Tungsten Nitrosyl Research Articles

Effects of the η(5)-C5H4(i)Pr Ligand on the Properties Exhibited by Its Tungsten Nitrosyl Complexes.

Reaction of Na[η(5)-C5H4(i)Pr] with W(CO)6 in refluxing THF for 4 days generates a solution of Na[(η(5)-C5H4(i)Pr)W(CO)3] that when treated with N-methyl-N-nitroso-p-toluenesulfonamide at ambient temperatures affords (η(5)-C5H4(i)Pr)W(NO)(CO)2 (1) that is isolable in good yield as an analytically pure orange oil. Treatment of 1 with an equimolar amount of I2 in Et2O at ambient temperatures affords (η(5)-C5H4(i)Pr)W(NO)I2 (2) as a dark brown solid in excellent yield. Sequential treatment at low temperatures of 2 with 0.5 equiv of Mg(CH2CMe3)2 and Mg(CH2CH═CMe2)2 in Et2O produces the alkyl allyl complex, (η(5)-C5H4(i)Pr)W(NO)(CH2CMe3)(η(3)-CH2CHCMe2) (3), as a thermally sensitive yellow liquid. Complex 3 may also be synthesized, albeit in low yield, in one vessel at low temperatures by reacting 1 first with 1 equiv of PCl5 and then with the binary magnesium reagents specified above. Interestingly, similar treatment of 1 in Et2O with PCl5 and only 0.5 equiv of Mg(CH2CH═CMe2)2 results in the formation of the unusual complex (η(5)-C5H4(i)Pr)W(NO)(PCl2CMe2CH═CH2)Cl2 (4), which probably is formed via a metathesis reaction of the binary magnesium reagent with (η(5)-C5H4(i)Pr)W(NO)(PCl3)Cl2. The C-D activation of C6D6 by complex 3 has been investigated and compared to that exhibited by its η(5)-C5Me5, η(5)-C5Me4H, and η(5)-C5Me4(n)Pr analogues. Kinetic analyses of the various activations have established that the presence of the η(5)-C5H4(i)Pr ligand significantly increases the rate of the reaction, an outcome that can be attributed to a combination of steric and electronic factors. In addition, mechanistic studies have established that in solution 3 loses neopentane under ambient conditions to generate exclusively the 16e η(2)-diene intermediate complex (η(5)-C5H4(i)Pr)W(NO)(η(2)-CH2═CMeCH═CH2), which then effects the subsequent C-D activations. This behavior contrasts with that exhibited by the η(5)-C5Me5 analogue of 3 which forms both η(2)-diene and η(2)-allene intermediates upon thermolysis. Sixteen-electron (η(5)-C5H4(i)Pr)W(NO)(η(2)-CH2═CMeCH═CH2) has been isolated as its 18e PMe3 adduct. All new organometallic complexes have been characterized by conventional spectroscopic and analytical methods, and the solid-state molecular structures of two of them have been established by single-crystal X-ray crystallographic analyses.

Trisphosphine-chelate-substituted molybdenum and tungsten nitrosyl hydrides as highly active catalysts for olefin hydrogenations.

