert-butylphosphanylmethylpyrrole (HpyrmPtBu2 ), by treating 2-dimethylaminomethylpyrrole (HpyrmNMe2 ) with tBu2 PH at 135 °C in the absence of any solvent, has allowed the preparation of the new PGeP germylene Ge(pyrmPtBu2 )2 (1), by treating [GeCl2 (dioxane)] with LipyrmPtBu2 , in which the Ge atom is stabilized by intramolecular interactions with one (solid state) or both (solution) of its phosphane groups. Reactions of germylene 1 with Group 10 metal dichlorido complexes containing easily displaceable ligands have led to [MCl{κ3 P,Ge,P-GeCl(pyrmPtBu2 )2 }] [M=Ni (2), Pd (3), Pt (4)], which have an unflawed square-planar metal environment. Treatment of germylene 1 with [AuCl(tht)] (tht=tetrahydrothiophene) rendered [Au{κ3 P,Ge,P-GeCl(pyrmPtBu2 )2 }] (5), which is a rare case of a T-shaped gold(I) complex. The hydrolysis of 5 gave the linear gold(I) derivative [Au(κP-HpyrmPtBu2 )2 ]Cl (6). Complexes 2-5 contain a PGeP pincer chloridogermyl ligand that arises from the insertion of the Ge atom of germylene 1 into a M-Cl bond of the corresponding metal reagent. The bonding in these molecules has been studied by DFT/NBO/QTAIM calculations. These results demonstrate that the great flexibility of germylene 1 makes it a better precursor to PGeP pincer complexes than the previously known germylenes of this type.

Reactions of GeCl2 with the Thiolate LiSC(SiMe3 )3 : From thf Activation to Insertion of GeCl2 Molecules into C-S Bonds.

The reaction system GeCl2 ⋅dioxane/LiSTsi (Tsi=C(SiMe3 )3 ) opens a fruitful area in germanium chemistry, depending on the stoichiometry and solvent used during the reaction. For example, the reaction of GeCl2 ⋅dioxane in toluene with two equivalents of the thiolate gives the expected germylene Ge(STsi)2 in excellent yield. This germylene readily reacts with hydrogen and acetylene, however, in a non-selective way. By using an excess amount of the thiolate and toluene as the solvent, the germanide [Ge(STsi)3 ][Li(thf)] is obtained. Performing the same reaction in thf leads to a C-H activation of thf to give (H7 C4 O)Ge[STsi](μ2 -S)2 Ge[STsi]2 , in which the thf molecule is still intact. Using a sub-stoichiometric amount of the thiolate leads to the heteroleptic compound [ClGe(STsi)]2 and to the insertion product (thf)Ge[S-GeCl2 -Tsi]2 , in which additional GeCl2 molecules insert into the C-S bonds of Ge(STsi)2 . The synthesis and the experimentally determined structures of all compounds are presented together with first reactivity studies of Ge(STsi)2 .

Reversible Carbene Insertion into a Ge-N Bond and Insights into CO and Carbene Substitution Reactions Involving Amidinatogermylenes and Fischer Carbene Complexes.

The formation of the five-membered-ring germylene complexes [M(CO)5 {Ge(tBu2 bzamC(OEt)Me)tBu}] (3M ; M=Cr, W), which occurs readily at room temperature from the germylene Ge(tBu2 bzam)tBu (1tBu ) and Fischer carbenes [M(CO)5 {C(OEt)Me}] (2M ; M=Cr, W), has been found to be reversible. Upon heating at 60 °C, complexes 3M undergo epimerization to an equilibrium mixture of 3M and 3'M . At that temperature, the chromium epimers (but not the tungsten ones) release CO to end in the mixed germylene-Fischer carbene complexes [Cr(CO)4 {C(OEt)Me}{Ge(tBu2 bzam)tBu}] (cis-4Cr and trans-4Cr ). The latter decompose at 120 °C to [Cr(CO)5 {Ge(tBu2 bzam)tBu}] (6Cr ). Because the formation of cis-4Cr and trans-4Cr from 3Cr or 3'Cr requires the presence of free 1tBu and 2Cr in the reaction solutions, the reactions of 1tBu with 2M to give 3M (and 3'M at 60 °C) should be reversible. This proposal has been proven by germylene-exchange crossover reactions in which free 1tBu and [M(CO)5 {Ge(tBu2 bzamC(OEt)Me)CH2 SiMe3 }] (5'M ; M=Cr, W) were formed when complexes 3M were treated at room temperature with the germylene Ge(tBu2 bzam)CH2 SiMe3 (1tmsm ). A clear differential behavior between N-heterocyclic carbenes (NHCs) and amidinatogermylenes (1tBu and 1tmsm ) in their reactivity against group 6 metal Fischer carbene complexes is demonstrated. The higher electron-donor capacity of amidinatogermylenes with respect to NHCs and the bias of the former to get involved in ring expansion processes are responsible for this differential behavior.

