Structures of tetrasilylmethane derivatives (XMe2Si)2C(SiMe3)2 (X = H, Cl, Br) in the gas phase, and their dynamic structures in solution.

The structures of the molecules (XMe2Si)2C(SiMe3)2, where X = H, Cl, Br, have been determined by gas electron diffraction (GED) using the SARACEN method of restraints, with all analogues existing in the gas phase as mixtures of C1- and C2-symmetric conformers. Variable temperature (1)H and (29)Si solution-phase NMR studies, as well as (13)C NMR and (1)H/(29)Si NMR shift correlation and (1)H NMR saturation transfer experiments for the chlorine and bromine analogues, are reported. At low temperatures in solution there appear to be two C1 conformers and two C2 conformers, agreeing with the isolated-molecule calculations used to guide the electron diffraction refinements.

A conformational study of phospha(III)- and phospha(V)-guanidine compounds.

Spectroscopic, crystallographic, and computational studies of the substituent distribution about the "NCN" unit in a series of phospha(III)- and phospha(V)-guanidines, R(2)PC{NR'}{NHR'} and R(2)P(E)C{NR'}{NHR'} (R = Ph, Cy; R' = (i)Pr, Cy; E = S, Se), are reported. In the phosphorus(III) systems, the P-diphenyl substituted compounds are observed as only one isomer, shown by NMR spectroscopy to be the E(syn)-(alpha) configuration. In contrast, the corresponding P-dicyclohexyl derivatives exist as a mixture of E(syn)-(alpha) and Z(anti) in solution.

Reactions between a sodium amide Na[N(SiMe3)R1] (R1 = SiMe3, SiMe2Ph or But) and a cyanoalkane RCN (R = Ad or Bu(t)).

Reactions between sodium amides Na[N(SiMe3)R1] [R1 = SiMe3 (1), SiMe2Ph (2) or But (3)] and cyanoalkanes RCN (R = Ad or But) were investigated. In each case the nitrile adduct [Na{mu-N(SiMe3)2}(NCR)]2 [R = Ad (1a) or But (1b)], trans-[Na{mu-N(SiMe3)(SiMe2Ph)}(NCR)]2 [R = Ad (2a) or But (2b)], [(Na{mu-N(SiMe3)But})3(NCAd)3] (3a) or [(Na{mu-N(SiMe3)But})3(NCBut)n] [n = 3 (3b) or 2 (3c)] was isolated. The reaction of complexes 3a or 3b with benzene afforded the ketimido complex [Na{mu-N=C(Ad)(Ph)}]6.

Synthesis of protected gamma-carboxyglutamates and gamma-acylglutamates by rearrangement of N,N-diacylglutamates.

A new method for gamma-acylation of protected glutamic acids, involving intramolecular rearrangement of an acyl urethane, has been devised to prepare the protected gamma-carboxyglutamates 7, 9 and 11 and the protected 4-acylglutamates 15 and 22 from N,N-bisurethanes or N-acyl-N-urethanes of general structure 1. When the formyl-urethane 17 was used in the reaction, then the intermediate 18 in the intramolecular rearrangement was obtained.

Isolation of two seven-membered ring C58 fullerene derivatives: C58F17CF3 and C58F18.

Fluorination of C60 at 550 degrees C leads to milligram quantities of two stable fullerene derivatives with 58-carbon cage structures: C58F18 and C58F17CF3. The compounds were characterized by mass spectrometry and fluorine nuclear magnetic resonance spectroscopy, and the data support a heptagonal ring in the framework. The resulting strain, which has hindered past attempts to prepare these smaller quasi-fullerenes, is mitigated here by hybridization change of some of the carbons in the pentagons from sp2 to sp3 because of fluorine addition.

C1 C70F38 contains four planar aromatic hexagons; the parallel between fluorination of [60]- and [70]fullerenes.

