Bryan D. Neaves

Reactions of coordinated nitride to generate novel rhenium and molybdenum imido complexes: The crystal and molecular structures of [Mo(NCPh3)(S2CNMe2)3)]BF4 and [Mo(NSO2Ph)(S2CNMe2)3]PF6

Abstract The nitrido complexes [MoN(S 2 CNR 2 ) 3 ] (R 2  Me 2 , Et 2 ) and [ReN)S 2 CNR 2)2 -(PMe 2 Ph) n ] (R 2  Me 2 ; Et 2 ; n  0, 1) react with halides R′X (R′  PhCO, PhSO 2 , 2,4-(NO 2)2 C 6 H 3 , 2,4-(NO 2)2 C 6 H 3 S; X  Cl, R′  Me, X  I), [R′3 O ]BF 4 (R′  Me, Et) or [Ph 3 C]BF 4 to give the imido complexes [Mo(NR′)(S 2 CNR 2 ) 3 ]+ and [Re(NR′)(S 2 CNR 2 ) 2 (PME 2 Ph) n ] (R′  Me, Et, Ph 3 C + , PhSO 2 , PhCO, 2,4(O 2 N) 2 -C 6 H 3 , 2,4-(O 2 N) 2 C 6 H 3 S); the X-ray crystal structures of [Mo(NCPh 3 )(S 2 -CNMe 2 )3]BF 4 and [Mo(NSO 2 Ph)(S 2 CNMe 2 )3]PF 6 have been determined. Both complexes have approximately pentagonal bipyramidal geometries although the NSO 2 Ph complex is more distorted. The NCPh 3 and NSO 2 Ph complexes have MoNC and MoNS angles of 175.1(5) ° and 161.3(13)° and MoN distances of 1.731(2) and 1.70(2)A, respectively.

Studies of molybdenum thiolato-complexes. The crystal and molecular structures of two triply bridged Mo(V) dimers, [Bu 4 n N][Mo2O2Cl5(SPh)2] and [Mo2O3(SPh)2(S2CNMe2)2]

SummaryThe complex [Bu4nN][Mo2O2Cl5(SPh)2] has been prepared by reaction of [Bu4nN][MoO(SPh)4] with stoichiometric amounts of HCl and characterised by single crystal X-ray structure analysis. The dimer is bridged by two oxo-groups and one chloride and each Mo has pseudo-octahedral co-ordination. The related compound [Mo2O3(SPh)2(S2CNMe2)2] was synthesised by reaction of [MoO2(S2CNMe2)2] with thiophenol in methanol and has also been characterised crystallographically. In this case the triple-bridge consists of two thiophenolate sulphurs and one oxo-group, each molybdenum having pseudo-octahedral geometry. These structures are compared with other triply-bridged species.

Molybdenum, rhenium, and tungsten complexes with bi- and tri-dentate phosphinothiolato-ligands; structures of [Mo{PhP(CH2CH2S)2}2] and [Mo(NNMe2){PhP(CH2CH2S)2}2]

[ReOCl3(PPh3)2] reacts with two equivalents of Ph2PCH2CH2SH in tetrahydrofuran to give [ReOCl(Ph2PCH2CH2S)2]. An excess of tridentate PhP(CH2CH2SH)2 reacts with [ReOCl3(PPh3)2] to yield [Re{PhP(CH2CH2S)2}{PhP(CH2CH2S)(CH2CH2SH)}] containing a pendant unto-ordinated SH group. This complex reacts reversibly with CO to form [Re{PhP(CH2CH2S}{PhP(CH2-CH2S)(CH2CH2SH)}(CO)][ν(CO) at 1 980 Cm–1]. The MIV complexes [MCl4L2][M = MO or W, L = PPh3 or MeCN) react with PhP(CH2CH2SH)2 in MeOH to give [M(PhP(CH2CH2S)2)2]. An X-ray crystal-structure determination for the complex with M = MO showed a distorted octahedral structure with an average MO–S distance of 2.44 A. The complex crystallises in the triclinic space group p, with a= 10.601(7), b= 10.867(4), c= 12.347(1)A, α= 66.98(3), β= 85.60(4), γ= 63.70(4)°, and Z= 2. 1 337 Unique reflections with I0 3σ(I0) used in the solution converged at R= 0.0979. The hydrazido(2–) complexes [MCl(NNMe2)2(PPh2)2]Cl react with PhP(CH2CH2SH)2 in MeOH to give [M(NNMe2){PhP(CH2CH2S)2}2](M = MO or W). An X-ray crystal-structure determination of the complex with M = MO revealed a distorted pentagonal-bipyramidal structure with a linear apical NNMe2 ligand. The complex crystallises in the monoclinic space group P21/n, with a= 11.349(2), b= 12.403(3), c= 19.302(4)A, β= 104.28(2)°, and Z= 4. 2 796 Unique reflections with I0 > 3σ(I0) used in the solution converged at R= 0.605.

