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Three ferrocene analogues, D 5h (η5-CB5H5)2M (M = Fe2−, Co−, and Ni), with triplet aromatic CB5H5 ligands have been predicted at TPSSh/6–311+G(d,p) level. We find that the M atom interacts drastically with the two CB5H5 ligands through a nearly fully-filled 3d subshell, which is different from (η5-C5H5)2Fe. The natural population analyses suggest that (η5-CB5H5)2M have an unconventional charge distribution, i.e., the M atom is negatively charged, while the two boron rings are positively charged. The analyses of the electronic and dynamic stabilities indicate that (η5-CB5H5)2Co− is the most stable among (η5-CB5H5)2M. Thus, we theoretically confirm that the triplet aromatic CB5H5 cluster can be regarded as a potential new ligand. Our theoretical predictions are awaiting future experimental verification.

Reaction of in situ generated {η5-[MeOC(O)]C5H4}Co(PPh3)2 with methyl 3-phenyl-2-propynoate followed by diphenylacetylene in refluxing toluene resulted in the formation of the cobalt sandwich compound {η5-[MeOC(O)]C5H4}Co{η4-C4Ph3[C(O)OMe]} (1), having methyl ester units on both the cyclopentadienyl (Cp) and cyclobutadiene (Cb) rings. Hydrolysis of the ester groups using aqueous KOH resulted in the dicarboxylic acid {η5-C5H4[C(O)OH]}Co{η4-C4Ph3[C(O)OH]} (2). The dicarboxylic acid 2 was converted to the novel bis(oxazolinyl) derivative [η5-(4-iPr-2-Ox)C5H4]Co[η4-C4Ph3(4-iPr-2-Ox)] (3; Ox = oxazolinyl) by its reaction with oxalyl chloride, (S)-2-amino-3-methyl-1-butanol, triethylamine, and mesyl chloride. Reaction of the chiral bis(oxazoline) ligand 3 with Pd(OAc)2 in acetic acid at 60 °C resulted in the formation of the novel chiral palladacycle 4, resulting from an unprecedented cyclopalladation involving one of the cyclobutadiene-bound phenyl groups. Palladacycle 4 has two trans-oriented oxazolinyl units...

The cocondensation of Mn atoms, I 2 and toluene at 77 K yields small quantities of [Mn(η-C 6 H 5 Me) 2 ] + I − . A single crystal X-ray structure determination shows that the manganese sits on a crystallographic inversion centre with a Mn ring steroid distance of 1.56(1) A.

The salt [Mo(η-C6H6)2][PF6] has been prepared by iodine oxidation of [Mo(η-C6H6)2] followed by metathesis with NaPF6. The cyclic voltammogram of [Mo(η-C6H6)2][PF6] in MeCN exhibits a reversible redox couple (E½) at –730 mV vs. a saturated calomel electrode (SCE). The solid-state room-temperature EPR spectrum exhibits an isotropic resonance centred at g= 1.993 which is consistent with an assignment of a 2A1g ground state for the 17-electron [Mo(η-C6H6)2]+ radical cation. The salt [Mo(η-C6H6)2][FeBr4] has been synthesised from [NEt4][FeBr4] and [Mo(η-C6H6)2][PF6]. It crystallises in the orthorhombic space group Pbca, a= 18.527(17), b= 12.521(5), c= 14.915(6)A; R and R′= 0.051 and 0.059. The salt [Mo(η-C6H6)2][FeBr4] consists of segregated chains of cations and anions. The solid-state room-temperature EPR spectrum exhibits two resonances centred at g= 1.987 and 2.008 assignable to the cation and anion respectively. The solid-state magnetic susceptibility data for [Mo(η-C6H6)2][FeBr4] can be fitted to the Curie–Weiss law between 40 and 300 K with C= 3.93 and θ=–5.4 K. Below 15 K the [FeBr4]– anion sub-lattice orders antiferromagnetically leaving a magnetic susceptibility which is dominated by the [Mo(η-C6H6)2]+ cations.

