John G. Crossley

An examination of the structures of iodosylbenzene (PhIO) and the related imido compound, PhINSO2-4-Me-C6H4, by X-ray powder diffraction and EXAFS (extended X-ray absorption fine structure) spectroscopy

Structural data derived from X-ray powder diffraction and EXAFS spectroscopy are presented for iodosylbenzene (PhIO) and the imido analogue, PhINSO2-4-Me-C6H4, which indicate that these compounds are polymeric in the solid state.

Synthesis of the 17-electron cations [FeL(L′)(NO)2]+(L, L′= PPh3, OPPh3): structure and bonding in four-co-ordinate metal dinitrosyls, and implications for the identity of paramagnetic iron dinitrosyl complex catalysts

The complex [FeL2(NO)2](L = PEt31a, L = PPh31b or L2= dppe 1c) prepared from [{Fe(µ-I)(NO)2}2] and PPh3 or Ph2PCH2CH2PPh2(dppe){in the presence and absence of [Co(cp)2](cp =η5-C5H5) respectively} undergo one-electron oxidation at a platinum electrode in CH2Cl2. The complex [{Fe(µ-dppm)(NO)2}2]2, prepared from [{Fe(µ-I)(NO)2}2] and Ph2PCH2PPh2(dppm) in the presence of [Co(cp)2], undergoes two sequential one-electron oxidations. Complex 1b with [Fe(cp)2]+ gave 1b+, X-ray studies of which show a distorted tetrahedral geometry with near C2v symmetry. Oxidation of 1b leads to substantial lengthening of the Fe–P bonds and changes in the P–Fe–P and N–Fe–N angles. These changes are consistent with significant Fe–P π-bonding character in the singly occupied molecular orbital of 1b+. Cation 1b+ reacts with halide ions, giving [FeX(PPh3)(NO)2](X = Cl or I) and then [FeX2(NO)2]–, and with OPPh3 to give [Fe(OPPh3)(PPh3)(NO)2]+3. X-Ray studies on the last, as its [PF6]– salt, show a distorted tetrahedral geometry; the co-ordination angles at iron approach trigonal bipyramidal with the PPh3 ligand in one apical site and the other apical site vacant. The complex [Fe(OPPh3)2(NO)2]+4+ resulted from the reaction between [{Fe(µ-I)(NO)2}2] and OPPh3 in the presence of TlPF6. An analysis of the ESR spectra of the paramagnetic cations 1b+, 3+ and 4+, together with extended-Huckel MO calculations on models of 1b+ and 3+, suggest that the complex catalysts formed from [{Fe(µ-Cl)(NO)2}2] and Ag+ or Tl+ are also four-co-ordinate 17-electron radicals. A crystallographic database study of four-co-ordinate dinitrosyl complexes of iron and other metals confirms that the N–Fe–N and O ⋯ Fe ⋯ O angles are linearly related. Consideration of these geometric effects, and those resulting from oxidation of 1b, in the light of a model proposed by Summerville and Hoffmann provides insight into the bonding in these and related species.

A STUDY OF CRYSTAL PACKING IN A SERIES OF CLOSELY RELATED SQUARE-PLANAR PALLADIUM(II) AND PLATINUM(II) COMPLEXES

Abstract The crystal structures of the series of four-coordinate complexes [PdL1Cl) · CH2Cl2 (1·CH2Cl2), [PtL1Cl]·CH2Cl2 (2·CH2Cl2), [PdL3Cl][PF6 · CH2Cl2 (3 · CH2Cl2) and [PdL4Cl][PF6 (4) [HL1 = 6-(2-hydroxyphenyl)-2,2′-bipyridine; L3 = 6-(2-dimethylaminophenyl)-2,2′-bipyridine; L4 = 2-(2-dimethylaminophenyl)-1,10-phenanthroline] are compared and contrasted to examine the extent to which aromatic π-stacking interactions contribute to crystal packing. Complexes 1 and 2 have very similar planar molecular structures but stack in different ways; molecules of 1 form a linear stack in which overlap of the aromatic ligands is maximized between adjacent molecules and there is no PdPd interaction, whereas in 2 there are axial PtPt interactions within the linear stack but less overlap between adjacent aromatic ligands. In 3 the ligand L3 is not planar but substantially twisted about the bond between the phenyl and bipyridyl fragments. The phenyl rings of the complex cations form an interleaved stack in the crystal, but the bipyridyl fragments are not involved in any close stacking interactions. Replacing the bipyridyl group by a phenanthrolinyl group in 4 changes the crystal packing; the structure of the individual complex cations is very similar to that of 3, but both fragments of the twisted ligand (the phenyl and phenanthrolinyl parts) are involved in separate stacking interactions with adjacent molecules.