Reaction of [M(NO)Cl3 (NCMe)2 ] (M=Mo, W) with (iPr2 PCH2 CH2 )2 PPh (etp(i) p) at room temperature afforded the syn/anti-[M(NO)Cl3 (mer-etp(i) p)] complexes (M=Mo, a; W, b; 3 a,b(syn,anti); syn and anti refer to the relative position of Ph(etp(i) p) and NO). Reduction of 3 a,b(syn,anti) produced [M(NO)Cl2 (mer-etp(i) p)] (4 a,b(syn)), [M(NO)Cl(NCMe)(mer-etp(i) p)] (5 a,b(syn,anti)), and [M(NO)Cl(η(2) -ethylene)(mer-etp(i) p)] (6 a,b(syn,anti)) complexes. The hydrides [M(NO)H(η(2) -ethylene)(mer-etp(i) p)] (7 a,b(syn,anti)) were obtained from 6 a,b(syn,anti) using NaHBEt3 (75 °C, THF) or LiBH4 (80 °C, Et3 N), respectively. 7 a,b(syn,anti) were probed in olefin hydrogenations in the absence or presence of a hydrosilane/B(C6 F5 )3 mixture. The 7 a,b(syn,anti)/Et3 SiH/B(C6 F5 )3 co-catalytic systems were highly active in various olefin hydrogenations (60 bar H2 , 140 °C), with maximum TOFs of 5250 h(-1) (7 a(syn,anti)) and 8200 h(-1) (7 b(syn,anti)) for 1-hexene hydrogenation. The Et3 SiH/(B(C6 F5 )3 co-catalyst is anticipated to generate a [Et3 Si](+) cation attaching to the ONO atom. This facilitates NO bending and accelerates catalysis by providing a vacant site. Inverse DKIE effects were observed for the 7 a(syn,anti)/Et3 SiH/(B(C6 F5 )3 (kH /kD =0.55) and the 7 b(syn,anti)/Et3 SiH/(B(C6 F5 )3 (kH /kD =0.65) co-catalytic mixtures (20 bar H2 /D2 , 140 °C).

Hydrogenation of imines catalyzed by trisphosphine-substituted molybdenum and tungsten nitrosyl hydrides and co-catalytic acid.

Hydride complexes Mo,W(CO)(NO)H(mer-etp(i)p) (iPr2PCH2CH2)2PPh=etp(i)p) (2 a,b(syn), syn and anti of NO and Ph(etp(i)p) orientions) were prepared and probed in imine hydrogenations together with co-catalytic [H(Et2O)2][B(C6F5)4] (140 °C, 60 bar H2). 2 a,b(syn) were obtained via reduction of syn/anti-Mo,W(NO)Cl3(mer-etp(i)p) and syn,anti-Mo,W(NO)(CO)Cl(mer-etp(i)p). [H(Et2O)2][B(C6F5)4] in THF converted the hydrides into THF complexes syn-[Mo,W(NO)(CO)(etp(i)p)(THF)][B(C6F5)4]. Combinations of the p-substituents of aryl imines p-R(1)C6H4CH=N-p-C6H4R(2) (R(1),R(2)=H,F,Cl,OMe,α-Np) were hydrogenated to amines (maximum initial TOFs of 1960 h(-1) (2 a(syn)) and 740 h(-1) (2 b(syn)) for N-(4-methoxybenzylidene)aniline). An 'ionic hydrogenation' mechanism based on linear Hammett plots (ρ=-10.5, p-substitution on the C-side and ρ=0.86, p-substitution on the N-side), iminium intermediates, linear P(H2) dependence, and DKIE=1.38 is proposed. Heterolytic splitting of H2 followed by 'proton before hydride' transfers are the steps in the ionic mechanism where H2 ligand addition is rate limiting.

Coordination Properties of Multidentate Phosphanylborane Ligands in Tungsten Nitrosyl Complexes