From a Diphosphanegermylene to Nickel, Palladium, and Platinum Complexes Containing Germyl PGeP Pincer Ligands.

The PGeP pincer-type germylene Ge(NCH2 PtBu2 )C6 H4 (1) has been used to prepare a family of group 10 metal complexes, namely, [MCl{κ3 P,Ge,P-GeCl(NCH2 PtBu2 )2 C6 H4 }] (M=Ni (2Ni ), Pd (2Pd ), Pt (2Pt )), featuring a chloridogermyl PGeP pincer ligand and a Cl-Ge-M-Cl bond sequence. Their reactivity is not initially centered on the metal atom but on their Ge atom. Complexes 2Ni and 2Pd easily led to the hydrolyzed products [Ni2 Cl2 {μ-(κ3 P,Ge,P-Ge(NCH2 PtBu2 )2 C6 H4 )2 O}], which features a Cl-Ni-Ge-O-Ge-Ni-Cl bond sequence, and [PdCl{κ3 P,Ge,P-Ge(OH)(NCH2 PtBu2 )2 C6 H4 }], which contains a hydroxidogermyl PGeP pincer ligand (2Pt is reluctant to undergo hydrolysis). Simple chloride exchange reactions led to the methoxidogermyl, methylgermyl, and phenylgermyl derivatives [MCl{κ3 P,Ge,P-GeR(NCH2 PtBu2 )2 C6 H4 }] (M=Pd, Pt; R=OMe, Me, Ph). Whereas the palladium complexes [PdCl{κ3 P,Ge,P-GeR(NCH2 PtBu2 )2 C6 H4 }] (R=Me, Ph) reacted with more MeLi or PhLi to give palladium black and GeR2 (NCH2 PtBu2 )2 C6 H4 (R=Me, Ph), similar reactions with the analogous platinum complexes afforded the transmetalation derivatives [PtR{κ3 P,Ge,P-GeR(NCH2 PtBu2 )2 C6 H4 }] (R=Me, Ph). The short length of the CH2 PtBu2 arms of the PGeP pincer ligands forces the metal atoms of all these complexes to be in a very distorted square-planar ligand environment. The reactivity results have been rationalized with theoretical calculations.

MnBrL(CO)4] (L = Amidinatogermylene): Reductive Dimerization, Carbonyl Substitution, and Hydrolysis Reactions

The manganese(I) carbonyl complex [MnBr{Ge(iPr2bzam)tBu}(CO)4] (1; iPr2bzam = 1,3-di(isopropyl)benzamidinate), which contains an amidinatogermylene ligand, reacts with LiPh or LitBu at room temperature undergoing a reductive dimerization process that leads to the manganese(0) dimer [Mn2{Ge(iPr2bzam)tBu}2(CO)8]. This complex and the monosubstituted derivative [Mn2{Ge(iPr2bzam)tBu}(CO)9] have also been prepared by reacting [Mn2(CO)10] with Ge(iPr2bzam)tBu at high temperature (110 °C). These binuclear complexes contain their germylene ligands in axial positions (trans to the Mn–Mn bond). The large volume of the germylene ligand clearly affects the reactivity of complex 1 with neutral two-electron donor reagents, since for bulky reagents, the CO substitution occurs trans to the germylene ligand, as in trans-mer-[MnBrL{Ge(iPr2bzam)tBu}(CO)3] (L = Ge(iPr2bzam)tBu, PMe3), whereas for small reagents, the CO substitution occurs cis to the germylene ligand, as in fac-[MnBr(CNtBu){Ge(iPr2bzam)tBu}(CO)3]. The IR spectra (νCO) of these complexes have confirmed that the germylene Ge(iPr2bzam)tBu is a very strong electron-donating ligand, even stronger than the most basic trialkylphosphanes and N-heterocyclic carbenes. The hydrolysis of complex 1 leads to the salt [iPr2bzamH2][MnBr{Ge(OH)2tBu}(CO)4], the anion of which contains an unprecedented germanato(II) ligand, [Ge(OH)2tBu]−, in cis to the Br atom. This hydrolysis product and its precursor 1 have been tested as catalyst precursors for the electrolytic reduction of CO2, showing no significant activity.

