Peter J. Nichols

Symmetry-Aligned Supramolecular Encapsulation of C60: [C60⊂(L)2], L=p-Benzylcalix[5]arene or p-Benzylhexahomooxacalix[3]arene

C60-encapsulated species, [C60⊂(1)2]⋅8 toluene and [C60⊂(2)2], are obtained exclusively when p-benzylcalix[5]arene (1) or p-benzylhexahomooxacalix[3]arene (2) react with C60 or fullerite in toluene. The C5 or C3 symmetry axis, respectively, of each calixarene is aligned with the same symmetry element of C60 and highlights the importance of symmetry matching in the design of host molecules for fullerenes.

Metal-Containing Rigid Concave Surfaces: An Entry to the Confinement of Globular Molecules

A remarkably adaptable nickel macrocycle, 1, acts as a divergent receptor towards the globular cage molecues C60, o-C2B10H12, and P4S3. The macrocycle either interacts with two cages, or one cage perched in each cavity, or self-associates as a dimeric divergent receptor with a cage perched in the available cavity of each macrocycle (see below).

The synthesis, reactivity and magnetic susceptibilities of Cr(IV)porphyrin imido complexes, CrN(R), and attempts to form heterobinuclear μ-imido compounds with CrN(R)V and CrN(R)Fe bridges

Abstract The reactions of arylazides with chromium(II) porphyrin compounds lead to the production of paramagnetic (d2) imides, CrIV(Por)N(R). The complexes undergo reaction with PPh3, benzaldehyde, CS2, CH3I and styrene leading to transfer of the imido group. Reaction of Cr(Por)N(R) compounds with VIVO(acac)2 and iron(II) salicylaldimines results in the formation of imido-bridged CrIIIN(R)V(V) and CrIIIN(R)Fe(III) species, as indicated by magnetic susceptibility vs temperature measurements down to 4.3 K.

Synthesis and characterisation of mononuclear and binuclear iron(II) complexes of pentadentate and bis(pentadentate) ligands derived from 1,4,7-triazacyclononane

Abstract Mononuclear iron(II) complexes of the pentadentate ligand 1,4-bis(2-pyridylmethyl)-1,4,7-triazacyclononane (dmptacn) of composition [Fe11(dmptacn)Cl]PF6 (I) and [Fe11(dmptacn)NCS]PF6 (II) been prepared and characterised, II, C19N25N6F6FePS, crystallises in the monoclinic space group P21/n (No. 14) with cell dimensions a = 13.856(6); b = 10.980(4); c = 16.580(5) A ; β = 110.33(3)° ; V = 2365(1) A 3 and Z = 4 . The structure of II shows that the Fe atom is in a distorted octahedral geometry defined by a N6 donor set derived from dmptacn and an N-bound thiocyanate. Complex I is high spin while complex II is low spin. Replacement of a chloride by a thiocyanate ligand induces sufficient change to the ligand field to cause a change in spin state. Analogous binuclear iron(II) complexes of the bis(pentadentate) ligand 1,2-bis(N,N′-bis(2-pyridylmethyl)-1,4,7-triazacyclonon-1-yl)ethane (tmpdtne) III and IV are also reported. III·2dmf crystallines in the monoclinic space group P21/c (No. 14) with cell dimensions a = 11.745(2); b = 14.817(3); c = 15.725(3) A ; β = 95.35(2)°; V = 2724.8(8) A 3 and Z = 2 . The X-ray structure of III · 2dmf shows that, in the centrosymmetric binuclear cation, each iron atom adopts a distorted octahedral geometry defined by an N3 compartment of tmpdtne and a chloro ligand. The longest FeN distance corresponds to the nitrogen atom which links the two macrocyclic compartments together. Mossbauer and magnetic moment data confirmed that both [Fe3(tmpdtne)Cl2](PF6)2(III) and [Fe2(tmpdtne) (NCS)2](ClO4)2 (IV) were high spin.

