Organotransition-Metal Complexes of Multidentate Ligands 5. Structural Characterization of Cis-Tetracarbonyl(3,5-Dimethylpyrazol-1-Yl) Methanemolybdenum(0)

The title compound crystallizes in space group P 2₁/c of the monoclinic system in a cell of dimensions: a = 9.231(2), b = 15.931(2), c = 12.420(2) Å, β = 108.37(1)°. The observed density is 1.60 g/cm³ and the density calculated for four molecules in the cell is 1.58 g/cm³. The refinement converged with R = 0.029 and R_w = 0.028 based on 2569 reflections with I > 2.5 σ. The molecule has approximate C_s symmetry with a mirror plane roughly containing the central Mo atom and two cis-carbonyls, C(1)O(1) and C(4)O(4), while bisecting the bidentate, H₂CPz₂, and two trans-carbonyls. The four carbonyls and tine bidentate adopt a quasi-octahedral arrangement around the Mo atom. The C(NN)₂Mo linkage of the (H₂CPz′₂)Mo fragment is observed to be in the boat form. The two cis-carbonyls are bent away by the bulky H₂CPz′₂ bidentate giving ∠C(1)-Mo-C(4) ? 167.3(1)°. The distortion explains the facile allyl bromination and decarbonylation observed for the title compound.     

Sulfenamides as ligands in transition metal chemistry Pentacarbonyl(Sulfenamide)Chromium(0) Complexes

The complexes Cr(CO)₅(R′SNR₂) [R′ = CH₃; NR₂ = N(CH₃)₂, N(C₄H₈)O. R′ = C₆H₅; NR₂ = N(CH₃)₂, N(C₄H₄)O, N(CH₂? C₆H₅)₂, N(C₆H₁₁)₂] have been prepared by reaction of the sulfenamides with Cr(CO)₅ · THF and characterized by analytical and spectroscopic methods. The IR, ¹H-NMR, UV-VIS, and mass spectra of the complexes support the coordination of the sulfenamide via the sulfur atom. π-acceptor abilities of sulfenamides in the prepared coordination compounds, determined from IR and UV-VIS data, were compared with those of other divalent sulfur conpounds.     

Umsetzungen von Allyldichlorphosphit und Allyldifluorphosphit mit einigen Verbindungen von Übergangsmetallen; Darstellung und spektroskopische Untersuchung von Allyldichlor- bzw. Allyldifluorphosphit-Carbonyl-Metall(0)-Koordinationsverbindungen (MetallCr,Mo, W,Fe)

Reactions of Allyldichlorophosphite and Allyldifluorophosphite with some Transition Metal Compounds; Synthesis and Spectroscopic Identification of Allyldichloro- and Allyldifluorophosphite-Carbonyl-Metal(0) Coordination Compounds (Metal?Cr, Mo, W, Fe) In the reactions of allyldifluorophosphite ( 1 ) and allyldichlorophosphite ( 2 ) with the carbonyl compounds (C₇H₈)M(CO)₃ (M?Cr, Mo; C₇H₈ ? cycloheptatriene), W(CO)₅THF (THF = tetrahydrofuran), Fe(CO)₅ or Fe₂(CO)₉ the allyldichloro- and allyldifluorophosphite-carbonyl-metal compounds fac-(AllOPF₂)₃Cr(CO)₃ 3 a , mer-(AllOPF₂)₃Cr(CO)₃ 3 b , fac-(AllOPF₂)₃Mo(CO)₃ 4 , fac-(AllOPCl₂)₃Mo(CO)₃ 5 , (AllOPF₂)W(CO)₅ 6 , (AllOPCl₂)W(CO)₅ 7 , (AllOPF₂)Fe(CO)₄ 8 and (AllOPCl₂)Fe(CO)₄ 9 were formed (All = CH₂?CHCH₂). In 8 and 9 the ligands 1 or 2 are axially orientated. The validity of the concept of hard and soft acids and bases (HSAB-concept) and of the 18-valency electron rule (18-VE-rule) was confirmed. The allyl dihalophosphites 1 and 2 coordinate via phosphorus. The allylic π-system was not involved in the coordinative bond. The characterization of the coordination compounds 3 , 4 , 5 a , 5 b und 6 ? 9 was based on their IR and NMR spectra, and on the mass spectra.     

