Lin-Shu Liou

Dimolybdenum complexes containing bridging acetate ligands and anions of N, N'-di(2-methoxyphenyl)formamidine

Abstract The syntheses, structures and NMR spectra of quadruply bonded complexes containing three, two or one bridging acetate ligands and anions of N , N ′-di(2-methoxyphenyl)formamidine ( o -HDMophF), of the types Mo 2 (O 2 CCH 3 ) 3 ( o -DMophF) ( 1 ), trans -Mo 2 (O 2 CR) 2 ( o -DMophF) 2 (R=CH 3 , 2 ; CF 3 , 3 ; Pr n , 4 ) and Mo 2 (O 2 CCH 3 )( o -DMophF)Cl 2 (PMe 3 ) 2 ( 5 ), are discussed. Complex 1 was prepared by reaction of Mo 2 (O 2 CCH 3 ) 4 with excess o -HDMophF in THF. The reactions of Mo 2 (O 2 CCH 3 ) 4 and Mo 2 (O 2 CPr n ) 4 with excess lithiated formamidine afforded complexes 2 and 4 , respectively. Complex 3 was prepared by reaction of Mo 2 (O 2 CCF 3 ) 4 with o -HDMophF in THF and complex 5 was prepared by reaction of 1 with (CH 3 ) 3 SiCl and PMe 3 in THF/CH 2 Cl 2 . Their UV–Vis and NMR spectra have been recorded and their structures have been determined by X-ray crystallography. The o -DMophF − ligands show two different conformations, s - trans , s - trans and s - cis , s - trans , in compounds 1 – 5 . The study on 31 P{ 1 H} NMR spectrum of 5 concluded that the through metal–metal quadruple bonding coupling | 3 J PMoMoP | is about 16±1 Hz. The position of the monodentate phosphine ligand, i.e. cis or trans to the acetate or similar ligands, can be determined by evaluating the | 3 J CP | coupling constant.

Synthesis and structural characterization of two chain complexes of Mn(II) containing 2-aminopyridinium

Abstract The 2-aminopyridine ligand has been exploited in preparation of divalent metal complexes of the formulae [H(2-ampy)][MnCl3(H2O)] 1 and [H(2-ampy)]2[Mn2Cl6(2-ampy)2] 2, where 2-ampy is 2-aminopyridine. Their crystal structures have been determined by X-ray crystallography. Both complexes self-assemble through similar hydrogen bonding motifs which involve three N–H⋯Cl interactions between the 2-aminopyridinium cation and the chloride atoms. Each repeating unit of complexes 1 and 2, [MnCl3(H2O)]− and [Mn2Cl6(2-ampy)]2−, respectively, is doubly edge-sharing to form one-dimensional chains which are cross-linked by hydrogen bonding to the [H(2-ampy)]+ cations. In complex 2, two different 2-aminopyridine molecules were observed. One bridges the Mn atoms directly, while the other, through hydrogen bonding interaction, bridges Mn atoms via the chloride atoms. The structural role of the 2-aminopyridinium cation on the aggregation of the metal ions is discussed.

Quadruply bonded dimolybdenum complexes containing pairs of bridging diphosphine and acetate ligands; synthesis and structural characterization of trans-Mo2Cl2(OAc)2(μ-dppa)2 and its transformation to Mo2Cl4(μ-dppa)2, where dppa is N,N-bis(diphenylphosphino)amine

Abstract By reaction of Mo 2 (OAc) 4 with (CH 3 ) 3 SiCl and dppa (dppa=Ph 2 PN(H)PPh 2 ) in THF, two complexes can be prepared. The red complex trans -Mo 2 Cl 2 (OAc) 2 (μ-dppa) 2 ( 1 ) was obtained in 42% yield while the green complex Mo 2 Cl 4 (μ-dppa) 2 ( 2 ) was prepared in 31% yield. Complex 2 can also be derived by reacting K 4 Mo 2 Cl 8 or Mo 2 Cl 4 (PPh 3 ) 2 (CH 3 OH) 2 with dppa in methanol and acetone, respectively. Reaction of 1 with (CH 3 ) 3 SiCl leads to the formation of 2 . Their UV-Vis and 31 P{ 1 H} NMR spectra have been recorded and the structures of both 1 and 2 have been determined. Crystal data for 1 : space group Pbca , a = 16.699(1), b = 16.784(1), c = 19.728(2) A , V = 5529.3(7) A 3 , Z = 4 , with final residuals R = 0.0606 and R w = 0.0620. The diphosphine ligands are bridged to the metal centers with an eclipsed configuration around the metal-metal bond. The chloride atoms are forced to coordinate to the Mo atoms in the axial positions. Crystal data for 2 : space group Ibca , a = 16.165(2), b = 16.576(2) A , c = 37.024(3) A , V = 9921(2) A 3 , Z = 8 , with final residuals R = 0.0933 and R w = 0.0990. The two dppa ligands are bridged to the metal centers. The interconversions between 1 and 2 are discussed.

