"Push-push and push-pull" polystannanes.

The synthesis and characterization of polystannanes with "push" or "pull" moieties attached to the tin backbone are described. Precursor tetra aryl- (1, 2) stannanes were converted to mono- (3) and dichloro- (4, 5) stannanes by either sequential chlorination or by redistribution reactions with SnCl4. Compounds 4 and 5 were transformed to polymerisable tin dihydride monomers 6 and 7 using a large excess (10×) of NaBH4. Homopolymer 8 with electron donating aryl substituents (p-MeOC6H4-) was synthesized by dehydrogenative polymerization using Wilkinson's catalyst. Attempts to prepare the homopolymer 9 with electron withdrawing aryl substituents (p-CF3C6H4-) from the dehydrocoupling of 7 using similar conditions led only to the formation of low molecular weight oligomeric species. Two alternating polymers, 10 and 11, were synthesized by condensation polymerization of (n-Bu)2Sn(NEt2)2 with monomers 6 or 7. The first was a "push-push" alternating polymer, 10, comprised of a repeating unit consisting of two different electron donating groups (p-MeOC6H4-, n-Bu) at neighboring tin centres. The second was a "push-pull" alternating polymer, 11, bearing both an electron donating group (n-Bu) and a strongly electron withdrawing substituent (p-CF3C6H4-) at neighboring tin atoms. All small molecule stannanes and tin-containing polymers were characterized by NMR (1H, 13C, 119Sn, and where required 19F) spectroscopy, MS or EA. The absolute molecular weights of tin polymers (8, 10, 11) were determined by triple detection GPC and in the range of 1.07 × 104 to 1.95 × 104 Da. Rapid photodegradation of polymers was observed by UV-Vis spectroscopy, with a slower degradation observed for the "push-pull" polymer, 11, compared to the "push-push" polymer, 10.

Molecular lemmings: strategies to avoid when designing BODIPY ferrocene dyads for dye-sensitized solar cell applications.

BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacenes) dyes possess intense absorption profiles that can be exploited in various light harvesting applications. However, redox stability and optimization of frontier molecular orbital energies in these dyes are critical for their successful incorporation into new solar cell materials. This article describes the synthesis and characterization of a family of ß-substituted BODIPY-ferrocene dyads with push-pull architectures. Designed to stabilize the photo-oxidized BODIPY for dye-sensitized solar cell (DSSC) applications, some deleterious electron transfer behaviours emerged when the ferrocene unit was conjugated to electron deficient BODIPYs. These findings are discussed herein.

A stable open-shell redox active ditopic ligand.

Herein we describe the synthesis, structure and electronic properties of an unusual redox-active ditopic ligand with a stable open-shell configuration. This stable phenoxyl radical features intense and very low energy electronic transitions in the near infrared (NIR) part of the spectrum and is structurally set up to strongly spin couple coordinated transition metal ions in [2 × 2] grid-type structures.

Structure and magnetic properties of an unusual homoleptic iron(III) thiocyanate dimer.

We describe the structural and variable temperature magnetic susceptibility properties of an unusual homoleptic bimetallic iron(III) thiocyanate tetraanion. This work represents the first structurally characterized bis(µ-1,3-thiocyanato) dimer of iron(III). A weak antiferromagnetic exchange interaction is observed between the two iron(III) ions, which is supported by broken symmetry density functional theory (DFT) calculations.

B-H activation by frustrated Lewis pairs: borenium or boryl phosphonium cation?

Catechol borane reacts with the frustrated Lewis pairs tBu2RP (R = tBu, 2-C6H4(C6H5)) and B(C6F5)3 to give the species [(C6H4O2)BPtBu2R][HB(C6F5)3] that can formally be described as either borenium cation or boryl-phosphonium salts; the nature of these species was probed with DFT calculations.

The three-dimensional structural characterization of hexachlorocyclopentenyl-dibromocyclooctane (HCDBCO).

The 1H NMR spectrum and the crystal structure of HCDBCO [(1R,2R,5R,6R,9S,10S)-5,6-dibromo-1,10,11,12,13,13-hexachlorotricyclo[8,2,1,0(2,9)]-tridec-11-ene)] are reported. The measured dihedral angles from the X-ray structure correlate very well with those calculated from the proton-proton coupling constants indicating that the conformations in solution and in the solid state are probably very similar. Attempts at calculating the 3D model structure of HCDBCO only produced a very poor match between the measured dihedral angles between vicinal protons and the observed proton-proton coupling constants from the 1H NMR spectrum. GC/MS analysis with an injector temperature of 250 degrees C produced minor amounts of debrominated HCDBCO. Reducing the temperature to 200 degrees C eliminated this problem.

