Triple Bonds Between Iron and Heavier Group 15 Elements in AFe(CO)3− (A=As,Sb, Bi) Complexes

Heteronuclear transition‐metal–main‐group‐element carbonyl complexes of AsFe(CO)₃^?, SbFe(CO)₃^?, and BiFe(CO)₃^? were produced by a laser vaporization supersonic ion source in the gas phase, and were studied by mass‐selected IR photodissociation spectroscopy and advanced quantum chemistry methods. These complexes have C_3v structures with all of the carbonyl ligands bonded on the iron center, and feature covalent triple bonds between bare Group 15 elements and Fe(CO)₃^?. Chemical bonding analyses on the whole series of AFe(CO)₃^? (A=N, P, As, Sb, Bi, Mc) complexes indicate that the valence orbitals involved in the triple bonds are hybridized 3d and 4p atomic orbitals of iron, leading to an unusual (dp–p) type of transition‐metal–main‐group‐element multiple bonding. The σ‐type three‐orbital interaction between Fe 3d/4p and Group 15 np valence orbitals plays an important role in the bonding and stability of the heavier AFe(CO)₃^? (A=As, Sb, Bi) complexes.     

Preparation and Characterization of Uranium–Iron Triple‐Bonded UFe(CO)3− and OUFe(CO)3− Complexes

We report the preparation of UFe(CO)₃⁻ and OUFe(CO)₃⁻ complexes using a laser‐vaporization supersonic ion source in the gas phase. These compounds were mass‐selected and characterized by infrared photodissociation spectroscopy and state‐of‐the‐art quantum chemical studies. There are unprecedented triple bonds between U 6d/5f and Fe 3d orbitals, featuring one covalent σ bond and two Fe‐to‐U dative π bonds in both complexes. The uranium and iron elements are found to exist in unique formal U(I or III) and Fe(−II) oxidation states, respectively. These findings suggest that there may exist a whole family of stable df–d multiple‐bonded f‐element‐transition‐metal compounds that have not been fully recognized to date.     

Alkali Metal Covalent Bonding in Nickel Carbonyl Complexes ENi(CO)3−

The alkali metal‐nickel carbonyl anions ENi(CO)₃^? with E=Li, Na, K, Rb, Cs have been produced and characterized by mass‐selected infrared photodissociation spectroscopy in the gas phase. The molecules are the first examples of 18‐electron transition metal complexes with alkali atoms as covalently bonded ligands. The calculated equilibrium structures possess C_3v geometry, where the alkali atom is located above a nearly planar Ni(CO)₃^? fragment. The analysis of the electronic structure reveals a peculiar bonding situation where the alkali atom is covalently bonded not only to Ni but also to the carbon atoms.     

Stable Di‐ and Tri‐coordinated Carbon(II) Supported by an Electron‐Rich β‐Diketiminate Ligand

Complexes of the ubiquitous β‐diketiminates (NacNac) ligands have been reported with most elements of the periodic table, including Group 14 Si, Ge, Sn, and Pb. The striking absence of carbon representatives has been attributed to the extreme electrophilicity of the putative C‐NacNac adducts. An electron enriched 2,4‐(dimethylamino)diketiminato backbone is described, which allowed for the synthesis and isolation of such stable pyrimidin‐1,3‐diium and pyrimidinium‐2‐ylidene salts. Structural and preliminary reactivity studies are reported, including an air‐stable gold complex. An unforeseen original class of stable N‐heterocyclic carbenes and, more generally, the potential of electron‐rich NacNac patterns for taming highly electrophilic centers are showcased.     

CO Oxidation by Group 3 Metal Monoxide Cations Supported on [Fe(CO)4]2−

Infrared photodissociation spectroscopy of mass‐selected heteronuclear cluster anions in the form of OMFe(CO)₅⁻ (M=Sc, Y, La) indicates that all these anions involve an 18‐electron [Fe(CO)₄]²⁻ building block that is bonded with the M center through two bridged carbonyl ligands. The OLaFe(CO)₅⁻ anion is determined to be a CO‐tagged complex involving a [Fe(CO)₄]²⁻[LaO]⁺ anion core. In contrast, the OYFe(CO)₅⁻ anion is characterized to have a [Fe(CO)₄]²⁻[Y(η²‐CO₂)]⁺ structure involving a side‐on bonded CO₂ ligand. The CO‐tagged complex and the [Fe(CO)₄]²⁻[Sc(η²‐CO₂)]⁺ isomer co‐exist for the OScFe(CO)₅⁻ anion. These observations indicate that both the ScO⁺ and YO⁺ cations supported on [Fe(CO)₄]²⁻ are able to oxidize CO to CO₂. Theoretical analyses show that [Fe(CO)₄]²⁻ coordination significantly weakens the MO⁺ bond and decreases the energy gap of the interacting valence orbitals between MO⁺ and CO, leading to the CO oxidation reactions being both thermodynamically exothermic and kinetically facile.     