Intramolecular electron transfer in linear trinuclear complexes of copper(I), silver(I) and gold(I) bound to redox-active cyanomanganese ligands

The reaction of [Cu(NCMe)4][PF6] with 2 equivalents of [Mn(CN)Lx]{Lx=(CO)(dppm)2, cis-or trans-(CO)2[P(OR)3](dppm)(R = Ph or Et, dppm = Ph2PCH2PPh2)} in CH2Cl2 gave [Cu{µ-NC)MnLx}2][PF6]. With 2 equivalents of [Mn(CN)Lx] in toluene, AgPF6 gave [Ag{(µ-NC)MnLx}2]+{Lx=cis- or trans-(CO)2[P(OR)3](dppm)(R = Ph or Et)} but in CH2Cl2cis-[Mn(CN)(CO)2(PEt3)(dppe)](dppe = Ph2PCH2CH2PPh2) or trans-[Mn(CN)(CO)(dppm)2] and AgX (X = BF4–, PF6– or SbF6–) gave the tricationic manganese(II) complexes [Ag{(µ-NC)Mn(CO)(dppm)2}2][PF6]3 and [Ag{(µ-NC)MnLx}2]X3{Lx=trans-(CO)2(PEt3)(dppe)]; the complexes [Ag{(µ-NC)MnLx}2][PF6]3{Lx=trans-(CO)2(P(OR)3](dppm)(R = Ph or Et)} were prepared directly from Ag[PF6] and trans-[Mn(CN)(CO)2{P(OR)3}(dppm)][PF6](R = Ph or Et) in CH2Cl2. Treatment of [AuCl(tht)](tht = tetrahydrothiophene) with [Mn(CN)Lx] in CH2Cl2 in the presence of Tl[PF6] yielded [Au{(µ-NC)MnLx}2][PF6]{Lx=(CO)(dppm)2, cis- or trans-(CO)2[P(OR)3](dppm)(R = Ph or Et)}. X-Ray structural studies on [Ag{(µ-NC)MnLx}2][PF6]{Lx=trans-(CO)2[P(OPh)3](dppm)}, [Au{(µ-NC)MnLx}2][PF6]{Lx=trans-(CO)2[P(OEt)3](dppm)}, and [Ag{(µ-NC)MnLx}2][PF6]3[Lx=(CO)(dppm)2] showed, in each case, near linear Mn–CN–M′–NC–Mn skeletons (M′= Ag or Au); the Mn–P and P–substituent bond lengths are consistent with octahedral MnI and MnII centres in the monocations and trication respectively. Each of the complexes [M′{(µ-NC)MnLx}2][PF6]{M′= Cu or Au, Lx=(CO)(dppm)2; M′= Cu or Ag, Lx=trans-(CO)2[P(OR)3](dppm)(R = Ph or Et)} showed one reversible two-electron oxidation wave at a platinum electrode in CH2Cl2; the trication [Cu{(µ-NC)Mn(CO)(dppm)2}2]3+ was generated in solution by controlled potential electrolysis of [Cu{(µ-NC)Mn(CO)(dppm)2}2]+, and [Au{(µ-NC)Mn(CO)(dppm)2}2][PF6]3 was prepared by chemical oxidation of [Au{(µ-NC)Mn(CO)(dppm)2}2][PF6] with [Fe(cp)2][PF6](cp =η-C5H5) in CH2Cl2. Magnetic and ESR spectroscopic studies provided further evidence for the presence of two isolated low-spin MnII centres in the trications [Ag{(µ-NC)MnLx}2]3+{Lx=(CO)(dppm)2, trans-(CO)2[P(OR)3](dppm)(R = Ph or Et) or trans-(CO)2(PEt3)(dppe)}. By contrast, [Au{(µ-NC)MnLx}2]+{Lx=trans-(CO)2[P(OR)3(dppm)(R = Et or Ph)} showed two reversible one-electron oxidation waves corresponding to the stepwise formation of di- and tri-cations. Electrolytic oxidation of [Au{(µ-NC)MnLx}2]+ in tetrahydrofuran, or chemical oxidation with [N(C6H4Br-p)3]+ or [Fe(η-C5H4COMe)(cp)]+ in CH2Cl2, gave solutions of [Au{(µ-NC)MnLx}2]2+{Lx=trans-(CO)2[P(OEt)3](dppm)}, IR spectroscopic and voltammetric studies on which are compatible with weak interaction between the two manganese centres in the mixed-valence dication.

