Paul J. Toscano

Protonation sites in a heteropolyvanadate of phosphorus: X-ray crystal structure of (Me3NH)4(NH4)[H4PV14O42]

Abstract The reaction of (NH4)2HPO4 with (NH4)2Na2K2V10O28, followed by addition of Me3NHCl, yields dark crystals of the phosphovanadate cluster (Me3NH)4(NH4)[H4PV14O42]. The structure consists of an α-Keggin framework capped by two [VO] subunits. The protonation sites were identified as the doubly-bridging oxygens, O10. Crystal data: orthorhombic space group Fddd, a=10.706(2), b=23.581(4), c=37.271(8) A, V=9409.3(22) A3, Z=8. X-ray data were collected on a Siemens R3m/V diffractometer using a θ/2θ scan technique with graphite monochromated MoKα radiation. A total of 2733 reflections was collected (to 2θ=55°), of which 1850 were used in subsequent structure solution and refinement (I>3σ(I)). The structure was solved by direct methods, and least-squares refinement converged at R=0.033.

Thermal and structural characterization of a series of homoleptic Cu(II) dialkyldithiocarbamate complexes: bigger is only marginally better for potential MOCVD performance

Abstract A series of Cu(II) dialkyldithiocarbamate complexes, Cu(S2CNRR′)2, with R=R′=n-Bu (1); i-Bu (2); c-Hex (3); CH2Ph (4); R=n-Bu, R′=Et (5); R=n-Pr, R′=c-PrCH2 (6); R=R′=n-Pr (7); i-Pr (8); allyl (9), were prepared. The thermal properties of the complexes were investigated to determine if their potential performance in chemical vapor deposition processes was affected by the nature of the peripheral substituents of the ancillary ligands. Modest gains in volatility were noted for 2 and 7 over the most often utilized complex with R=R′=Et, while 1 and 8 had thermal parameters and stability comparable to this standard. Unsymmetrical substitution, such as in 5, also improved volatility, with some loss of stability for this particular compound. X-ray diffraction studies of complexes 1–6 suggested that long range Cu⋯S interactions in the solid-state have little bearing on the thermal properties of this class of Cu(II) complexes.

Synthesis and physical and structural characterization of Ag(I) complexes supported by non-fluorinated β-diketonate and related ancillary ligands

Abstract A series of Ag(I) complexes, [Ag(X)L], where X is the anion of 2,2,6,6-tetramethyl-3,5-heptanedione (tmhdH), 2,2,7-trimethyl-3,5-octanedione (tmodH), 2-sila-2,2,6,6-tetramethyl-3,5- heptanedione (tmshdH), 5-mercapto-2,2,6,6-tetramethyl-4-hepten-3-one (S-tmhdH), 5-mercapto-2,2,7-trimethyl-4-octen-3-one (S-tmodH), or 5-amino-2,2,6,6-tetramethyl-4-hepten-3-one (N-tmhdH) and L=triphenylphosphine (PPh3) or tri-n-butylphosphine (PBu3), were prepared by treatment of silver nitrate with either the diketone derivative in the presence of a base or with the preformed sodium salt of the diketone derivative. The thermal properties of the new complexes were investigated for potential application in chemical vapor deposition (CVD) processes. Results of thermogravimetric analysis showed that the vast majority of the silver complexes have little promise for CVD, since the ligands dissociate at elevated temperatures without volatilization. The first ever reported single crystal X-ray diffraction studies of silver complexes, with simple, ancillary, non-fluorinated β-diketonate supporting ligands, revealed [Ag(tmhd)(PPh3)] (1a) to be monomeric and [Ag(S-tmhd)(PPh3)]2 (4a) to be dimeric in the solid state, respectively.

SYNTHESIS AND CHARACTERIZATION OF TITANIUM COMPLEXES CONTAINING THE 1-(3-BUTENYL)-2,3,4,5-TETRAMETHYLCYCLOPENTADIENYL LIGAND

Abstract A series of titanium complexes containing the 1-(3-butenyl)-2,3,4,5-tetramechylcyclopentadienyl ligand C 2 Me 4 CH 2 CH 2 CHCH 2 (Cp = ) have been synthesized and characterized. The dichloro complex Cp = 2 TiCl 2 was prepared by the reaction of LiCp = and TiCl 3 in dimethoxyethane, followed by oxidation using lead dichloride. Cp = 2 TiCl 2 was converted into the dimethyl derivative Cp = 2 TiMe 2 , the molecular structure of which was confirmed by an X-ray structural analysis, which showed it to be a peralkyl titanocene complex containing the two pendent 3-butenyl side chains in the lateral positions of the bent metallocene unit. The reaction of Cp = 2 TiMe 2 with B(C 6 F 5 ) 3 was monitored by NMR spectroscopy. Cp = TiCl 3 , which was used to synthesize Cp = CpTiCl 2 by reacting with LiCp, was prepared from the reaction between Cp + SiMe 3 and TiCl 4 . Cp = CpTiCl 2 was further converted into Cp = CpTiMe 2 and Cp = CpTi(OTf) 2 . A significantly improved method for the preparation of 1-(3-butenyl)-2,3,4,5-tetramethylcyclopentadiene was developed.

