S. Kannan

Lanthanum(III) and Uranyl(VI) Diglycolamide Complexes: Synthetic Precursors and Structural Studies Involving Nitrate Complexation

The synthesis and structural characterization of lanthanum(III) and uranyl(VI) complexes coordinated by tridentate diglycolamide (DGA) ligands O(CH2C(O)NR2)2[R=i-Pr (L1), i-Bu (L2)] are described. Reaction of L with UO2Cl2(H2O) n forms the uranyl(VI) cis-dichloride adducts UO2Cl2L [L=L1 (1a), L2 (1b)], while reaction of excess L with the corresponding metal nitrate hydrate produces [LaL3][La(NO3)6] [L=L1 (2a), L2 (2b)] for lanthanum and UO2(NO3)2L [L=L1 (3a), L2 (3b)] for uranium. Compounds 2b and 3a have been structurally characterized. The solid-state structure of the cation of 2b shows a triple-stranded helical arrangement of three tridentate DGA ligands with approximate D3 point-group symmetry, while the counteranion consists of six bidentate nitrate ligands coordinated around a second La center. The solid-state structure of 3a shows a tridentate DGA ligand coordinated along the equatorial plane perpendicular to the OUO unit as well as two nitrate ligands, one bidentate and oriented in the equatorial plane and the other monodentate and oriented parallel to the uranyl unit with the oxygen donor atom situated above the mean equatorial plane. Ambient-temperature NMR spectra for 3a and 3b indicated an averaged chemical environment of high symmetry consistent with fluxional nitrate hapticity, while spectroscopic data obtained at -30 degrees C revealed lower symmetry consistent with the slow-exchange limit for this process.

Preparation and characterization of phenylselenolato-bridged dinuclear platinum(II) complexes

Complexes of the type [Pt2X2(μ-Y)(μ-SePh)(PR3)2] [X = Cl; Y = Cl, or SePh; PR3 = PEt3, PBun3, PMe2Ph, PMePh2, PPh3, PBut3 and PR3 = PC (metalated tri-tert-butylphosphine)] were prepared and characterized by elemental analyses and 1H, 31P, 77Se and 195Pt NMR spectroscopy. Treatment of [Pt2(μ-SePh)2(PC)2] with anhydrous HCl in diethyl ether gave [Pt2Cl2(μ-SePh)2(PBut3)2]. A few bridge-cleavage reactions of [Pt2Cl2(μ-Cl)(μ-SePh)(PBun3)2] have been investigated. The stereochemistry of the complexes in solution is discussed.

Synthesis and characterization of sulphoxide adducts of uranyl bis(β-diketonates): The crystal and molecular structure of [UO2(DBM)2·C6H5CH2SOCH3]

Abstract The uranyl complexes of the type [ UO 2 ( OO ) 2 · S ] (where OO = thenoyltrifluoroacetonate ion, [C4H3SCOCHCOCF3]−; dibenzoylmethanate ion, [C6H5COCHCOC6H5]−; S = PhCH2SOCH3, PhSOPh or PhCH2SOCH2Ph) were prepared and characterized by elemental analyses, IR, 1H, 13C{1H} and 19F{1H} NMR spectroscopic techniques. The structure of the complex [UO2(DBM)2·PhCH2SOCH3] was solved by a single-crystal X-ray diffraction method. The structure determination shows that the uranium atom has a pentagonal bipyramidal geometry.

The camphor adducts of uranyl bis(β-diketonates). The low temperature 19F NMR behaviour of [UO2(TTA)2·camphor] and the crystal structure of [UO2(DBM)2·camphor]

Abstract Uranyl bis(β-diketonate)-neutral ligand complexes of the type [UO2( )2−X] were prepared = thenoly trifluoroacetonate (TTA), dibenzoylmethanate (DBM); X=camphor) and characterised by elemental analyses, IR, 1H, 13C{1H} and 19F NMR spectroscopic techniques. The low temperature behaviour of the complex [UO2(TTA)2·camphor] was studied by 19F NMR and the structure of [UO2(DBM)2·camphor] was solved by single-crystal X-ray diffraction. The structure determination shows that the uranium atom has pentagonal-bipyramidal geometry. The crystal is monoclinic with space group P2 1 /n, a=14.151(3), b=15.117(2), c=16.766(4) A , β=94.847(8) and Z=4. The structure was refined to final R1=0.034 for 3600 reflections with I⩾2σ(I).