The main C(1) isomer of C(70)F(38) is shown by single-crystal X-ray analysis to contain four planar aromatic hexagons and four isolated C=C bonds, has two fluorines on the equator, and is related to C(2) C(70)F(38) by means of three 1,3-fluorine shifts. The C(1) and C(2) isomers thus parallel the T and C(3)/C(1) isomers of C(60)F(36) in containing three and four aromatic rings, respectively, and in the fluorine shift relationship.

Kinetic stability of heteroleptic (beta-diketiminato) heavier alkaline-earth (Ca, Sr, Ba) amides.

The potential of the heteroleptic heavier alkaline-earth hexamethyldisilazides [{HC(C(Me)2N-2,6-iPr2C6H3)2}Ae{N(SiMe3)2}(THF)](Ae = Ca, Sr, Ba) as kinetically-stable reagents for further protolytic reaction chemistry has been assessed. Only the previously reported calcium complex was found to be stable to solution dismutation and dynamic ligand exchange. The barium complex was isolated in sufficient purity to enable characterisation by an X-ray analysis.

C2 C70F38 is aromatic, contains three planar hexagons, and has equatorial addends.

Single crystal X-ray analysis shows the main (C(2)) isomer of C(70)F(38) to contain three planar delocalised aromatic hexagons (two equivalent and one centred on the C(2) axis), together with seven C[double bond, length as m-dash]C bonds (three pairs and one straddling the C(2) axis); C(70)F(38) is the first high addition level [70]fullerene derivative to be fully characterised, is the first to have equatorial addends, and is calculated to have high stability.

Self-organisation in P-substituted guanidines leading to solution-state isomerisation.

Different isomeric forms of the amidine unit have been identified in Ph2P(E)C[NR'][NHR'] (E = S, Se; R' = iPr, Cy), using both solid- and solution-state techniques.

Solution- and solid-state characterisation of a configurationally-stable beta-diketiminato-supported calcium primary amide.

'Selective' protonolysis of the beta-diketiminato calcium derivative [Ca[(NDippCMe)(2)CH][N(SiMe(3))(2)](THF)] Dipp = C(6)H(3)(i)Pr(2)-2,6) with H(2)N(CH(2))(2)OCH(3) produced the dimeric species [Ca[(NDippCMe)(2)CH][mu-NH(CH(2))(2)OMe]](2), which has been fully characterised in solution and in the solid state.

Electrophilic aromatic substitution by the fluorofullerene C60F18.

The FeCl3-catalysed arylation of C60F18 gives tri-substituted compounds C60F15Ar3, where Ar=phenyl, 4-tolyl, 4-methoxyphenyl, 4-phenoxyphenyl, 4-chlorophenyl, 3,4-dichlorophenyl, 2-biphylenyl and 2-fluorenyl, together with some bis- and mono-substituted product. Bis-substitution was achieved with biphenylene and fluoranthene, and mono-substitution with biphenylene (2-position), pyrene (1-position), and naphthalene (1- and 2-positions); the tris-phenyl and tris-biphenylene derivatives are fluorescent. The 2-naphthyl substituent freely rotates at 328 K, whereas rotation of the 1-naphthyl substituent is prevented by interaction of the peri-hydrogen atom with fluorine.

Reactions of Li- and Yb-coordinated N,N'-bis(trimethylsilyl)-beta-diketiminates: one- and two-electron reductions, deprotonation, and C-N bond cleavage.

The synthesis and characterisation of novel Li and Yb complexes is reported, in which the monoanionic beta-diketiminato ligand has been (i) reduced (SET or 2 [times] SET), (ii) deprotonated, or (iii) C-N bond-cleaved. Reduction of the lithium beta-diketiminate Li(L(R,R'))[L(R,R')= N(SiMe(3))C(R)CHC(R')N(SiMe(3))] with Li metal gave the dilithium derivative [Li(tmen)(mu-L(R,R'))Li(OEt(2))](R = R'= Ph; or, R = Ph, R[prime or minute]= Bu(t)). When excess of Li was used the dimeric trilithium [small beta]-diketiminate [Li(3)(L(R,R[prime or minute]))(tmen)](2)(, R = R'= C(6)H(4)Bu(t)-4 = Ar) was obtained.