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).     

Functionalised Tris(pyrazolyl)methane Ligands and Re(CO)3 Complexes Thereof

The synthesis of new tripodal nitrogen ligands derived from tris(pyrazolyl)methane (Tpm^R, R = H, tBu, Ph in 3‐position) is described. After deprotonation of the parent tris(pyrazolyl)methane Tpm^R, the carbanion reacts readily with ethylene oxide to yield the 3,3,3‐tris(3′‐substituted pyrazolyl)propanol ligands[(3‐Rpz)₃CCH₂CH₂OH, R = H, tBu, Ph, 1a – c ]. These ligands can be easily derivatised at the alcohol function. Microwave‐assisted reactions of these ligands and [Re(CO)₅Br] yields the complex [( 1a )Re(CO)₃]Br ( 4 ) in the case of ligand 1a , whereas in the case of the substituted ligands 1b and 1c degradation was observed. The degradation products are identified as [(Hpz^R)₂Re(CO)₃Br] [R = tBu ( 7b ), Ph ( 7c )]. These complexes were also prepared directly from [Re(CO)₅Br] and the corresponding pyrazoles by microwave‐assisted synthesis. The Re(CO)₃ complexes 4 and [( 1a )Re(CO)₃]OTf ( 5 ) are water‐soluble. The structures of 5· H₂O and [{(pz)₃CCH₂CH₃}Re(CO)₃]OTf · 1.5H₂O · ¹/₂CH₃CN ( 6· 1.5H₂O · ¹/₂CH₃CN) as well as the structure of 7b have been elucidated by X‐ray crystallography.     

Structure and Reactivity of Iron(0)-Phenyltellurolate [PPN][PhTeFe(CO)4]

Anionic iron(0) tetracarbonyl with terminal phenyltellurolate ligand PhTe^?, [PhTeFe(CO)₄]^?, has been synthesized and characterized. The title compound was obtained by addition of (PhTe)₂ to [PPN][HFe(CO)₄] THF solution dropwise. [PPN][PhTeFe(CO)₄] crystallizes in the monoclinic space group C c, with a = 16.119(4) Å, b = 13.141(3) Å, c = 19.880(8) Å, β = 93.04(3)°, V = 4205(2) ų, and Z = 4. The [PhTeFe(CO)₄]^? anion is a trigonal-bipyramidal complex in which the phenyltellurolate ligand occupies an axial position with Fe-Te bond length 2.630(5) Å and the Fe-Te-C(Ph) angle is 103.4(5)°. The neutral iron(0)-telluroether compound, (PhTeMe)Fe(CO)₄, was prepared by alkylation of the [PhTeFe(CO)₄]^?. Protonation of [PhTeFe(CO)₄]^?and reaction of H₂Fe(CO)₄ and PhTe)₂ ultimately lead to formation of the known dimer Fe₂(μ-TePh)₂(CO)₆ and H₂.     

Monosubstituted Trinuclear and Tetranuclear VIB Metal Carbonyl Complexes: Syntheses of [{M(CO)5}3(Pf-Pf-Pf)] [Pf-Pf-Pf = PhP(CH2CH2PPh2)2] and [{M(CO)5}4(P-Pf3)] [P-Pf3 = P(CH2CH2PPh2)3] (M = Cr,Mo) and Crystal Structures of the Latter Three

