William E. Streib

Single‐Crystal X‐Ray Diffraction Studies of α‐N2 and β‐N2

The structure of α‐N2 is cubic in the space group P213 with four molecules per unit cell. A total of 49 independent observed single‐crystal x‐ray diffraction maxima yield R=Σ ‖Fo|−|Fc ‖ /Σ|Fo|=0.13. Two faint reflections, (501) and (520), violate the space group Pa3, which yields R=0.21. Molecular centers are displaced by 0.1 to 0.2 A from the centrosymmetric positions in Pa3 along the [111] directions so that the symmetry is reduced to P213.Some corrections have been made in the Lorentz factors for upper levels and for the absorption of x rays in the experimental arrangement in the β‐N2 study. The value of R improves from 0.09 to 0.04 for the freely rotating model, and the best precession angle is 56.0° rather than 54.5° (both ±2.5°) for the precession model, which we prefer.

Synthesis and X-ray crystal structures of the one-dimensional ribbon chains [MOBut•ButOH]∞ and the cubane species [MOBut]4 (M = K and Rb)

Abstract The series [MOBut·ButOH]∞ (M = K, Rb and Cs) have been prepared by the reaction of M with ButOH in THF. Single-crystal X-ray diffraction studies revealed for M = K or Rb that [MOBut·ButOH]∞ crystallizes from tetrahydrofuran-n-pentane at −20°C in the triclinic space group P 1 , with unit cell dimensions [K, Rb]: a = 9.862(3), 9.886(2) A; b = 9.929(4), 9.914(2) A; c = 6.330(2), 6.640(1) A; β = 90.66(2), 90.46(1)° and Z = 2, as a one-dimensional chain linked by hydrogen-bonding. The strong hydrogen-bonding within the chain O(2)O(7) (2.46, 2.44 A) also results in a near linear O(7)HO(2) angle (167.4, 172.61°) with the hydrogen atom closer to O(7) (1.22, 1.18 A), than O(2) (1.24, 1.27 A). These alcohol adducts may be readily converted into the compounds [MOBut]4 (M = K, Rb and Cs) by sublimation. Single-crystal X-ray diffraction studies reveal for M = K or Rb, that [MOBut]4 crystallizes from toluene at −20°C in the cubic space group P 4 3M; with unit cell dimensions [K, Rb]; a = 8.372(1), 8.514(1) A, and Z = 4, as cubane structures. Within the cubane-like structures the OMO angles are found to deviate only slightly from 90°, with OMO (90.18, 89.11°) and MOM (89.82, 90.89°) for M = K and Rb, respectively. The alcohol adducts undergo an alkoxide ligand exchange process that is rapid on the 1H NMR time scale at room temperature.

Characterization of aluminium isopropoxide and aluminosiloxanes

Abstract Aluminium isopropoxide, in the form of a crystalline solid of melting point 127°C, has been shown by X-ray diffraction to be a tetrameric molecular species of formula Al[(μ-OiPr)2Al(OiPr)2]3, consistent with earlier proposals and spectroscopic data. A central aluminium achieves coordination number six via two bridging alkoxide groups from each of three Al(OiPr)4− groups. The resulting planar Al(μ2-O)2Al rings have widened (∼ 132°) angles at oxygen to increase the non-bonded AlAl distance. While the terminal OiPr groups show the shortest (1.70 A) AlO distances in the molecule, they are nevertheless strongly bent (∼ 140°) at oxygen. The 1H NMR spectrum of Al4(OiPr)12 is analysed based on the structure reported here. Characterization of aluminosiloxane derivatives Al(OiPr)3-x(OSiMe3)x (x = 1−3) by 1H and 27Al NMR, mass spectrometry and IR spectroscopy is also reported. For x = 1 and 2, these show co-existence of several oligomers. The effect of incorporation of OSiMe3 groups is to favour smaller oligomers.

