1‐Azaallyl Complexes of NiII,PdII, and TiIII

The metal complexes [Ni{N(Ar)C(R)C(H)Ph}₂) ( 2 ) (Ar = 2,6‐Me₂C₆H₃, R = SiMe₃), [Ti(Cp₂){N(R)C(Bu^t)C(H)R}] ( 3 ), M{N(R)C(Bu^t)C(H)R}I [M = Ni ( 4 a ) or Pd ( 4 b )] and [M{N(R)C(Bu^t)C(H)R}I(PPh₃)] [M = Ni ( 5 a ) or Pd ( 5 b )] have been prepared from a suitable metal halide and lithium precursor of ( 2 ) or ( 3 ) or, alternatively from [M(LL)₂] (M = Ni, LL = cod; M = Pd, LL = dba) and the ketimine RN = C(Bu^t)CH(I)R ( 1 ). All compounds, except 4 were fully characterised, including the provision of X‐ray crystallographic data for complex 5 a .     

Siliciumhaltige carben-komplexe: VIII. HSiR3-eliminierung aus carben-komplexen des typs (CO)5MC(NHR′)SiR3 (M = Cr,Mo, W)

Upon heating solid monoalkylamino(silyl)carbene complexes (CO)₅MC(NHR′)SiR₃ (M = W: SiR₃ = SiPh₃, R′ = Me, Et, Buⁿ, C₆H₁₁, Ph; SiR₃ = SiMePh₂, R′ = Me, Et. M = Mo, Cr: R = Ph, R′ = Me, Et) beyond their melting points, HSiR₃ elimination with formation of the isonitrile complexes (CO)₅MNCR′ and (CO)₄M(CNR′)₂ and (CO)₆M takes place quantitatively. Deuteration experiments show that the silane hydrogen stems from the NH group and that the reaction partially or exclusively proceeds by an intermolecular pathway.     

Alkali Blues: Blue-Emissive Alkali Metal Pyrrolates

2-Iminopyrroles [H^tBuL, 4-tert-butyl phenyl(pyrrol-2-ylmethylene)amine] are non-fluorescent π systems. However, they display blue fluorescence after deprotonation with alkali metal bases in the solid state and in solution at room temperature. In the solid state, the alkali metal 2-imino pyrrolates, M(^tBuL), aggregate to dimers, [M(^tBuL)(NCR)]₂ (M=Li, R=CH₃, CH(CH₃)CNH₂), or polymers, [M(^tBuL)]_n (M=Na, K). In solution (solv=CH₃CN, DMSO, THF, and toluene), solvated, uncharged monomeric species M(^tBuL)(solv)_m with N,N′-chelated alkali metal ions are present. Due to the electron-rich pyrrolate and the electron-poor arylimino moiety, the M(^tBuL) chromophore possesses a low-energy intraligand charge-transfer (ILCT) excited state. The chelated alkali cations rigidify the chromophore, restricting intramolecular motions (RIM) by the chelation-enhanced fluorescence (CHEF) effect in solution and, consequently, switch-on a blue fluorescence emission.     

Synthesis and coordination chemistry of tetrabutyldithioimidodiphosphinates

Butyl substituted imidodithiophosphinates R₂P(S)NP (S)R′₂ (R=ⁿBuⁱBu^sBuR′=ⁿBuⁱBu^sBu) have been synthesised via an HBr elimination reaction between R₂P(S)NH₂ and R′₂P(S)Br The compounds were characterised spectroscopically Crystallographic and spectroscopic studies reveal ⁿBu₂P(S)NHP(S)ⁿBu₂ and ^sBu₂P(S)NHP(S)ⁱBu₂ to be hydrogen bonded transoid dimers and ⁱBu₂P(S)NHP(S)ⁱBu₂ to be a transoid hydrogen bonded chain Reactions of the imidodithiophosphinates with ZnCl₂ or MCl₂COD gave the coordination complexes M[R₂P(S)NP (S)R′₂]₂ (R=ⁿBuⁱBu^sBuR′=ⁿBuⁱBu^sBuM=ZnPd: R=ⁿBuⁱBu^sBuPt).     