Structural investigations of copper(II) complexes containing fluorine-substituted β-diketonate ligands

Abstract The crystal structures of the β-diketonate complexes Cu(pta)2, Cu(pta)2·EtOH, and Cu(F6-thd)2 (where pta is the anion of 1,1,1-trifluoro-5,5-dimethylhexane-2,4-dione and F6-thd is the anion of 2,2-bis(trifluoromethyl)-6,6-dimethylheptane-3,5-dione) were determined. The solid-state structures of Cu(pta)2 and Cu(F6-thd)2 are square planar, while Cu(pta)2·EtOH is approximately square pyramidal with the EtOH ligand occupying the apical position. In each case, only one geometrical isomer (cis or trans) was observed in the crystals; arguments are presented that both isomers are present in bulk samples. Calculations of molecular volumes for structurally related Cu(II) complexes containing non-fluorinated versus fluorinated ancillary ligands show that fluorine substitution does not significantly affect packing efficiency in the solid-state; however, solvent coordination decreases packing efficiency slightly. [Cu(tdf)(py)(μ-C3F7CO2)]2 (where tdf is the anion of 1,1,1,2,2,3,3,7,7,8,8,9,9,9-tetradecafluorononane-4,6-dionate), a derived impurity from preparations of Cu(tdf)2, was isolated in low yield. The copper coordination geometries in the centrosymmetric structure are intermediate between square pyramidal and trigonal bipyramidal, with two unsymmetrically bridging μ,η1:η1-C3F7CO2 ligands.

Synthesis of fluorinated α-sila-β-diketones and their copper(II) complexes

Abstract Fluorinated α-sila-β-diketones, synthesized in good yields via the Claisen condensation of the esters of fluorinated acids or fluorinated acid fluorides and the lithium enolates of acetyltrialkylsilanes, were employed in the preparation of volatile copper complexes for copper metallization. The thermal properties of the corresponding copper(II) complexes were determined by TGA and DSC to evaluate the potential of these materials as copper metal–organic chemical vapor deposition (MOCVD) precursors; the new copper compounds have greater volatility and stability than the corresponding copper complexes of non-fluorinated α-sila-β-diketonates.

The first metal complex containing a silylated β-diketonate ligand: bis(2,2,6,6-tetramethyl-2-sila-3,5-heptanedionato) copper(II)

Abstract A facile preparation of 2,2,6,6-tetramethyl-2-sila-3,5-heptanedione (tmshdH), exemplar of a new class of ligands, the sila-β-diketones, has been developed. Silicon substitution in the ligands has profound effects on the volatility, thermal properties, crystal packing, and electronic spectrum of the homoleptic Cu(II) complex, Cu(tmshd)2.

Synthesis and characterization of diphenylglyoximato cobalt(III) complexes. The molecular structures of trans-bis(diphenylglyoximato)(alkyl)(pyridine)cobalt(III), with alkyl = CH2SiMe3, CH2CMe3 and CF3

Abstract A series of Co(III) diphenylglyoximato (dpgh) complexes, pyCo(dpgh)2R, with R=Cl (2a), CH3 (3a), CH2Me (4a), (CH2)2Me (5a), (CH2)3Me (6a), CHMe2 (7a), CH2SiMe3 (8a), CH2CMe3 (9a), CH2CHCH2 (10a), CH2Ph (11a), and CF3 (12a) were prepared, using Co(dpgh)(dpgh2)Cl2 (1a) as an entry to this system. The compounds were thoroughly characterized by 1H and 13C NMR spectroscopy, the spectra of which were compared to the corresponding Co(III) dimethylglyoximato (DH) complexes, pyCo(DH)2R (2b–12b). The NMR results suggest that the dpgh ligand is less electron-donating than DH. X-ray diffraction studies of complexes 8a, 9a and 12a demonstrate that subtle, but detectable structural changes occur upon substitution of dpgh for DH, due to increased interactions of the axial alkyl ligand with the equatorial ligand set.

Physical and Structural Characterization of Ce(IV) β-Diketonate Complexes: Evidence for Geometrical Isomers in the Solid-State

The Ce(IV) β-diketonate complexes CeL 4 [where L is txhd (2,2,6-trimethyl-3,5-heptanedionate) 1; tmod (2,2,7-trimethyl-3,5-octanedionate) 2; tmhd (2,2,6,6-tetramethyl-3,5-heptanedionate) 3] were prepared by the interaction of the sodium salt of the diketonate with cerium(III) nitrate hexahydrate in aqueous ethanol solution. Differential scanning calorimetry and thermogravimetric analysis showed that 1 has a significantly lower sublimation temperature, but higher decomposition temperature than 3. The solid-state structures of the three complexes were determined via single crystal x-ray diffraction methods. Complex 2, which does not sublime, had significantly closer intermolecular contacts than those found for 1 and 3.

SYNTHESIS AND CHARACTERIZATION OF POLYFLUORINATED β-DIKETONATE TRANSITION METAL COMPLEXES1,2

Abstract The preparations of 1,1,1,2,2,3,3,7,7,8,8,9,9,9-tetradecafluorononane-4,6-dione (tdfH) and the Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Pd(II) metal complexes of its monoanion (tdf) are described. The metal complexes have been characterized by elemental analysis, IR and visible spectroscopies, magnetic moment for the paramagnetic compounds, and 1H and 19F NMR spectroscopy for the Zn(II) and Pd(II) complexes. X-ray structural studies of Cu(tdf)2 · C2H5OH, Cu(tdf)2 · 2H2O, and Mn(tdf)2 · 2H2O were undertaken. The geometry of the Cu(II) ethanolate complex is square pyramidal, while the Cu(II) dihydrate complex is distorted octahedral with the two aquo ligands occupying trans coordination sites. The Mn(II) dihydrate complex appears also to have distorted octahedral geometry with the two aquo ligands situated cis to each other.