J. R. Dilworth

New synthetic routes to mono-, di- and tri-carbonyl halido complexes of rhenium(I) and rhenium(III) with tertiary phosphine

Abstract Carbonylation of tertiary phosphine complexes under reducing conditions is shown to be a reliable and direct route to rhemium mono- and poly-carbonyl complexes.

Molybdenum(IV) complexes with terminal imido- and nitrido-ligands the crystal and molecular structures of [MoN(N3)(Ph2P(CH2)2PPh2)2] and [MoBr(NH)(Ph2P(CH2)2PPh2)2] Br·MeOH

Abstract The structures of [MoN(N3)(Ph2P(CH2)2PPh2)2] (I) and [MoBr(NH)(Ph2P(CH2)2PPh2] Br·MeOH (II) have been determined. Crystal data (I): Space Group Pl. a = 11540(2), b = 13.102(2), c = 9.612(2) A, α = 99.58(1), β = 108.88(1), γ = 110.46(1)°, V = 1211.50 A3, Z = 1;2731 reflections to give R = 0.061. Crystal data (II): Space Group P21/n; a = 18.111(2) A, b = 16.548(3), A, c = 18.064(2) A, α = 90.0°, β = 105.30(1)°, γ = 90.0°; V = 5395.15 A3; Z = 4; 1837 reflections to give R = 0.054. In I the geometry is pseudooctahedral and the Mo-nitride distance is unusually long at 1.79(2) A. The trans azido-group is nearly linear (

Cyclopentadienyl titanium complexes with aryldiazenido- or phosphiniminato-ligands

[Ti(η5-C5H5)Cl3] reacts with Me3Si—N=N—Ph to give [Ti(η5-C5H5)Cl2(N2Ph)], and this gives [Ti(η5-C5H5)2Cl(N2Ph)] on treatment with sodium cyclopentadienide in THF at —80°C. [Ti(η5-C5H4R)Cl3] (R = H, Me) reacts analogously with Me3Si—N=PR3 (PR3 = PPh3, PPh2Me) to give [Ti(η5-C5H4R)Cl2(NPR3)]. Under similar conditions TiCl4 gives [TiCl4(Me3SiNPR3)].