Kraftkonstanten von Verbindungen des Typs (CH3)3ElCl+X− (El = N,P, As,Sb; X− = SbCl6−)

Force Constants of Compounds of the Type (CH₃)₃ElCl⁺X^?(El = N, P, As, Sb; X^? = SbCl₆^?) For the cations (CH₃)₃NCl⁺ ( 1 ), (CH₃)₃PCl⁺ ( 2 ), (CH₃)₃AsCl⁺ ( 3 ), and (CH₃)₃SbCl⁺ ( 4 ) a normal coordinate analysis using a general valence force field is performed by the method of Fadini. The force constants are discussed. Calculations of the potential energy distribution show, that the skeletal vibrations in 4 are all characteristic vibrations, but there is a strong coupling of vibrations in 1 .     

Highly Selective and Catalytic Oxygenations of C−H and C=C Bonds by a Mononuclear Nonheme High‐Spin Iron(III)‐Alkylperoxo Species

The reactivity of a mononuclear high‐spin iron(III)‐alkylperoxo intermediate [Fe^III(t‐BuL^Urea)(OOCm)(OH₂)]²⁺( 2 ), generated from [Fe^II(t‐BuL^Urea)(H₂O)(OTf)](OTf) ( 1 ) [t‐BuL^Urea=1,1′‐(((pyridin‐2‐ylmethyl)azanediyl)bis(ethane‐2,1‐diyl))bis(3‐(tert‐butyl)urea), OTf=trifluoromethanesulfonate] with cumyl hydroperoxide (CmOOH), toward the C?H and C=C bonds of hydrocarbons is reported. 2 oxygenates the strong C?H bonds of aliphatic substrates with high chemo‐ and stereoselectivity in the presence of 2,6‐lutidine. While 2 itself is a sluggish oxidant, 2,6‐lutidine assists the heterolytic O?O bond cleavage of the metal‐bound alkylperoxo, giving rise to a reactive metal‐based oxidant. The roles of the urea groups on the supporting ligand, and of the base, in directing the selective and catalytic oxygenation of hydrocarbon substrates by 2 are discussed.     

Darstellung von N-Methyl-N-chlornitryl-hexafluorometallaten ON(Cl)CH3+MF6− (M = As,Sb)

Preparation of N-Methyl-N-chlornitryl Hexafluoro Metallates ON(Cl)CH₃⁺MF₆^? (M = As, Sb) . The preparation of ON(Cl)CH₃⁺MF₆^? (M = As, Sb) by methylation of ONCl with CH₃OSO⁺MF₆^? (M = As, Sb) is reported. Both salts were unlimited stable at - 78°C. The nitryl cation which is isoelectronic with acetyl chloride was identified by vibrational spectroscopy as N-chloro-N-hydroxy-methaneiminium cation in the solid state.     

Reaction of Group 15 Trichlorides ECl3 with the Anion [Mo2Cp2(CO)4(μ-PH2)]−; Synthesis and Characterization of the First Complexes Featuring a Hetero μ,η2-PE ligand (E=As,Sb)

An Me ₂ PE tetrahedrane framework is seen in complexes 2 a – c (E=P, As, Sb), which are prepared from the appropriate trichlorides and 1 in THF. The structures of the new antimony- and arsenic-containing compounds 2 b and 2 c have been determined—this is the first structural characterization of complexes with μ,η²-PE heteroligands from elements of Group 15.     

Actinide–Pnictide (An−Pn) Bonds Spanning Non‐Metal,Metalloid, and Metal Combinations (An=U,Th; Pn=P,As, Sb,Bi)

The synthesis and characterisation is presented of the compounds [An(Tren^DMBS){Pn(SiMe₃)₂}] and [An(Tren^TIPS){Pn(SiMe₃)₂}] [Tren^DMBS=N(CH₂CH₂NSiMe₂Bu^t)₃, An=U, Pn=P, As, Sb, Bi; An=Th, Pn=P, As; Tren^TIPS=N(CH₂CH₂NSiPrⁱ₃)₃, An=U, Pn=P, As, Sb; An=Th, Pn=P, As, Sb]. The U?Sb and Th?Sb moieties are unprecedented examples of any kind of An?Sb molecular bond, and the U?Bi bond is the first two‐centre‐two‐electron (2c–2e) one. The Th?Bi combination was too unstable to isolate, underscoring the fragility of these linkages. However, the U?Bi complex is the heaviest 2c–2e pairing of two elements involving an actinide on a macroscopic scale under ambient conditions, and this is exceeded only by An?An pairings prepared under cryogenic matrix isolation conditions. Thermolysis and photolysis experiments suggest that the U?Pn bonds degrade by homolytic bond cleavage, whereas the more redox‐robust thorium compounds engage in an acid–base/dehydrocoupling route.     