Reactions of m-Terphenyl-Stabilized Germylene and Stannylene with Water and Methanol: Oxidative Addition versus Arene Elimination and Different Reaction Pathways for Alkyl- and Aryl-Substituted Species

Reactions of the divalent germylene Ge(ArMe6)2 (ArMe6 = C6H3-2,6-{C6H2-2,4,6-(CH3)3}2) with water or methanol gave the Ge(IV) insertion product (ArMe6)2Ge(H)OH (1) or (ArMe6)2Ge(H)OMe (2), respectively. In contrast, its stannylene congener Sn(ArMe6)2 reacted with water or methanol to produce the Sn(II) species {ArMe6Sn(μ-OH)}2 (3) or {ArMe6Sn(μ-OMe)}2 (4), respectively, with elimination of ArMe6H. Compounds 1–4 were characterized by IR and NMR spectroscopy as well as by X-ray crystallography. Density functional theory calculations yielded mechanistic insight into the formation of (ArMe6)2Ge(H)OH and {ArMe6Sn(μ-OH)}2. The insertion of an m-terphenyl-stabilized germylene into the O–H bond was found to be catalytic, aided by a second molecule of water. The lowest energy pathway for the elimination of arene from the corresponding stannylene involved sigma-bond metathesis rather than separate oxidative addition and reductive elimination steps. The reactivity of Sn(ArMe6)2 with water or methanol contrasts with ...

Reactions of Alkenes and Alkynes with an Acyclic Silylene and Heavier Tetrylenes under Ambient Conditions

Cycloaddition reactions of the acyclic silylene Si(SAriPr4)2 (AriPr4 = C6H3-2,6(C6H3-2,6-iPr2)2) with a variety of alkenes and alkynes were investigated. Its reactions with the alkynes phenylacetylene and diphenylacetylene and the diene 2,3-dimethyl-1,3-butadiene yielded silacycles (AriPr4S)2Si(CH═CPh) (1), (AriPr4S)2Si(PhC═CPh) (2), and (AriPr4S)2SiCH2CMeCMeCH2 (3) at ambient temperature. The compounds were characterized by X-ray crystallography, 1H, 13C, and 29Si NMR spectroscopy, and IR spectroscopy. No reaction was observed with more substituted alkenes such as propene, (Z)-2-butene, tert-butylethylene, cyclopentene, 1-hexene, or the alkyne bis(trimethylsilyl)acetylene under the same reaction conditions. The germylene Ge(SArMe6)2 and stannylene Sn(SArMe6)2 (ArMe6 = C6H3-2,6(C6H2-2,4,6-Me3)2) analogues of Si(SArMe6)2 displayed no reaction with ethylene. Quantum chemical calculations using model tetrylenes E(SPh)2 (E = Si, Ge, Sn; Ph = C6H5) show that cyclization reactions are endothermic in the case of...

Mechanisms of Reactions of Open-Shell, Heavier Group 14 Derivatives with Small Molecules: n−π* Back-Bonding in Isocyanide Complexes, C–H Activation under Ambient Conditions, CO Coupling, and Ancillary Molecular Interactions†This Award Article summarizes, including more recent results, one of the themes of a lecture presented on March 26th, 2012, at the 243rd Chemical Society National Meeting American in San Diego, CA, in