AbstractThe ambiphilic and small‐bite‐angle diphosphanylborane ligands Ph2PCH(PPh2)CH2B(C8H14) (2) and Ph2PCH2CH[B(C8H14)]PPh2 (3) containing the Lewis acidic 9‐boranorbornyl group B(C8H14) have been prepared in one step by regioselective anti‐Markovnikov hydroborations of 1,1‐bis(diphenylphosphanyl)ethylene and 1,2‐bis(diphenylphosphanyl)ethylene with 9‐borabicyclo[3.3.1]nonane (9‐BBN) under relatively drastic reaction condition. The coordination properties of Ph2PCH2CH2B(C8H14) (1) and the newly prepared 2 and 3 towards the tungsten nitrosyl fragment {WNO}6 have been studied structurally and spectroscopically. Herein, we report the cis and trans tungsten nitrosyl complexes cis‐[W(CO)2(1)2(NO)(Cl)] (cis‐4a), cis‐[W(CO)2(1)2(NO)(H)] (cis‐4b), trans‐[W(CO)2(1)2(NO)(Cl)] (trans‐4a), trans‐[W(CO)2(1)2(NO)(H)] (trans‐4b), cis‐[W(CO)2(2)(NO)(Cl)] (cis‐5a), cis‐[W(CO)2(2)(NO)(H)] (cis‐5b), cis‐[W(CO)2(3)(NO)(Cl)] (cis‐6a), cis‐[W(CO)2(3)(NO)(H)] (cis‐6b), which were readily obtained from straightforward ligand‐substitution reactions of the tungsten carbonyl nitrosyl precursor [W(NO)(CO)4(ClAlCl3)] in tetrahydrofuran. The crystal structures of the tungsten chloride complexes cis‐4a, trans‐4a, and cis‐5a revealed that the trialkyl boron centers are free pendants in the secondary coordination spheres, whereas in the hydride complexes trans‐4b, cis‐5b, and cis‐6b the hydride ligand trans to the nitrosyl ligand is σ coordinated to the tethered B(C8H14) group and form three‐center, two‐electron (3c–2e) W–H–B bonds, which were observed in their crystal structures. The authenticity of the 3c–2e W–H–B bond in the tungsten hydride complex cis‐5b was further checked by a DFT structural optimization and natural bond order (NBO) analysis.

Molybdenum and Tungsten Nitrosyl Complexes in Hydrogen Activation

AbstractTwo transition‐metal hydride complexes of the type [M(dippe)2(NO)(H)] [M = W (2a), Mo (2b); dippe = 1,2‐bis(diisopropylphosphanyl)ethane] have been prepared by the reaction of [M(dippe)2(NO)(Cl)] [M = W (1a), Mo (1b)] with LiBH4. The nitrosyl groups of the tungsten complexes 1a and 2a are capable to coordinate a LiBH4 molecule to form the stable adducts W(dippe)2(Cl)(NO···LiBH4) (1c) and W(dippe)2(H)(NO···LiBH4) (2c). Addition of ethylenediamine to a toluene solution of 2c led to rupture of the 2c adduct and afforded 2a in good yield. After the interaction of 2a with [H(Et2O)][BF4], the stable seven‐coordinated cationic dihydride [W(dippe)(H)2(dippe)(NO)][BF4] (6a) was isolated. The reaction between 2b and [H(Et2O)][BF4] led to the formation of [Mo(dippe)2(NO)(FBF3)] (6b) in which BF4– was found to be coordinated to the metal centre. The [H(Et2O)2][BArF4] [ArF = 3,5‐(CF3)2C6H3] acid interacted with 2a to yield the seven‐coordinated complex [W(dippe)(H)2(dippe)(NO)][BArF4] (5a) similar to 6a. In the reaction between 2b and [H(Et2O)2][BArF4], the 16e– five‐coordinated complex [Mo(dippe)2(NO)][BArF4] (4b) was formed. X‐ray diffraction revealed that 4a has a weak agostic interaction trans to the NO ligand. Complex 4b was found to react rapidly with hydrogen gas under ambient conditions to form the dihydride complex [Mo(dippe)(H)2(dippe)(NO)][BArF4] (5b), which is unstable in the absence of a hydrogen atmosphere. The equilibrium constant for the reversible reaction of 4b with hydrogen was found to be K = 2.6 bar–1 at 25 °C. Complex 4b was tested as a catalyst for acetone hydrogenation; a maximum TON of 7 was found.