Verbindungen des Germainums und Zinns. 17. Alkylarylstannylen-Komplexe des Chroms und Molybdäns ohne Donorstabilisierung

Compounds of Germanium and Tin. 17 [1]. Alkylarylstannylene Complexes of Chromium and Molybdenum without Donor Stabilization Reaction of the complexes [(OC)₅M(THF)], M = Cr, Mo, with the alkylarylstannylene RR′Sn: R = 2,4,6-tBu₃C₆H₂, R′ = CH₂C(CH₃)₂-3,5-tBu₂C₆H₂, provides the donor-free stannylene complexes [(OC)₅Cr?SnRR′] ( 6 ) and [(OC)₅Mo?SnRR′] ( 8 ), respectively. The X-ray structure analyses of the isotypic compounds 6 and 8 reveal the three coordinate tin atoms in strictly planar environments and acute CSnC angles of 91.2° ( 6 ) and 91.3° ( 8 ).     

[NiL2X2] oder [HL][NiLX3] – Reaktion sterisch anspruchsvoller Trialkylphosphine L mit NiX2 (X = Cl,Br) in Ethanol

[NiL₂X₂] or [HL][NiLX₃] – Reaction of Sterically Demanding Trialkylphosphines L with NiX₂ (X = Cl, Br) in Ethanol The reaction of some sterically demanding trialkylphosphines L = PR₂R′ (R = ⁱPr, R′ = ^tBu; R = ^tBu, R′ = ⁱPr, Me) with NiX₂ (X = Cl, Br) in ethanol affords instead of the expected non-electrolytes [NiL₂X₂] tertiary phosphonium nickelates [HL][NiLX₃] due to participation of the solvent. In case of the less bulky P^tBu₂Me both complex types were obtained. [Ni(P^tBu₂Me)₂Cl₂] is tetrahedral and therefore one of the two examples of paramagnetic bis(trialkylphosphine)dihalogenonickel(II) complexes known so far. In solution the latter compound undergoes an equilibrium of tetrahedral (paramagnetic) and planar (diamagnetic) conformer. Vis spectra as well as the results of magnetic measurements and ¹H and ³¹P NMR investigations are reported.     

Synthesis of transition-metal Lewis acid adducts of trans-[ReCl(CNR)(Ph2PCH2CH2PPh2)2] (R = alkyl). A chemical and a quantum-chemical study of electrophilic β-addition to ligating isocyanide

Treatment of trans-[ReCl(CNR)(dppe)₂] (R = Me or Bu^t, dppe = Ph₂PCH₂CH₂ PPh₂) with CoCl₂(THF)_1.5, [ReOCl₃(PPh₃)₂] or [WCl₄L₂] (L = PPh₃ or PEtPh₂) affords the dinuclear adducts [ReCl(CN(M)R)(dppe)₂] (M = CoCl₂(THF), ReOCl₃(PPh₃) or WCl₄L, respectively) (formed via electrophilic β-addition of the electron-acceptor molecules to the isocyanide ligands), which undergo dissociation oxidation (for M = CoCl₂(THF) or ReOCl₃(PPh₃)). These reactions are considered in the light of results of extended Hückel calculations.     

