Structural Studies of Perfluoroaryldiselenadiazolyl Radicals: Insights into Dithiadiazolyl Chemistry.

The synthesis and structural characterization of a series of perfluoroaryldiselenadiazolyls [DSeDA; p-XCFCNSeSeN (X = F, Cl, Br, CF, NO, and CN for 2a-2f, respectively)] are described. Concentration-dependent solution UV/vis measurements on 2a follow the Beer-Lambert law and the transitions assigned through time-dependent density functional theory (TD-DFT) studies, indicating little propensity for dimerization in solution (10-10 M). Solution electron paramagnetic resonance (EPR) spectra reveal that these radicals exhibit a broad featureless singlet around g = 2.

Use of crown ethers to isolate intermediates in ammonia-borane dehydrocoupling reactions.

The presence of 18-crown-6 in the Lewis acid-promoted dehydrocoupling reaction of ammonia borane permits isolation of [(THF)BH2NH3](+) and [BH2(NH3)2](+) cations. [(THF)BH2NH3](+) reacts with Lewis bases to give either boron adducts or by deprotonation at nitrogen to give borazine and ammonia-borane.

Synthesis and structure of the extended phosphazane ligand [(1,4-C6H4){N(μ-PN(t)Bu)2N(t)Bu}2](4).

The reaction of the phenylene-bridged precursor (1,4-C6H4)[N(PCl2)2]2 with (t)BuNH2 in the presence of Et3N gives the new ligand precursor (1,4-C6H4)[N(μ-N(t)Bu)2(PNH(t)Bu)2]2, deprotonation of which with Bu2Mg gives the novel tetraanion [(1,4-C6H4){N(μ-N(t)Bu)2(PN(t)Bu)2}2](4-).

Multiple deprotonation of primary aromatic diamines by LiAlH4.

Reaction of LiAlH4 with 1,2-phenylenediamine (1H4) in THF results in formation of the metallocyclic amido-/imido complex [{Al(1H2)}2{Al(1H)2}2][Li(THF)2]4 (3), while in the presence of various Lewis base ligands 1,8-diaminonaphthalene (2H4) gives the amido-('ate') complexes [Al(2H2)2](-)[Li(LL')](+) [L = THF, L' = PMDETA (N,N,N',N',N''-pentamethyldiethylenetriamine) (4); L = L' = TMEDA (N,N,N',N'-tetramethylethylenediamine) (5)]. The latter complexes provide evidence of intermediates in the proposed reaction pathway for formation of the cyclic framework of the tetraanion [{Al(1H2)}2{Al(1H)2}2](4-) of 3.

Reactivity and catalytic activity of tert-butoxy-aluminium hydride reagents.

The reactivity and catalytic activities of the tert-butoxy aluminium hydride reagents [((t)BuO)xAlH3-x] [x = 1 (1), 2 (2)] and (L)Li[((t)BuO)2AlH2] [L = THF (3), 1,4-dioxane (4)] are investigated. The structural characterisation of the novel compounds 3 and 4 shows that the nature of the hydridic species present is affected dramatically by the donor ligand coordinating the Li(+) cation. Stoichiometric reaction of 1 with pyridine gives [(1,4-H-pyrid-1-yl)4Al](-)[(pyridine)4AlH2](+) (5) while reaction with the amine-borane Me2NHBH3 in the presence of PMDETA [(Me2NCH2CH2)2NMe] affords [(PMDETA)AlH2](+)[(BH3)2NMe2](-) (6).

Direct access to [(Mes*P)2As](-), a 1,3-diphosphaarsa-2-allyl anion, isoelectronic with the allyl anion (Mes* = 2,4,6-(t)Bu3C6H2).

The reaction of As(NMe2)3 with Mes*PHLi provides a direct source of the 1,3-diphosphaarsa-2-allyl anion, [(Mes*P)2As](-) (isoelectronic with the allyl anion). The equilibrium between the E,E and E,Z isomers of this anion depends on the extent of Li(+) ion-pairing.

Stoichiometric and catalytic reactions of LiAlH4 with Me2NHBH3.