The triligate trimetallic complexes, [{M(CO)₅}₃(Pf-Pf-Pf)] and tetraligate tetrametallic complexes, [{M(CO)₅}₄(P-Pf₃)] (M = Cr and Mo), were prepared from [M(CO) ₆] and the corresponding ligands in MeCN/CH₂Cl₂ promoted by Me₃NO at 0 °C. Crystals of trimer lb are monoclinic, space group P 2₁/n, with a = 13.407(3), b = 15.002(5), c = 26.52(1) Å, β = 90.65(2)°, Z = 4, and R = 0.060 for 2760 observed reflections. Crystals of tetramer 2a are monoclinic, space group P 2₁/c, with a – 14.183(8), b = 29.880(4), c = 16.103(2) Å, β = 94.98(3)°, Z = 4, and R = 0.039 for 5014 observed reflections. Crystals of 2b are monoclinic, space group C 2/c, with a = 42.120(8), b = 13.679(1), c = 23.486(2) Å, β = 92.14(1)°, Z = 8, and R = 0.032 for 6897 observed reflections. Each phosphorus atom of the ligands is coordinated to the M(CO)₅ moiety in each title compounds. The geometry of the four metals is a distorted tetrahedron for the tetramers.     

Syntheses and Characterization of Manganese-Tellurolate Complexes by Using Chelating Metalloligand cis-[Mn(Co)4(TePh)2]− and Potential Electrophilic TeMe+ Reagent

The cis-[Mn(CO)₄(TePh)₂]^?, similar to bidentate ligand PhTe(CH₂)₃TePh, acts as a “chelating metalloligand” for the synthesis of metallic tellurolate compounds. The reaction of cis[Mn(CO)₄(TePh)₂]^? with BrMn(CO)₅ in THF leads to a mixture of products[(CO)₃,BrMn(μ-TePh)₂Mn(CO)₄]^? (1) and Mn₂(μ-TePh)₂(CO)_g (2). Complex 1 crystallizes in the triclinic space group Pl? with a = 11.309(3) Å, b = 14.780(5) Å, c = 19.212(6) Å, a = 76.05(3)° β = 72.31(3)°, γ = 70.41(3)° V = 2848(2) Å₃, Z = 2. Final R = 0.034 and R_w = 0.035 resulting from refinement of 10021 total reflections with 677 parameters, Dropwise addition of (MeTe)₂ to a solution of [Me₃O][BF₄] in CH₃CN leads to formation of [Me₂TeTeMe][BF₄], a potential MeTe⁺ donor ligand. In contrast to oxidative addition of diphenyl ditelluride to [Mn(CO)s]^? to give cis-[Mn(CO)₄(TePh)₂]^? which was thermally transformed into [(CO)₃Mn(μ-TePh)₃Mn(CO)₃]^?, reaction of [Mn(CO)₅]^?with [Me₂TeTeMe]⁺ proceeded to give the monomeric species MeTeMn(CO)₅ as initial product which was then dimerized into Mn₂(μ-TeMe)₂(CO)_g (4).     

Alternativ-Liganden. XXIII. Rhodium(I)-Komplexe mit Donor/Akzeptor-Liganden des Typs (Me2PCH2CH2SiX2 und (2-Me2PC6H4)SiXMe2 (X = F,Cl)

Alternative Ligands. XXIII Rhodium(I) Complexes with Donor/Acceptor Ligands of the Type (Me₂PCH₂CH₂)₂SiX₂ and (2-Me₂PC₆H₄)SiXMe₂ (X = F, Cl) Donor/acceptor ligands of the type (Me₂PCH₂CH₂)₂SiX₂ and (2-Me₂PC₆H₄)SiXMe₂ (X = F, Cl) react with [Rh(CO)₂Cl]₂ (₁) to give the mononuclear complexes RhCl(CO)(Me₂PCH₂CH₂)₂SiX₂ [X = F( 4 ), Cl ( 5 )] and RhCl(CO)[2-Me₂PC₆H₄)SixMe₂]₂ [X = F ( 8 ), Cl ( 9 )], respectively. In case of the ligands (Me₂PCH₂CH₂)₂SiCl₂ ( 3 ) and (2-Me₂PC₆H₆)SiClMe₂ ( 7 ) the Rh(I) complexes formed in the first step partly undergo oxidative addition reactions of SiCl bonds yielding rhodium(III) compounds of low solubility. Only for 8 the coordination shifts Δδ = δ(complex)?δ(ligand) and coupling constants give some indication to possible Rh→Si interactions. However, the molecular structure of 8 determined by X-ray diffraction does not show RhSi or RhF bonding contacts. The new compounds were characterized by analytical (C, H) and spectroscopic investigations (MS, IR,-NMR).     