The lithium-cyclopropylethynylamidinates Li[c-C3H5-C[triple bond, length as m-dash]C-C(NR)2] (1a: R = (i)Pr, 1b: R = cyclohexyl (Cy)) have been used as precursors for the preparation of five new series of half-sandwich complexes. These complexes contain the large flat cyclooctatetraenyl ligand (C8H8(2-), commonly abbreviated as COT), and were isolated as solvated, unsolvated and inverse sandwich complexes. Treatment of the halide precursors [(COT)Pr(μ-Cl)(THF)2]2 with 1b and [(COT)Nd(μ-Cl)(THF)2]2 with 1a and 1b in THF in a 1 : 2 molar ratio, respectively, afforded (COT)Ln[μ-c-C3H5-C[triple bond, length as m-dash]C-C(NR)2]2Li(L) (2: Ln = Pr, R = Cy, L = Et2O; 3: Ln = Nd, R = (i)Pr, L = THF; 4: Ln = Nd, R = Cy, L = THF). Treatment of the dimeric cerium(iii) bis(cyclopropylethynylamidinate) complexes [{c-C3H5-C[triple bond, length as m-dash]C-C(NR)2}2Ce(μ-Cl)(THF)]2 (5: R = (i)Pr; 6: R = Cy) in situ with K2C8H8 in a 1 : 1 molar ratio in THF at room temperature afforded the inverse-sandwich complexes (μ-η(8):η(8)-COT)[Ce{c-C3H5-C[triple bond, length as m-dash]C-C(NR)2}2]2 (7: R = (i)Pr; 8: R = Cy). This reaction represents a new method for encapsulation of a planar (C8H8)(2-) ring in lanthanide complexes containing amidinate ligands in the outer decks. Novel unsolvated dinuclear lanthanide half-sandwich complexes were prepared by using the precursors 1a, 1b and COT(2-). Unlike the complexes 2-4, the reaction of [(COT)Pr(μ-Cl)(THF)2]2 with 1a afforded the unsolvated centrosymmetric complex [(COT)Pr(μ-c-C3H5-C[triple bond, length as m-dash]C-C(N(i)Pr)2)]2 (9). These dimeric structures could be also accessed by reaction of LnCl3 (Ln = Ce or Nd) with 1a or 1b and K2COT in a 1 : 1 : 1 molar ratio as a one-pot reaction to give novel [(COT)Ln(μ-c-C3H5-C[triple bond, length as m-dash]C-C(NR)2)]2 complexes (10: Ln = Ce, R = (i)Pr; 11: Ln = Ce, R = Cy; 12: Ln = Nd, R = (i)Pr). Similar treatment of HoCl3 with 1a or 1b and K2COT as three-component reactions in a 1 : 1 : 1 molar ratio afforded the solvated half-sandwich complexes (COT)Ho(c-C3H5-C[triple bond, length as m-dash]C-C(NR)2)(THF) (13: R = (i)Pr; 14: R = Cy). A unique multidecker sandwich complex [(μ-η(8):η(8)-COT){Nd(c-C3H5-C[triple bond, length as m-dash]C-C(NCy)2)(μ-Cl)}2]4 (15) was prepared by reaction of anhydrous NdCl3 with K2COT and 1b in a one-pot reaction. The solid state structure of 15 revealed the presence of an unprecedented macrocyclic sandwich compound ("giant neodymium wheel") consisting of four COT rings sandwiched between eight Nd(3+) ions, and each Nd(3+) ion is bonded to one amidinate ligand and bridged by two chlorine atoms with the neighbouring Nd(3+) ion.

The dicarboxylic diester of the cyclobutadiene linked dimeric cobalt sandwich compound, {[η5-C5H4(C(O)OMe)]Co(η4-C4Ph3)}2 on controlled reduction with LiAlH4 gave the bis(hydroxymethyl) compound {[η5-C5H4(CH2OH)]Co(η4-C4Ph3)}2 1 in 98% yield. The diester was also reduced to the dimethyl derivative {[η5-C5H4(Me)]Co(η4-C4Ph3)}2 2 using LiAlH4 and AlCl3. Compound 1 was reacted with NaN3 in acetic acid at 50 °C to get the diazido methyl derivative {[η5-C5H4(CH2N3)]Co(η4-C4Ph3)}2 3 whereas the bis (2-acetoxy methyl) derivative {[η5-C5H4(CH2OC(O)Me]Co(η4-C4Ph3)}2 4 was obtained in almost quantitative yield by heating compound 1 with acetic acid at 80–85 °C. Click reaction of compound 3 with phenylacetylene resulted in the bis triazole derivative {[η5-C5H4(CH2N3C2HPh)]Co(η4-C4Ph3)}2 5 whereas reduction of 3 with LiAlH4 gave the bis (aminomethyl) compound {[η5-C5H4(CH2NH2)]Co(η4-C4Ph3)}2 6. The diacetyl derivative [{η5-C5H4[C(O)Me]}Co(η4-C4Ph3)}]2 7 was prepared by the reaction of in-situ generated {η5-C5H4[C(O)Me]}Co(PPh3)2, diphenyl acetylene and diphenyl diacetylene in 2:1:3 molar ratio in 42% yield. A novel dimeric derivative having two different functional groups on the cyclopentadienyl rings [{η5-C5H4[C(O)OMe]}Co(η4-C4Ph3)][{η5-C5H4[C(O)Me]}Co(η4-C4Ph3)] 8 was synthesized in 52% yield by reacting the ethynyl ester {η5-C5H4[C(O)OMe]}Co[η4-C4Ph3(C CPh)] with {η5-C5H4[C(O)Me]}Co(PPh3)2 and diphenyl acetylene in 1:2:3 molar ratio. Structural studies on compounds 1–4, 7 and 8 indicated that the two cobalt sandwich units were oriented almost anti to each other whereas compound 3 had the two cyclobutadiene rings oriented at an angle of 55.7(1)° to each other. The identity of compounds 5 and 6 was confirmed by 1H NMR, 13C NMR, IR and mass spectrometry.