Molybdenum-hydrazido(2−) complexes with tridentate thiolate ligands

Abstract Recent EXAFS [1] studies of nitrogenase and other molybdo-proteins have stimulated interest in molybdenum complexes with sulfur ligands. However, none of the complexes so far reported bind or activate dinitrogen. In fact, there are very few examples of molybdenumsulfur complexes which interact with small molecules that can function as inhibitors or alternative substrates for nitrogenase or indeed with any ligands relevant to nitrogen fixation. Hydrazido(2−) complexes are proven intermediates in both protonation [2] and the alkylation [3] or coordinated dinitrogen. This paper reports their use to probe the properties of a molybdenum site ligated to thiolate-containing ligands of the type L = HSCH2CH2XCH2CH2SH2, where X = NR, PR, O, and S. t001 . Comparison of MoNN Geometries in Molybdenum-hydrazido and Molybdenum-diazenido Complexes, Complex MoN NN MoNN Ref. a. Six coordinate Mo [MoO(N2R2)(dtc)2] a 1.799 1.29 168.0 7 [Mo(N2Ph2)(dtc)2] 1.790 1.31 169.9 8 [Mo(N2PhMe)2(dtc)2] 1.790 1.30 172.6 9 [MoO(N2Ph2)(S2N2)] b 1.778 1.309 172.9 10 [Mo(N2Ph)(S2N2)] 1.82 1.28 170.4 10 [MoO(N2Me2)(C9H6NO)2] 1.800 1.28 155.5 11 [S2MoS2Mo(N2Me2)2S2MoS2]2− 2.15 1.19 167.0 12 b. Seven coordinate Mo [Mo(N2Ph)(dtc)3] 1.781 1.233 171.5 13 [Mo(N2PhEt)(dtc)3]+ 1.715 1.37 170.0 14 [Mo(N2MePh)(NHHMePh)(dtc)+2 1.75 1.29 169.6 15 [Mo(N2CO2Me)(NHNHCO2Me)(dtc)2] 1.74 1.30 177.1 16 [Mo(NNMe2)(SPS)] e 1.775 1.265 178.3 c. Five coordinate Mo [MoO(N2Me2)(SPh)3]+ 1.806 1.30 176.7 17 [MoO(N2Me2)(SSS)] c 1.78 1.29 176.2 18 [MoO(N2Me2)(SOS)] 1.79 1.29 174.3 This work [MoCl(N2Me2)2(PPh3)2]+ 1.761 1.25 173.9 19 [S2MoS2Mo(N2Me2)2(PPh3)2] 1.78 1.30 165.0 20 1.80 1.27 178.2 a dtc = dithiocarbamate, (S2CNR2)−. b S2N2 = (SCH2CH2NRCH2CH2NRCH2CH2S)−. c SSS = (SCH2CH2SCH2CH2S)2−. e SPS = (SCH2CH2PPLCH2CH2S)2−. The synthesis and structural characterization of the precursor species Mo2O3L2, where X = NR, O and S have been described elsewhere [4, 5]. Reactions of these complexes with phenylhydrazine result in the isolation of yellow, diamagnetic monomers MoO(NNHC6H5)L, I, whose structure is illustrated in Fig. 1. Reaction of I with Me3SiCl in dry methanol results in protonation of the hydrazido-ligand to give the hydrazido(1−) species, [MoO(N2H2Ph)L]+, III, isolated as the BPh−4 salt. Protonation appears to occur at the metal-bound nitrogen to give the dihapto-coordination type previously described for [Mo(dtc)3(NNMePh)] BPh4 [6], shown schematically in Fig. 2. Reactions of the precursor materials with disubstituted hydrazines, such as H2NNMe2, yield exclusively bis-hydrazido(2−) complexes, of the type Mo(NNMe2)2L, deep purple, diamagnetic monomeric materials, whose structural identification is in progress. When L is −SCH2CH2PPhCH2CH2S−, the major product isolated upon reaction of the molybdenum precursor with disubstituted hydrazine is [Mo(NNMe2)L2], II, a seven coordinate diamagnetic monomer, whose coordination geometry is illustrated in Fig. 3. The geometry of the molybdenum-hydrazido(2−) grouping is similar both I and II. Linear MoNN moieties, with considerable double bond character in both the MoN and NN bonds, are common to the structural chemistry of molybdenum-hydrazido(2−) species, as illustrated in Table I. The exceptions to the common geometric type [Mo3S8(NNMe2)2]2− [7] and [MoO(NNPh2)(oxime)2] [8] show unusual protonation chemistry and suggest that the course of protic degradation reactions of metal-bound hydrazides are sensitive to the MNN geometry. Crystal Data. Complex I, MoC10H14O2N2S2, crystallizes in the triclinic space group P1 with a = 9.307(2) A, b = 11.108(3) A, c = 14.139(3) A, α = 89.7(1)°, β = 91.88(1), γ = 107.91(2)°, V = 1390.0(9) A3 and Z = 4 to give Dcalc = 1.69 g cm−3 and μ = 12.15 cm−1 (MoKα, λ = 0.71069 A. A total of 1956 reflections with I ⩾ 3.0σ(I) formed the basis for a full-matrix least squares refinement. Analysis converged at R = 0.045 and Rw = 0.042, with a ‘goodness of fit’ of 1.21.

The effects of steric hindrance on the chemistry of rhenium and molybdenum nitrosyl thiolato-complexes. The structures of [Mo(SC6H2Pr3i)3(NH3)(NO)] and [Re(SC6H3Pr2i)4(NO)]

