Ying-Yann Wu

Dimolybdenum complexes of bis(2-pyridyl)amine (Hdpa) ligand and its anion (dpa−); transformation of chelating η2-Hdpa to bridging η2-dpa−

Abstract The reaction of trans-Mo2(O2CCR3)2X2(PPh3)2 with 1 equiv. of Hdpa (Hdpa=bis(2-pyridyl)amine) in CH2Cl2 afforded the complex cis-Mo2(O2CCR3)2X2(η2-Hdpa) (R=H, X=Cl, 1; R=H, X=Br, 2; R=F, X=Cl, 3, R=F, X=Br, 4). Layering of a Mo2(O2CCF3)4 solution in CH2Cl2 with Hdpa in ether produced red and yellow crystals, which were characterized as Mo2(η2-dpa)4 (5), and Mo2(O2CCF3)4(η1-HO2CCF3)2 · 2Hdpa (6), respectively. Complex 5 can also be prepared by reaction of trans-Mo2(O2CCR3)2X2(PPh3)2 with excess Hdpa. Their UV–Vis and IR spectra have been recorded and the structures of 4, 5 and 6 have been determined. The Hdpa ligand in 4 is coordinated to the metal centers via two terminal pyridine nitrogen atoms with a cis-N conformation. The dpa− ligands in 5 are bridged to the metal centers via one terminal nitrogen atom and the central nitrogen atom. The aligned-N conformation of the dpa− ligand is stabilized by both the intramolecular Mo⋯N and C–H⋯N interactions. In 6, the CF3COOH ligands coordinate to the metal centers in the axial positions with η1-bonding modes and the Hdpa molecules adapt cis-N conformations.

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 X-ray structures of some metal carbonyl complexes containing dipyridylformamidine ligands

Abstract Five metal carbonyl complexes of N,N′-di(2-pyridyl)formamidine (HDpyF) and N,N′-di(6-methyl-2-pyridyl)formamidine (HDMepyF) are reported. Complexes of the type ReBr(CO)3L (L=HDpyF, 1; L=HDMepyF, 2) were prepared by the reactions of ReBr(CO)5 with HDpyF and HDMepyF in THF, respectively, while the complexes M(CO)4(L) (M=Mo, L=HDpyF, 3; M=Mo, L=HDMepyF, 4; M=W, L=HDMepyF, 5) were prepared by the reactions of HDpyF or HDMepyF with corresponding Group 6 metal hexacarbonyls. The neutral dipyridylformamidine ligands in 1 and 2 adopt the s-cis-syn-s-cis and s-trans-anti-s-trans conformations, respectively, while those in complexes 3–5 adopt the s-trans-anti-s-cis conformation.

Linear and cyclic tetranuclear copper(I) complexes containing anions of N, N'-bis(pyrimidine-2-yl)formamidine

The reaction of Kpmf (pmf = anion of N,N[prime or minute]-bis(pyrimidyl-2-yl)formamidine, Hpmf) with CuSCN afforded the complexes K[Cu4(pmF)3(SCN)2], 1, and Cu(4)(pmf)4, 2. Reaction of 1 with [(n-Bu)4N]PF6 in THF gave the complex [(n-Bu)4N][Cu4(pmf)3(SCN)2], 3. Their structures were characterized by X-ray crystallography. Complexes 1 and 3 are the first linear tetranuclear complexes containing only Cu(I) atoms, while complex 2 is cyclic. The four Cu(I) atoms of complexes 1 and 3 are helically bridged by three tetradentate pmf- ligands. The [Cu4(pmf)3(SCN)2]- anions of 1 show weak interactions with adjacent [K(THF)5]+ cations through the sulfur atoms, forming infinite chains which are subjected to a series of intermolecular pi-pi interactions. In complex 2, the pmf- ligands are coordinated to the copper atoms in bidentate fashion through the two central amine nitrogen atoms, leaving the pyrimidine nitrogen atoms uncoordinated. Unexpected fluxional behaviors were observed for complexes 1 and 3 in solution. By the DNMR analysis, the free energy of activation (DeltaGc(not equal)) for the exchange is 12.8 kcal mol(-1) at 278 K (T(c)), and the rate constant of exchange (K(c)) is 470 s(-1) for 1. The DeltaGc(not equal) and Kc are 12.6 kcal mol(-1) at 273 K and 433 s(-1), respectively, for 3.

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.