The reactions of Cu2(O2CMe)4(H2O)2 with 2,2′-bipyridine (bpy): Influence of the Cu: bpy ratio, and the structure of a linear polymer comprising two alternating types of Cu2 units

Abstract Further investigation of the Cu 2 (O 2 CMe) 4 (H 2 O) 2 /bpy reaction system is described, including the determination of the influence of the Cu II : bpy ratio ( x ) on the identity of the reaction products. Values of x in the 1-2 range have been employed. Reaction of Cu 2 (O 2 CMe) 4 (H 2 O) 2 with two equivalents of bpy ( x = 1) in MeCN yields [Cu 2 (O 2 CMe) 4 (bpy) 2 ]·2H 2 O ( 1 ) in 79% yield. Treatment of Cu 2 (O 2 CMe) 4 (H 2 O) 2 with 1.33 equivalent of bpy ( x = 1.5) in MeCN leads to precipitation of the polymeric compound [—Cu 2 (O 2 CMe) 2 (bpy) 2 —O 2 CMe—Cu 2 (O 2 CMe) 4 —O 2 CMe—] n ( 2 ); from the filtrate 1 slowly crystallizes in 15% yield. A high yield (89%) of pure 2 can be obtained by increasing x from 1.5 to 2. Treatment of 1 with Cu 2 (O 2 CMe) 4 (H 2 O) 2 in MeCN provides an additional route to 2 . Compound 2 reacts with equimolar bpy in EtOH to yield complex 1 . Complex 1 undergoes facile carboxylate substitution in MeCN with an excess of PhCOOH, leading to reasonable yields (40-65%) of [Cu 2 (O 2 CPh) 4 (bpy) 2 ]· MeCN ( 3a ) or [Cu 2 (O 2 CPh) 4 (bpy) 2 ]· 2H 2 O ( 3b ), depending on the rate of crystallization. Complex 2 is converted to the known compound Cu 2 (O 2 CPh) 4 (EtOH) 2 ( 4 ) or 3b by treatment with excess PhCOOH in EtOH or MeCN, respectively. Complexes 1 and 2 undergo a variety of additional reactions that lead to the dinuclear complexes [Cu 2 (O 2 CMe) 3 (bpy) 2 ](ClO 4 ) ( 5 ), [Cu 2 (OH)(H 2 O)(O 2 CMe)(bpy) 2 ](ClO 4 ) 2 ( 6 ), Cu 2 (OH) 2 (bpy) 2 (ClO 4 ) 2 ( 7 ), [Cu 2 (O 2 CMe) 2 (H 2 O) 2 (bpy) 2 ](ClO 4 ) 2 · H 2 O ( 8 ) and Cu 2 (O 2 CMe) 2 (ClO 4 ) 2 (bpy) 2 ( 9 ). Complex 1 crystallizes in the triclinic space group P 1 with (at — 143°C) a = 8.842(2), b = 12.266(2), c = 7.708(1) A, α = 98.72(1), β = 106.35, γ = 109.68(1)°, Z = 1 and V = 726.68 A 3 . A total of 2318 unique reflections with F > 3.00σ( F ) were refined to values of R and R w of 2.67 and 2.87%, respectively. Compound 2 crystallizes in the triclinic space group P 1 with (at — 155°C) a = 9.272(2), b = 14.718(3), c = 8.023(1) A α = 102.66(1), β = 103.89(1), γ = 94.00(1)°, Z = 1 and V = 1028.21 A 3 . A total of 2319 unique reflections with F > 3.00σ( F ) were refined to values of R and R w of 3.68 and 3.96%, respectively. The structure of 1 consists of a [Cu 2 (O 2 CMe) 4 (bpy) 2 ] molecule located at a centre of symmetry with two syn,anti acetate bridges. The molecules of 1 form infinite ladder-like chains as a result of hydrogen-bonding interactions with the water molecules. The structure of 2 is composed of one-dimensional, well-separated polymeric chains and contains two different types of copper(II) dinuclear units, each at a crystallographic centre of symmetry. The chains are formed by alternating Cu 2 (O 2 CMe) 4 and [Cu 2 (O 2 CMe) 2 (bpy) 2 ] 2+ units which are linked by syn,anti bridging acetates. The Cu 2 (O 2 CMe) 4 unit has a tetra-bridged structure with four syn,syn bridging acetates and two oxygens from the two syn,anti acetates occupying the axial positions. The other dinuclear unit has a structure with two acetate groups forming mono-atomic bridges. From the IR and UV-vis solution spectra, it is concluded that the polymeric structure of 2 is not retained in MeCN. A cyclic voltammetric study of 1 in MeCN reveals a quasi-reversible reduction at −0.82 V vs ferrocene, and an irreversible reduction at −1.82 V yielding copper metal which deposits on the electrode. Complex 3b displays almost identical processes. Compound 2 displays two reduction processes at −0.84 and −1.82 V.