Structural and in situ NMR spectroscopic studies show that N-H deprotonation, B-N bond cleavage and B-N bond formation can occur in the stoichiometric and catalytic reactions of LiAlH4 with Me2NHBH3.

Group 11 complexes containing the [C5(CN)5]- ligand; 'coordination-analogues' of molecular organometallic systems.

The reactions of Na[C(5)(CN)(5)] (Na[1]) with group 11 phosphine complexes [(P)(n)MCl] (M = Cu, Ag, Au, P = Ph(3)P; M = Cu, P = dppe (Ph(2)PCH(2)CH(2)PPh(2))] give a range of compounds containing the pentacyanocyclopentadienide ligand, [C(5)(CN)(5)](-) (1). The new complexes [(Ph(3)P)(2)M{1}](2) [M = Cu (3); M = Ag (5)], [(Ph(3)P)(3)Ag{1}] (4), [(dppe)(3)Cu(2){1}(2)] (6) and [Au(PPh(3))(2)][1] (7) include the first complete series of group 11 complexes of any cyclopentadienide ligand to be structurally characterised.

Transition metal complexes of the pentacyanocyclopentadienide anion.

The ready formation of a range of transition metal complexes of the pentacyanocyclopentadienide anion via ligand transfer reactions employing Na[C(5)(CN)(5)] indicates that the [C(5)(CN)(5)](-) anion has an extensive transition metal coordination chemistry and is not such a weakly coordinating anion.

Oxidative dehydrocoupling of N-H bonds using a redox-active main group superbase.

Reaction of the redox-active base Sn(NMe(2))(2)/(n)BuLi with o-phenylene diamine leads to oxidative dehydrocoupling and rearrangement into the triazolyl anion.

A quadruply-bonded [Cr2(guanidinate)4]4- tetraanion.

The reaction of chromocene, Cp(2)Cr, with dilithiated 2,3-diphenylguanidine [(PhNH)(2)C=NH = L(2)H(3)] gives the novel, quadruply-bonded tetraanion [Cr(2)(L(2)H)(4)](4-).

Confinement of halide ions within homologous inverse coordination hosts; modification of halide-ion selectivity.

The structures of a series of spherical host-guest complexes [{MeE(PPh)(3)Li(4)·3thf}(4)(μ(4)-X)](-) (E = Al, [1X](-); E = Ga, [2X](-); E = In, [3X](-)) reveal that changing the halide ions (X = Cl, Br, or I) within their central tetrahedral Li(4) sites has negligible effect on the structural parameters.

A simple approach to coordination compounds of the pentacyanocyclopentadienide anion.

Deprotonation of [Et(3)NH][C(5)(CN)(5)] with metal bases provides a very simple approach to coordination compounds containing the pentacyanocyclopentadienide anion [C(5)(CN)(5)](-) (1). The three-dimensional polymer [Na(thf)(1.5)(1)](∞) and the molecular dimer [{(tmeda)(2)Na(1)}(2)] are obtained by reaction of this precursor with NaH in the presence of thf or tmeda (Me(2)NCH(2)CH(2)NMe(2)).

Synthesis and characterisation of 3,4-dialkoxy-substituted benzo-1,3,2-dithiazolyl radicals.

The conversion of 3,4-dialkoxy-benzenes into dialkoxy-benzo-1,3,2-dithiazolyls is described and representative examples (1 and 2) derived from benzodioxole and veratrol, respectively, are reported. Whilst 1 is a dimeric pi*-pi* dimer, the dimethoxy derivative 2 is monomeric in the solid state and exhibits antiferromagnetic interactions.

Stoichiometric and catalytic Sn-mediated dehydrocoupling of primary phosphines.

The room-temperature reactions of stannocene, Cp*(2)Sn, with a range of primary phosphines, RPH(2), result in diphosphanes [RP(H)P(H)R]. The reactions involving Cp*(2)SnCl(2), however, result in catalytic dehydrocoupling; the first example of main group metal catalysed dehydrocoupling to be identified.

The regioselective photochemical rearrangement of alpha-[PN(t)Bu](4).