Redox and catalytic properties of alkoxides based on tris(3,5-dimethylpyrazolyl)borato tungsten nitrosyls

Abstract Previously we reported on the catalytic properties of species based on the {Mo(NO)(Tp Me2 )O 2 } moiety in the cathodic reduction of chloroform. Here, we have performed cyclic voltammetry and spectroscopic studies of the tungsten bis -alkoxide [W(NO)(Tp Me2 )(OEt) 2 ], a novel chelate [W(NO)(Tp Me2 )O(CH 2 ) 4 O], and a mono -alkoxide [W(NO)(Tp Me2 )Cl(OEt)] [Tp Me2 = hydrotris(3,5-dimethylpyrazol-1-yl)borate]. All these complexes efficiently catalyse the cathodic reduction of chloroform which proceeds even at ca. −1.77 V versus Fc + /Fc in the presence of the chloro(ethoxy) complex. The chelate complex exhibits a quasi-reversible one-electron reduction at a potential 180 mV more anodic than its bis(ethoxy) counterpart. The UV–Vis spectrum of the former complex shows a red-shifted band (by 70 nm) in the visible region when compared with the latter.

Transformations of Cyclic Olefins Mediated by Tungsten Nitrosyl Complexes

This report describes investigations that have elucidated the nature, extent, and mechanism of the cyclic-olefin oligomerization effected by a series of tungsten precatalysts, with particular focus on Cp*W(NO)(CH2CMe3)2 (1) and Cp*W(NO)(CH2SiMe3)(η2-CPhCH2) (2). Upon thermolysis, these precatalysts oligomerize simple cyclic olefins, from cyclopentene to cyclooctene, into ring-retaining oligomers as high as dodecamers (depending on the substrate) with remaining sites of unsaturation. Precatalyst initiation involves the coupling of one equivalent of the substrate with the reactive 16e intermediate thermally generated by the precatalyst (i.e., an alkylidene by 1 or an η2-alkyne complex by 2), followed by rearrangement of the coupled ligand in the metal’s coordination sphere either to an olefin or to a diene (with concomitant loss of two hydrogen atoms). The rearranged ligand is displaced from the metal center as two equivalents of substrate coordinate to form a putative bis-olefin complex, Cp*W(NO)(cyclic ol...

Redox activity of bimetallic complexes based on tris(3,5-dimethylpyrazolyl)borato molybdenum(II) and tungsten(II) nitrosyls. Complexes derived from ethane-1,2-diol and the crystal structure of anti-[Mo(NO){HB(3,5-Me 2C 3HN 2) 3}(OCH 2CH 2O)] 2 · 4CHCl 3

The bimetallic complexes [{M(NO)(Tp Me2)X} 2(OCH 2CH 2O)] [Tp Me2 = HB(3,5-Me 2C 3HN 2) 3; M = Mo, X = Cl, Br or I; M = W, X = Cl] have been synthesised and characterised spectroscopically and electrochemically. These species can occur as mixture of two diastereoisomers and one of them could be separated following a thermal treatment of the mixture. A direct synthesis of single diastereoisomers (M = Mo, X = I; M = W, X = Cl) is also described. The bimetallic species exhibit two one-electron reduction processes separated by a modest potential difference, Δ E 1/2, ca. 300 mV (M = Mo, X = Cl, Br) indicating an intermediate metal–metal interaction. In the crystal structure of anti-[{Mo(NO)(Tp Me2)(OCH 2CH 2O)} 2] · 4CHCl 3 two nonequivalent dinuclear molecules (point group C 2 h ) are found, with crystallographically identical, doubly bridged {Mo(NO)(Tp Me2)} distorted octahedral units.

Competition between NO reduction and NO decomposition over reduced V–W–O catalysts

The SCR of NO and NO decomposition were investigated over a V–W–O/Ti(Sn)O 2 catalyst on a Cr–Al steel monolith. The conversions of NO and NH 3 over the reduced and oxidised catalysts were determined. The higher conversion of NO than of NH 3 was observed in SCR over the reduced catalyst and very close conversions of both substrates were found over the oxidised one. The increase of the pre-reduction temperature was found to cause an increase in catalyst activity and its stability in direct NO decomposition. The surface tungsten cations substituted for vanadium ones in vanadia-like active species are considered to be responsible for the direct NO decomposition. The results of DFT calculations for the 10-pyramidal clusters: V 10O 31H 12 (V–V) and V 9WO 31H 12 (V–W) modelling (0 0 1) surfaces of vanadia and WO 3–V 2O 5 solid solution (s.s.) active species, respectively, show that preferable conditions for NO adsorption exist on W sites of s.s. species and that reduction causes an increase in their ability for electron back donation to the adsorbed molecule. Electron back donation is believed to be responsible for the electron structure reorganisation in the adsorbed NO molecule resulting in its decomposition. The high selectivity of NO decomposition to dinitrogen was considered to be connected with the formation of the tungsten nitrosyl complexes solely via the W–N bond.