The co-stacking of a planar metal complex and a novel 1,3-dithiole: The synthesis and crystal structure of [Pt(mnt)(CNMe)2]·(NC)2C2S2

The reaction of [NBu4n]2Cu(mnt)2] with [Pt(CNMe)4][PF6]2 gives [Pt(mnt)(CNMe)2]·(NC)2C2S2CNMe, an X-ray study of which reveals co-stacking of neutral planar metal and organic molecules.

The structure of amorphous Ph3SbO: information from EXAFS (extended X-ray absorption fine structure) spectroscopy

EXAFS data for amorphous Ph3SbO are consistent with a structure in which trigonal-bipyramidal SbPh3O2 units share their axial oxygens to form a chain kinked at the oxygen atoms.

New linear chain mixed metal compounds: complex salts of [Pt(CNMe)4]2+

The X-ray crystal structures of the salts [Pt(CNMe)4][Pd(mnt)2], [Pt(CNMe)4][Pd(mnt)2]2·2MeCN and [Pt(CNMe)4][Au(mnt)2]2·MeCN [mnt = 1,2-S2C2(CN)2] show a variety of stacking and layer motifs in the solid state; inter-complex interactions lead to low-dimensional molecular aggregates.

Arenediazonium ion insertion into an iron-phosphine bond ; synthesis and crystal structure of [Fe(NO)2{PPh2CH2CH2P(Ph)2NN(C6H4F-p)}][PF6].OC4H8

The reaction of [Fe(NO)2(dppe)](dppe = Ph2PCH2CH2PPh2) with [N2C6H4F-p][PF6] gave [Fe(NO)2{PPh2CH2CH2P(Ph)2NN(C6H4F-p)}][PF6] X-ray studies on which revealed the formation of a novel chelating ligand bound to iron through phosphine and η2-NN functionalities and resulting from insertion of an arenediazo group into an iron–phosphorus bond.

Linear molecular aggregation in solution: EXAFS studies of ML4 complexes

Analysis of Pt or Ir LIII-edge EXAFS spectra for K2[Pt(CN)4]0.3Br·3H2O (1), K2[Pt(CN)4]·3H2O (2), [Pt(CNMe)3Et]PF6(3), and [Ir(CNMe)4]Cl (4) in solid and solution phases shows evidence for metal ⋯ metal interactions in solid (1), (3), and (4) and in solutions of (4).

Dynamic disorder in crystalline [Fe2Os(CO)12] and direct evidence for rotation of the Fe2Os triangle in the solid state from variable temperature X-ray diffraction and 13C MAS NMR studies

Single-crystal X-ray diffraction data have been collected for [Fe2Os(CO)12] at 120, 223, 288, 292 and 323 K. The two studies at ambient temperature (288 and 292 K) reveal a ≈12 : 1 disorder of the metal triangle as previously reported. At the two lowest temperatures there is no evidence of disorder, while at 323 K the ratio of the major : minor component of disorder decreases significantly to ≈1.4 : 1. Data collected on the same crystal specimens indicate unequivocally that this disorder is dynamic in nature. Two-dimensional exchange and one-dimensional variable-temperature 13C magic angle spinning (MAS) NMR spectroscopy showed that carbonyl exchange is rapid above 306 K in the crystalline solid. Two independent exchange processes of similar energy are observed. The first is consistent with the crystallographic evidence, and involves an ‘in-plane’ rotation of the Fe2Os triangle in steps of 60° within a relatively rigid icosahedral carbonyl manifold. The second involves localised axial–equatorial exchange in the Os(CO)4 group. The Os LIII and Fe K edge X-ray absorption fine structure spectra are consistent with identical structures being present in tetrahydrofuran solution and in the solid phase.