Yttrium complexes incorporating the chelating diamides [ArN(CH2)xNAr]2- (Ar = C6H3-2,6-iPr2, x= 2, 3) and their unusual reaction with phenylsilane.

Novel yttrium chelating diamide complexes [(Y[ArN(CH(2))(x)NAr](Z)(THF)(n))(y)] (Z = I, CH(SiMe(3))(2), CH(2)Ph, H, N(SiMe(3))(2), OC(6)H(3)-2,6-(t)Bu(2)-4-Me; x = 2, 3; n = 1 or 2; y = 1 or 2) were made via salt metathesis of the potassium diamides (x = 3 (3), x = 2 (4)) and yttrium triiodide in THF (5,10), followed by salt metathesis with the appropriate potassium salt (6-9, 11-13, 15) and further reaction with molecular hydrogen (14). 6 and 11(Z = CH(SiMe(3))(2), x = 2, 3) underwent unprecedented exchange of yttrium for silicon on reaction with phenylsilane to yield (Si[ArN(CH(2))(x)NAr]PhH) (x = 2 (16), 3) and (Si[CH(SiMe(3))(2)]PhH(2)).

Synthetic and structural experiments on yttrium, cerium and magnesium trimethylsilylmethyls and their reaction products with nitriles; with a note on two cerium beta-diketiminates.

The yttrium, cerium and magnesium bis(trimethylsilyl)methyls [Ln[CH(SiMe3)2]3][Ln = Y (1), Ce (2)], and the known compound Mg[[CH(SiMe3)2]2 (C) and [Mg(mu-Br)[CH(SiMe3)2](OEt2)]2 (D) formed the crystalline nitrile adducts [1(NCBut)2] (5), [2(NCPh)] (6), [C(NCR)2][R = But (8), Ph (9), C6H3Me2-2,6 (10)] and [Mg(mu-Br)[CH(SiMe3)2](NCR)]2 [R = But (11), Ph (12), C6H3Me2-2,6 (13)], rather than beta-diketiminato-metal insertion products. The beta-diketiminato-cerium complex [Ce[(N(SiMe3)C(C6H4But-4))2CH][N(SiMe3)2]2] (16) was obtained from [Ce[N(SiMe3)2]3] and the beta-diketimine H[[N(SiMe3)C(C6H4But-4)]2CH]]. The cerium alkyl 2 and [Ln[CH(SiMe3)(SiMe2OMe)]3][Ln = Y (3), Ce (4)] were obtained from the appropriate lithium alkyl precursor and [Ce(OC6H2But2-2,6-Me-4)3] or LnCl3, respectively.

Design and synthesis of multi-component 18 pi annulenic fluorofullerene ensembles suitable for donor-acceptor applications.

A series of trannulene (all-trans annulene) derivatives of [60]fullerene have been prepared by reacting C(60)F(18) with methanetricarboxylate esters that incorporate a range of photoactive functions. All the compounds have the intense emerald-green colour of fullerene trannulenes, characterised by strong bands at ca. 612 and 667 nm.

Unusual addition patterns in trifluoromethylation of [60]fullerene.

From pyrolytic trifluoromethylation of [60]fullerene with CF3CO2Ag at 300 degrees C we have isolated ca. sixty C60(CF3)n isomers (numbers in parentheses) as follows: n = 2(1), 4(8), 6(13), 8(21), 10(11), 12(5), 14(4), twenty-one of which have been characterised by 19F NMR. Compounds with addition levels up to n = 20 have also been identified.

Synthesis of 18pi annulenic fluorofullerenes from tertiary carbanions: size matters!

A range of tertiary carbanions XCH(CO2Et)2 of differing sizes have been reacted with C60F18 to assess the steric effect of X on the position of nucleophilic substitution. For X = CO2Et, NO2, P(O)(OMe)2, SO2CH2Ph, the all trans annulenes (trannulenes) were obtained as a result of extended S(N)2' (i.e.