The existence of the bis(borole) nickel sandwich compound (η 5 -C 4 H 4 BCH 3 ) 2 Ni suggests the possibility of mixed methylborole nickel carbonyls. The structures and thermochemistry of the binuclear methylborole nickel carbonyls (C 4 H 4 BCH 3 ) 2 Ni 2 (CO) n ( n = 3, 2, 1) have been compared with those of the isoelectronic cyclopentadienylcobalt derivatives (C 5 H 5 ) 2 Co 2 (CO) n and cyclobutadiene nickel derivatives (C 4 H 4 ) 2 Ni 2 (CO) 3 . For the tricarbonyls ( n = 3) the lowest energy structures in all three systems have two terminal carbonyl groups, one bridging carbonyl group, and metal–metal single bonds. However, for the unsaturated derivatives (C 4 H 4 BCH 3 ) 2 Ni 2 (CO) n ( n = 2, 1) the pendant methyl groups are not “innocent bystanders”. Instead structures with one of the methyl hydrogens functioning as an agostic hydrogen to the nickel atom are competitive in energy with structures analogous to those of the (C 5 H 5 ) 2 Co 2 (CO) n and (C 4 H 4 ) 2 Ni 2 (CO) n analogues. Thus for (C 4 H 4 BCH 3 ) 2 Ni 2 (CO) 2 a structure with two bridging carbonyl groups and a formal Ni Ni double bond of length ∼2.37 A and a structure with one bridging carbonyl group, one terminal carbonyl group, a C–H–Ni agostic hydrogen atom, and a Ni–Ni single bond of length ∼2.48 A have essentially the same energies. For (C 4 H 4 BCH 3 ) 2 Ni 2 (CO) the two lowest energy structures also have agostic C–H–Ni hydrogen atoms and Ni–Ni single bonds. The thermochemistry for the synthesis of (C 4 H 4 BCH 3 ) 2 Ni 2 (CO) n derivatives from Ni(CO) 4 + (η 5 -C 4 H 4 BCH 3 ) 2 Ni is not favorable since such reactions are endothermic requiring, for example, 13 kcal/mol of energy for the reaction Ni(CO) 4 + (η 5 -C 4 H 4 BCH 3 ) 2 Ni → (C 4 H 4 BCH 3 ) 2 Ni 2 (CO) 3 + CO.

The synthesis of novel cyclobutadiene linked dimers of [η5-RCp]Co(η4-C4Ph4) was reported recently from a three-component reaction of 1,4-diphenylbutadiyne, diphenylacetylene and [η5-RCp]Co(PPh3)2 [R = H or MeOC(O)]. The chiral bis oxazoline derivative of this dimer was found to form cobalt oxazolinyl palladacycles which were excellent chiral catalysts for the Overman–Claisen rearrangement of trichloroacetimidates, similar to the well-known COP catalysts. In this paper, we report reactions carried out for identifying the intermediates in the formation of the dimeric sandwich compound {[η5-MeOC(O)Cp]Co(η4-C4Ph3)}2(1). On varying the stoichiometric ratio of the reactants of the three component reaction, two new cobalt sandwich compounds [η5-MeOC(O)Cp]Co[η4-C4Ph3(C≡CPh)] (2) and [η5-MeOC(O)Cp]Co[η4-C4-Ph2(C≡CPh)2] (3) were found to form as viscous oily liquids. The identity of 2 was ascertained by oxidizing its alkyne moiety to yield crystalline [η5-MeOC(O)Cp]Co{η4-C4Ph3[C(O)-C(O)Ph]} (4) which was structurally characterized. Further, the role of phenylethynyl derived monomeric sandwich compound 2 as a precursor to the dimeric compound 1 was established by reacting 2 with diphenylacetylene and CpCo(COD) which yielded the first example of an unsymmetrical cyclobutadiene linked dimeric cobalt sandwich compound {η5-[MeOC(O)Cp]Co(η4-C4Ph3)}[(η5-Cp)Co(η4-C4Ph3)] (5) which was also structurally characterized.