C-H activation with elemental sulfur: synthesis of cyclic thioureas from formaldehyde aminals and S8.

The C-H activation of cyclic formaldehyde aminals LCH2 (L = RN-CH2CH2CH2-NR and RNCH2CH2-NR, R = Me, Et, iPr, tBu, or Ph) with S8 proceeds at unusually low temperatures (T< 160 degrees C) and results in the formation of the respective thioureas LC=S and H2S. The reaction constitutes a new, solvent-free method for the synthesis of thioureas that eliminates the toxic and highly flammable CS2. For R = tBu, the ionic carbenium thiocyanates [LCH]+ SCN- dominate the product spectrum and the respective thioureas are obtained in low yield. The reactivity of the analogous sulfur and oxygen ring systems towards S8 was investigated. 1,3-Dithiolane is cleanly converted into 1,3-dithiolane-2-thione (S8, 14 d, 190 degrees C) and resembles the cyclic formaldehyde aminals in this respect. 1,3-Dioxolane (L = OCH2CH2O) is completely inert towards sulfur even under forceful reaction conditions (190 degrees C, 14 d). The formation of thioureas from aminals was investigated at the CBS-4 and B3LYP/6-31G(d) levels of theory.

Hydrogen-bonded adducts of ferrocene-1,1'-diylbis(diphenylmethanol): monomeric and dimeric 1:1 adducts with 1,2-bis(4-pyridyl)ethane and 1,2-diaminoethane.

In ferrocene-1,1'-diylbis(diphenylmethanol)-4,4'-ethylenedipyridine (1/1), [Fe(C(18)H(15)O)(2)].C(12)H(12)N(2), there is an intramolecular O-H...O hydrogen bond in the ferrocenediol component and a single O-H...N hydrogen bond linking the two components into a finite monomeric adduct. Ferrocene-1,1'-diylbis(diphenylmethanol)-ethylenediamine (1/1), [Fe(C(18)H(15)O)(2)].C(2)H(8)N(2), crystallizes with Z' = 2 in space group P1, and there are two independent four-component aggregates in the structure, both of which are centrosymmetric. In the first type of aggregate, the molecular components are linked by O-H...N and N-H...O hydrogen bonds, in which both diamine N atoms participate; in the second type of aggregate, the diamine component is disordered over two sets of sites, but only one N atom is involved in the hydrogen bonding.

Sodium 2-nitroethanaloximate forms a layered-framework structure.

In the title compound, [Na(C(2)H(3)N(2)O(3))], the Na(+) cation lies on a centre of inversion in space group P2(1)/m and all the atoms of the anion lie on a mirror plane. Na is octahedrally coordinated by four O and two N atoms from six different anions and each anion is coordinated to six different Na(+) cations, forming chains of confacial octahedra which link the anion layers. Within these layers, the individual anions are linked by both O-H...O and C-H...O hydrogen bonds.

N,N'-Dimethylpiperazinium(2+) phosphonoacetate: hydrogen-bonded anion sheets containing cation-templated R(6)(6)(28) rings.

In the title compound, C(6)H(16)N(2)(2+).2C(2)H(4)O(5)P(-), the cations lie across centres of inversion; in the anions, two of the H-atom sites have 0.50 occupancy. The anions are linked by short O-H...O hydrogen bonds [O...O 2.465 (3)-2.612 (3) A and O-H...O 165-171 degrees ] into sheets of alternating R(2)(2)(12) and R(6)(6)(28) rings, both of which are centrosymmetric; the cations lie at the centres of the larger rings linked to the anion sheet by N-H...O hydrogen bonds [N...O 2.642 (2) A and N-H...O 176 degrees ].

Hydrogen-bonded bilayers in piperazinium(2+) bis(mandelate) bis(methanol) solvate.

In the title compound, C(4)H(12)N(2)(2+).2C(8)H(7)O(3)(-).2CH(4)O, the cations lie across centres of inversion and are disordered over two orientations with equal occupancy; there are equal numbers of (R)- and (S)-mandelate anions present (mandelate is alpha-hydroxybenzeneacetate). The anions and the neutral water molecules are linked by O-H...O hydrogen bonds [O...O 2.658 (3) and 2.682 (3) A, and O-H...O 176 and 166 degrees] into deeply folded zigzag chains. Each orientation of the cation forms two symmetry-related two-centre N-H...O hydrogen bonds [N...O 2.588 (4) and 2.678 (4) A, and N-H...O 177 and 171 degrees] and two asymmetric, but planar, three-centre N-H...(O)(2) hydrogen bonds [N...O 2.686 (4)-3.137 (4) A and N-H...O 137-147 degrees], and by means of these the cations link the anion/water chains into bilayers.