Investigations on organotin,organolead, lead(IV), and lead(II) dithiolates

Bis(triorganometal) 1,2-dithiolates (R₃M)₂S₂R′ [(HS)₂R′ = C₇H₈S₂ for toluene-dithiol-3,4 (H₂TDT); M = Sn, Pb; R = Ph; or (HS)₂R′ = C₁₀H₁₄S₂ for 1,2-dimethyl-4,5-bis(mercaptomethyl)benzene (H₂DBB); M = Sn, R = CH₃, C₆H₅; M = Pb, R = C₆H₅], diorganometal 1,2-dithiolates R₂MS₂R′ [(HS)₂R′ = C₆H₆S₂ for 1,2-dimercaptobenzene (H₂DMB); M = Pb, R = CH₃, C₂H₅, C₆H₅; or (HS)₂R′ = H₂TDT; M = Sn, R = CH₃, C₆H₅; M = Pb, R = C₆H₅; or (HS)₂R′ = H₂DBB; M = Sn, R = CH₃, C₆H₅; M = Pb, R = CH₃, C₂H₂, C₆H₅; or (HS)₂R′ = C₈H₆N₂S₂ for 2,3-dimercaptoquinoxaline (H₂QDT); M = Pb, R = C₆H₅] and some lead(IV) and lead(II) dithiolates Pb(S₂R′)_n [(HS)₂R′ = H₂DMB, n = 2; (HS)₂R′ = H₂TDT, n = 2; (HS)₂R′ = H₂DBB, n = 1 or 2] have been prepared. Vibrational, ¹H NMR, and Mössbauer spectroscopic data are consistent with pentacoordination of tin in R₂SnTDT and with tetracoordination of tin in R₂SnS₂R′ and (R₃Sn)₂S₂R′ in the solid state. The soluble compounds are monomeric in solution. Coupling constants for the methyltin compounds indicate tetracoordination in solution.     

Synthesis and spectral studies of diorganotin(IV) dialkyldithiophosphates

Two series of diorganotin(IV) dialkyldithiophosphates, [RR′Sn{SSP(OR″)₂}₂](R = Me or Et; R′= Ph; R″ = Et, Prⁿ, Prⁱ or Buⁿ) and [RR′Sn(Cl){SSP(OR″)₂}] (R = R′= Me, Et or Ph; R″ = Ph; R″ = Et, Prⁱ or Buⁿ) were prepared and characterised by i.r. and NMR (¹H, ¹³C, ³¹P, ¹⁹⁹Sn) spectroscopy. The NMR data indicate five and six coordinate geometries for [RR′Sn(Cl){SSP(OR″)₂}] and [RR′Sn{SSP(OR″)₂}₂] complexes, respectively. The chloro complexes showed ²J (PSn) whereas such couplings were not observed in the spectra of [RR′Sn{SSP(OR″)₂}₂].     

Organometallic Niobium and Tantalum Complexes with Primary Phosphine Ligands: Syntheses and Molecular Structures of [Cp*MCl4(PH2R)] (M = Nb,Ta; Cp* = C5Me5;R = But,Ad, Cy,Ph, 2, 4, 6‐Me3C6H2 (Mes))

The reaction of [Cp*MCl₄] (M = Nb, Ta; Cp* = C₅Me₅) with PH₂R in toluene at room temperature gives the primary phosphine complexes [Cp*MCl₄(PH₂R)] [Cp* = C₅Me₅; M = Nb: R = Bu^t ( 1a ), Ad ( 2a ), Cy ( 3a ), Ph ( 4a ), 2, 4, 6‐Me₃C₆H₂ (Mes) ( 5a ); M = Ta: R = Bu^t ( 1b ), Ad ( 2b ), Cy ( 3b ), Ph ( 4b ), Mes ( 5b )] in high yield. 1—5 were characterized spectroscopically (NMR, IR, MS) and by crystal structure determinations. The starting material [Cp*TaCl₄] is monomeric in the solid state, as shown by crystal structure determination.     

The chemical oxidation and electronic spectra of the complexes trans-[M(CNR)2(Ph2PCH2CH2PPh2)2] (M = Mo or W)

Oxidation of the complexes $\text{trans}$-[M(CNR)₂(dppe)₂] (A) (M = Mo or W; R = Me, Bu^t or CH₃C₆H₄-$\text{4}$; dppe = Ph₂PCH₂CH₂PPh₂) with diiodine or silver (I) salts gives the paramagnetic cations $\text{trans}$-[M(CNR)₂(dppe)₂]⁺, (M = Mo, R = CH₃C₆H₄-$\text{4}$; M = W, R = Bu^t) and $\text{trans}$-[M(CNR)₂(dppe)₂]²⁺ (M = Mo, R = Me or CH₃C₆H₄-$\text{4}$; M = W, R = Me or Bu^t). Mixtures of products are generally produced when dichlorine or dibromine are the oxidising agents, however pure salts, the seven-coordinate complex cations [MX(CNC₆H₄CH₃-$\text{4}$)₂(dppe)₂]⁺ (B, X = Cl or Br) have been isolated. A simple molecular orbital scheme is proposed for complexes (A) and used to discuss their electronic spectra and their oxidation.     

