The compound tetraphenylphosphonium tetrachlorooxo-S,S-diphenylsulfiliminatouranium, [Ph4P][UOCl4(NSPh2)], has been prepared in high yield from [Ph4P][UOCl5] and [Ph2S=NSiMe3]. An X-ray structure of this compound shows that the uranium atom has a pseudooctahedral geometry with oxygen and nitrogen atoms in trans positions. The structure of the analogous phosphoriminato complex [Ph4P][UOCl4(NPPh3)] has been determined for comparison. Derivatization of the sulfide group shows that only a limited range of functionalization confers stability toward reduction. The emission spectrum of the first electronic excited state reveals a greatly reduced energy compared with that of the uranyl ion. This red shift in the transition is consistent with the weakening of the U-N bond relative to the U-O bond.

The diastereoselectivity in the alkylation of the enolates of bicyclic lactams 2 derived from pyroglutaminol 1a has been found to depend upon the nature of the hemiaminal ether protecting group. Although exo-alkylation has been widely reported for 2a,b,e, endo-alkylation is favoured for 2d. It is postulated that this is a result of the opening of the bicyclic structure of the enolate derived from 2d, and the consequent stereoelectronic facilitation of endo-facial attack.

Variable-temperature single-crystal X-ray experiments have been performed on the thiourea pyridinium chloride, bromide, and iodide inclusion compounds. Two phases were found for the chloride, three for the bromide, and two for the iodide. As previously reported for the bromide, at room-temperature all three halides were found to form orthorhombic crystals in space group Cmcm. For each compound, the pyridinium cation is disordered in the square cross section thiourea channels. On cooling, the chloride undergoes a phase change between 200 and 230 K to give an orthorhombic form in Pbca with the a axis doubled and the pyridinium ions partially ordered. The bromide undergoes a phase change between 170 and 165 K to a partially ordered form in space group Cmc2(1) with the a axis tripled. A second phase change occurs between 140 and 150 K to a fully ordered phase in space group P2(1)cn. with cell dimensions approximately the same as the room-temperature form. The iodide undergoes a single-phase transition at 120-130 K to a fully ordered form isomorphous with the low-temperature form of the bromide. The phase transitions have also been studied by VT H-2 NMR of the perdeuteriopyridinium salts. These data have been correlated with the XRD data and with models for the motion of the pyridinium cation.

The deoxycholic acid inclusion complex (DCA)(2):ferrocene (1) undergoes a "gradual" phase transition above ambient temperature, "completed" by similar to 360 K. The phase transition is characterized by using single-crystal X-ray diffraction and C-13 CP/MAS NMR spectroscopy. 13C CP/MAS NMR spectra of 1 suggest two DCA molecules in the crystallographic unit cell, which on heating become increasingly similar, until beyond similar to 345 K only one molecular type is detected. The crystal structure has been determined at 360, 294, 200, and 100 K. Single-crystal diffraction data show a similar phase change at around 350 K. At T less than or equal to 294 K the structure is solved in P2(1)2(1)2(1), and at 360 K, the a axis is halved in a high-temperature form with symmetry P22(1)2(1). In the temperature region 320-340 K, the single-crystal X-ray diffraction structure cannot be solved adequately. The atomic displacement ellipsoids of the ferrocene molecule at the various temperatures are consistent with a wobble about the molecular 5-fold axis proposed previously from H-2 NMR studies. The transition, although most clearly observed in the positions of the deoxpcholic acid molecules, is largely dominated by the dynamic behavior of the included guest ferrocene molecules. The mechanistic nature of and the similarities and differences in the way this transition is detected by NMR and XRD techniques are discussed.