The main themes of this review are the mechanisms of the reactions of germanium and tin analogues of carbenes with isocyanides, CO, ammonia, and related molecules. The treatment of Ge(Ar(Me6))2 (Ar(Me6) = C6H3-2,6(C6H2-2,4,6-Me3)2) with MeNC or Bu(t)NC afforded 1:1 complexes, but the increase in the electron density at germanium leads to C-H activation at the isocyanide methyl or tert-butyl substituents. For MeNC, the initial adduct formation is followed by a migratory insertion of the MeNC carbon into a Ge-C(ipso) bond of an aryl substituent. The addition of excess MeNC led to sequential insertions of two further MeNC molecules. The third insertion led to methylisocyanide methyl group C-H activation, to afford an azagermacyclopentadienyl species. The Bu(t)NC complex (Ar(Me6))2GeCNBu(t) spontanously transforms into (Ar(Me6))2Ge(H)CN and isobutene with C-H activation of the Bu(t) substituent. The germylene Ge(Ar(Me6))(Ar(Pr(i)4)) [Ar(Pr(i)4) = C6H3-2,6(C6H3-2,6-Pr(i)2)2] reacted with CO to afford α-germyloxyketones. The initial step is the formation of a 1:1 complex, followed by migratory insertion into the Ge-C bond of the Ar(Pr(i)4) ligand to give Ar(Me6)GeC(O)Ar(Pr(i)4). Insertion of a second CO gave Ar(Me6)GeC(O)C(O)Ar(Pr(i)4), which rearranges to afford α-germyloxyketone. No reaction was observed for Sn(Ar(Me6))2 with RNC (R = Me, Bu(t)) or CO. Spectroscopic (IR) results and density functional theory (DFT) calculations showed that the reactivity can be rationalized on the basis of Ge-C (isocyanide or CO) Ge(n) → π* (ligand) back-bonding. The reaction of Ge(Ar(Me6))2 and Sn(Ar(Me6))2 with ammonia or hydrazines initially gave 1:1 adducts. However, DFT calculations show that there are ancillary N-H---N interactions with a second ammonia or hydrazine, which stabilizes the transition state to form germanium(IV) hydride (amido or hydrazido) products. For tin, arene elimination is favored by a buildup of electron density at the tin, as well as the greater polarity of the Sn-C(ipso) bond. Germanium(IV) products were observed upon reaction of Ge(Ar(Me6))2 with acids, whereas reactions of Sn(Ar(Me6))2 with acids did not give tin(II) products. In contrast to reactions with NH3, there is no buildup of negative charge at tin upon protonation, and its subsequent reaction with conjugate bases readily affords the tin(IV) products.

Mechanistic Study of Stepwise Methylisocyanide Coupling and C–H Activation Mediated by a Low-Valent Main Group Molecule

An experimental and DFT investigation of the mechanism of the coupling of methylisocyanide and C-H activation mediated by the germylene (germanediyl) Ge(Ar(Me6))2 (Ar(Me6) = C6H3-2,6(C6H2-2,4,6-Me3)2) showed that it proceeded by initial MeNC adduct formation followed by an isomerization involving the migratory insertion of the MeNC carbon into the Ge-C ligand bond. Addition of excess MeNC led to sequential insertions of two further MeNC molecules into the Ge-C bond. The insertion of the third MeNC leads to methylisocyanide methyl group C-H activation to afford an azagermacyclopentadienyl species. The X-ray crystal structures of the 1:1 (Ar(Me6))2GeCNMe adduct, the first and final insertion products (Ar(Me6))GeC(NMe)Ar(Me6) and (Ar(Me6))GeC(NHMe)C(NMe)C(Ar(Me6))NMe were obtained. The DFT calculations on the reaction pathways represent the first detailed mechanistic study of isocyanide oligomerization by a p-block element species.

A divalent germanium complex of calix[5]arene

The reaction of the germylene Ge[N(SiMe(3))(2)](2) with calix[5]arene yields the first example of a group 14 calix[5]arene complex. The crystal structure of this material has been obtained and contains two calix[5]arene macrocycles held together by a Ge(2)O(2) rhombus.

Ge[N(SiMe2iPr)2]2: Ein neues Germylen und dessen Koordinationschemie führt zu der kürzesten Ge–Co‐Bindung

AbstractGe[N(SiMe2iPr)2]2: A New Germylene and its Coordination Chemistry leads to the Shortest Ge–Co BondThe high temperature reaction of Germanium with HBr, which is used for the synthesis of GeBr leads at a higher reaction pressure to a mixture of GeBr and GeBr2. GeBr2 reacts with the lithiumsalt LiN(SiMe2iPr)2 in good yield to the germylene Ge[N(SiMe2iPr)2]2. Subsequent reaction of this germylene with Co2(CO)8 leads to the germanium cobalt cluster compound {Co(CO)3Ge[N(SiMe2iPr)2]2}2 featuring the shortest Ge–Co bond giving hints to a possibly multiple bonded system.