Carbon–hydrogen bond activation in cyclopentadienyl dimethyl tungsten nitrosyl and carbonylBased on the presentation given at Dalton Discussion No. 4, 10–13th January 2002, Kloster Banz, Germany. Theoretical studies of inorganic and organometallic reaction mechanisms. Part 21.1

Mechanisms for generating tungsten carbene complexes from CpW(NO)(CH3)2, Cp*W(NO)(CH3)2 and [CpW(CO)(CH3)2]− by methane elimination were studied by density functional (B3LYP) computations. Based on the calculations, a one-step (σ-bond metathesis like) mechanism is preferred in nitrosyl complexes, while a two-step (oxidative addition then reductive elimination) mechanism is preferred in the carbonyl complex. The one-step mechanism is strongly assisted by the metal as the transition state for this mechanism has a W–H distance that is only ≈0.1 A longer than the W–H single bond in the oxidative addition intermediate. Stronger π backbonding of the NO ligand is responsible for the difference.

Redox activity of bimetallic molybdenum and tungsten nitrosyls containing ligands based on 4-hydroxyphenylalkanols

The redox-active bimetallic complexes, [{M(NO)L *X} 2Q] [L * = tris(3,5-dimethylpyrazolyl)borate, HB(3,5-Me 2pyz) 3; M = Mo, X = Cl or I; M = W, X = Cl; Q = OC 6H 4(CH 2) n O ( n = 1–3) or NHC 6H 4(CH 2) n O ( n = 2, 3)], have been prepared and characterized spectroscopically and electrochemically (cyclic voltammetry, coulometry). The electrochemical data indicate that there can be weak interactions between the two metal-based redox centres.

Strong Lewis acids derived from molybdenum and tungsten nitrosyls containing the tri-2-pyridylmethane ligand. Dynamic NMR studies of their adducts with aldehydes, ketones, and esters

Strong Lewis acids derived from molybdenum and tungsten nitrosyls containing the tri-2-pyridylmethane ligand. Dynamic NMR studies of their adducts with aldehydes, ketones, and esters

Monometallic, homo- and heterobimetallic complexes based on redox active tris(3,5-dimethylpyrazolyl)borato-molybdenum and -tungsten nitrosyls—I. Meta substituent effects on the reduction potentials of monometallic arylamide complexes

The complexes [Mo(NO)LCl(NHC 6H 4-3-Z)] (L = HB(3,5-Me 2C 3N 2H) 3; Z = F, Cl, Br, Me, OMe, CF 3, NO 2), [W(NO)L(NHC 6H 4-3-Z)] (Z = F, Cl, Br, Me, OMe, COME, CF 3, NO 2) and [W(NO)L(NHC 6H 4-3-CF 3) 2] have been synthesized and characterized by spectroscopic methods. All of the monoarylamide complexes undergo one-electron reduction processes at potentials which vary according to the nature of Z. A linear correlation was found between the reduction potentials within each of the two series and the Hammett meta substituent parameters, σ m , for Z. The respective reaction constants, ϱ m , and intercepts, E f 0, are for [Mo(NO)LCl(NHC 6H 4-3-Z)], ϱ m = 5.50 (0.39), E f 0 = −0.848 (0.009) V and for [W(NO)L(NHC 6H 4-3-Z)], ϱ m = 4.75 (0.50), E f 0 1.291 (0.011) V.

