Terphenyl-Ge as μ-Ge-bis(hexahapto-Trip) Bridging Ligand to Form a New Transition Metal-Only Chelating Lewis Base.

Terphenylgermanium Ar*Ge [Ar*=CH(2,6-Trip), Trip=2,4,6-CHiPr] was found to act as a novel μ-Ge-bis(hexahapto-Trip) bridging ligand. Deprotonated terphenyl germanium trihydride [Li(thf)][Ar*GeH] (1) undergoes reductive elimination and transfer of hydrogen in reaction with dimeric [(COD)RhCl] to yield the dinuclear complex [Ar*GeRh(COE)RhCl(COD)] (2). Subsequent chloride abstraction from compound 2 using Na[BAr ] or Li[Al(OBu)] results in the cationic complexes [Ar*GeRh(COE)Rh(COD)][WCA] (3) {WCA: [BAr ] (Ar=CH-3,5-(CF)), [Al(OBu)]}.

Formally Zerovalent Bis(arene) Germylene Complexes of Zirconium and Hafnium.

Tetrachlorides of zirconium and hafnium form adducts (2, 3) with an intramolecular germylene phosphine Lewis pair. Two electron reduction treating the adducts with [NacnacMg] gives the low-valent metal complexes (4, 5) featuring η-Trip coordination at the Zr(II) and Hf(II) metal atom. Reduction of the M(II)-complexes gives the zerovalent metal complexes of zirconium (6) and hafnium (7), which have been structurally characterized.

Germaborene reactivity study - addition of carbon nucleophiles, cycloaddition reactions, coordination chemistry.

NHC substituted germaborenium cation 2 was synthesized directly in reaction of bromo-substituted germaborene 1b with NHC. The adamantyl isonitrile substituted germaborenium cation 4 was obtained stepwise: substitution of the chloride atom against adamantyl isonitrile at the B-Cl unit in 1a, simultaneous migration of the chloride to the germanium atom followed by chloride abstraction using Na[BAr ] gives the germaborenium cation 4. Substitution of the bromide atom in 1b against carbon monoxide followed by bromide abstraction using Ag[Al(OBu)] leads to compound 6 exhibiting a B[double bond, length as m-dash]C double bond substituted at the boron atom by a germylium cation.

Synthesis and Investigation of a Soluble Distannene with no Trans-Bent Angle or Twisting in the Solid-State.

By treating KSiPr with Sn[N(SiMe)] the distannene Sn(TIPS) (TIPS=SiPr) is formed in a metathesis reaction. The crystal structure analysis of Sn(TIPS) reveals a planar arrangement of the substituents in the solid-state and hence the second planar alkene like distannene of its kind. Due to the TIPS substituents, Sn(TIPS) is well soluble in all commonly used organic solvents, opening the door for various analytics and reactivity studies.

Synthesis of Cobalt-Tin and -Lead Tetrylidynes-Reactivity Study of the Triple Bond.

Tetrylidynes [TbbSn≡Co(PMe ) ] (1 a) and [TbbPb≡Co(PMe ) ] (2) (Tbb=2,6-[CH(SiMe ) ] -4-(t-Bu)C H ) are accessed for the first time via a substitution reaction between [Na(OEt )][Co(PMe ) ] and [Li(thf) ][TbbEBr ] (E=Sn, Pb). Following an alternative procedure the stannylidyne [Ar*Sn≡Co(PMe ) ] (1 b) was synthesized by hydrogen atom abstraction using AIBN from the paramagnetic hydride complex [Ar*SnH=Co(PMe ) ] (4) (AIBN=azobis(isobutyronitrile)). The stannylidyne 1 a adds two equivalents of water to yield the dihydroxide [TbbSn(OH) CoH (PMe ) ] (5).

Authentic Sn═B-Double Bonds in Polar Stannaborene Derivatives.