Rhodium-catalyzed dehydrocoupling of the sterically encumbered phosphine-borane adduct tBu(2)PH.BH(3): synthesis of the linear dimers tBu(2)PH-BH(2)-tBu(2)P-BH(3) and tBu(2)PH-BH(2)-tBu(2)P-BH(2)Cl.

The dehydrocoupling of the sterically hindered phosphine-borane adduct tBu(2)PH.BH(3) above 140 degrees C is catalyzed by the rhodium complexes [Rh(1,5-cod)(2)][OTf] or Rh(6)(CO)(16) to give the four-membered chain tBu(2)PH-BH(2)-tBu(2)P-BH(3) (1), which was isolated in 60% yield and characterized by multinuclear NMR spectroscopy, mass spectrometry, and elemental analysis. Thermolysis of 1 in the temperature range 175-180 degrees C led to partial decomposition and the formation of tBu(2)PH.BH(3). When the dehydrocoupling of tBu(2)PH.BH(3) was performed in the presence of [[Rh(mu-Cl)(1,5-cod)](2)] or RhCl(3) hydrate, the chlorinated compound tBu(2)PH-BH(2)-tBu(2)P-BH(2)Cl (2) was formed which could not be obtained free of 1. The molecular structures of tBu(2)PH.BH(3), tBu(2)PH-BH(2)-tBu(2)P-BH(3) (1), and tBu(2)PH-BH(2)-tBu(2)P-BH(2)Cl (2) together with 1 were determined by single-crystal X-ray diffraction studies.

Tuning the strain and polymerizability of organometallic rings: the synthesis, structure, and ring-opening polymerization behavior of [2]ferrocenophanes with C-SI, C-P, and C-S bridges.

A series of novel [2]ferrocenophanes with unsymmetrical C-E bridges has been prepared in which the covalent radius of the second-row element, E, and hence the ring strain present is varied. Species [Fe(eta-C(5)Me(4))(eta-C(5)H(4))CH(2)ER(x)] (7, ER(x) = SiMe(2); 8a, ER(x) = PPh; 8b, ER(x) = PMes; 9, ER(x) = S) were synthesized via reaction of the PMDETA (N,N,N',N' ',N' '-pentamethyldiethylenetriamine) adduct of [(eta-C(5)H(4)Li)Fe(eta-C(5)Me(4))CH(2)Li] with Cl(2)ER(x) (E = Si or P) or S(SO(2)Ph)(2). Studies of 7-9 by single-crystal X-ray diffraction confirmed the presence of ring-tilted structures: for 7, alpha (angle between the planes of the Cp rings) = 11.8(1) degrees; for 8a, alpha(average) = 14.9(3) degrees; for 8b, alpha(average) = 18.2(2) degrees; and for 9, alpha = 18.5(1) degrees. The least tilted compound, 7, was found to be resistant to thermal, anionic, and transition metal catalyzed ROP. In contrast, the significantly more tilted compounds 8a, 8b, and 9 were all found to polymerize thermally with small negative values of DeltaH(ROP) of ca. 10-20 kJ.mol(-1) determined by DSC. Whereas thermal ROP of 8a yielded the soluble high molecular weight polycarbophosphaferrocene [(eta-C(5)Me(4))Fe(eta-C(5)H(4))CH(2)PPh](n) (11), species 9 formed the insoluble polycarbothiaferrocene [(eta-C(5)Me(4))Fe(eta-C(5)H(4))CH(2)S](n) (14). Attempted anionic ROP of 8a and 9 with (n)BuLi was unsuccessful and treatment of 8a with CF(3)SO(3)Me resulted in the formation of the novel phosphonium salt [(eta-C(5)Me(4))Fe(eta-C(5)H(4))CH(2)PMePh][CF(3)SO(3)] (13), which was found to be resistant to thermal ROP as a result of its less strained structure (for 13, alpha = 11.4(7) degrees ). Treatment of 9 with CF(3)SO(3)Me or BF(3).Et(2)O resulted in the first example of cationic ROP for a transition metal-containing heterocycle to yield polycarbothiaferrocene 14. In the presence of excess 2,6-di-tert-butylpyridine as a selective proton trap, ROP of 9 was only observed with CF(3)SO(3)Me, and not BF(3).Et(2)O, which indicated that Me(+) and H(+) are the probable cationic initiators, respectively. Thermal copolymerization of 9 with trimethylene sulfide resulted in the isolation of the soluble, high molecular weight, random copolymer [(eta-C(5)Me(4))Fe(eta-C(5)H(4))CH(2)S](n)[(CH(2))(3)S](m), 15.