ChemInform Abstract: Monometallic, Homo‐ and Heterobimetallic Complexes Based on Redox‐Active Tris(3,5‐dimethylpyrazolyl)borato Molybdenum and Tungsten Nitrosyls. Part 7. Compounds Containing Strongly Interacting Redox Centers Derived from para‐Substituted Anilines and Phenols.

AbstractThe mononuclear complexes (I) are prepared by 1:2 molecular reaction of analogous dihalide complexes with corresponding p‐substituted anilines.

ChemInform Abstract: Monometallic, Homo‐ and Heterobimetallic Complexes Based on Redox‐Active Tris(3,5‐dimethylpyrazolyl)borato Molybdenum and Tungsten Nitrosyls. Part 8. Complexes Exhibiting Weak or Intermediate Interaction Between Two Redox Centers.

AbstractThe mono‐ and bimetallic complexes (I)‐(V) are prepared from the corresponding mononuclear dihalide complexes ML(NO)X2 and stoichiometric amounts of diamines or dioles, or in the case of the binuclear complexes by equimolar reactions of ML(NO)X2 with appropriate monometallic compounds (I) or (IV), respectively.

ChemInform Abstract: Catalysis of Diene Polymerization and Diels‐Alder Reactions by an Octahedral Tungsten Nitrosyl Lewis Acid. X‐Ray Crystal Structure of the η1‐Acrolein Complex (cis‐Me3P)(trans‐NO)(CO)3W‐O=C(H)C(H)=CH2.

ChemInformVolume 19, Issue 17 Organoelement Compounds ChemInform Abstract: Catalysis of Diene Polymerization and Diels-Alder Reactions by an Octahedral Tungsten Nitrosyl Lewis Acid. X-Ray Crystal Structure of the η1-Acrolein Complex (cis-Me3P)(trans-NO)(CO)3W-O=C(H)C(H)=CH2. R. V. HONEYCHUCK, R. V. HONEYCHUCK Dep. Chem. Biochem., Univ. Calif., Los Angeles, CA 90024, USASearch for more papers by this authorP. V. BONNESEN, P. V. BONNESEN Dep. Chem. Biochem., Univ. Calif., Los Angeles, CA 90024, USASearch for more papers by this authorJ. FARAHI, J. FARAHI Dep. Chem. Biochem., Univ. Calif., Los Angeles, CA 90024, USASearch for more papers by this authorW. H. HERSH, W. H. HERSH Dep. Chem. Biochem., Univ. Calif., Los Angeles, CA 90024, USASearch for more papers by this author R. V. HONEYCHUCK, R. V. HONEYCHUCK Dep. Chem. Biochem., Univ. Calif., Los Angeles, CA 90024, USASearch for more papers by this authorP. V. BONNESEN, P. V. BONNESEN Dep. Chem. Biochem., Univ. Calif., Los Angeles, CA 90024, USASearch for more papers by this authorJ. FARAHI, J. FARAHI Dep. Chem. Biochem., Univ. Calif., Los Angeles, CA 90024, USASearch for more papers by this authorW. H. HERSH, W. H. HERSH Dep. Chem. Biochem., Univ. Calif., Los Angeles, CA 90024, USASearch for more papers by this author First published: April 26, 1988 https://doi.org/10.1002/chin.198817270AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume19, Issue17April 26, 1988 RelatedInformation

ChemInform Abstract: Monometallic, Homo‐ and Hetero‐bimetallic Complexes Based on Redox Active Tris(3,5‐dimethylpyrazolyl)borato Molybdenum and Tungsten Nitrosyls. Part 6. Synthesis and Electrochemistry of Complexes Containing Saturated Heterocyclic Amide Ligands. X‐Ray Crystal and Molecular Structure of ((Mo(NO)(HB(Me2pz)3)Cl)2(NC4H8N)).

AbstractThe reaction of the appropriate dichloro complexes with an excess of the cyclic amines leads to the coordinatively unsaturated complexes (I).