In the present research, the temperature dependence of heat capacity C p,m ∘ = f ( T ) of crystalline bis-(η6-cumene)chromium fulleride [(η6-PhCH(CH3)2)2Cr] +[C60] − has been measured between Т = (6 and 310) K in the precision adiabatic vacuum calorimeter and reported for the first time. Also, for the first time, the temperature dependence of EPR signal parameters of bis-(η6-cumene)chromium fulleride over the range from T = (120 to 290) K was investigated by electron paramagnetic resonance. In the interval from T = (196 to 240) K the reversible endothermic transformation was detected and its thermodynamic characteristics were estimated. This transformation was caused by dissociation of dimer ( C 60 - ) 2 and formation of fulleride [(η6-PhCH(CH3)2)2Cr] +[C60] − during heating. The experimental results have been used to calculate the standard (р° = 0.1 MPa) thermodynamic functions C p,m ∘ / R , Δ T 1 T 2 H m ∘ / RT , Δ T 1 T 2 S m ∘ / R , and Φ m ∘ / R = Δ T 1 T 2 S m ∘ / R - Δ T 1 T 2 H m ∘ / RT (where R is the universal gas constant) for dimeric fulleride over the range from T → (0 to 196) K and for monomeric complex [(η6-PhCH(CH3)2)2Cr] +[C60] − between Т = (240 and 310) K.

Owing to the strong Lewis acidity of ruthenium porphyrins, a commercial carbonyl ruthenium porphyrin and an amino acid hydrazide can assemble into a sandwich structure. The nature of such a structure is diagnostic of the absolute configuration of the amino acid by circular dichroism.

The reaction of 3,4-dichlorotetragermetene derivative 2 with Na(2)[Fe(CO)(4)] in THF produced a (tetragermacyclobutadiene)tricarbonyliron complex, [{η(4)-((t)Bu(2)MeSi)(4)Ge(4)}]Fe(CO)(3)4, which has a slightly folded Ge(4) ring perhaptocoordinated to the Fe center. Structural and spectral characteristics of 4 show a remarkable π-donating ability of the tetragermacyclobutadiene ligand toward the transition metal, surpassing that of tetrasilacyclobutadiene and cyclobutadiene ligands. Reduction of 2 with KC(8) resulted in exclusive formation of the dipotassium salt of the tetragermacyclobutadiene dianion derivative 3(2-)·[K(+)(thf)(2)](2), representing a rare example of a 6π-electron compound that, on the basis of its structural and magnetic properties, was recognized as a nonaromatic species. Reaction of 3(2-)·[K(+)(thf)(2)](2) with CpCoI(2)(PPh(3)) produced a (cyclopentadienyl)(tetragermacyclobutadiene)cobalt complex, [{η(4)-((t)Bu(2)MeSi)(4)Ge(4)}]CoCp 7, as the first example of a sandwich compound featuring an all-germanium-containing cyclic polyene ligand.

Rhodium bis(diolefin) complexes of the general composition [Rh(η4-diene)2(L)]X (diene = butadiene, isoprene, 2,3-dimethylbutadiene; L = PiPr3, PCy3, PtBu2Me, AsiPr3, SbiPr3, CO, CNtBu, CN-2,6-C6H3iPr2; X = CF3SO3, B(Arf)4) were prepared from the nonionic compounds [Rh{μ-O2S(O)CF3}(η2-C8H14)2]2 (1) and [Rh{κ1-OS(O)2CF3}(η4-diene)2] (2−4) as precursors. The reaction of 1 with 1,3-cyclohexadiene led to the formation of [(η6-C6H6)Rh(η4-C6H8)]CF3SO3, whereas from 1 and 6,6′-dimethylfulvene the unsymmetrical sandwich compound [{η5-C5H4CH(CH3)2}Rh{η5-C5H4C(═CH2)CH3}]CF3SO3 was obtained. From [Rh{κ2-O2S(O)CF3}(PiPr3)2] and 1,3-cyclohexadiene or 6,6′-dimethylfulvene the four-coordinated diene complexes [Rh(η4-diene)(PiPr3)2]CF3SO3 were prepared, the cyclohexadiene derivative of which slowly rearranged at room temperature to cis,cis,trans-[Rh{κ2-O2S(O)CF3}(H)2(PiPr3)2] and benzene. Similarly, [Rh(η4-C6H8){κ2-iPr2P(CH2)3PiPr2}]CF3SO3, obtained from [Rh(η4-C4H6){κ2-iPr2P(CH2)3PiPr2}]CF3SO3 and 1,3-cyclohexadiene, rea...

Molecular wires of the oligophenyleneethynylene (OPE)-type are potentially rigid entities. The idea of the work reported herein was to replace some, not all, of the phenylene moieties with ferrocene units, thereby introducing limited conformational flexibility with the ferrocene units acting as hinges as a consequence of the facile rotation around the Cp― Fe―Cp axis. In this context, the syntheses of a number of 1,1'-diaryl-disubstituted ferrocene building blocks are described. The new terminal diynes 22 and 24 were used to construct the first representatives of ferrocene-based molecular wires with three ferrocene hinges. The study includes an X-ray structure analysis of the thiophene-based diyne 24 as well as cyclovoltammetric analyses of a number of the compounds prepared.