Syntheses and structural characterization of chromium(III) complexes containing hydrotris (1-pyrazolyl) borate

Abstract The syntheses and structural characterization of several chromium(III) complexes containing hydrotris(1-pyrazolyl)borate ligands are reported. The reaction of Cr 2 (OAc) 4 (H 2 O) 2 with two equivalents of KTp (Tp = hydrotris(1-pyrazolyl) borate) in diglyme produced a red product that is proposed to be Cr 2 (OAc) 2 Tp 2 (H 2 O) 2 . This red product react with (CH 3 ) 3 SiCl in CH 2 Cl 2 to yield the green complex [Cr(Tp) 2 ][CrCl 3 (Tp)] ( 1 ). The complex CrCl 2 (Tp) (THF) ( 2 ) was prepared by reaction of Cr 2 (OAc) 4 (H 2 O) 2 with (CH 3 ) 3 SiCl, followed by addition of two equivalents of KTp in THF. Reactions of 2 with PMe 3 in CH 2 Cl 2 gave [HPMe 3 ][CrCl 3 (Tp)] ( 3 ). Crystal data for 1 : space group P 2 1 / n , a = 12.081(1), b = 21.952(2), c = 14.123(1)A, β = 98.06(5)°, V = 3708.5(4)A 1 , Z = 4, with final residuals R = 0.0501 and Rw = 0.0513. Crystal data for 2 : space group P 2 1 / n , a = 10.051(2), b = 12.442(2), c = 14.349(2)A, β = 98.99(2)°, V = 1772.4(6)A 3 , Z = 4, with final residuals R = 0.0648 and Rw = 0.0672. Crystal data for 3 : space group Pl¯, a = 9.229(2), b = 14.870(3), c = 15.049(3)A, α = 83.45(1), β = 88.77(1), γ = 75.88(1)°, V = 1989.6(9)A 3 , Z = 4, with final residuals R = 0.0856 and Rw = 0.0865. The structure of [Cr(Tp) 2 ] [CrCl 4 ] is also discussed.

Chiral quadruple-bonded dimolybdenum complexes containing chelating diphosphine ligands; structural and chiroptical properties of α-Mo2Cl4[(R,R)-Me-DuPHOS]2 and α-Mo2Cl4[S,S)-Me-DuPHOS]2, where Me-DuPHOS is 1,2-bis(2,5-dimethylphospholano)benzene

Abstract The complexes α-Mo2Cl4[(R,R)-Me-DuPHOS]2, 1, and α-Mo2Cl4[(S,S)-Me-DuPHOS]2, 2, were prepared by reactions of (NH4)5Mo2Cl9 with (R,R)-Me-DuPHOS and (S,S)-Me-DuPHOS, respectively, in methanol. Their UV-vis and circular dichroism spectra have been recorded and the X-ray crystal structure of 1 has been determined. The chiral disphosphine ligands are chelated to the metal centers with an average twist angle of 5.2° about the metalmetal bond in the clockwise direction. The absorption spectra are typical for compounds with a MoMo quadruple bond. The lowest energy band sat 690 nm for both 1 and 2 can be assigned to δ xy → δ xy ∗ transitions. The CD spectra of both complexes 1 and 2 show two prominent bands at 695 and 520 nm and form mirror images of each other.