Oligoethyl ether derivatives of ester functionalised nickel(II) macrocycles

γ,γ′-Ester functionalisation of the macrocycle 5,7,12,14-tetramethyldibenzo[b,i]-1,4,8,11-tetraazacyclotetradecinenickel(II) (Ni(TMTAA)), using two alternative methods, either based on oxalyl chloride or ‘triphosgene’, has been effective in the synthesis of novel cyclic crown ether-type molecules containing a rigid, saddle shaped nickel(II) macrocycle and an oligoethyl ether chain. Mono-ester derivatisation using triphosgene allows access to compounds with two Ni(TMTAA) units bridged by oligoethyl ethers of various chain length.

Synthesis and crystal structure determination of tetraphenylarsonium p-bromophenylthio-chromate

The initial step in the reaction of [Cr 2 O 7 ] 2− with p -bromothiophenol in dimethylformamide is the formation of the chromium(VI)-thioester [ p -BrC 6 H 4 SCrO 3 ] − , which has been isolated as the [Ph 4 As] + salt and its structure determined by a single crystal X-ray diffraction study, thus confirming the proposed first step in the mechanism for the overall oxidation of thiophenols by dichromate.

Chromium(VI)-thioester formation in N,N-dimethylformamide

Abstract The interaction of thiols (RSH; R = n-butyl, t-butyl, p-bromophenyl, p-nitro- phenyl and phenyl) with dichromate in dimethylformamide (DMF) has been studied and found to involve the formation of chromium(VI) thioester anions ([RSCrO3]−) followed by much slower redox reactions resulting in the formation of chromium(III) and disulphide species. The chromium(VI) thioesters can be precipitated from DMF/ether solutions as tetraphenylarsonium or bis(triphenylphosphine)iminium salts. They show characteristic visible absorptions around 420 nm (extinction coefficients ca 2000 mol−1 dm3 cm−1) and IR absorptions at ca 945 cm-1 [v(CrO)assym] and 890 cm− [v(CrO)sym]. The initial interaction between thiols and dichromate in DMF is an acid-catalysed hydrolysis of dichromate followed by the substitution of protonated chromate by the thiol. Arylthiols catalyse the hydrolysis more effectively, and substitute chromate more rapidly, than alkyl- thiols. Chromium(VI) arylthioesters decompose more rapidly than the alkyl thiol derivatives with chromium(V) intermediates being involved in the process.

A 1,3-Sigmatropic Rearrangement Revealed in the Solid and Solution State Structures of a Chiral Sodium 1-Azaallyl Complex Derived from (S)-N-(α-Methylbenzyl)allylamine

The reaction of nBuNa with (S)-N-(α-methylbenzyl)allylamine, followed by the addition of tmeda, gives a chiral sodium 1-azaallyl complex, {[(S)-α-[PhC(H)MeN−··C(H)−··CHCH3)]Na·tmeda}2, as confirmed by single crystal X-ray diffraction and solution NMR spectroscopy, and is most likely the result of a 1,3-sigmatropic rearrangement and subsequent delocalisation within the resulting enamide. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

The redox synthesis, structure and magnetic properties of the heterobimetallic μ-oxo compound [(py)(TPP)CrOFe(tmtaa)]

Abstract The oxidation of FeII(tmtaa) 1 by CrIVO(TPP) 1 in pyridine-tetrahydrofuran solution leads to the formation of the heterobimetallic complex [(py)(TPP)CrOFe(tmtaa)]. Crystal structure determination of the bis-tetrahydrofuran solvate shows that the CrOFe linkage is almost linear [176.6(9)°)], while the Fe-tmtaa stereochemistry differs from that previously known for five-coordinate tmtaa complexes. Mossbauer spectra and magnetic data (to 4 K) are reported for the solvent free complex. The S = 3 2 : S = 5 2 complex shows strong antiferromagnetic coupling with a 2J value of −299 cm−1.

The synthesis of organo-imido complexes of Cr(IV) and Fe(III)

Abstract The reaction of p-tolylazide with (5,10,15,20- tetraphenylporphyrinato) chromium(II) (Cr(TPP)) yields the high spin chromium(IV) organo-imido complex, CH3C6H4NCr(TPP). N,N′-ethylene- bis-(salicylideneiminato)iron(II), (Fe(salen)), however reacts with arylazides to produce iron(III) organo-imido-bridged compounds of general formula, [Fe(salen)]2NR showing magnetic coupling between the Fe(III) centres.