The photochemical dyotropic (two-bond shift) rearrangement of the phosphazane cage alpha-[PN(t)Bu](4) (alpha) into the isomer beta-[PN(t)Bu](4) (beta) occurs via a multi-step radical mechanism; the structures of the alpha and beta isomers are directly analogous to isovalent alpha- and beta-As(4)S(4) and P(4)S(4).

Recent perspectives on main group-mediated dehydrocoupling of P-P bonds.

Transition metal-mediated dehydrocoupling is a developing synthetic tool for the preparation of an extensive range of main group element-element bonded species, with broad applications to molecular and polymeric materials. Recent results have stressed the relationship between this class of transition metal reagents and their entirely main group counterparts. But what are the similarities and differences between transition metal and main group systems?

Formation of a new class of 7pi radicals via sterically induced P-P bond cleavage of the dimers [(CH)2(NR)2P]2.

The 2c-2e- P-P bonded dimers [(CH)2(NR)2P]2 dissociate in solution to give the persistent new 7pi radicals [(CH)2(NR)2P]*, which are isoelectronic with the well known S/N thiazolyl radicals.

A mechanistic study of the C-P bond cleavage reaction of 1,2-(PH2)2-C6H4 with nBuLi/Sb(NMe2)3.

In situ 31P NMR spectroscopic studies of the reaction of the primary diphosphine 1,2-(PH2)2-C6H4 with the mixed-metal base system nBuLi/Sb(NMe2)3, combined with X-ray structural investigations, strongly support a mechanism involving a series of deprotonation steps followed by antimony-mediated reductive C-P bond cleavage. The central intermediate in this reaction is the tetraphosphide dianion [C6H4P2]2(2-) ([]) from which the final products, the 1,2,3-triphospholide anion [C6H4P3]- () and [PhPHLi] (.Li), are evolved.

The 6pi, phosphide-stabilised stannylene dianion [C6H4P2Sn]2-; the first member of a new class of Arduengo-type carbene analogues.

Dilithiation of 1,2-(PH2)2C6H4 with nBuLi followed by reaction with Sn(NMe2)2 in the presence of the Lewis base donor tmeda [Me2NCH2CH2NMe2] gives [(C6H4P2Sn)(Li.tmeda)2] , containing the phosphide-stabilised, 6pi stannylene dianion [C6H4P2Sn]2-.

pi-Bonding versus oligomerisation in the aromatic anions [C(6)H(4)N(2)E](-): formation of the cyclic tetrameric tetraanion [C(6)H(4)N(2)Sb](4)(4-).

The reaction of 1,2-(NH(2))(2)C(6)H(4) with Sb(NMe(2))(3)/(n)BuLi gives the formally-aromatic heterocyclic anion [C(6)H(4)N(2)Sb](-) which oligomerises into a cyclic tetrameric arrangement in the complex [C(6)H(4)N(2)SbLi.PMDETA](4) () (PMDETA = {Me(2)NCH(2)CH(2)}(2)NMe) using a donor-acceptor bonding mode that is unique in related main group heterocyclic anions.

Direct synthesis of the 1,2,3-[C6H4P...P...P]- anion, isoelectronic with the indenyl anion [C6H4CH...CH...CH]-.

The two products obtained from the reaction of 1,2-(PH(2))(2)C(6)H(4) with the mixed-metal base (n)BuLi-Sb(NMe(2))(3) in the presence of 12-crown-4, [Li(12-crown-4)(2)]+[C(6)H(4)P(3)]- (1) and {[Li(12-crown-4)(2)]+}3[Sb(11)]3- (2), represent thermodynamic sinks in which P-P and Sb-Sb bonding are maximized at the expense of P-Sb bonding, providing access to the 1,2,3-[C(6)H(4)P(3)]- phospholide anion.

Synthesis and magnetic properties of the novel dithiadiazolyl radical, p-NCC6F4C6F4CNSSN*.

The dithiadiazolyl radical p-NCC6F4C6F4CNSSN* (4) retains its monomeric nature in the solid state with molecules linked together into chains via supramolecular CN-S interactions. Variable temperature magnetic studies on 4 show that it behaves as a near-ideal Curie paramagnet (|theta| less than 0.1 K), indicating negligible intermolecular exchange.