In the first proven SN2' fullerene reaction, both C3 and C1 C60F36 hydrolyse to C1 isomers of C60F35OH that eliminate HF to give epoxides C60F34O; C60F36O oxides are shown to be ethers, and a fourth isomer of C60F36 exists.

On standing in organic solvents containing traces of water, C3 and C1 isomers of C60F36 slowly convert to C1 isomers of C60F35OH. Both fluorofullerenols eliminate HF during EI mass spectrometry to give C60F34O epoxides, one fullerenol being much less stable than the other to the extent that the mass spectrum shows only the epoxide. Both C60F35OH isomers have C1 symmetry, one being identified by the remarkable linear relationship between chemical shifts in its 19F NMR spectrum and those in the spectrum of C1 C60F36; the spectrum of the other shows the pattern of C3 C60F36 rendered asymmetrical by the replacement of one F by OH.

Electrophilic substitution of C60F18 into phenols: HF elimination between OH and a 1,3-shifted fluorine giving benzofurano[2',3':10,26]hexadecafluro[60]fullerene and derivatives.

The reaction of C60F18 with phenol, 2-naphthol and quinol in the presence of ferric chloride leads to initial electrophilic substitution (aryldefluorination). This occurs at both ortho and para positions for phenol, at the ortho position for quinol, and at the relatively hindered but most reactive 1-position for 2-naphthol. It is followed, where sterically favourable, by HF loss either between the OH group and F (rendered adjacent as a result of a 1,3-shift) or to attack of the OH group at an adjacent double bond with loss of a beta-fluorine, giving benzofurano[2',3':10,26]hexadecafluoro[60]fullerene derivatives.

[60]- and [70]Fullerenes are trifluoromethylated across 5:6-bonds.

Trifluoromethylation of [60]- and [70]fullerenes occurs across both 6:6- and 5:6-bonds giving unsymmetrical tetramethyl adducts having four contiguous CF3 groups; both fullerenes give bis adducts which do not involve 6:6-addition, and unsymmetrical hexa-adducts (with contiguous CF3 groups) are also obtained from [60]fullerene.

Formation of novel sulfur-containing C60F16 cycloadducts between tetrathiafulvalene and C60F18; a unique six-electron cycloaddition of a fullerene involving F2 loss.

Co-evaporation of solutions of C(60)F(18) and tetrathiafulvalene in toluene produces an unsymmetrical C(60)F(16):tetrathiafulvalene adduct through a unique six-electron cycloaddition involving displacement of two fluorine atoms by a terminal Cdbond;C double bond of the fulvalene. The adduct rearranges into two further adducts, one of which is characterised as a new type of fullerene derivative, a thiiranofullerene, formed by elimination of a thioketene moiety from the tetrathiafulvalene adduct. The initial addition also produces a bisadduct in which the addends comprise one tetrathiafulvalene molecule and one in which carbon disulfide has been eliminated.

A light-harvesting fluorinated fullerene donor-acceptor ensemble; long-lived charge separation.

In a first example of a trannulene-based donor-acceptor dyad visible light photoexcitation generates a long-lived (870 ns) charge-separated state.

Fluorine takes a hike: remarkable room-temperature rearrangement of the C1 isomer of C60F36 into the C3 isomer via a 1,3-fluorine shift.

In a toluene/CDCl3 solution at room temperature, the C1 isomer of C60F36 rearranges into the C3 isomer over a period of four days, as a result of a unique 1,3-shift of fluorine; this rare example of addend migration across a fullerene cage surface is accelerated by air.

C60F36: there is a third isomer and it has C1 symmetry.

From fluorination of [60]fullerene with MnF3/K2NiF6 at 480 degrees C we have isolated and characterized by both 19F NMR spectrum and single crystal X-ray analysis, a C1 isomer of C60F36; it has three planar delocalized aromatic rings, three short C=C bonds (due to compression from the adjacent fluorines), the longest FC-CF bond (1.684 A) yet found in a fluorofullerene, and its stability is predicted by calculations.