Actinide–Pnictide (An−Pn) Bonds Spanning Non‐Metal,Metalloid, and Metal Combinations (An=U,Th; Pn=P,As, Sb,Bi)

The synthesis and characterisation is presented of the compounds [An(Tren^DMBS){Pn(SiMe₃)₂}] and [An(Tren^TIPS){Pn(SiMe₃)₂}] [Tren^DMBS=N(CH₂CH₂NSiMe₂Bu^t)₃, An=U, Pn=P, As, Sb, Bi; An=Th, Pn=P, As; Tren^TIPS=N(CH₂CH₂NSiPrⁱ₃)₃, An=U, Pn=P, As, Sb; An=Th, Pn=P, As, Sb]. The U−Sb and Th−Sb moieties are unprecedented examples of any kind of An−Sb molecular bond, and the U−Bi bond is the first two‐centre‐two‐electron (2c–2e) one. The Th−Bi combination was too unstable to isolate, underscoring the fragility of these linkages. However, the U−Bi complex is the heaviest 2c–2e pairing of two elements involving an actinide on a macroscopic scale under ambient conditions, and this is exceeded only by An−An pairings prepared under cryogenic matrix isolation conditions. Thermolysis and photolysis experiments suggest that the U−Pn bonds degrade by homolytic bond cleavage, whereas the more redox‐robust thorium compounds engage in an acid–base/dehydrocoupling route.     

Die Darstellung der Methylthio(trihalogen)phosphonium-Salze ClnBr3−nPSCH3+MF6−(n = 0–3; M = As,Sb) und Hal3PSCH3+SbCl6−(Hal = Br,Cl)

The Preparation of Methylthio(trihalogeno)phosphonium Salts Cl_nBr_3?nPSCH₃⁺MF₆^?(n = 0–3; M = As, Sb) and Hal₃PSCH₃⁺SbCl₆^?(Hal = Br, Cl) The methylthio(trihalogeno) phosphonium salts Br_nCl_3?nPSCH₃⁺MF₆^? (n = 0–3; M = As, Sb) are prepared by methylation of the corresponding thiophosphorylhalides Br_nCl_3?nPS in the system SO₂/CH₃F/MF₅. The hexachloroantimonates Hal₃PSCH₃⁺SbCl₆^?(Hal = Br, Cl) are synthesized by thiomethylation of PBr₃ and PCl₃ with CH₃SCl/SbCl₅. All salts are characterized by vibrational and NMR spectroscopy.     

Einfache Trithio- und Perthiocarbonatokomplexe mit interessanter Koordinationschemie: [E(CS3)2]2− (E = Sn,Zn, Cd), [E(CS3)3]3− (E = As,Sb, Bi,Co), {Cu(CS3)−}∞ und [Zn(CS4)2]2−

Simple Trithio- and Perthiocarbonato Complexes with Interesting Bond Properties: [E(CS₃)₂]^2? (E = Sn, Zn, Cd), [E(CS₃)₃]^3? (E = As, Sb, Bi, Co), {Cu(CS₃)^?}_∞ and [Zn(CS₄)₂]^2? By reactions of potassium trithiocarbonate ( 1 ) with solutions of zinc(II)- acetylacetonate, cadmium(II)-chloride, tin(II)-chloride, arsenic(III)-sulfide (suspension), antimony(III)-chloride, bismuth(III)-chloride and copper(II)-chloride in dimethyl sulfoxide, as well as of trisodium hexanitrito cobaltate(III) in water, and the precipitation of the complexes with an aqueous solution of tetraphenylphosphonium chloride the compounds (PPh₄)₂[Zn(CS₃)₂] ( 2 ), (PPh₄)₂[Cd(CS₃)₂] ( 3 ), (PPh₄)₂[Sn(CS₃)₂] ( 4 ), (PPh₄)₃[As(CS₃)₃] ( 5 ), (PPh₄)₃[Sb(CS₃)₃] ( 6 ), (PPh₄)₃[Bi(CS₃)₃] ( 7 ), (PPh₄)₃[Co(CS₃)₃] ( 8 ) and (PPh₄)Cu(CS₃) ( 9 ) have been isolated. (PPh₄)₂[Zn(CS₄)₂] · CH₃NO₂ ( 10 ) has been prepared by heating a solution of 2 in nitromethane to 60--70°C in presence of air. The reaction of 1 in dimethyl sulfoxide with an aqueous tetraphenylphosphonium chloride solution in presence of oxygen leads to (PPh₄)₂[C₂S₆] ( 11 ). The compounds have been characterized by spectroscopical studies (IR, Raman, UV/Vis, ¹¹³Cd/⁵⁹Co-NMR), magnetic susceptibility measurements, powder diffractometry, elemental analyses and single crystal X-ray structure analysis ( 4 – 7 , 10 and 11 ). The difficult growing of single crystals has been reported in detail. For crystal data see Inhaltsübersicht.     