The synthesis and characterization of volatile lithium alkoxides, and the single crystal X-ray structure of [LiOCMe2Ph]6

Abstract The lithium alkoxides, [LiOR]n, [R = But (1) and PhMe2C (2)], have been prepared and fully characterized in solution by IR, 1H, 13C and 7Li NMR, and cryoscopy in benzene, which gave a value of n = 6. Single-crystal X-ray diffraction studies on [LiOC Me2Ph]6 (2) at −169°C revealed that this molecule crystallizes in the monoclinic space group P21/n, with unit cell dimensions, a = 12.555(2), b = 12.010(2), c = 16.405(3) A; β = 99.44(1)°, Z = 2, dcalc = 1. 161 g cm−3, as a hexagonal prism. The oxygen and lithium atoms in the hexameric species are arranged into two Li3O3 planes.

One-dimensional polymerization of M2(OAc)4 (M = Cu, Rh) units using 2-(aminomethyl)pyridine: preparation and characterization of [Rh2(OAc)4(amp)]n and [Cu4(OAc)8(amp)2]n

Abstract Synthetic procedures are described for the preparation of polymeric complexes of the general formula [M2(OAc)4(amp)]n (M = Rh, Cu; amp = 2-(aminoethyl)pyridine). Reaction of Rh2(OAc)4(MeOH)2 (1) with one equivalent of amp in MeCN produces [Rh2(OAc)4(amp)]n·n/2MeCN (2·n/2MeCN) in good yield (73%). The dinuclear RhII carboxylate core remains intact and has a metal-metal distance of 2.410(1)A. The coordination sphere of Rh(1) is completed by a pyridine nitrogen atom of one amp ligand while the coordination sphere of Rh(2) is completed by the amine nitrogen atom of a second amp ligand. These amp groups then bridge to adjacent Rh4+2 units to give a one-dimensional polymer [Rh2(OAc)4(amp)]n. Hydrogen bonding is evident between the amp amine groups and the carboxylate oxygen atoms [N(25)⋯O(3) = 2.964 A]. The peak with the highest m/z value in the FAB mass spectrum of 2 from a chloroform/p-nitrobenzylalcohol matrix corresponds to the fragment [Rh2(OAc)4]3(amp)2. Reaction of Cu2(OAc)4(H2O)2 (3) with one equivalent of amp in MeCN, followed by recrystallization from EtOH/Et2O, produces crystals of [Cu4(OAc)8(amp)2]n. The structure of 4 consists of well-separated, one-dimensional polymeric chains composed of alternating [Cu2(OAc)4] and [Cu2(OAc)2(amp)2]2+ units which are linked by syn, anti bridging acetates. The [Cu2(OAc)4] units closely resemble the starting material, with the two copper centres bridged by four η1 : η1 : μ AcO− ligands over a metal-metal separation of 3.282(1) A. The axial coordination sites are occupied by an oxygen atom of the syn, anti bridging acetates. The [Cu2(OAc)2(amp)2]2+ units contain two monoatomically bridging acetate groups, with the coordination sphere of the metals completed by a chelating amp ligand and the second oxygen atom of the syn, anti bridging acetates. Hydrogen bonding between the amine group of the amp ligands and the mono-atomic bridging acetate groups is evident [N(22)⋯O(25) = 2.877 A].

Single‐Crystal X‐Ray Diffraction Study of β‐Fluorine

Three‐dimensional x‐ray diffraction data from a single crystal of β‐F2 have yielded a crystal structure like that later found for the γ‐O2 phase in which no dimers are present. The unit cell is cubic, contains eight molecules, and has a lattice dimension of a=6.67±0.07 A. The two molecules at 000 and ½ ½ ½ are approximately spherically disordered, and the six molecules approximately at ¼ ½ 0, ¾ ½ 0, 0 ¼ ½, 0 ¾ ½, ½ 0 ¼, and ½ 0 ¾ are highly disordered, respectively, in the planes x=¼, x=¾, y=¼, y=¾, z=¼, and z=¾. The value of R=Σ ‖ Fo |−| Fc ‖/Σ | Fo | is 0.10 for the 28 observed reflections.

