Hans-Jürgen Haupt

Methyl(2‐phosphanylphenolato[P,O])nickel(II) Complexes – Synthesis, Structure, and Activity as Ethene Oligomerization Catalysts

Reactions of various substituted 2-phosphanylphenols 1a–f with half-molar amounts of cis-[MeNi(μ-OMe)(PMe3)]2 have been found to yield square-planar methyl(2-phosphanylphenolato)(trimethylphosphane)nickel(II) complexes 2a–f. 2JPP coupling constants of 305–316xa0Hz at low temperature indicate a trans-configuration for the products, while broad 31P-NMR signals at room temperature can be attributed to rapid dissociation of PMe3. Reaction with excess 1 gave rigid bis(2-phosphanylphenolato)nickel(II) complexes as exemplified by 3e, whereas addition of PMe3 to 2a led to the pentacoordinate methyl(2-phosphanylphenolato)bis(trimethylphosphane)nickel(II) complex 4a. Higher yields of 4a and 4d were obtained by reactions of 1a and 1d with Me2Ni(PMe3)3. Single-crystal X-ray diffraction analyses of 3e and 4a have revealed the structures as square-planar trans-bis- and trigonal-bipyramidal mono(2-phosphanylphenolato)nickel(II) P1O-chelate complexes, respectively. The methylnickel complexes 2 and 4 have been found to be effective one-component catalysts for the oligomerization of ethene. High conversions (> 96%) were achieved with the P-basic derivatives 2e, 2f, and 4d bearing one or two branched alkyl groups (isopropyl, tert-butyl), whereas the diphenylphosphanyl derivatives were less active; 4d gave shorter oligomers than 2e or 2f.

A Triangular Iron(III) Complex Potentially Relevant to Iron(III)-Binding Sites in Ferreascidin.

An asymmetric triangular Fe(III) complex has been synthesized by an unusual Fe(II) -promoted activation of salicylaldoxime. Formation of the ligand 2-(bis(salicylideneamino)methyl)phenol in situ is believed to occur through the reductive deoximation of salicylaldoxime by ferrous ions. The trinuclear ferric complex has been characterized on the basis of elemental analysis, IR, variable-temperature magnetic susceptibility, and EPR and Mössbauer spectroscopies. The molecular structure established by X-ray diffraction consists of a trinuclear structure with a [Fe3 (μ3 -O)(μ2 -OPh)](6+) core. Two iron ions are in a distorted octahedral environment having FeN2 O4 coordination spheres, and the five-coordinated third iron ion, with an FeNO4 coordination sphere, is in a trigonal bipyramidal environment. The magnetic susceptibility measurements revealed an St = 5/2 ground state with the antiparallel exchange interactions J = - 34.3 cm(-1) , J = - 4.7 cm(-1) , and D = - 0.90 cm(-1) . The EPR results are consistent with a ground state of S = 5/2 together with a negative D5/2 value. The Mössbauer isomer shifts together with the quadrupole splitting also provide evidence for the high-spin state of the three ferric sites. Magnetic Mössbauer spectra lead to the conclusion that the internal magnetic fields possibly lie in the plane of the three ferric ions.

Novel cholesteric glassy liquid crystals of monosubstituted ferrocenes: synthesis and selective reflection properties of a dimesogen, and crystal structure of a monomesogen

Several monomesogens of ferrocene derivatives bearing the N‐benzoyl‐N′‐arylthiourea (BATU) bidentate ligand have been synthesized. A non‐symmetric dimesogen in which two structurally different mesogenic groups, namely the BATU and cholesteryl moieties, inter‐linked by a flexible spacer has also been synthesized. The achiral monomesogens exhibit enantiotropic smectic C and nematic phases, while the chiral monomesogens show exclusively a cholesteric phase with selective reflection in the infrared region. The dimesogen, on the other hand, exhibits an enantiotropic cholesteric phase with selective reflection in the visible region with iridescent colours. This represents the first ferrocene based organometallic liquid crystalline compound exhibiting this unique property. The cholesteric phases formed transform to glassy liquid crystals which can be fixed on sudden cooling to 0°C. The Grandjean texture observed in the cholesteric temperature range was retained in the glassy state depicting helical orientation in the glassy solid. Furthermore, X‐ray crystal structure determination of one of the compounds (Fc‐BATU‐12) provided evidence implying the involvement of structure‐determining intra‐ and inter‐molecular interactions in all the liquid crystalline compounds involving BATU units. The crystallographic data confirms that these systems fulfil the two prerequisites for calamitic (rod‐like) mesomorphism, namely critical length/depth ratio (>5) and an extended linear shape.