Four differently substituted mixed ligand sandwich complexes CpRu(p-BrC6H4)Tp (3), CpRu(p-BrC6H4)TpMe (4), Cp∗Ru(p-BrC6H4)Tp (5), CpiPrRu(p-BrC6H4)Tp (6), incorporating cyclopentadienyl (Cp) and functionalized tris(pyrazolyl)borate (Tp) ligands, have been synthesized and characterized. Air-stable 6 has been converted to benzoic acid-functionalized CpiPrRu(p-(CO2H)C6H4)Tp (7), which has been structurally characterized in the solid state by X-ray diffraction. Compound 7 may be readily coupled to biomolecules as exemplified by the coupling to phenylalanine-methylester to give CpiPrRu(p-(CO-Phe-OMe)C6H4Tp) (8). In a solid phase peptide synthesis (SPPS), 7 has been coupled to the pentapeptide Enkephalin, to provide CpiPrRu(p-(CO-Tyr-Gly-Gly-Phe-Leu-OH)C6H4Tp) (9) as the first example of a mixed ligand sandwich ruthenium bioconjugate.

The reaction of the pentalene salt C8H4{(SiPr3)-Pr-i-1,4}(2)[K](2) with [SmCp*(mu-I)(THF)(2)](2) yields not the expected Sm(II) pentalene-bridged dimer but the Sm(III) sandwich complexes [Sm(eta(8)-C8H4{(SiPr3)-Pr-i-1,4}(2))(eta(5)-Cp*)] (1) and [Sm(eta(8)-C8H4{(SiPr3)-Pr-i-1,4}(2))(eta(5)-C8H5{(SiPr3)-Pr-i-1,4}(2))] (2) and the mixed-valence cluster [Cp*Sm-6(6)(OMe)(8)O][K(THF)(6)] (3) via solvent activation of THF. The samarium(III) sandwich compound 2 incorporates an eta(8)-pentalene ligand and an eta(5)-hydropentalenyl ligand. X-ray crystallography shows the Sm(II)/Sm(III) mixed-valence cluster compound 3 to contain a centrosymmetric hexanuclear array of Cp*Sm units, bridged by face-centered mu(3)-methoxy groups, with a central oxo unit.

The reaction of the iodide complex [(η5-C9H2Me5)RhI2]2 (1) or the acetonitrile complex [(η5-C9H2Me5)Rh(MeCN)3]2+ with Tl[Tl(η-7,8-C2B9H11)] afforded rhodacarborane (η5-C9H2Me5)Rh(7,8-C2B9H11) (2). The cationic triple-decker complex with the bridging boratabenzene ligand [Cp*Fe(μ-η:η-C5H3Me2BMe)Rh(η5-C9H2Me5)]2+ (3) was synthesized by the reaction of the nitromethane solvate [(η5-C9H2Me5)Rh(MeNO2)3]2+ with the sandwich compound Cp*Fe(η-C5H3Me2BMe). The structure of 2 was established by X-ray diffraction.

Extrapolation from ferrocene and dibenzenechromium suggests the currently unknown 18-electron sandwich compound (η 7 -C 7 H 7 ) 2 Ti as a possible stable molecule. However, density functional theory (DFT) methods using the B3LYP and BP86 functionals predict (η 7 -C 7 H 7 ) 2 Ti to distort by ring slippage to give a singlet 16-electron complex (η 7 -C 7 H 7 )-Ti(η 5 -C 7 H 7 ) having an uncomplexed C=C double bond in one of the C 7 H 7 rings but otherwise closely related to the known (η 7 -C7H7)Ti(η 5 -C5H5). The situation is similar with (C 7 H 7 ) 2 V except that the corresponding structures have doublet spin multiplicity. However, an analogous (η 7 -C 7 H 7 )-Cr(η 5 -C 7 H 7 ) structure is not found for chromium. Instead the most stable (C 7 H 7 ) 2 Cr structure is a singlet d° six-coordinate formally Cr VI complex with two tridentate cyclopropyldivinyl C 7 H 7 ligands. The latter rearrangement of the C 7 H 7 rings bonded to chromium can involve initially a (η 6 -C 7 H 7 ) 2 Cr diradical sandwich compound followed by a bis(η 5 -norcaradienyl)Cr intermediate. For the later first-row transition metals the lowest energy (C 7 H 7 ) 2 M structures are predicted to be doublet (η 7 -C 7 H 7 )Mn(η 3 -C 7 H 7 ) rather than (η 5 -C 7 H 7 ) 2 Mn for manganese, singlet cis and trans structures (η 5 -C 7 H 7 ) 2 Fe for iron, doublet (η 3 -C 7 H 7 ) 2 Co for cobalt, and two singlet (η 3 -C 7 H 7 ) 2 Ni stereoisomers for nickel.