Monometallic, homo- and hetero-bimetallic complexes based on redox-active tris(3,5-dimethylpyrazolyl)borato molybdenum and tungsten nitrosyls. Part 8. Complexes exhibiting weak or intermediate interaction between two redox centres

The complexes [ML(NO)X(NHQNH2)][L = tris(3,5-dimethylpyrazolyl)borate; M = Mo, X = I, Q =(C6H4)2Y where Y = O, SO2, CH2, or CH2CH2; M = W, X = Cl, Q =(C6H4)2O], [MoL(NO)I(NHCH2CH2C6H4NH2)], [ML(NO)X(OQOH)][M = Mo, X = I, Q =(C6H4)2Y where Y = nothing or S; X = Cl, Q =(C6H4)2S], and [ML(NO)X(OCH2C6H4CH2OH)](M = Mo, X = I; M = W, X = Cl) have been prepared. The bimetallic complexes [{ML(NO)X}2(NHQNH)][M = Mo, X = I, Q =(C6H4)2Y where Y = O, SO2, CH2, or CH2CH2; M = W, X = Cl, Q =(C6H4)2O], [{MoL(NO)I}2(NHCH2CH2C6H4NH)], [{MoL(NO)X}2(OQO)][X = I, Q =(C6H4)2 Y where Y = nothing or S; X = Cl, Q =(C6H4)2 Y where Y = nothing, S, SO2, CO, or COC6H4C6H4CO], and [{ML(NO)X}2(OCH2C6H4CH2O)](M = Mo, X = I; M = W, X = Cl) were obtained either from the monometallics by reaction with [ML(NO)X2] or by direct reaction of the latter with the appropriate arylamine or phenol. The heterobimetallic [MoL(NO)I(NHC6H4OC6H4NH)WL(NO)Cl] was also prepared and all compounds were characterised spectroscopically. The monometallic species underwent a single, usually reversible, one-electron reduction determined by cyclic voltammetry (in CH3CN using a Pt electrode). Values of E½ were dependent on M, X, and the nature of the heteroatom ligand. The bimetallic species underwent two one-electron reductions, investigated by differential pulse polarography. The separation between the redox potentials (ΔE½) varied from 45 mV (negligible interaction between redox centres) to 138 mV (weak interaction), depending on the nature of the bridging ligand.

Monometallic, homo- and hetero-bimetallic complexes based on redox-active tris(3,5-dimethylpyrazolyl)borato molybdenum and tungsten nitrosyls. Part 7. Compounds containing strongly interacting redox centres derived from para-substituted anilines and phenols

The compounds [ML(NO)X(NHC6H4ZH)][L = tris(3,5-dimethylpyrazolyl)borate; Z = NH; M = Mo, X = I; M = W, X = Cl; Z = O; M = Mo, X = I; M = W, X = Cl; Z = S, M = Mo, X = Cl], [{ML(NO)X}2(NHC6H4NH)](M = Mo, X = Cl or I; M = X = Cl), [{ML(NO)X}2(NHC6H4O)](M = Mo, X = Cl or I; M = W, X = Cl), [{MoL(NO)Cl}2(OC6H4O)], and [MoL(NO)I(YC6H4Z)WL(NO)Cl](Y = Z = NH; Y = O, Z = NH; Y = NH, Z = O) have been prepared. Cyclic voltammetric and coulometric studies established that the monometallic species undergo a one-electron reduction, whereas the bimetallic species are reduced in two one-electron steps. The electrochemical data suggest that the redox centres in the bimetallic complexes influence each other strongly.

ChemInform Abstract: Monometallic, Homo‐ and Hetero‐Bimetallic Complexes Based on Redox Active Tris(3,5‐dimethylpyrazolyl)borato‐molybdenum and ‐tungsten Nitrosyls. Part 4. Effects of Ligating Atom Type on the Reduction Potentials of Monometallic Complexes.

AbstractThe complexes (Ia)‐(Ic) are prepared by substitution reaction of their dichloro analogues (Id) with HY and characterized.