Steric Control of Cyclometallation Reactions in Schiff-Base Complexes of Cobalt(I) Containing an Anchoring Diphenylphosphanyl Group

2-(Diphenylphosphanyl)alkyliminobenzaldehydes(2-Ph2PC6H4CHNR) react with [CoCH3(PMe3)4] forming five-membered metallacycles in complexes [(2-Ph2PC6H4CNR-C,P)Co(PMe3)3] [1: R = C2H5, 2: R = CH(CH3)2, 3: R = cyclo-C6H11] while the ortho-metallation pathway is selectively followed in the formation of [{2-Ph2PC6H3(CHNR)-C1,P}Co(PMe3)3] [4: R = C(CH3)3]. The presence of a four-membered cobaltocycle in the molecular structure of 4 was confirmed by X-ray analysis. Carbonylation of 2 and 3 gives the monocarbonyl derivatives [(2-Ph2PC6H4CNR-C,P)Co(CO)(PMe3)2] [5: R = CH(CH3)2, 6: R = cyclo-C6H11] while 4 undergoes ring expansion by insertion forming [{2-Ph2PC6H3(CHNR)CO-C,P}Co(CO)(PMe3)2] [7: R = C(CH3)3]. Monosubstitution occurs under 1 bar of ethene giving the π-ethene complexes [(2-Ph2PC6H4CNR-C,P)Co(C2H4)(PMe3)2] [8: R = CH(CH3)2, 9: R = cyclo-C6H11] and [{2-Ph2PC6H3(CHNR)-C1,P}Co(C2H4)(PMe3)2] [10: R = C(CH3)3]. The molecular structure of 9 shows an equatorial π-ethene ligand. Iodomethane oxidizes 2 and 3 to afford the cobalt(II) complexes [(2-Ph2PC6H4CNR-C,P)CoI(PMe3)2] [11: R = CH(CH3)2, 12: R = cyclo-C6H11] and oxidatively adds to 4 to give mer-trans-[{2-Ph2PC6H3(CHNR)-C1,P}CoI(CH3)(PMe3)2] [13: R = C(CH3)3]. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Thermotropic properties of monosubstituted ferrocene derivatives bearing bidentateN-benzoyl-N′-arylthiourea ligands—novel building blocks for heterometallic liquid crystal systems

Ferrocene-based derivatives such as 4-{3-[4-(octyloxy)benzoyl]thioureido}phenyl 4-ferrocenylbenzoate and other higher homologues (n=12,16 and 18; n=length of alkoxy chain) were prepared by reacting 4-alkoxybenzoyl isothiocyanates with the corresponding amines containing the ferrocenyl moiety. Their mesomorphic properties were investigated by means of polarized optical microscopy and differential scanning calorimetry. All the compounds exhibit enantiotropic nematic phases and the nematic range increases with increasing terminal alkyl chain length. On cooling, the nematic phase persists below 0 °C in the first three compounds and in the case of n=18, a phase transformation, possibly to the SCphase, around 72 °C during cooling was observed. In all cases, a glass transition was observed around Tg=18–35 °C, which is remarkable for low molecular mass calamitic metallomesogen systems.

Reaction of 2-nitrophenols with high-valent trimethylphosphine complexes of cobalt

Abstract Acylphenolato(hydrido)cobalt(III) complexes Co(η 2 -CO,O)H(PMe 3 ) 3 (CO,O=1-carbonyl-2-oxo-5- tert -butyl-cyclohexendiyl; 1-carbonyl-2-oxo-cyclohexendiyl) by reaction with 2-nitrophenol eliminate dihydrogen and are converted to 2-nitrophenolatocobalt(III) compounds. With the former dianionic ligand an intermediate tris(phosphine) compound 1 containing a η 1 -nitrophenolato group is shown to adopt a meridional configuration in the crystal. In solution a η 2 -nitrophenolato coordination mode is usually attained after dissociation of one of the trimethylphosphines resulting in cis and trans isomers of bis(phosphine) compounds 2 and 3 . bis(Phosphine) complexes 5 – 7 ( cis , trans ) were also obtained from Co(η 2 -CO,O)H(PMe 3 ) 3 (CO,O-1-carbonyl-2-oxo-3,4-benzo-cyclohexendiy1; 1-carbonyl-2-oxo-1,2-diphenyl-ethendiyl) and 2-nitronaphthol. No reduction of nitro groups neither by free PMe 3 nor by excess CoH complex was observed although the corresponding nitrosonaphtholato complexes 8 and 9 were readily formed upon combining Co(η 2 -CO,O)H(PMe 3 ) 3 (CO,O=1-carbonyl-2-oxo-5- tert -butyl-cyclohexendiyl; 1-carbonyl-2-oxo-1,2-diphenyl-ethendiyl) and 2-nitrosonaphthol.