SCHWEFELDIIMIDE MIT SILYL-, GERMYL-, STANNYL- UND PHOSPHINYL-HETEROSUBSTITUENTEN. SYNTHESE UND NMR-SPEKTROSKOPISCHE CHARAKTERISIERUNG

Abstract

Reactions of the salts K₂SN₂ and K[(NSN)R] (R = ′Bu, SiMe₃ and P′Bu₂) with organoelement chlorides R′R′ěl have been used to prepare four series of model sulfur diimides: R′R″E(NSN)ER″R′, ′Bu(NSN)ER″R′, Me₃Si(NSN)E″R′ and ^tBu₂P(NSN)ER″R′, respectively (E = C, Si, Ge, Sn; R′ and R″ = alkyl or aryl group). All compounds have been characterized by ′H and ¹³C NMR and—if possible—by ³¹P, ²⁹Si and ¹¹⁹Sn NMR spectroscopy. The configuration (Z or E) of the substituents R and E″R′ has been assigned in several cases using ^tBu(NSN)^tBu (1) as a reference. The E,Z assignment of ¹H, ¹³C and ¹⁵N nuclei in 1 is based on selectively ¹H-decoupled refocused INEPT ¹⁵N NMR and two-dimensional (2D) ¹³C/¹H heteronuclear shift correlations. The sulfur diimides under study are in general fluxional in solution.     

Über Cyanatverbindungen und deren reaktives Verhalten. XXI. Reaktionsverhalten von Niob(V)- und Tantal(V)-thiocyanat gegenüber N-Donatoren

Cyanate Compounds and their Reactivity. XXI. Reactivity of Niobium(V) and Tantalum(V) Thiocyanates to N-Donators M₂(NCS)₁₀ reacts with ammonia or primary and secondary aliphatic amines to complexes of the types [M(NCS)(NH₂)₂NH]_x, [M(NCS)₃(NHR)₂ H₂NR], or [M(NCS)₃(NR′₂)₂ HNR′₂], with N-heterocyclic amines in a first step to [M(NCS)₅L]-complexes and in a further step through a redox mechanism to [M(NCS)₄L₂] complexes. [M(NCS)₅(CH₃CN)] mCH₃CN reacts with ammonia, or primary amines in acetonitrile over acetamidine and amidinolytic cleavage of M-NCS bonds to complexes of the type [M(NCS)_a(NC(NHR″)CH₃)_b(CH₃C(NH)NHR″)]_x. The prepared compounds are characterized by analytical data, derivatographic measurements, and IR or visible absorption spectra (M = Nb, Ta; x = 2; R = n-C₄H₉; R′ = C₂H₅; L = pyridine or 4-methyl-pyridine; m = 0, 1, 2; a = 1 or 4; b = 4 or 1; R″ = H, n-C₄H₉).     

A Comparative Study on the Thermodynamics of Halogen Bonding of Group 10 Pincer Fluoride Complexes

The thermodynamics of halogen bonding of a series of isostructural Group 10 metal pincer fluoride complexes of the type [(3,5-R₂-^tBuPOCOP^tBu)MF] (3,5-R₂-^tBuPOCOP^tBu=κ³-C₆HR₂-2,6-(OPtBu₂)₂ with R=H, tBu, COOMe; M=Ni, Pd, Pt) and iodopentafluorobenzene was investigated. Based on NMR experiments at different temperatures, all complexes 1-tBu (R=tBu, M=Ni), 2-H (R=H, M=Pd), 2-tBu (R=tBu, M=Pd), 2-COOMe (R=COOMe, M=Pd) and 3-tBu (R=tBu, M=Pt) form strong halogen bonds with Pd complexes showing significantly stronger binding to iodopentafluorobenzene. Structural and computational analysis of a model adduct of complex 2-tBu with 1,4-diiodotetrafluorobenzene as well as of structures of iodopentafluorobenzene in toluene solution shows that formation of a type I contact occurs.     