We report on the synthesis of an authentic Sn═B-moiety realized in a stannaborenyl anion and stannaborenium cation. Starting with an oxidative addition of boron tribromide to a stannylene-phosphine Lewis pair [-CH(Ar*BrSn-BBr-PPh)] () [Ar* = CH(2,6-Trip), Trip = 2,4,6-CHPr] was synthesized. Reduction of with magnesium yields the Grignard-type stannaborene [-CH(Ar*Sn═B{PPh}MgBr{thf})] () featuring a Sn═B double bond and a B-Mg interaction.

Stiba-, Arsa- and Phosphastannenes: Syntheses and Reactivities.

A facile synthesis for unprecedented stibastannene (10) featuring a Sn=Sb-double bond together with the homologous arsa- (9) and phosphastannenes (8) is presented. Chloride abstraction from respective stannyl pnictinidenes [E=P (5), As (6), Sb (7)], which were made accessible by reduction of ECl addition products at an intramolecular phosphine-stabilized stannylene, gave the pnictastannenes in moderate yields. The pnictastannenes coordinate Pd(PPh ) fragments (12-14) and the phosphastannene forms also a nickel coordination compound with the Ni(PPh ) -fragment (11).

Boradigermaallyl: (4+3) Cycloaddition-Initiated Boron Insertion into Benzene.

The 2π electron 1,3-dipole boradigermaallyl, valence-isoelectronic to an allyl cation, is synthesized from a bis(germylene). It reacts with benzene at room temperature by insertion of a boron atom into the benzene ring. Computational investigation of the mechanism shows the boradigermaallyl reacting with a benzene molecule in a concerted (4+3) or [π4s+π2s] cycloaddition reaction.

Heavy metalla vinyl-cations show metal-Lewis acid cooperativity in reaction with small molecules (NH, NH, HO, H).

Halide abstraction from tetrylidene complexes [TbbE(Br)IrH(PMe)] [E = Ge (1), Sn (2)] and [Ar*E(Cl)IrH(PMe)] gives the salts [TbbEIrH(PMe)][BAr ] [E = Ge (3), Sn (4)] and [Ar*EIrH(PMe)][BAr ] [E = Ge (3'), E = Sn (4')] (Tbb = 2,6-[CH(SiMe)]-4-(-Bu)CH, Ar* = 2,6-TripCH, Trip = 2,4,6-triisopropylphenyl). Bonding analysis suggests their most suitable description as metalla-tetrela vinyl cations with an Ir[double bond, length as m-dash]E double bond and a near linear coordination at the Ge/Sn atoms. Cationic complexes 3 and 4 oxidatively add NH, NH, HO, HCl, and H selectively to give: [TbbGe(NH)IrH(PMe)][BAr ] (5), [TbbE(NHNH)IrH(PMe)][BAr ] [E = Ge (7), Sn (8)], [TbbE(OH)IrH(PMe)][BAr ] [E = Ge (9), Sn (10)], [TbbE(Cl)IrH(PMe)][BAr ] [E = Ge (11a), Sn (12a)], [TbbGe(H)IrH(PMe)][BAr ] (13), [TbbSn(μ-H)Ir(PMe)][BAr ] (14), and [TbbSn(H)IrH(PMe)][BAr ] (15).

Molecular Ln(III)-H-E(II) Linkages (Ln=Y, Lu; E=Ge, Sn, Pb).

Following the alkane-elimination route, the reaction between tetravalent aryl tintrihydride Ar*SnH and trivalent rare-earth-metallocene alkyls [Cp* Ln(CH{SiMe } )] gave complexes [Cp* Ln(μ-H) SnAr*] implementing a low-valent tin hydride (Ln=Y, Lu; Ar*=2,6-Trip C H , Trip=2,4,6-triisopropylphenyl). The homologous complexes of germanium and lead, [Cp* Ln(μ-H) EAr*] (E = Ge, Pb), were accessed via addition of low-valent [(Ar*EH) ] to the rare-earth-metal hydrides [(Cp* LnH) ]. The lead compounds [Cp* Ln(μ-H) PbAr*] exhibit H/D exchange in reactions with deuterated solvents or dihydrogen.

Hydridotetrylene [Ar*EH] (E = Ge, Sn, Pb) coordination at tantalum, tungsten, and zirconium.