Abstract The Re(II) nitrosyl complex [ReCl2(OMe)(NO)(PPh3)2] reacts with excess 2,6-Pr2iC6H3S−(DIPT−) in methanol to give the Re(III) complex [Re(DIPT)4(NO)] (I) whereas thiophenolate gives a thiolatobridged Re(II) dimer. Crystal data for(I): crystallizes in the orthorhombic space group Pbca, a = 13.218(6) A, b = 19.534(9) A, c = 38.115(13) A, V = 9841.3(6) A3 to give Dcalc = 1.35 g cm−3 for Z = 8. Structure solution and refinement are based on 3047 reflections with Io>3σ|Io| and yielded a final R value of 0.064. The overall geometry about Re is trigonal bipyramidal with an apical NO group with a nearly linear ReNO system (ReNO, 173.6(14)°). The polymeric species ‘{Mo(NO)(NH2O)}n’ reacts with excess 2,4,6-Pr3iC6H2S−(TIPT− to give[Mo(TIPT)3(NH3)(NO)]·C5H12 (II) (C5H12 = n-pentane) whereas thiophenolate anion gives [Mo(SPh)4(NO)]−. Crystal data for (II): space group P21/n with a = 10.477(3) A, b = 26.359(5) A, c = 20.124(4) A, β = 87.21(1)°, with V = 5550.9(12) A3 to give Dcalc = 1.05 g cm−3 for Z = 4. Structure refinement was based on 1040 reflections with Io>3σ|Io| and yielded a final R value of 0.079. The geometry about Mo is again trigonal bipyramidal with apical NO and NH3 groups and again an essentially linear MoNO system (MNO = 174.2(3)°).

A convenient route to complexes of the type [MoO(SR)4]–(R = aryl) and [MoO{S(CH2)nS}2]–(n= 2 or 3) preparation and crystal structure of [PPh4][Mo(NNMe2)O(SC6H5)3]·(C2H5)2O

The complexes [MoO(SR)4]–(R = aryl) and [MoO{S(CH2)nS}2]–(n= 2 or 3) can be prepared by reaction of an MoVI butanediolato-complex with thiolate anion in methanol. The complexes [MoO(SPh)4]– react with R′2NNH2[R′2= Me2 or (CH2)5] in refluxing CH3CN to give [Mo(NNR′2)O(SPh)3]–. Crystal Data for [PPh4][Mo(NNMe2)O(SC6H5)3]·(C2H5)2O : space group Pbca, a= 12.789(4), b= 19.375(3), c= 36.941(3)A, Z= 8.3 225 Independent reflections with I > 3σ(I) gave R= 0.076. The geometry is essentially square-pyramidal with an apical oxo-group and the NNMe2 group in the basal plane. Although the MO–N and N–N distances of 1.821(9) and 1.292(14)A respectively are analogous to other hydrazido(2–) complexes, the Mo–N–NMe2 system is anomalously bent with MO–N–N = 152.5(10)°.

Complexes of osmium with metal-nitrogen multiple bonds

New arylimido-complexes of osmium [OsCl2(NC6H4X)(PPh3)2] (X = H, Cl, or OMe) were prepared from [OsCl3O(PPh3)2] and Ph3P=NCOC6H4X. The preparations of [Os(N3)2(PMe2Ph)4] and [OsCl2(N3)(PR2Ph)3] (R = Me, Et, Prn, or Bun) were also achieved. Attempts to obtain nitrido-complexes by decomposition of these azides were not successful.

Dinitrogen complexes of rhenium(I) and rhenium(II)

Dinitrogen complexes of rhenium(I) are prepared by the reaction of benzoylazo-complexes, [Re(NNCOPh)Cl2(PPh3)xLy](L = monodentate ligand or ½ bidentate ligand; x= 0 or 2, x+y= 3), with certain ligands in boiling methanol. The dinitrogen complexes are of the type trans-[ReCl(N2)LxL′y](L = a variety of organophosphines; L′= L or some other organophosphine, CO or PF3; x+y= 4). For L = L′= PMe2Ph the dinitrogen complex has an exceptionally low ν(N2)(1925 cm–1). Despite its low ν(N2), it is not easily reduced and strong Bronsted acids protonate the metal rather than the bound dinitrogen. On oxidation, the dinitrogen complexes form moderately stable paramagnetic cations, e.g., trans-[ReCl(N2)(Ph2PCH2CH2PPh2)2]+.

From Phosphorus Towards Sulphur: The Development of New Dinitrogen Binding Sites

The binding and activation of dinitrogen by molybdenum and tungsten tertiary phosphine complexes is now well established and has been reviewed extensively (Henderson et al. 1983). Recent work in this area at the Unit of Nitrogen Fixation has concentrated on detailed investigations of the mechanism of the protonation reaction and attempts to render it cyclic or catalytic via electrochemical methods.