Darstellung von CF3SClF+MF6− (M = As,Sb) und Kristallstruktur von CF3SCl2+SbF6−

Preparation of CF₃SClF⁺MF₆^? (M = As, Sb) and Crystal Structure of CF₃SCl₂⁺SbF₆^? CF₃SClF⁺MF₆^? (M = As, Sb) is prepared by oxidative fluorination of CF₃SCl with XeF⁺MF₆^?. The new salt is characterized by IR, Raman and NMR spectra in comparison with CF₃SF₂⁺MF₆^? and CF₃SCl₂⁺MF₆^?. In SO₂ solution CF₃SClF⁺SbF₆^? symmetrizises into CF₃SF₂⁺SbF₆^? and crystalline CF₃SCl₂⁺SbF₆^? with the monoclinic space group P2₁/c with a = 773.5(14) pm, b = 954.8(15) pm, c = 1242.0(18) pm, β = 100.24(8)°, Z = 4.     

Über die Darstellung der N-Chlor-N-Methylammoniumsalze (CH3)nNCl4–n+MF6− (n = 1–3; M = As,Sb) und (CH3)2NCIX+MF6− (X = F,Br)

About the Preparation of N-Chloro-N-Methylammonium Salts (CH₃)_nNCl_4–n⁺MF₆^? (n = 1–3; M = As, Sb) and (CH₃)₂NClX⁺MF₆^? (X = F, Br) Simple one-step methods for the preparation of the methylated chloroammonium salts (CH₃)_nNCl_4–n⁺MF₆^? (n = 1–3; M = As, Sb) and for (CH₃)₂NClX⁺MF₆^? (X = F, Br) are reported. Their vibrational and NMR-spectroscopical data are discussed in comparison.     

O−O Bond Formation and Liberation of Dioxygen Mediated by N5‐Coordinate Non‐Heme Iron(IV) Complexes

Formation of the O?O bond is considered the critical step in oxidative water cleavage to produce dioxygen. High‐valent metal complexes with terminal oxo (oxido) ligands are commonly regarded as instrumental for oxygen evolution, but direct experimental evidence is lacking. Herein, we describe the formation of the O?O bond in solution, from non‐heme, N₅‐coordinate oxoiron(IV) species. Oxygen evolution from oxoiron(IV) is instantaneous once meta‐chloroperbenzoic acid is administered in excess. Oxygen‐isotope labeling reveals two sources of dioxygen, pointing to mechanistic branching between HAT (hydrogen atom transfer)‐initiated free‐radical pathways of the peroxides, which are typical of catalase‐like reactivity, and iron‐borne O?O coupling, which is unprecedented for non‐heme/peroxide systems. Interpretation in terms of [Fe^IV(O)] and [Fe^V(O)] being the resting and active principles of the O?O coupling, respectively, concurs with fundamental mechanistic ideas of (electro‐) chemical O?O coupling in water oxidation catalysis (WOC), indicating that central mechanistic motifs of WOC can be mimicked in a catalase/peroxidase setting.     

Die Darstellung der N-Methyl-halogennitrilium-Salze XCNCH3+MF6− (X = Cl,Br, I; M = As,Sb) und der N-Methyl-trifluoracetonitrilium-Salze CF3CNCH3+MG6−

Preparation of N-Methylhalidonitrilium Salts XCNCH₃⁺MF₆^? (X = Cl, Br, I; M = As, Sb) and the N-Methyl-trifluoroacetonitrilium Salts CF₃CNCH₃⁺MF₆^? The N-methyl-halidonitrilium salts XCNCH₃⁺MF₆^? (X = Cl, Br, I; M = As, Sb) are synthesized by methylation of cyanogen halides with CH₃F/MF₅ in SO₂ at low temperatures. The N-methyl-trifluoroacetonitrilium salts CF₃CNCH₃⁺MF₆^? (M = As, Sb) are formed analogous with trifluoroacetonitrile. All salts are characterized by vibrational and NMR spectroscopy.