In a reaction of tantalocene trihydride with the low valent aryl tin cation [Ar*Sn(CH)][Al(OC{CF})] (1a) the hydridostannylene complex [CpTaH-Sn(H)Ar*][Al(OC{CF})] (2) was synthesized. Hydride bridged adducts [CpWHEAr*][Al(OC{CF})] (E = Sn 3a, Pb 3b) were isolated as products of the reaction between CpWH and cations [Ar*E(CH)][Al(OC{CF})] (E = Sn 1a, Pb 1b). The tin adduct 3a exhibits a proton migration to give the hydridostannylene complex [CpW(H)[double bond, length as m-dash]Sn(H)Ar*][Al(OC{CF})] 4a.

Reactivity of organogermanium and organotin trihydrides.

The organogermanium and organotin trihydrides (TbbEH) [E = Ge (3), Sn (7)] with the Tbb substituent were synthesized by hydride substitution (Tbb = 2,6-[CH(SiMe)]-4-(-Bu)CH). Deprotonation of the organoelement trihydrides 3 and 7 was studied in reaction with bases MeLi, BnK and LDA (Bn = benzyl, LDA = lithium diisopropylamide) to yield the deprotonation products (8-11) as lithium or potassium salts. Hydride abstraction from TbbSnH using the trityl salt [PhC][Al(OC{CF})] gives the salt [TbbSnH][Al(OC{CF})] (12) which was stabilized by thf donor ligands [TbbSnH(thf)][Al(OC{CF})] (13).

Carbocyclic pincer carbene complexes of ruthenium: syntheses and reversible hydrogenation.

The ruthenium carbene pincer complex 2 was synthesized treating the benzo annulated cycloheptatriene bisphosphine 1 with RuCl. Addition of three equivalents of hydrogen to the carbocyclic carbene complex 2 was achieved in reaction of 2 with hydrogen at elevated temperatures. Hydrogenated complex 4, exhibiting a rigid chair conformation in solution, was dehydrogenated by heating a toluene solution of complex 4 to reflux for 5-7 d.

Phosphine-Stabilized Pnictinidenes.

The reaction of the intramolecular germylene-phosphine Lewis pair (o-PPh )C H GeAr* (1) with Group 15 element trichlorides ECl (E=P, As, Sb) was investigated. After oxidative addition, the resulting compounds (o-PPh )C H (Ar*)Ge(Cl)ECl (2: E=P, 3: E=As, 4: E=Sb) were reduced by using sodium metal or LiHBEt . The molecular structures of the phosphine-stabilized phosphinidene (o-PPh )C H (Ar*)Ge(Cl)P (5), arsinidene (o-PPh )C H (Ar*)Ge(Cl)As (6) and stibinidene (o-PPh )C H (Ar*)Ge(Cl)Sb (7) are presented; they feature a two-coordinate low-valent Group 15 element.

Phosphine-Stabilized Germasilenylidene: Source for a Silicon-Atom Transfer.

A phosphine-stabilized germasilenylidene is synthesized following the pathway of SiCl oxidative addition at a germylene-phosphine Lewis pair. Low-temperature reduction using {(Nacnac)Mg} resulted in a chlorosilylene intermediate and finally a molecule exhibiting a Ge═Si: motif. Inside the chelating phosphine-germylene, a low-valent silicon atom is stabilized and was transferred to diazabutadiene to give N-heterocyclic silylenes.

Low valent lead and tin hydrides in reactions with heteroallenes.

Low valent organoelement hydrides of tin and lead, [(Ar*SnH)] and [(Ar*PbH)], were reacted with diorganocarbodiimide and adamantylisocyanate to give products of hydroelementation reactions. Carbon dioxide also reacts with both low valent hydrides, but a reaction product was only characterized in the tin hydride case. A hydride was transferred to the carbon atom and the formed formate anion [HCO] shows coordination at two tin atoms.

Synthesis and Hydrogenation of Heavy Homologues of Rhodium Carbynes: [(Me P) (Ph P)Rh≡E-Ar*] (E=Sn, Pb).