Synthesis and structural characterization of face-sharing bioctahedral complexes containing poly(pyrazolyl)borate ligands: [HB(Me2Pz)3BH][X3Mo(μ-X)2(μ-H)MoTp*] (X=Cl or Br; Tp*=HB(Me2Pz)3; Pz=pyrazolyl)

Abstract From a solution prepared by reaction of Mo2(O2CCH3)4 with KTp* (Tp*=hydridotris(3,5-dimethylpyrazolyl)borate, HB(Me2Pz)3), in glyme at room temperature, followed by addition of (CH3)3SiCl and (CH3)3SiBr to the red solution in refluxing THF, brown [HB(Me2Pz)3BH][Cl3Mo(μ-Cl)2(μ-H)MoTp*] (1), and [HB(Me2Pz)3BH][Br3Mo(μ-Br)2(μ-H)MoTp*] (2), respectively, can be prepared. A pink product [HB(Me2Pz)3BH][MoBr4(Me2PzH)2] (3), was also obtained during the preparation of 2. Their structures have been determined by X-ray crystallography. The anions of complexes 1 and 2 consist of two octahedra sharing a common triangular face, so that the Mo atoms are bridged by one H and two halogen atoms. The unsymmetrical metal centers are also chelated by tridentate Tp* ligands and coordinated by three halogen atoms. In contrast to the symmetrical [Mo2X8H]3− (X=Cl, Br or I) ions whose MoMo distances are hardly affected by the change in the size of the bridging halide atom, the variation of the MoMo distance from 1 to 2 is approximately 0.040 A. The formation of the cation [HB(Me2Pz)3BH]+ and the anion [MoBr4(Me2PzH)2]− shows the ready BN bond cleavage of the Tp* ligand.

Optical activity of dimolybdenum complex induced by chiral, chelating diamine ligand; syntheses and structures of [Mo2(O2CCF3)2(S,S-dach)2(CH3CN)2][BF4]2 and [Mo2(O2CCF3)2(R,R-dach)2(CH3CN)2][BF4]2 (dach=1,2-diaminocyclohexane)

Abstract The first structurally characterized, quadruply bonded complexes containing chiral diamine ligands, [Mo2(O2CCF3)2(S,S-dach)2(CH3CN)2][BF4]2 (1), and [Mo2(O2CCF3)2(R,R-dach)2(CH3CN)2][BF4]2 (2); (dach=1,2-diaminocyclohexane) were prepared by reactions of [Mo2(O2CCF3)2(CH3CN)6][BF4]2 with S,S-dach and R,R-dach, respectively, in CH3CN. Their UV–Vis and circular dichroism (CD) spectra have been recorded and their structures determined by X-ray crystallography. Crystals of complexes 1 and 2 conform to the space groups P2 with two independent half molecules in the asymmetric unit. The two molecules have a similar structure consisting of a Mo2 unit bridged by two cis-trifluoroacetate ligands and chelated by two dach ligands. Two acetonitrile molecules are coordinated to the Mo centers along the MoMo bond. The absorption wavelength at 507 nm for both 1 and 2 can be assigned to δxy→δxy* transitions. The solution CD spectra of these two complexes show two prominent bands at 525 and 385 nm and form mirror images of each other. The solid CD spectra of complexes 1 and 2 show marked red-shift in the absorption energies as compared with those measured in solution. The one-electron static coupling mechanism was invoked to explain the CD spectra for these complexes and the second lowest energy bands were assigned to be δxy→δx2−y2 transitions.

Bridging bonding mode in a metal-pteridine complex. Synthesis and structural characterization of Pt2Cl4(Hmp)2 (Hmp=4-hydroxy-2-mercaptopteridine)

Abstract Reaction of PtCl2 with Hmp (Hmp=4-hydroxy-2-mercaptopteridine) afforded the unique platinum–pteridine complex Pt2Cl4(Hmp)2, in which the Hmp ligand bridges the metal centers through the pyrazine ring nitrogen atom and the sulfur atom in a neutral form. This bonding mode is in marked contrast to the usual O4,N5-chelation mode of the pteridine units found in all the other reported complexes.

A metal complex with a pair of nonlinear N–H—Pd(II) interactions; synthesis and structural characterization of PdCl2(R-Bpeap)2 (Bpeap=6-bromo-2-phenylethylaminopyridine)

Abstract Reaction of PdCl2 with R-(+)-6-bromo-2-phenylethylaminopyridine (R-Bpeap) afforded the title complex PdCl2(R-Bpeap)2, which shows a pair of nonlinear N–H—Pd(II) interactions.