Heterobimetallic Activation of Dioxygen: Characterization and Reactivity of Novel Cu(I)−Ge(II) Complexes

Reaction of the known germylene Ge[N(SiMe3)2]2 and a new heterocyclic variant Ge[(NMes)2(CH)2] with [L(Me2)Cu]2 (L(Me2) = the beta-diketiminate derived from 2-(2,6-dimethylphenyl)amino-4-(2,6-dimethylphenyl)imino-2-pentene) yielded novel Cu(I)-Ge(II) complexes L(Me2)Cu-Ge[(NMes)2(CH)2] (1a) and L(Me2)Cu-Ge[N(SiMe3)2]2 (1b), which were characterized by spectroscopy and X-ray crystallography. The lability of the Cu(I)-Ge(II) bond in 1a and b was probed by studies of their reactivity with benzil, PPh3, and a N-heterocyclic carbene (NHC). Notably, both complexes are cleaved rapidly by PPh3 and the NHC to yield stable Cu(I) adducts (characterized by X-ray diffraction) and the free germylene. In addition, the complexes are highly reactive with O2 and exhibit chemistry which depends on the bound germylene. Thus, oxygenation of 1a results in scission and formation of thermally unstable L(Me2)CuO2, which subsequently decays to [(L(Me2)Cu)2(mu-O)2], while 1b yields L(Me2)Cu(mu-O)2Ge[N(SiMe3)2]2, a novel heterobimetallic intermediate having a [Cu(III)(mu-O)2Ge(IV)]3+ core. The isolation of the latter species by direct oxygenation of a Cu(I)-Ge(II) precursor represents a new route to heterobimetallic oxidants comprising copper.

Ge(NR 2) 2 (R = SiMe 3) insertion into LAu–Cl bonds

Photoluminescent Au–Ge complexes LAu–GeX(NR 2 ) 2 (X = Cl, F) are formed in reactions of Ge(NR 2 ) 2 (R = SiMe 3 ) with Au(I) complexes. Germylene Ge(NR 2 ) 2 (R = SiMe 3 ) inserts into the Au–Cl bond of LAuCl (L = PPh 3 , PCy 3 , PEt 3 , PMe 2 Ph, PMePh 2 ) giving LAu–GeCl(NR 2 ) 2 ( 1 ). Treatment of [(PPh 3 Au) 3 (μ-O)]BF 4 with Ge(NR 2 ) 2 results in fluoride abstraction from BF 4 - and formation of LAu–GeF(NR 2 ) 2 ( 2 ). Complexes 1 and 2 are photoluminescent and NMR data indicate dynamic behavior in solution most likely as a result of phosphine exchange.

Time-resolved spectroscopic studies of the photochemistry of some diphenylgermylene (Ph2Ge:) precursors

The photochemistry of diphenylbis(trimethylsilyl)germane (2a) and 1,4-dihydro-5-methyl-1,2,3,4,9,9-hexaphenyl-1,4-germanonaphthalene (11) has been studied in solution by steady-state and laser flash photolysis methods with a view to detecting the transient germylene derivative diphenylgermylene (Ph2Ge), which has previously been shown to be the major product of photolysis of 2a and a closely related derivative of 11. Steady-state trapping experiments confirm the formation of Ph2Ge as the major germanium containing primary product in both cases; with 2a, the results indicate that other transient species are also formed in minor yields, including phenyl(trimethylsilyl)germylene (Ph(TMS)Ge, ca. 6%) and diphenyl(trimethylsilyl)germyl radicals (Ph2(TMS)Ge, ≥15%). Laser flash photolysis of 2a in deoxy genated hexane solution yields a complex mixture of overlapping transient absorptions, which is shown to be comprised of Ph2Ge, tetraphenyldigermene (15) and its oligomerization products, and another species with spectral characteristics similar to the Ph2(TMS)Ge radical. The latter has been independently generated by hydrogen abstraction from diphenyl(trimethylsilyl)germane by tert-butoxyl radicals. Compound 11 extrudes Ph2Ge more cleanly and efficiently upon photolysis in solution, yet laser flash photolysis affords excited triplet and triplet-derived species as the only detectable transient products; interpretation of the results for this compound is made difficult by its slow thermal decomposition to 5-methyl-1,2,3,4-tetraphenylnaphthalene. It is concluded that in spite of the fact that both 2a and 11 afford Ph2Ge in high yield upon photolysis, they are poor precursors for study of the species in solution by time-resolved UV–vis methods, owing to the formation of other, more strongly absorbing transient products than Ph2Ge, whose lowest energy absorption is characteristically weak.Key words: germylene, germyl radical, flash photolysis, disilylgermane, photochemistry.