Crystal Structures and Characterizations of Bis(pyrrolidinedithiocarbamato)Cu（Ⅱ） and Zn(Ⅱ） Complexes

The structures of [Cu (S₂CN (CH₂)₄)₂] (1) and [Zn₂(S₂CN‐(CH₂)₄)₄] (2) have been determined by X‐ray crystallography analysis. They are all isomorphous and triclinic, space group of P1^?, with Z = 1. The lattice parameters of compound 1 is: a = 0.63483(2) nm, b = 0.74972(3) nm, c=0.78390(1) mn, α = 75.912(2)°, β = 78.634(2)° and γ = 86.845(2)°; compound 2: a = 0.78707(6) nm, b=0.79823(6) nm, c = 1.23246(9) nm, α = 74.813(2)°, β = 73.048(2)° and γ = 88.036(2)°. The copper atom is located on a crystallographic inversion center and zinc atom lies across centers of symmetry. The Cu(II) ion has a square‐planar geometry while Zn(II) has a distorted tetrahedral geometry. The thermal gravity (TG) data indicate that no structural transitions in the two compounds were abserved and the decomposition products can adsorb gas. Also they all have a high thermal stability.     

Bis(cyclopentadienyl)methan-verbrückte Zweikernkomplexe,V. Heteronukleare Co/Rh-, Co/Ir-, Rh/Ir- und Ti/Ir-Komplexe mit dem Bis(cyclopentadienyl)methan-Dianion als Brückenliganden

Bis(cyclopentadienyl)methane-bridged Dinuclear Complexes, V^[1]. – Heteronuclear Co/Rh-, Co/Ir-, Rh/Ir-, and Ti/Ir Complexes with the Bis(cyclopentadienyl)methane Dianion as Bridging Ligand^* The lithium and sodium salts of the [C₅H₅CH₂C₅H₄]^- anion, 1 and 2 , react with [Co(CO)₄I], [Rh(CO)₂Cl]₂, and [Ir(CO)₃Cl]n to give predominantly the mononuclear complexes [(C₅H₅-CH₂C₅H₄)M(CO)₂] ( 3, 5, 7 ) together with small amounts of the dinuclear compounds [CH₂(C₅H₄)₂][M(CO)₂]₂ ( 4, 6, 8 ). The ¹H- and ¹³C-NMR spectra of 3, 5 , and 7 prove that the CH₂C₅H₅ substituent is linked to the π-bonded ring in two isomeric forms. Metalation of 5 and 7 with nBuLi affords the lithiated derivatives 9 and 10 from which on reaction with [Co(CO)₄I], [Rh(CO)₂Cl]₂, and [C₅H₅TiCl₃] the heteronuclear complexes [CH₂(C₅H₄)₂][M(CO)₂][M′(CO)₂] ( 11–13 ) and [CH₂(C₅H₄)₂]-[Ir(CO)₂][C₅H₅TiCl₂] ( 17 ) are obtained. Photolysis of 11 and 12 leads almost quantitatively to the formation of the CO-bridged compounds [CH₂(C₅H₄)₂][M(CO)(μ-CO)M′(CO)] ( 14, 15 ). According to an X-ray crystal structure analysis the Co/Rh complex 14 is isostructural to [CH₂(C₅H₄)₂][Rh₂(CO)₂(μ-CO)] ( 16 ).     

