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.

A donor-supported silavinylidene and silylium ylides: boroles as a flexible platform for versatile Si(ii) chemistry.

Electron-deficient, -aromatic 2,5-disilyl boroles are shown to be a flexibly adaptive molecular platform with regards to SiMe mobility in their reaction with the nucleophilic donor-stabilised precursor dichloro silylene SiCl(IDipp). Depending on the substitution pattern, selective formation of two fundamentally different products of rivalling formation pathways is achieved. Formal addition of the dichlorosilylene gives the 5,5-dichloro-5-sila-6-borabicyclo[2.

Linear and Bent Cp* Si: Reversible Phase Transition of a Key Molecule.

The solid-state structure of decamethylsilicocene Cp* Si with a bent and a linear molecule in the same unit cell was so far considered an exception in relation to the structures of its all-bent heavier analogues Cp* E with E=Ge, Sn, Pb. Here, we present the solution to this conundrum by reporting a low-temperature phase, where all three symmetrically independent molecules are present in a bent formation. This reversible enantiotropic phase transition occurs in the temperature range between 80 K and 130 K and provides a rationale for the unexpected linear molecule based in entropy beyond hand-waving explanations such as electronic reasons or packing effects.

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).

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.

Isolation and Properties of the Long Elusive Deep Blue Soluble [K {(N Bu) S} ] Cage Radical.

The reaction of potassium metal with sulfurtriimide S(N Bu) (II) gives the long elusive deep blue cage radical [K {(N Bu) S} ] (1_K) that crystallizes at -35 °C from toluene solution. The subsequent physical characterization via X-ray structure analysis, UV/Vis-, and EPR spectroscopy from solution reveals the existence of one unpaired electron delocalized within the whole cage, i.e.

Borole-based half-sandwich complexes of germanium and tin.

The synthesis and initial observations regarding the reactivity of borole-based half-sandwich complexes with apical divalent group 14 elements germanium and tin are described. The 2,5-disilylborole substitution pattern allows their access salt metathesis of the respective borole dianions.

A Boratafulvene.

Structurally authenticated free B-alkyl boroles are presented and electronic implications of alkyl substitution were assessed. Deprotonation of a boron-bound exocyclic methyl group in a B-methyl borole yields the first 5-boratafulvene anion-an isomer to boratabenzene. Boratafulvene was structurally characterized and its electronic structure probed by DFT calculations.

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.

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) ].

A Neutral Silicon(II) Half-Sandwich Compound.

Metathesis reaction of a dilithio borole dianion, a cyclic π-ligand isoelectronic to ubiquitous cyclopentadienyls, with two equivalents of "silicocenium" cation [Cp*Si] as a source of low-valent Si(II), cleanly gives a borole half-sandwich π-complex of Si(II) and silicocene. The resulting half-sandwich complex is a neutral isoelectronic analogue to the iconic silicocenium cation and features the rare structural motif of an apical silicon(II) atom with an energetically high lying lone pair of electrons that is shown to be accessible for coordination chemistry toward tungsten carbonyl. Protonation at the Si(II) atom with [H(OEt)][Al{OC(CF)}] induces formal oxidation, and the compound rearranges to incorporate the Si atom into the carbocyclic base to give an unprecedented cationic 5-sila-6-borabicyclo[2.

A Cationic NHC-Supported Borole.

This work describes the synthesis and characterization of a highly reactive cationic borole. Halide abstraction with Li{Al[OC(CF ) ] } from the NHC-chloroborole adduct yields the first stable NHC-supported 1-( NHC)-2,5-(SiMe ) -3,4-(Ph*) -borole cation. Electronically, it features both a five-membered cyclic conjugated 4 π-electron system and a cationic charge and thus resembles the yet elusive cyclopentadienyl cation.

2,5-Bis-trimethylsilyl substituted boroles.

This manuscript includes a comprehensive study of the synthesis and spectroscopic features of 2,5-disilyl boroles. Reacting boron trichloride BCl3 with 2,3-Ph*2-1,4-(SiMe3)2-1,4-dilithiobuta-1,3-diene (Ph* = 3,5-t-Bu2(C6H3)) allowed reliable access to 1-Chloro-2,5-(SiMe3)2-3,4-(Ph*)2-borole in good yields (60%). Unlike 2,3,4,5-tetraphenyl haloboroles, this 2,5-bis-trimethylsilyl substituted chloroborole is thermally stable in solution to up to 130 °C.

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).

Activation of Protic, Hydridic and Apolar E-H Bonds by a Boryl-Substituted Ge Cation.