The synthesis and spectral properties of the novel monodentate(s) coordinated thiosemicarbazide and thiosemicarbazone complexes [Fe(CO)2L(η5-C5H5)][PF6] (L = H2NNHCSNH2, cy-C5H10CNNHCSNH2 or R′R″CNNHCSNH2, R′ = R″ = Me; R′= H,R″ = Ph; R′= H,R″ = p-NO2Ph,R′= Me,R″ = p-MePh)

The acetone complex [Fe(CO)₂(Me₂CO)(η⁵-C₅H₅)][PF₆] reacts with L (L = H₂NNHCSNH₂, cy-C₅H₁₀CNNHCSNH₂, or R′R″CNNHCSNH₂ where R′ = R″ = Me; R′ = H, R″ = Ph; R′ = H, R″ = p-NO₂Ph; R′ = p-MePh) in refluxing trichloromethane to give the new complexes [Fe(CO)₂L(η⁵-C₅H₅)][PF₆]. The complexes are clearly coordinated through the sulphur atom since the thiosemicarbazide complex reacts with benzaldehyde to afford the corresponding thiosemicarbazone compound.     

Chemistry of mixed transition-metal complexes : VII. Iron- and nickel-substituted cyclobutadiene complexes of cobalt

The preparation of π-cyclopentadienyl(substituted cyclobutadiene)cobalt complexes by the reaction of π-C₅H₅Co(PPh₃)(RCCR′) (R, R′ = Ph, CO₂CH₃ with ethynyl complexes R″CCM (R″ = Ph for M = π-C₅H₅Fe(CO)(L);R″ = Ph, Co₂CH₃ for M = π-C₅H₅Ni(PPh₃)) is described.     

Molecular ions of 3,3′-bi(2-R-5,5-dimethyl-4-oxopyrrolinylidene) 1,1′-dioxides

The electrochemical reduction of 3,3′-bi(2-R-5,5-dimethyl-4-oxopyrrolinylidene) 1,1′-dioxides (R = CF₃, Me, Ph, Bu^t), which are cyclic dinitrons with conjugated C=C bond, in acetonitrile is an EE process producing stable radical anions and dianions, whereas the electrochemical oxidation is an EEC (R = Me, Ph) or EE process (R = Bu^t) with formation of radical cations (except for the case of R = CF₃) and dications (R = Bu^t) stable under standard conditions. Radical cations of the dioxides with R = Me, Ph, and Bu^t and radical anions of the whole series of the compounds studied, including R = CF₃, were characterized by ESR spectroscopy combined with electrochemical measurements and quantum-chemical calculations. The electrochemical behavior of the Bu^t-substituted dinitron is unique: the EE processes in the region of negative and positive potentials with formation of the dianion, radical anion, radical cation, and dication stable at T = 298 K were observed for the first time within one cycle of potential sweep in the CV curve measured in MeCN. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1148–1154, May, 2005.     

An Air-Stable Heterobimetallic Si2M2 Tetrahedral Cluster

Air- and moisture-stable heterobimetallic tetrahedral clusters [Cp(CO)₂MSiR]₂ (M=Mo or W; R=SitBu₃) were isolated from the reaction of N-heterocyclic carbene (NHC) stabilized silyl(silylidene) metal complexes Cp(CO)₂M=Si(SitBu₃)NHC with a mild Lewis acid (BPh₃). Alternatively, treatment of the NHC-stabilized silylidene complex Cp(CO)₂W=Si(SitBu₃)NHC with stronger Lewis acids such as AlCl₃ or B(C₆F₅)₃ resulted in the reversible coordination of the Lewis acid to one of the carbonyl ligands. Computational investigations revealed that the dimerization of the intermediate metal silylidyne (M≡Si) complex to a tetrahedral cluster instead of a planar four-membered ring is due to steric bulk.     