Reduction of 2-Nitrophenols by Low Valent Trimethylphosphine Complexes of Cobalt

2-Nitrophenols [C 6 H 3 R 4 R 6 (NO 2 )OH] react with Co(PMe 3 ) 4 to afford 2-nitrosophenolatocobalt (I) compounds Co[η 2 - N , O ][C 6 H 2 R 4 R 6 (NO)O](PMe 3 ) 3 ( 1 : R 4 =R 6 =H; 2 : R 4 =Me, R 6 =CMe 3 ). In the molecular structure of 2 the cobalt atom is centered in a trigonalbipyramid of axial O , P and equatorial N , P 2 donor atoms, whereas an isosteric molecule Ni[η 2 - C , O ][C 6 H 2 R 4 R 6 (CO)O](PMe 3 ) 3 ( 2C : R 4 =Me, R 6 =CMe 3 ) containing axial C,P and equatorial O,P 2 donor atoms crystallizes in a different space group. From 2-nitronaphthol-1 or 2-nitrosonaphthol-1 and Co(PMe 3 ) 4 a nitrosocobalt(I) complex Co[η 2 - N , O ][C 10 H 6 (NO)O](PMe 3 ) 3 ( 3 ) is obtained. 2-Nitronaphthol-1 reacting with excess Co(PMe 3 ) 4 affords dinuclear compounds Co 2 [η 3 - O ,μ 2 - N ][C 10 H 6 (N)O](PMe 3 ) 5 ( 4 ) and Co 2 {[η 3 - O ,μ 2 - NH ][C 10 H 6 (NH)O]} 2 (PMe 3 ) 4 ( 5 ). The molecular structure of 4 shows a rather long metal to metal bond (Coue5f8Co=2.628(1) A) which attains a normal value in that of 5· 2THF (Coue5f8Co=2.399(1) A). Reactions of low-valent carbonyl(trimethylphosphine)cobalt complexes with 2-aminophenol afford Co 2 [μ 2 - CO ; η 3 - O ,μ 2 - NH ][C 10 H 6 (NH)O](CO)(PMe 3 ) 4 ( 6 ).

Diastereomeric metallatetrahedron complexes of the type Re2(MPPh3)(M′PPh3)(μ-PCy2)(CO)7(−)-thiocamphanate (M = Ag, Au, M′ = Cu, Ag, Au): synthesis, structure and CD data

Four pairs of diastereomeric metallatetrahedron complexes of the type Re2(MPPh3)(M′PPh3) (μ-PCy2)(CO)7(−)-thiocamphanate have been synthesized, with identical (M = M′ n= Au (5a, 5b) and Ag (6a, 6b)) and with mixed coinage metals (M = Au, M′ n= Ag (8a, 8b) and Cu (9a, 9b)). After separation, the absolute configuration was determined by single crystal X-ray crystallography for 6a, 8a and 9a. nIn agreement with solution (31P and 1H NMR) spectral data, the thiocamphanate acts as a μ-S bridging bidentate ligand along the Re-coinage metal edge; in the mixed coinage metal complexes coordination involves the lower homologue of the coinage metals. Signs of the long wavelength absorption bands in the CD spectra were found to correlate with the counter (A) or clockwise (C) configuration of the chiral transition metal core.

Ring cleavage of imidazole to oxamide by reaction with dioxygen in the presence of a CuI–amine complex. Structure of μ-oxamidato-bis[(1,4,7-trimethyl-1,4,7-triazacyclononane)copper(II)] triiodide iodide

An oxamidato group in a trans conformation bridges two trimethyltriazacyclononane moieties. Each Cu atom is fivefold coordinated by four N and one O atoms. The N and O atoms of the oxamidato ligand are disordered over two sites giving two different trans conformations. The cations are packed along [100] with iodide and triiodide anions between them. The I 3 - ions are disordered and have asymmetric I-I bond lengths

A pseudo-trigonal bipyramidally ­coordinated Pt atom in dicarbonyl­bis(octacarbonyl-μ-di­cyclo­hexyl­phosphidodirhenio)­platinum(II)

In the title compound, [PtRe4(C12H22P)2(CO)18] or [(mu-PCy2)(CO)8Re2]2Pt(CO)2 (Cy is cyclohexyl), two phosphido-bridged dirhenium groups are linked by a Pt(CO)2 unit and show different bonding patterns for stereochemical reasons. The Re--Re distances are 3.2620 (15) and 3.0739 (15) A, and the Pt--Re distances are 2.9165 (12), 2.9025 (15) and 2.8548 (13) A.