The complex [U{N(SiMe(3))(2)}(2){N(SiMe(3))(SiMe(2)CH(2)B(C(6)F(5))(3))}] (1) is formed in the reaction between the hydride complex [U{N(SiMe(3))(2)}(3)(H)] and B(C(6)F(5))(3), and H(2) is evolved. The X-ray [C(36)H(53)BF(15)N(3)Si(6)U.3.5C(6)D(6), triclinic, space group P&onemacr;, Z = 2, 90 K, a = 14.065(1) Å, b = 14.496(1) Å, c = 18.759(1) Å, alpha = 82.898(1) degrees, beta = 74.415(1) degrees, gamma = 62.919(1) degrees ] and neutron structure [C(36)H(53)BF(15)N(3)Si(6)U.3.5C(6)D(6), triclinic, space group P&onemacr;, Z = 2, 20 K, a = 13.993(1) Å, b = 14.484(1) Å, c = 18.720(1) Å, alpha = 82.810(1) degrees, beta = 74.200(1) degrees, gamma = 63.054(1)E] of compound 1, which crystallizes with 3.5 molecules of C(6)D(6) per asymmetric unit, show the electron deficiency of the uranium atom to be effectively compensated by the formation of multicenter bonds between U and three Si-CH(2) units of the amido ligands. The reaction of the uranium complex [U{C(Ph)(NSiMe(3))(2)}(2)(Cl)(2)] with [Na(BH(4))] gives the complex [U{C(Ph)(NSiMe(3))(2)}(2){&mgr;(3)-BH(4)}(2)] (2). The X-ray structure of 2 [C(26)H(54)B(2)N(4)Si(4)U, monoclinic, space group C2/c, Z = 4, 90 K, a = 21.613(1) Å, b = 9.233(1) Å, c = 18.132(1) Å, beta = 98.804(1) degrees ] proves unequivocally the &mgr;(3) coordination of the BH(4) moieties. In both single-crystal X-ray structure determinations, all hydrogen and deuterium atoms could be located and isotropically refined, including those which are directly coordinated to the uranium. The reliability of the refined hydrogen and deuterium positions for compound 1 is confirmed by comparison of the X-ray and neutron structure determinations. The ability to locate the hydrogen and deuterium positions in these uranium compounds by single-crystal X-ray diffraction is due to good crystal quality, the measurement of data at low temperature, and the use of image plate technology for data collection.

The complex [U{N(SiMe(3))(2)}(2){N(SiMe(3))(SiMe(2)CH(2)B(C(6)F(5))(3))}] (1) is formed in the reaction between the hydride complex [U{N(SiMe(3))(2)}(3)(H)] and B(C(6)F(5))(3), and H(2) is evolved. The X-ray [C(36)H(53)BF(15)N(3)Si(6)U.3.5C(6)D(6), triclinic, space group P&onemacr;, Z = 2, 90 K, a = 14.065(1) Å, b = 14.496(1) Å, c = 18.759(1) Å, alpha = 82.898(1) degrees, beta = 74.415(1) degrees, gamma = 62.919(1) degrees ] and neutron structure [C(36)H(53)BF(15)N(3)Si(6)U.3.5C(6)D(6), triclinic, space group P&onemacr;, Z = 2, 20 K, a = 13.993(1) Å, b = 14.484(1) Å, c = 18.720(1) Å, alpha = 82.810(1) degrees, beta = 74.200(1) degrees, gamma = 63.054(1)E] of compound 1, which crystallizes with 3.5 molecules of C(6)D(6) per asymmetric unit, show the electron deficiency of the uranium atom to be effectively compensated by the formation of multicenter bonds between U and three Si-CH(2) units of the amido ligands. The reaction of the uranium complex [U{C(Ph)(NSiMe(3))(2)}(2)(Cl)(2)] with [Na(BH(4))] gives the complex [U{C(Ph)(NSiMe(3))(2)}(2){&mgr;(3)-BH(4)}(2)] (2). The X-ray structure of 2 [C(26)H(54)B(2)N(4)Si(4)U, monoclinic, space group C2/c, Z = 4, 90 K, a = 21.613(1) Å, b = 9.233(1) Å, c = 18.132(1) Å, beta = 98.804(1) degrees ] proves unequivocally the &mgr;(3) coordination of the BH(4) moieties. In both single-crystal X-ray structure determinations, all hydrogen and deuterium atoms could be located and isotropically refined, including those which are directly coordinated to the uranium. The reliability of the refined hydrogen and deuterium positions for compound 1 is confirmed by comparison of the X-ray and neutron structure determinations. The ability to locate the hydrogen and deuterium positions in these uranium compounds by single-crystal X-ray diffraction is due to good crystal quality, the measurement of data at low temperature, and the use of image plate technology for data collection.