Synthesis and structural characterization of a face-sharing bioctahedral complex [HB(Me2Pz)3)BH][Br3Mo(μ-Br)3MoTp*] and an edge-sharing tetramolybdenum complex [Mo4(μ3-O)2(μ2-O)2(μ2-OH)2(O)4(Me2PzH)6](Br)4(Me2PzH2)2 (Tp*=hydridotris(3,5-dimethylpyrazolyl)borate); Pz=pyrazolyl)

Abstract From a solution prepared by a reaction of Mo2(O2CCH3)4 with KTp* (Tp*=hydridotris(3,5-dimethylpyrazolyl)borate, HB(Me2Pz)3), in diglyme at room temperature followed by addition of excess (CH3)3SiBr to the red solution in refluxing THF, the complexes [HB(Me2Pz)3)BH][Br3Mo(μ-Br)3MoTp*] (1), [Mo4(μ3-O)2(μ2-O)2(μ2-OH)2(O)4(Me2PzH)6](Br)4(Me2PzH2)2 (2) and MoBr2Tp*(Me2PzH) (3), were obtained. Their structures have been determined by X-ray crystallography. The anion of complex 1 consists of two octahedra sharing a common triangular face so those three Br atoms bridge the Mo atoms. The metal centers are also chelated by a tridentate Tp* ligand and coordinated by three Br atoms. Structural comparison of 1 and [HB(Me2Pz)3)BH][Br3Mo(μ-Br)2(μ-H)MoTp*] shows that replacement of the bridging hydride atom by the bromide atom led to the lengthening of the Mo–Mo bond distance by about 0.36 A. In complex 2, the four octahedra are bridged together through edges. The two molybdenum atoms in the asymmetric unit have different environments although both are formally seven-coordinated. The average oxidation state of molybdenum is +5, and the four electrons available for Mo–Mo bonding form two localized Mo–Mo single bonds. Complex 2 can be classified into the structural type Mo4XaYbZc, in which a+b+c=16. The formation of the cation, [HB(Me2Pz)3)BH]+, 2 and 3 shows the ready cleavage of the B–N bond of the Tp* ligand.

Quadruply bonded complexes containing η2- or η3-tridentate phosphine ligands; syntheses, structures and 31P{1H} NMR spectra of Mo2Cl4(η3-etp)(L) and Mo2Cl4(η2-etp)2 (L = CH3OH, PMe3 and PEt3; etp = Ph2PCH2CH2P(Ph)CH2CH2PPh2)

The reactive complex Mo2Cl4(η3-etp)(CH3OH) (etp = Ph2PCH2CH2P(Ph)CH2CH2PPh2) (1) was synthesized by reacting (NH4)5Mo2Cl9 with 1 equiv. of etp in CH3OH. Reactions of 1 with PMe3 and PEt3 in THF gave Mo2Cl4(η3-etp)(PMe3) (2) and Mo2Cl4(η3-etp)(PEt3) (3) respectively. The complex α-Mo2Cl4(η2-etp)2 (4) was synthesized by refluxing Mo2Cl4(η3-etp)(CH3OH) with 1 equiv. of etp in CH3OH, where η3-etp is transformed to η2-etp. Complex 4 can also be prepared by reacting (NH4)5Mo2Cl9 with 2 equiv. of etp in refluxing CH3OH. Their UV-Vis and 31P NMR spectra were recorded and the structures of 3 and 4 were determined. Crystal data for 3·C7H8: space group P21/n, a = 11.846(2), b = 29.349(3), c = 15.429(3) A, β = 112.52(1)°, V = 4955(2) A3, Z = 4, with final residuals R = 0.0797 and Rw = 0.0811. Crystal data for 4·2C7H8: space group P21/c, a = 14.555(2), b = 14.988(2), c = 20.220(3) A, β = 106.80(1)°, V = 4222(1) A3, Z = 2, with final residuals R = 0.0882 and Rw = 0.0893. The etp ligands in 1–3 are coordinated to the Mo centers in tridentate fashion with chelating/bridging bonding modes. The etp ligands in 4 are chelated to the Mo centers in bidentate fashion through the central phosphorus atom and one terminal phosphorus atom. Complex 4 appears to be the first binuclear biligate complex chelated by linear tridentate ligands. Study of the 31P{1H} NMR spectrum of 3 leads to the conclusion that the through metal-metal quadruple bonding coupling |4JPMoMoP| is in the range from 18.18 to 24.28 Hz for complexes of the type Mo2Cl4(η3-etp)(L) (L = monodentate ligand).