Synthesis and Characterization of Aminophosphines,Bis(amino)phosphine Derivatives,and Their Molybdenum(0) Complexes

Functionalized bis(amino)phosphines of the type PhP(NHR)₂ ( 1a–c ) and aminophosphines of the type Ph₂PNHR ( 2a–c ) have been synthesized by treating PhPCl₂ or Ph₂PCl with corresponding primary amines of H₂N-R where R = -CH₂SO₃H, -C₆H₄SO₃H, and benzo-15-crown-5. The molybdenum(0) complex of the aminophosphine ( 3 ) has been obtained by reacting cis-[Mo(CO)₄(bipy)] with aminophosphine ( 2c ). The synthesized aminophosphines, bis(amino)phosphines, and the molybdenum(0) complex have been characterized by IR, ¹H NMR, ³¹P NMR, and MS spectroscopic techniques and by elemental analysis.     

Alternativ-Liganden. VIII. Chelatkomplexe des Typs M(CO)4(Me2XGeMe2CH2X′Me2) (M = Cr,Mo, W; X,X′ = N,P, As; Me = CH3)

Chelate Complexes of the Type M(CO)₄(Me₂XGeMe₂CH₂X′Me₂) (M) = Cr, Mo, W; X, X′ = N, P, As; Me = CH₃) The ligands (Me₂)XGeMe₂CH₂X′Me₂ (M) = Cr, Mo, W) react with M(CO)₄norbor (norbor = Norbornadiene) (M = Cr, Mo, W) yielding the chelate complexes M(CO)₄(Me)₂XGeMe₂CH₂X′Me₂). compounds of low thermal stability are formed with the ligands (Me₂NGeMe₂CH₂X′Me₂ because of the weak donor ability of the GeNMe₂ group and with Me₂AsGeMe₂CH₂NMe₂ caused by strong steric ring tension. The new compounds are characterized by analytical and spectroscopic (n.m.r., i.r., m.s.) investigations.     

KRISTALLSTRUKTUR VON BIS(DIETHYLDITHIOCARBAMATO)-PHENYLPHOSPHAN UND SYNTHESE EINIGER MONO- UND BIS(DIORGANYLDITHIOCARBAMATO)PHOSPHANE

Abstract

By reaction of organylchlorophosphanes with sodium dithiocarbamates compounds of the type RP(S₂CNR₂′)₂ with R = CH₃, C₆H₅; R' = CH₃, C₂H₅, CH(CH₃)₂, C₆H₅ and of the type (C₆H₅)₂PS₂CNR₂′ with R' = CH₃, CH(CH₃)₂ as well as compound [(C₆H₅)₂PS₂CN(CH₃)CH₂-]₂ are obtained. The crystal structure of C₆H₅P(S₂CN(C₂H₅)₂)₂ shows that the trend from bidentate to monodentate bonding of the dithiocarbamate ligands in the homologous series RE(S₂CN(C₂H₅)₂)₂; E = Bi, Sb, As, P is continued for E = P.

Durch Umsetzung der jeweiligen Chlorophosphane mit den entsprechenden Natriumdithiocarbamaten können folgende Verbindungen erhalten werden: Verbindungen des Typs RP(S₂CNR₂′)₂ mit R = CH₃, C₆H₅; R' = CH₃, C₂H₅, CH(CH₃)₂, C₆H₅; Verbindungen des Typs (C₆H₅)₂PS₂CNR₂′ mit R' = CH₃, CH(CH₃)₂ sowie [(C₆H₅)₂PS₂CN(CH₃)CH₂-]₂. Die Kristallstruktur von C₆H₅P(S₂CN(C₂H₅)₂)₂ zeigt, daß sich der Trend zu schwächer ausgeprägter zweizähniger Bindungsweise der Dithiocarbamatliganden in der homologen Reihe RE(S₂CN(C₂H₅)₂)₂; E = Bi, Sb, As, P für E = P fortsetzt.     

Organotransition-Metal Complexes of Multidentates 1. Synthesis and Characterization of N,N-Bis(Pyrazol-1-Ylmethyl)Aminomethane and N,N-Bis(3, 5-Dimethylpyrazol-1-Ylmethyl)-Aminomethane Derivatives of the Group VI Metal Carbonyls

N, N-bis(pyrazol-1-ylmethyl)aminomethane (bpam) and N, N-bis(3, 5-dimethylpyrazol-1-ylmethyl)aminomethane (bdmpam) reacted with M(CO)₆ or M(CO)₃(CH₃CN)₃ in acetonitrile to give respectively fac-(bpam)M(CO)₃ and fac-(bdmpam)M(CO)₃ in good yields (M=Cr, Mo, W). These complexes are characterized by elemental analysis, IR, and NMR and compared with the related polypyrazolylborate complexes of the group VI metal carbonyls.     