Crown ether compounds of actinide bis(β-diketonate). Synthesis, characterization and molecular structures of [UO2(TTA)2H2O]2(benzo-15,crown-5) (1) and [UO2(TTA)2(μ-H2O)]2(H2O)2(dibenzo-18,crown-6) (2)

Abstract Reaction of [UO 2 (TTA) 2 2H 2 O] with benzo-15,crown-5 in chloroform yielded the compound [UO 2 (TTA) 2 H 2 O] 2 (benzo-15,crown-5) ( 1 ) in which the benzo-15,crown-5 ether acts as a second sphere ligand. However, similar reaction with dibenzo-18,crown-6 yielded the compound [UO 2 (TTA) 2 (μ-H 2 O)] 2 (H 2 O) 2 (dibenzo-18,crown-6) ( 2 ) in which the dibenzo-18,crown-6 ether acts as a third sphere ligand. The solid state structure of 1 shows that the crown ether bridges two mononuclear [UO 2 (TTA) 2 H 2 O] by hydrogen bonds to give binuclear complex [UO 2 (TTA) 2 H 2 O] 2 crown. Two of such binuclear units are stabilized by C &0xF700; H ⋯ O interactions in the solid state. The structure of 2 shows that the crown ether bridges two binuclear [UO 2 (TTA) 2 (μ-H 2 O)] 2 (H 2 O) 2 by hydrogen bonds along the c -axis direction to give linear polymeric chain-like arrangement.

Synthesis and characterization of dinuclear platinum(II) complexes containing both μ-pyrazolato-N,N and group 16 donors (ER′; E = O, S, Se, Te) as bridging ligands

Abstract Dinuclear platinum(II) complexes containing both pyrazolato-N,N and group 16 donors, of the general formula [Pt 2 Cl 2 (μ-ER′)(μ-pz)(PR 3 ) 2 ] (E = O, S, Se, Te; R′ = alkyl or aryl; pzH = pyrazole; PR 3 = tertiary phosphine) have been synthesized. The complexes were characterized by elemental analyses and NMR ( 1 H and 31 P). The stereochemistry of the complexes has been discussed on the basis of NMR data.

Synthesis and characterization of binuclear arylthiolato-and phenylselenolato-bridged organoplatinum(II) complexes: crystal structure of [Pt2Ph2(μ-SPh2(PMe2Ph)2]

Binuclear organoplatinum(II) complexes of the type [Pt2 Ar2(μ-EAr′)2(PR3)2] (Ar  Ph or p-tol; E  S or Se; Ar′  Ph or p-tol; PR3  PPr3 PBu3 or PMe2Ph) have been synthesized and characterized by elemental analysis and nuclear magnetic resonance (1H 31P) spectroscopy. Some of these complexes were isolated exclusively as the trans isomer, but others were present at a mixture of cis and trans isomers. An X-ray diffraction study of [Pt2Ph2(μ-SPh)2(PMe2Ph)2] has shown that it has sym-trans geometry, with a planar four-membered Pt2S2 ring.

The dibenzylideneactone adducts of uranyl bis(β-diketonates). The low temperature NMR behaviour and molecular structure of [UO2(TTA)2·DBA]

Abstract Uranyl complexes of the type [UO2( OO )2·DBA] ( OO = TTA, DBM and BA) have been prepared and characterized by 1H, 19F and 13C{1H} NMR, IR spectroscopic techniques and elemental analyses. The low temperature behaviour of the complex [UO2 (TTA)2·DBA] was studied by the 19F NMR technique and its structure solved by single- crystal X-ray diffraction. The structure determination shows that the uranium atom has pentagonal-bipyramidal geometry with the four oxygen atoms of TTa and one oxygen atom of DBA lying on the basal plane and two uranyl oxygen atoms occupy the apices.

Binuclear complexes of palladium(II) and platinum(II) containing bridging ethylselenolato group: X-ray crystal structure of [Pt2Cl2(μ-SeEt)2(PEt3)2]

Abstract The reaction of [M2Cl2(μ-Cl)2(PR3)2] with NaSeEt in 1 : 1 and 1 : 2 stoichiometry gave [M2Cl2(μ-Cl)(μ-SeEt)(PR3)2]a nd [M2Cl2(μ-SeEt)2(PR3)2] (M = Pd or Pt; PR3 = PEt3, PBu3, PMe2Ph or PMePh2), respectively. These complexes were characterized by elemental analysis and NMR data (1H and 31P). The mixed chloro/ethylselenolato bridged complexes adopt a cis configuration with phospine trans to the bridging chloride. The molecular structure of [Pt2Cl2(μ-SeEt)2(PEt3)2] has been determined by single crystal X-ray diffraction. The complex has a planar four-membered “Pt2Se2” bridge.

Preparation and characterization of aryltellurolato-bridged dinuclear complexes of platinum(II)

Abstract Complexes of the type [Pt 2 Cl 2 (μ-X)(μ-TeAr)(PR 3 ) 2 ] (X = Cl or TeAr; Ar = Ph, 4-MeC 6 H 4 , 4-MeOC 6 H 4 , 4-EtOC 6 H 4 ; PR 3 = PEt 3 , P n Bu 3 or PMe 2 Ph) and [Pt 2 (μ-TeAr) 2 (PC) 2 ] (Ar = 4-MeC 6 H 4 , 4-MeOC 6 H 4 ; PC = t Bu 2 PCMe 2 CH 2 ) have been prepared. These complexes were characterized by elemental analyses, and multinuclear NMR ( 1 H, 13 C, 31 P, 125 Te and 195 Pt) spectroscopy. The stereochemistry of the complexes in solution has been discussed on the basis of NMR data.