Cationic 30 VE triple-decker complexes [Cp*Ru(μ-η 7 :η 7 -C 5 B 2 Me 6 H)ML] + [ML = Co(C 4 Me 4 ) (3a), RuCp* (4a), Rh(cod) (7a), and Ir(cod) (8a)] with a bridging hexamethyl-4-borataborepine ligand were obtained by electrophilic stacking of the sandwich compound Cp*Ru(η 7 -C 5 B 2 Me 6 H) (2a) with [ML] + complex fragments. The reaction of the phenyl-substituted derivative Cp*Ru(η 7 -7-PhC 5 B 2 Me 5 H) (2b) with [(C 4 Me 4 )Co(MeCN) 3 ] + selectively affords the triple-decker complex [Cp*Ru(μ-η 7 :η 7 -7-PhC 5 B 2 Me 5 H)Co(C 4 Me 4 )] + (3b), whereas a similar reaction with [Cp*RuCl] 4 /TlBF 4 produces a 1:3 mixture of cations, the triple-decker [Cp*Ru(μ-η 7 η 7 -7-PhC5B2Me5H)RuCp*] + (4b) and the arene-coordinated [Cp*Ru(μ-η 6 :η 7 -7-PhC5B2Me5H)RuCp*] + (5). Stacking of Cp*Ru(η 7 -7-PhCH 2 C 5 B 2 Me 5 H) (2c) with [CpRu(MeCN) 3 ] + selectively gives the triple-decker complex [Cp*Ru(μ-η 7 :η 7 -7-PhCH2C5B2Me5H)RuCp]+ (6c). The dinuclear cations 3-8 were isolated as deep-colored air-stable salts with [BF 4 ] - or [PF 6 ] - anions in moderate to high yields. Structures of 3bPF 6 , 4aBF 4 , 7aBF 4 , and 8aBF 4 were confirmed by X-ray diffraction studies. Energy decomposition analysis of complexes CpRu(ring) and [CpRu(ring)RuCp] + (ring = Cp, C 5 BH 6 , C 5 B 2 H 7 ) revealed that the insertion of BH units makes the bonding between [ring]- and [RuCp] + more covalent. According to Mulliken population analysis, weakening of it-donation and strengthening of 8-back donation occur in the same order. The electrostatic character of the bond and the contribution of σ-donation to the covalent bonding are higher in the case of bifacially bonded rings. The boron-containing triple-decker complexes are considerably more stable than the cyclopentadienyl analog.

Irradiation of Cp*(OC) 2 FeSiMe 2 ER n (ER n = NPh 2 , NMe 2 , OMe) in the presence of pyridine affords Cp*(OC)(C 5 H 5 N)FeSiMe 2 ER n , which are converted to Cp*(OC)Fe{η 3 (C,C,C)-C 5 H 5 NSiMe 2 ER n } upon mild heating via insertion of pyridine into the iron-silicon bond. This type of pyridine insertion does not proceed in the thermal reactions of Cp*(OC)(C5H5N)FeSiMe2R (R = Cl, Me) and the germanium analogues, Cp*(OC)(C 5 H 5 N)FeGeMe 2 ER n (ER n = NPh 2 , NMe 2 , Me), even under more severe conditions. Treatment of Cp*(OC)(C 5 H 5 N)RuMe with HSiMe 2 NPh 2 at room temperature gives a 5:4 equilibrium mixture of Cp*(OC)(C 5 H 5 N)RuSiMe 2 NPh2 and Cp*(OC)HRu{κ 2 (Si,C)-SiMe 2 N(o-C 6 H 4 )(Ph)}. Heating the mixture at 100 °C does not afford an analogous insertion product, although the equilibrium is shifted to the side of the orthometalated compound. These results indicate that the insertion of pyridine is specific for the heteroatom-substituted silyliron(II) system. The insertion reaction is considered to proceed via the mechanism that involves the initial formation of an η 2 (N,C)-pyridine complex. Migratory insertion of pyridine into the iron-silicon bond accompanied by coordination of the terminal heteroatom then results in a congested transition state, leading to the formation of an η 1 -allyl intermediate, Cp*(OC)Fe-{κ 2 (C,E)-C 5 H 5 NSiMe 2 ER 2 }. The formation of such a transition state is supported by kinetic analysis of the thermal conversion of Cp*(OC)(C 5 H 5 N)FeSiMe 2 NPh 2 to Cp*(OC)Fe{η 3 (C,C,C)-C 5 H 5 NSiMe 2 NPh 2 }, giving activation parameters of ΔH ‡ = 93(2) kJ mol -1 , ΔS ‡ = -53(6) J mol -1 K -1 , and ΔG ‡ 298 K = 109(3) kJ mol -1 . The η 3 -allyl complex is finally formed through dissociation of the amino part. Irradiation of Cp*(OC)Fe{η 3 (C,C,C)-C 5 H 5 NSiMe 2 NPh 2 } causes dissociation of a carbonyl ligand to produce a new type of sandwich compound, Cp*Fe(η 5 -C 5 H 5 NSiMe 2 NPh 2 ).