Synthesis, electrochemistry, and electron spin resonance spectra of some seventeen-electron complexes containing the {Mo(NO)}2+ core and the molecular structure of [Mo(NO){HB(Me2pz)3}(pyr)2]

The reactions between [Mo(NO)LI2][L = hydrotris(3,5-dimethylpyrazol-1-yl)borate] and several neutral, unsaturated nitrogen-heterocyclic ligands have been investigated in order to establish the nature of the paramagnetic species produced. The complexes [Mo(NO)L(A)2]+(A = imidazole, N-methylimidazole, pyrazole, 3,5-dimethylpyrazole, or pyridine) have been isolated as their [BPh4]– salts from such reactions with an excess of A. These complexes are paramagnetic and exhibit room-temperature e.s.r. signals in which hyperfine coupling to molybdenum isotopes is apparent. In the cases where A = pyridine or N-methylimidazole the complexes exhibited a reversible one-electron reduction process in their cyclic voltammograms. However, where an exchangeable proton was bound to a nitrogen atom in A, irreversible reduction was observed. The neutral diamagnetic complex [Mo(NO)L(pyr)2](pyr = pyrrol-1-yl) was also prepared, and was found to undergo a reversible one-electron reduction at more anodic potentials than its cationic counterparts. An X-ray diffraction study of [Mo(NO)L(pyr)2] revealed a linear nitrosyl ligand and an average Mo–N(pyrrolyl) distance of 2.040 A.

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.

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.

Molybdenum and tungsten nitrosyl complexes containing bulky alkoxy, aryloxy, and arylamido ligands: their electrochemical behaviour and the structure of [Mo{HB(Me2pz)3}(NO)I(OCH2CH2CH2Br)]

The complexes [Mo{HB(Me2pz)3}(NO)X(NHR′)](X = I, R′=o-C6H4Me, 2,5-Me2C6H3, CHPh2, p-C6H4CN, p-C6H4N2Ph, p-C6H4N2C6H4NO2-p; XCl, R′=p-C6H4I), [W{HB(Me2pz)3}(NO)Cl(NHR′)](R′= CHPh2 or p-C6H4I), [Mo{HB(Me2pz)3}(NO)I(OR)](R = CH2CH2CH2Br, p-CH2C6H4Br, or p-C6H4CN), and [W{HB(Me2pz)3}(NO)Cl(OR)](R = Ph, CH2CH2CH2Br, or p-CH2C6H4-Br)(Me2pz = 3,5- dimethylpyrazolyl) have been prepared and characterised spectroscopically. Electrochemical studies (cyclic voltammetry, coulometry) of these complexes in acetonitrile established that all underwent at least one one-electron reduction process, some of which were reversible. The E1/2 values for the reduction were dependent on the nature of the metal, the halide, and the NHR′ or OR group. The structure of [Mo{HB(Me2pz)3}(NO)I(OCH2CH2CH2Br)] was determined crystallographically. The six-co-ordinate nature of the complex was confirmed and the Mo–O bond distance was 1.89 A, comparable to that in other related compounds.

Electrochemical and chemical properties of di-iodonitrosyl[tris(3,5-dimethylpyrazolyl)borato]molybdenum, [Mo{HB(Me2pz)3}(NO)I2], and related complexes

Cyclic voltammetric (c.v.), coulometric, and e.s.r. spectroscopic studies have established that [Mo{HB(Me2pz)3}(NO)I2], (A)(Me2Pz = 3,5-dimethylpyrazolyl), can be reduced reversibly to a paramagnetic monoanion in tetrahydrofuran (thf) solution, and that (A)– dissociates I– giving [Mo{HB(Me2pz)3}(NO)I(solvent)], (B). The latter undergoes a reversible one-electron oxidation process. The electrochemical behaviour (c.v.) of [W{HB(Me2pz)3}(NO)(CO)2] and [Mo{HB(Me2pz)3}(NO)L2]z(L = NCMe, z=+1; L = CO, z= 0) has also been briefly examined. Reduction of complex (A) by Li(C6H4Me-p) in diethyl ether afforded the complex [Mo{HB(Me2pz)3}(NO)I2{Li(OEt2)2}], (E), whose characterisation and properties are described. It is thought that (E) contains the {Mo–(µ-I)2Li+} group.