Cationic dihydridoiridium(III) complexes of nitriles

The reaction of [IrL(CO)(PPh₃)₂]ClO₄ (PPh₃ = triphenylphosphine) with H₂ produces new cationic dihydridoiridium(III) complexes of nitriles (L), [Ir(H)₂L(CO)(PPh₃)₂]ClO₄ [L = CH₃CN (1), CH₃CH₂CN (2), CH₃CH₂CH₂CN (3) and C₆H₅CN (4)], where nitriles are coordinated through the nitrogen atom. Proton NMR spectral data for complexes 1–4 suggest that the two hydrides in each complex are cis to each other and trans to CO and nitrogen (nitrile), and the two PPh₃ are trans to each other.     

Komplexchemie polyfunktioneller Liganden. XLV. Tetracarbonylchrom-, -molybdän- und -wolframkomplexe mit 1,1,1-Tris(diphenylarsinomethyl)ethan

Complex Chemistry of Polyfunctional Ligands. XLV. Tetracarbonylchromium, -molybdenum, and -tungsten Complexes of 1,1,1-Tris(diphenylarsinomethyl)ethan Ultraviolet irradiation of M(CO)₆ (M = Cr, Mo, W) with the potentially tridendate chelating ligand CH₃C[CH₃As(C₆H₅)₂]₃ react in CH₃CN to the complexes cis-M(CO)₄CH₃C[CH₂As-(C₆H₅)₂]₃ in which always one arsenic donor of the ligand is uncoordinated. The vibrational spectra (i.r., f.i.r., and Raman) of the compounds are discussed in detail.     

Linking of CuI Units by Tetrahedral Mo2E2 Complexes (E=P,As)

The reaction of [Cp₂Mo₂(CO)₄(μ,η^2:2-E₂)] ( A : E=P, B : E=As, Cp=C₅H₅) with the WCA-containing Cu^I salts ([Cu(CH₃CN)₄][Al{OC(CF₃)₃}₄] (CuTEF, C ), [Cu(CH₃CN)₄][BF₄] ( D ) and [Cu(CH₃CN)_3.5][FAl{OC₆F₁₀(C₆F₅)}₃] (CuFAl, E )) affords seven unprecedented coordination compounds. Depending on the E₂ ligand complex, the counter anion of the copper salt and the stoichiometry, four dinuclear copper dimers and three trinuclear copper compounds are accessible. The latter complexes reveal first linear Cu₃ arrays linked by E₂ units (E=P, As) coordinated in an η^2:1:1 coordination mode. All compounds were characterized by X-ray crystallography, NMR and IR spectroscopy, mass spectrometry and elemental analysis. To define the nature of the Cu⋅⋅⋅Cu⋅⋅⋅Cu interactions, DFT calculations were performed.     

Reaktion von cyclopentadienyl-substituierten Molybdän(V)-tetrachloriden mit LiPH(2,4,6-BuC6H2) und KPPh2(Dioxan)2. Molekülstrukturen von [Cp0Mo(μ-Cl)2]2 und [CpMo2(μ-Cl)3(μ-PPh2)] (Cp0 = C5Me4Et)