Oligomerization and structural variation of alkali metal silyloxides

Abstract Lithium and potassium silyloxide complexes [Li(OSiPh3)]n (1), [K(thf)0.2 (OSiPh3)]n (3) and [K(OSiMe2tBu)]n (6) were prepared by deprotonation of HOSiPh3 or HOSiMe2tBu with [Li(nBu)] in hexane or KH in THF, respectively. Crystalline DME adducts [Li(μ-OSiPh3)(η2-DME)]2 (2) and [K4(μ3-OSiPh3)3(μ3-OSiPh2(η1-Ph))(η2-DME)]2 (μ-DME) (4) were prepared by dissolving 1 or 3, respectively, in dimethoxyethane followed by precipitation with alkane. The potassium-sequestered complexes [K(18-crown-6) (OSiPh3)]2 (5) and [K(18-crown-6)(OSiMe2tBu)]n (7) were prepared from 3 or 5, respectively, and one equiv. of 18-crown-6 ether. The complexes were characterized by single-crystal X-ray diffraction: [Li(μ-OSiPh3)(η2-DME)]2 (2): a dimer featuring tetrahedral lithium centres linked by bridging —OSiPh3 ligands. [Crystal data ( − 156°C): space group P 1 , a = 14.238(6), b = 15.182(7), c = 11.796(5) A, α = 110.57(2), β = 112.02(2), γ = 63.02(1) A, V = 2055.33 A3, Z = 2.] [K4(μ3-OSiPh3)3{μ3-OSiPh2(η1-Ph)}(η2-DME)]2(μ-DME) (4): (1) two cubanes each having every potassium vertex chemically distinct; (2) one chelating DME ligand, one DME ligand bridging between two cubanes; and (3) a K-ipso-phenyl carbon contact. [Crystal data ( − 133°C): a = 14.246(4), b = 30.939(9), c = 17.981(5) A, β = 112.33(1)° with Z = 2 in space group P21/c.] [K(18-crown-6)OSiPh3]2 (5): A dimer with slipped face-to-face stacking of the quasi-planar K(18-crown-6)+ part of the two Ph3SiOK(18-crown-6) molecules; these are linked by a dative bond from one ether oxygen of a given crown to potassium contained in the other crown. [Crystal data ( − 155°C): a = 9.324(2), b = 17.640(5), c = 18.148(15) A, β = 91.60(1)° with Z = 4 in space group P21/c.]

Eta-6 bonding of benzene to potassium in [(C6H6)KOSiMe2Ph]4

Abstract Reaction of KH with PhMe2SiOH in toluene, followed by recrystallization from benzene, gives [(C6H6)KOSiMe2Ph]4, characterized by elemental analysis, 1H and 29Si NMR and X-ray diffraction. The molecule is a cubane tetramer of rigorous S4 symmetry, in which the KO3 coordination environment is supplemented by h6-binding of one benzene to each potassium. Crystal data (− 169°C): a = 12.972(2), b = 18.006(2) A, with Z = 8 in space group I4.

A comparison of heterometallic alkoxide molecules containing copper(I) or copper(II) and zirconium

Abstract The synthesis, characterization and structure and thermal decomposition of ClCuIIZr2(OiPr)9 (1) and Cu2IZr2(OiPr)10 (2) are reported. Compound 1 has a CuZr2(μ3-OR)2(μ2-OR)3 central core, with chloride as a terminal ligand on copper. This paramagnetic CuII species is particularly interesting in that the 1H NMR signals of those alkoxides which are μ2- and μ3-bridged to copper undergo paramagnetic shifts (to 8.66 and 10.41 ppm at 25°C), but those of the remaining alkoxide groups are unperturbed from the region characteristic of the Zr2(OiPr)9− unit. Compound 2 consists of a Zr2(OiPr)9− face-sharing bioctahedron with two μ2-alkoxides bridging to a Cu2IOR+ fragment giving the copper a linear two-coordinate environment. Both 1 and 2 are highly soluble in hydrocarbon solvents. TGA studies of both compounds reveal information on possible mechanisms and products of thermolysis.