Tetrylidynes [(Me P) (Ph P)Rh≡SnAr*] (10) and [(Me P) (Ph P)Rh≡PbAr*] (11) are accessed for the first time via dehydrogenation of dihydrides [(Ph P) RhH SnAr*] (3) and [(Ph P) RhH PbAr*] (7) (Ar*=2,6-Trip C H , Trip=2,4,6-triisopropylphenyl), respectively. Tin dihydride 3 was either synthesized in reaction of the dihydridostannate [Ar*SnH ] with [(Ph P) RhCl] or via reaction between hydrides [(Ph P) RhH] and  [(Ar*SnH) ]. Homologous lead hydride [(Ph P) RhH PbAr*] (7) was synthesized analogously from [(Ph P) RhH] and  [(Ar*PbH) ].

Tetryl-Tetrylene Addition to Phenylacetylene.

Phenylacetylene adds [Ar*GeH -SnAr'], [Ar*GeH -PbAr'] and [Ar'SnH -PbAr*] at rt in a regioselective and stereoselective reaction. The highest reactivity was found for the stannylene, which reacts immediately upon addition of one equivalent of alkyne. However, the plumbylenes exhibit addition to the alkyne only in reaction with an excess of phenylacetylene.

Germaborenes: Borylene Transfer Agents for the Synthesis of Iminoboranes.

Halide and phenyl substituted germaborenes were shown to react with azides at room temperature and transfer a borylene moiety to give iminoboranes. This iminoborane synthesis based on a borylene transfer route was investigated computationally in the case of the phenyl substituted germaborene.

Conformation controlled stepwise hydride shuffling from the metal to the ligand backbone.

The benzo annulated cycloheptatriene PCP pincer ruthenium hydrido dicarbonyl complex syn-2 was prepared in one step by treatment of the ligand 1 with Ru3(CO)12. Protonation of syn-2 with the superacid [H(Et2O)2][BArF24] {[BArF24]- = tetrakis[bis(trifluoromethyl)phenyl]borate} initiates the highly stereoselective hydrogenation of one of the double bonds in the cycloheptatriene backbone. This results in the formation of the pentacoordinate cationic 16-electron dicarbonyl ruthenium complex 3.

Ge=B π-Bonding: Synthesis and Reversible [2+2] Cycloaddition of Germaborenes.

Phosphine-stabilized germaborenes featuring an unprecedented Ge=B double bond with short B⋅⋅⋅Ge contacts of 1.886(2) (4) and 1.895(3) Å (5) were synthesized starting from an intramolecular germylene-phosphine Lewis pair (1).

Hydridoorganostannylene Coordination: Group 4 Metallocene Dichloride Reduction in Reaction with Organodihydridostannate Anions.

Organodihydridoelement anions of germanium and tin were reacted with metallocene dichlorides of Group 4 metals Ti, Zr and Hf. The germate anion [Ar*GeH ] reacts with hafnocene dichloride under formation of the substitution product [Cp Hf(GeH Ar*) ]. Reaction of the organodihydridostannate with metallocene dichlorides affords the reduction products [Cp M(SnHAr*) ] (M=Ti, Zr, Hf).

Low valent lead hydride chemistry: hydroplumbylation of phenylacetylene and 1,1-dimethylallene.

Hydroplumbylation reactions of the low valent organolead hydride [(Ar*PbH)2] with phenylacetylene and 1,1-dimethylallene are presented. A vinyl plumbylene was isolated in the case of the alkyne reaction exhibiting a down field NMR signal for the CH unit attached to the low valent heavy atom. 1,1-Dimethylallene affords formation of an allyl plumbylene.

Deprotonation of Organogermanium and Organotin Trihydrides.

Terphenyltin and terphenylgermanium trihydrides were deprotonated in reaction with strong bases, such as LiMe, LDA, or KBn. In the solid state, the Li salts of the germate anion and exhibit a Li-Ge contact. In the Li salt of the dihydridostannate anion , the Li cation is not coordinated at the tin atom instead an interaction of the Li cation with the hydride substituents was found.