Reaction of Cyclopentadienyl Substituted Molybdenum(V) Tetrachlorides with LiPH(2,4,6-Bu C₆H₂) and KPPh₂(Dioxane)₂. Crystal Structures of [Cp⁰Mo(μ? Cl)₂]₂ and [Cp Mo₂(μ? Cl)₃(μ? PPh₂)] (Cp⁰ = C₅Me₄Et) The reaction of [Cp⁰Mo(CO)₃]₂ (Cp⁰ = C₅Me₄Et) and [Cp′Mo(CO)₃]₂ (Cp′ = C₅H₄Me) with PCl₅ in CH₃CN furnishes the Mo(V) complexes Cp⁰MoCl₄(CH₃CN) 1 and Cp′MoCl₄(CH₃CN) 2 in good yields. While 1 and 2 are reduced by LiPH(2,4,6-BuC₆H₂) to the Mo(III) complexes [Cp⁰Mo(μ? Cl)₂]₂ 3 and [Cp′Mo(μ? Cl)₂]₂ 4 , the reaction of 1 with KPPh₂(dioxane)₂ yields the reduction/substitution product [CpMo₂(μ? Cl)₃(μ? PPh)] 5 in low yield. 1 – 4 were characterized spectroscopically (i.r., mass, 3 and 4 also n.m.r.). An X-ray crystal structure determination was carried out on 3 and 5. 3 crystallizes in the triclinic space group P1 (No. 2) with a = 8.278(4), b = 12.508(7), c = 12.826(7) Å, α = 86.78(5), β = 81.55(2), γ = 75.65(4)°, V = 1 272.4 ų and two formula units in the unit cell (data collection at ? 67°C, 4 255 independent observed reflections, R = 2.9%); 5 crystallizes in the triclinic space group P1 (No. 2) with a = 11.536(8), b = 12.307(9), c = 13.157(9) Å, α = 91.41(6), β = 100.42(5), γ = 112.26(6)°, V = 1 688.7 ų and two formula units in the unit cell (data collection at ? 60°C, 6 147 independent observed reflections, R = 4.9%). The crystal structure of 3 shows the presence of centrosymmetric dimeric molecules with four bridging chloro ligands. In 5, two Mo atoms are bridged by three chloro ligands and one PPh₂ ligand. The Mo? Mo bond length in 3 and 5 (2.600(2), 2.596(2) Å and 2.6388(8) Å) is in agreement with a Mo? Mo bond.     

Isomere η2-Acyl- und σ-Alkyl(carbonyl)-Komplexe von Molybdän und Wolfram. Eine Studie zum Bildungs-mechanismus,zur Isomerisierungsgeschwindigkeit und zur Steuerung der Gleichgewichtslage

η²-Acyl and σ-Alkyl(carbonyl) Coordination in Molybdenum and Tungsten Complexes: Synthesis and Studies of the Isomerization Equilibria and Kinetics The anionic molybdenum and tungsten complexes [L_RM(CO)₃]^? (L_R^? = [(C₅H₅)Co{P(O)R₂}₃]^?, R = OCH₃, OC₂H₅, O-i-C₃H₇; M = Mo, W) have been alkylated with the iodides R′ I, R′ = CH₃, C₂H₅, i-C₃H₇, and CH₂C₆H₅. The reactivity pattern of the alkylation is in accord with a S_N2 mechanism. Depending on M, R′, reaction temperature, and time the η-alkyl (carbonyl) compounds [L_RM(CO)₃R′] and/or the isomeric η²-acyl compounds [L_RM(CO)₂(η²-COR′)] can be obtained. 8 new σ-alkyl(carbonyl) compounds and 15 new η²-acyl compounds have been isolated and characterized. The ¹H NMR and the IR spectra give conclusive evidence that the σ-alkyl(carbonyl) compounds [L_RM(CO)₃R′] are formed as the primary products of the alkylation and that they isomerize partly or completely to give the η²-acyl compounds [L_RM(CO)₂(η²-COR′)]. The position of the equilibrium σ-alkyl(carbonyl)/η²-acyl is controlled by the steric demands of the groups R′ and the ligands L_R^?. The molybdenum compounds isomerize much more readily than the tungsten compounds. The rate constants of the isomerization processes [L_RMo(CO)₃CH₃] → [L_RMo(CO)₂(η²-COCH₃)], R = OCH₃, OC₂H₅, and O-i-C₃H₇, measured at 305 K in acetone-d₆, are 6–8 x 10^?3 s^?1.