Organometallic oxo complexes [M(C5H4R)(2)O] reacted with the strong Lewis acid B(C6F5)(3) at their oxo functionality to yield [M(C5H4R)(2) {OB(C6F5)(3)}] (M = Mo, R = Me 1; M = W, R = H 2). The structure of 1 has been determined by X-ray crystallography. Density functional theory (DFT) calculations on [Mo(C5H5)(2)O] and [Mo(C5H5)(2)(OBF3)] have been used to model the changes in geometry to the [Mo(C5H5)(2)O] fragment on coordination by B(C6F5)(3) and indicate that this process is charge rather than orbitally controlled. Compound 1 reacted with PhNCO to yield [Mo(C5H4Me)(2){OC(O)NPh}{B(C6F5)(3)}]; spectroscopic evidence and DFT calculations suggest that the Lewis acid is bound to the molybdenum oxygen atom.

Reaction of the strong Lewis acid B(C6F5)3 with [M{N(SiMe3)2}3Me] (M = Zr or Hf) gave the compounds [M{N(SiMe3)2}3][MeB(C6F5)3]. Crystallographic analyses of these compounds revealed the formation of multicentre bonds between the SiCH3 units of the amide ligands and the otherwise electron-deficient metal centre. The new tris(amide) complexes [M{N(Ph)SiMe3}3Cl] and [M{N(Ph)SiMe3}3Me] (M = Zr or Hf) have also been synthesized.

The oxometal complexes [MoO2(eta(2)-O-NR2)(2)], R = Et or CH2Ph, reacted with the strong Lewis acid B(C6F5)(3) at their oxo functionality to give cis-[MoO{OB(C6F5)(3)} (eta(2)-ONR2)(2)], (R = Et 1 or CH2Ph 2). Reaction of the peroxo complex [MoO(O-2){eta(2)-PhN(O)C(O)Ph}(2)] with the same Lewis acid led initially to the formation of [MoO(O-2){B(C6F5)(3)} {eta(2)-PhN(O)C(O)Ph}(2)] 3, which decomposes to form [MoO{OB(C6F5)(3)}{eta(2)-PhN(O)C(O)Ph}(2)] 4. Compounds 1 and 4 have been characterised by X-ray crystallography.

Den größten bekannten Neigungswinkel [32.4(2)°] zwischen den Ebenen der Cyclopentadienylliganden weist das [1]Boraferrocenophan 1 auf. Diese Verbindung ist das erste [1]Ferrocenophan mit einem Brückenatom der ersten Achterperiode. Durch ringöffnende Polymerisation werden cyclische Polymere 2 erhalten.magnified image

The transition-metal oxo complexes [VO(acac) 2 ], [{TiO(acac) 2 } 2 ] and cis-[MoO 2 (acac) 2 ] (acac = C 5 H 7 O 2 ) reacted with the strong Lewis acid B(C 6 F 5 ) 3 to give the structurally characterized complexes [V{OB(C 6 F 5 ) 3 }(acac) 2 ], [Ti{OB(C 6 F 5 ) 3 }(acac) 2 ] and cis-[MoO{OB(C 6 F 5 ) 3 } (acac) 2 ]. The MO–B moiety is essentially linear.

The transition-metal oxo complexes [VO(acac)(2)],[{TiO(acac)(2)}(2)] and cis-[MoO2(acac)(2)] (acac = C5H7O2) reacted with the strong Lewis acid B(C6F5)(3) to give the structurally characterized complexes [V{OB(C6F5)(3)}(acac)(2)], [Ti{OB(C6F5)(3)}(acac)(2)] and cis-[MoO{OB(C6F5)(3)}(acac)(2)]. The M=O-B moiety is essentially linear.