Mu-1,4-benzenedicarboxylato-bis[trans-aqua(1,4,8,11-tetraazacyclotetradecane)nickel(II)] diperchlorate forms a three-dimensional hydrogen-bonded framework.

The title compound, [Ni2(C8H4O4)(C10H24N4)2(H2O)2](ClO4)2, contains two independent octahedral Ni(II) centres with trans-NiN4O2 chromophores. The bridging benzenedicarboxylate ligand is bonded to the two Ni atoms, each via one O atom of each carboxylate, while the other O atom participates in an intramolecular N-H...O hydrogen bond, forming an S(6) motif. The cations are linked to the perchlorate anions via O-H...O and N-H...O hydrogen bonds [O...O 2.904 (6) and 2.898 (6) A; O-H...O 158 (6) and 165 (6) degrees; N...O 3.175 (7) and 3.116 (7) A; N-H...O 168 and 166 degrees ] to form molecular ladders. These ladders are linked by further O-H...O and N-H...O hydrogen bonds [O...O 2.717 (6) and 2.730 (5) A; O-H...O 170 (4) and 163 (6) degrees; N...O 3.373 (7) and 3.253 (7) A; N-H...O 163 and 167 degrees ] to form a continuous three-dimensional framework. The perchlorate anions both participate in three hydrogen bonds, and both are thus fully ordered.

Ferrocenecarboxylic acid-1,4-diazabicyclo[2.2.2]octane (2/1): sheets built from O--H...N and C--H...O hydrogen bonds.

In the title compound, 2[Fe(C5H5)(C6H5O2)].C6H12N2, the molecular components are linked into finite three-component aggregates by strong O-H...N hydrogen bonds [O.N 2.578 (4) and 2.604 (5) A; O-H...N 170 (5) and 174 (6) degrees ]; these aggregates are further linked by C-H...O hydrogen bonds [C...O 3.327 (5)-3.401 (5) A; C-H...O 149-157 degrees ] into continuous sheets in the form of (6,3) nets.

Methoxy[meso-5,10,15,20-tetrakis-(2,6-difluorophenyl)porphyrinato]-iron(III), [Fe(TDFPP)(OCH3)].

The crystal structure of the title compound, [Fe(C(44)H(20)F(8)N(4))(CH(3)O)], has been determined. The Fe atom lies 0.485 (1) A out of the plane of the four N atoms to which it is coordinated and from the inversion centre at the origin of the unit cell. The methoxy group is axially coordinated to the Fe atom with O-Fe-N angles of 106.3 (2) and 102.4 (2) degrees, a C-O-Fe angle of 128.3 (5) degrees and an Fe-O distance of 1.788 (5) A. Difluorophenyl rings are tilted from the porphyrin (por) plane with torsion angles of -68.1 (6) and 77.7 (5) degrees across the two C(por)-C-C-C(ar) systems.

Hydrated salts of 3,5-dihydroxybenzoic acid with organic diamines: hydrogen-bonded supramolecular structures in two and three dimensions.

The trigonally trisubstituted acid 3,5-dihydroxybenzoic acid forms hydrated salt-type adducts with organic diamines. In 1,4-diazabicyclo[2.2.2]octane-3,5-dihydroxybenzoic acid-water (1/1/1) (1), where Z' = 2 in P2(1)/c, the constitution is [HN(CH(2)CH(2))(3)N](+).[(HO)(2)C(6)H(3)COO](-).H(2)O: the anions and the water molecules are linked by six O-H.O hydrogen bonds to form two-dimensional sheets and each cation is linked to a single sheet by one O-H.N and one N-H.O hydrogen bond. Piperazine-3,5-dihydroxybenzoic acid-water (1/2/4) (2) and 1,2-diaminoethane-3,5-dihydroxybenzoic acid-water (1/2/2) (3) are also both salts with constitutions [H(2)N(CH(2)CH(2))(2)NH(2)](2+).2[(HO)(2)C(6)H(3)COO](-).4H(2)O and [H(3)NCH(2)CH(2)NH(3)](2+).2[(HO)(2)C(6)H(3)COO](-).2H(2)O, respectively. Both (2) and (3) have supramolecular structures which are three-dimensional: in (2) the anions and the water molecules are linked by six O-H.O hydrogen bonds to form a three-dimensional framework enclosing large centrosymmetric voids, which contain the cations that are linked to the framework by two N-H.O hydrogen bonds; in (3) the construction of the three-dimensional framework requires the participation of cations, anions and water molecules, which are linked together by four O-H.O and three N-H.O hydrogen bonds.