In the present work, the temperature dependence of heat capacity C p , m ∘ = f ( T ) of crystalline bis-(η6-diphenyl)chromium (I) fulleride [(η6-Ph2)2Cr]+[C60] − has been measured by precision adiabatic vacuum calorimetry between T = (6 and 360) K with an uncertainty of ±0.2%. In this temperature interval, the transformations were detected and their thermodynamic characteristics were estimated. The experimental data were used for calculating standard (po = 0.1 MPa) thermodynamic functions C p , m ∘ / R , Δ 0 T H m ∘ / RT , Δ 0 T S m ∘ / R and Φ m ∘ / R = Δ 0 T S m ∘ / R - Δ 0 T H m ∘ / RT (where R is the universal gas constant) in the range T → (0 to 360) K.

A chiral self-assembled supramolecular M(4)L(6) assembly has been shown to be a suitable host for a series of reactive monocationic half-sandwich iridium guests 1, 3, and 4 that are capable of activating C-H bonds. Upon encapsulation, selective C-H bond activation of organic substrates occurs. Precise size and shape selectivity are observed in the C-H bond activation of aldehydes and ether substrates. The reactions exhibit significant kinetic diastereoselectivities. Thermodynamic studies have shown that the iridium starting materials and products are bound strongly by the host assembly. The encapsulation process is largely entropy-driven. Kinetic investigations with water-soluble phosphine traps and added salts have provided evidence for a unique stepwise mechanism of guest dissociation for [4 subset Ga(4)L(6)]. Iridium guest 4 first dissociates from the host cavity to form an ion pair with the host exterior. This species then fully dissociates from the host exterior into the bulk solution. Model ion pair intermediates were characterized directly with (1)H NMR NOESY techniques. The rate of iridium guest dissociation is slower than the rate observed for the C-H bond activation processes, indicating that the selective C-H bond activation reactivity occurs within the cavity of the supramolecular host.

The Cadiot-Chodkiewicz coupling of cis-1,4-diethynyl-1,4- dimethoxycyclohexa-2,5-diene and the corresponding ethynyl bromide gave a mixture of acetyenic macrocycles ranging from dimer to octamer in good isolable yields. The trimeric and tetrameric macrocycles have been structurally characterized by single-crystal X-ray crystallography. In the crystal structure of the trimeric macrocycle a molecule of benzene is sandwiched between a pair of macrocyles. The tetrameric macrocycle exhibited a tub-shaped conformation and encapsulated a molecule of ethyl acetate inside the tub. � 2006 American Chemical Society.

The reaction of [Pd(2)(CH(3)CN)(6)][BF(4)](2) (1) with 1,3,5-hexatriene, 1,6-diphenyl-1,3,5-hexatriene (DPHT), or 2,2,9,9-tetramethyl-3,5,7-decatriene (DBHT) afforded bi-eta(3)-allyldipalladium complexes 3, 4, or 5. The reaction of 1 and DBHT proceeded in a stereospecific (syn) manner when the reaction was carried out in CD(2)Cl(2) under aerobic conditions, while a mixture of two diastereomers was formed under N(2) atmosphere. The two diastereomers (5-E,Z,E-antifacial and 5-E,E,E-antifacial) formed from DBHT were isolated, and the structure of 5-E,Z,E-antifacial, which was kinetically formed from the reaction of 1 and (E,E,E)-DBHT, was determined by X-ray diffraction analysis. Addition of phosphine ligands (PPh(3) or dppm) to the dinuclear adduct 5-E,Z,E-antifacial or 5-E,E,E-antifacial in acetonitrile resulted in the stereospecific (syn) elimination of [Pd(2)(PPh(3))(2)(CH(3)CN)(4)][BF(4)](2) (2) or [Pd(2)(dppm)(2)(CH(3)CN)(2)][BF(4)](2) (6). During the PPh(3)-induced dinuclear elimination, the phosphine adducts 7 that retain bi-eta(3)-allyldipalladium structure were observed initially. The phosphine adduct generated from 5-E,E,E-antifacial was isolated and structurally characterized by X-ray diffraction analysis. The reaction of 1 and DPHT in CH(2)Cl(2) afforded unique dipalladium sandwich compounds [Pd(2)(mu-eta(3):eta(3)-DPHT)(2)][BF(4)](2) (8). Interconversion between the sandwich complexes and half-sandwich complexes occurred in a stereoretentive manner. The structure of the sandwich complex 8-E,Z,E formed from 4-E,E,E-antifacial and (E,Z,E)-DPHT was determined by X-ray diffraction analysis. Transfer of the dipalladium moiety [Pd(2)(CH(3)CN)(4)](2+) from DPHT ligand of 4-E,E,E-antifacial onto DBHT ligand proceeded in a stereoretentive manner. The observed stereoretentive dinuclear process is featured by the pairwise behavior of two palladium atoms sitting on the triene pi-plane. In the dinuclear elimination, the two Pd atoms that are initially in the divalent state and bound on the opposite faces (antifacial) come to the synfacial positions to form a Pd-Pd bond prior to dissociation. These results represent the unique property of conjugated olefin as the multidentate ligands for metal-metal moieties.