The synthesis of a boryl-substituted germanium(II) cation, [Ge{B(NDippCH) }(IPrMe)] , (Dipp=2,6-diisopropylphenyl) featuring a supporting N-heterocyclic carbene (NHC) donor, has been explored through chloride abstraction from the corresponding (boryl)(NHC)GeCl precursor. Crystallographic studies in the solid state and UV/Vis spectra in fluorobenzene solution show that this species dimerizes under such conditions to give [(IPrMe){(HCNDipp) B}Ge=Ge{B(NDippCH) }(IPrMe)] (IPrMe = 1,3-diisopropyl-4,5-dimethylimidazolin-2-ylidene), which can be viewed as an imidazolium-functionalized digermene. The dimer is cleaved in the presence of donor solvents such as [D ]thf or [D ]pyridine, to give monomeric adducts of the type [Ge{B(NDippCH) }(IPrMe)(L)] .

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).

A Neutral "Aluminocene" Sandwich Complex: η - versus η -Coordination Modes of a Pentaarylborole with ECp* (E=Al, Ga; Cp*=C Me ).

The pentaaryl borole (Ph*C) BXyl [Ph*=3,5-tBu (C H ); Xyl =3,5-(CF ) (C H )] reacts with low-valent Group 13 precursors AlCp* and GaCp* by two divergent routes. In the case of [AlCp*] , the borole reacts as an oxidising agent and accepts two electrons. Structural, spectroscopic, and computational analysis of the resulting unprecedented neutral η -Cp*,η -[(Ph*C) BXyl ] complex of Al revealed a strong, ionic bonding interaction.

Electronic Push-Pull Modulation by Peripheral Substituents in Pentaaryl Boroles.

Establishing access to a bulky tetraaryl dilithiobutadiene (Ph*C) Li (Ph*=3,5-tBu (C H )) allowed for the synthesis of five-membered heterocycles with incorporated main-group elements. Along with an amino borole, a set of substituted pentaaryl boroles (Ph*C) BAr has been synthesized. The examination of their absorption spectra and computational studies by means of DFT granted insight into the influence of peripheral substituents on the electronic features of the parent pentaphenyl borole (PhC) BPh.

Reductive Elimination and Oxidative Addition of Hydrogen at Organostannylium and Organogermylium Cations.

Bulkily substituted organodihydrogermylium and -stannylium cations [Ar*EH ] (E=Ge, Sn; Ar*=2,6-Trip C H , Trip=2,4,6-triisopropylphenyl) were characterized as salts of the weakly coordinating perfluorinated alkoxyaluminate anion [Al{OC(CF ) } ] . At room temperature, the stannylium cation liberates hydrogen to generate the low valent organotin cation [Ar*Sn] . In contrast, the dihydrogermylium cation transfers the hydrogen atoms to an aryl moiety of the terphenyl ligand and oxidatively adds either hydrogen under an atmosphere of hydrogen or a sp CH unit of the 1,2-difluorobenzene solvent.

PNacPNacE: (E = Ga, In, Tl) - monomeric group 13 metal(i) heterocycles stabilized by a sterically demanding bis(iminophosphoranyl)methanide.

The salt metathesis reaction of the sterically demanding bis(iminophosphoranyl)methanide alkali metal complexes LM (L = HC(PhP[double bond, length as m-dash]NDip), Dip = 2,6-PrCH; M = Li, Na, K) with "GaI", InBr or TlBr afforded the monomeric group 13 metal(i) complexes LE:, E = Ga (1), In (2) and Tl (3) in moderate yields, and small quantities of LGaI4 in the case of Ga, respectively. The molecular structures of LE: 1-3 from X-ray single crystal diffraction show them to contain puckered six-membered rings with N,N'-chelating methanide ligands and two-coordinated metal(i) centres. Reduction reactions of LAlI5, prepared by iodination of LAlMe, were not successful and no aluminium(i) congener could be prepared so far.

Structural snapshots of concerted double E-H bond activation at a transition metal centre.

Bond activation at a transition metal centre is a key fundamental step in numerous chemical transformations. The oxidative addition of element-hydrogen bonds, for example, represents a critical step in a range of widely applied catalytic processes. Despite this, experimental studies defining steps along the bond activation pathway are very rare.

Low-Valent Lead Hydride and Its Extreme Low-Field H NMR Chemical Shift.

Although hydrides of the group 14 elements are well-known as versatile starting materials in many chemical transformations, a hydride of lead in oxidation state II is so far unknown. In this work, we finally complete the jigsaw puzzle by reporting the isolation of the first low valent organolead hydride. The thermolabile dimeric organolead hydride was synthesized at low temperature and features a hydride H NMR signal (in solution 35.

Reductive Dehydrogenation of a Stannane via Multiple Sn-H Activation by Frustrated Lewis Pairs.

A bulky substituted stannane Ar*SnH (Ar*=2,6-(2',4',6'-triisopropylphenyl)phenyl) was treated with the well-known frustrated Lewis pair (FLP) PtBu /B(C F ) in varying stoichiometries. To some degree, hydride abstraction and adduct formation is observed, leading to [Ar*SnH (PtBu )] which is rather unreactive toward further dehydrogenation. In a competing process, the FLP proved to be capable of completely striping-off hydrogen and hydrides to generate the first cationic phosphonio-stannylene [Ar*Sn(PtBu )] .