Four-coordinate trispyrazolylboratomanganese and -iron complexes with a pyrazolato co-ligand: syntheses and properties as oxidation catalysts

A series of complexes of the type [(Tp^R1,R2)M(X)] (Tp=trispyrazolylborato) with R¹/R² combinations Me/tBu, Ph/Me, iPr/iPr, Me/Me and for M=Mn or Fe coordinating [Pz^Me,tBu]^? (Pz=pyrazolato) or Cl^? as co‐ligand X has been synthesised. Although the chloride complexes were very unreactive and stable in air, the pyrazolato series was far more reactive in contact with oxidants like O₂ and tBuOOH. The [(Tp^R1,R2)M(Pz^Me,tBu)] complexes proved to be active pre‐catalysts for the oxidation of cyclohexene with tBuOOH, reaching turnover frequencies (TOFs) ranging between moderate and good in comparison to other manganese catalysts. Cyclohexene‐3‐one and cyclohexene‐3‐ol were always found to represent the main products, with cyclohexene oxide occasionally formed as a side product. The ratios of the different oxidation products varied with the reaction conditions: in the case of a peroxide/alkene ratio of 4:1, considerably more ketone than alcohol was obtained and cyclohexene oxide formation was almost negligible, whereas a ratio of 1:10 led to a significant increase of the alcohol proportion and to the formation of at least small amounts of the epoxide. Pre‐treatment of the dissolved [(Tp^R1,R2)M(Pz^Me,tBu)] pre‐catalysts with O₂ led to product distributions and TOFs that were very similar to those found in the absence of O₂, so that it may be argued that tBuOOH and O₂ both lead to the same active species. The results of EPR spectroscopy and ESI‐MS suggest that the initial product of the reaction of [(Tp^Me,Me)Mn(Pz^Me,tBu)] with O₂ contains a Mn^III(O)₂Mn^IV core. Prolonged exposure to O₂ leads to a different dinuclear complex containing three O‐bridges and resulting in different TOFs/product distributions. Analogous findings were made for other complexes and formation of these overoxidised products may explain the deviation of the catalytic performances if the reactions are carried out in an O₂ atmosphere.     

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(tBu₂bzamC(OEt)Me)tBu}] ( 3_M ; M=Cr, W), which occurs readily at room temperature from the germylene Ge(tBu₂bzam)tBu ( 1 _{t Bu} ) and Fischer carbenes [M(CO)₅{C(OEt)Me}] ( 2_M ; M=Cr, W), has been found to be reversible. Upon heating at 60 °C, complexes 3_M undergo epimerization to an equilibrium mixture of 3_M 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(tBu₂bzam)tBu}] (cis- 4_Cr and trans- 4_Cr ). The latter decompose at 120 °C to [Cr(CO)₅{Ge(tBu₂bzam)tBu}] ( 6_Cr ). Because the formation of cis- 4_Cr and trans- 4_Cr from 3_Cr or 3′_Cr requires the presence of free 1 _{t Bu} and 2_Cr in the reaction solutions, the reactions of 1 _{t Bu} with 2_M to give 3_M (and 3′_M at 60 °C) should be reversible. This proposal has been proven by germylene-exchange crossover reactions in which free 1 _{t Bu} and [M(CO)₅{Ge(tBu₂bzamC(OEt)Me)CH₂SiMe₃}] ( 5′_M ; M=Cr, W) were formed when complexes 3_M were treated at room temperature with the germylene Ge(tBu₂bzam)CH₂SiMe₃ ( 1_tmsm ). A clear differential behavior between N-heterocyclic carbenes (NHCs) and amidinatogermylenes ( 1 _{t Bu} and 1_tmsm ) 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.