Addition of principally sigma-donating ligands such as THF, chelating diethers, or 1,2-bis(dimethyl)phosphinoethane to eta(9),eta(5)-bis(indenyl)zirconium sandwich complexes, (eta(9)-C(9)H(5)-1,3-R(2))(eta(5)-C(9)H(5)-1,3-R(2))Zr (R = alkyl or silyl), induces haptotropic rearrangement to afford (eta(6)-C(9)H(5)-1,3-R(2))(eta(5)-C(9)H(5)-1,3-R(2))ZrL adducts. Examples where L = THF and DME have been characterized by X-ray diffraction and revealed significant buckling of the eta(6) benzo ring, consistent with reduction of the arene, and highlight the importance of the zirconium(IV) canonical form. For the THF-induced haptotropic rearrangements, the thermodynamic driving force for ring migration has been measured as a function of indenyl substituent and demonstrates silylated sandwiches favor THF coordination and the eta(6),eta(5) bonding motif over their alkylated counterparts. In the case of chelating diethers, measurement of the corresponding equilibrium constants establish more stable eta(6),eta(5) adducts with five- over four-membered chelates and with smaller oxygen and carbon backbone substituents. Kinetic studies on both THF and DME addition to (eta(9)-C(9)H(5)-1,3-(SiMe(3))(2))(eta(5)-C(9)H(5)-1,3-(SiMe(3))(2))Zr established a first-order dependence on the incoming ligand, consistent with a mechanism involving direct attack of the incoming nucleophile on the eta(9),eta(5) sandwich. These results further highlight the ability of the indenyl ligand to smoothly adjust hapticity to meet the electronic requirements of the metal center.

Three alkali-metal-indium compounds K34In(92.30)Li(12.70) (I), K14Na20In(91.82)Li(13.18) (II), and K14Na20In(96.30) (III) (all Rm) have been synthesized and characterized by structural and physical property measurements and electronic structure calculations. Novel mixed In/Li anionic icosahedra and fused icosahedra form in I and II. All three contain In28 as the first triply fused In icosahedra, which are further linked into (In28)In(In28) sandwich adducts in compounds I and II and (In28)In2(In28) in III. Stabilization of these electron-poorer phases through electronic tuning occurs via two different structural (redox) perturbations, either by substitution of certain indium atoms in the clusters by electron-poorer lithium atoms or by the introduction of defects and disorder in the fused cluster (III). The preferential occurrence of either substitutions or defect formation in the clusters is consistent with extended Huckel band calculation results for both the ideal pure indium phase and the Li-substituted equivalent. Model (ideal) and experimental EF values (based on stoichiometries) fall around a pseudogap in DOS. All three compounds are metallic according to both EHTB band calculations and measured resistivities. The cations (A = K, Na) in all the three structures generate A136 clathrate-IotaIotatype networks with remarkably specific and transferable cation dispositions around the two types of anionic cluster units.

The reaction of nickel atoms with tBuCP affords a mixture of the isomeric complexes [Ni(η3-PC2But2)(η5-P3C2tBu2)] and [Ni(η4-P2C2But2)2]. The former complex has been structurally characterised in the solid sate as its [W(CO)5] adduct, which in solution undergoes fluxional behaviour. To cite this article: F.G.N. Cloke et al., C. R. Chimie 7 (2004).

Combination of trimeric perfluoro-ortho-phenylene mercury (1) with TTF and TCNQ in a 1:1 mixture of CH2Cl2 and CS2 followed by slow evaporation of the solvent leads to the formation of orange needles of [(1)2·TTF] (2) and light yellow needles of [(1)2·TCNQ] (3), respectively. The structure of both complexes has been determined by X-ray analysis. The solid-state structure of 2 consists of centrosymmetrical supramolecules of [(1)2·TTF], in which the TTF molecule is sandwiched by two molecules of 1. This supramolecule is held by multiple Hg···S secondary interactions ranging from 3.467(5) A to 3.533(5) A. The solid state of 3 also consists of centrosymmetrical molecules of [(1)2·TCNQ]. In this case, however, the TCNQ molecule is approximately perpendicular to the neighboring molecules of 1 with which it interacts by coordination of two nitrile groups. Examination of the atomic connectivity indicates the simultaneous coordination of the coordinated nitrile nitrogen atoms to the three mercury centers of 1. The resulting Hg···N distances range from 3.102(11) to 3.134(11) A. To cite this article: M.R. Haneline et al., C. R. Chimie 7 (2004).

The stereochemistry of propylene insertion/propagation reactions with a variety of C s and C 1 symmetric bridged cyclopentadienyl-fluorenyl ligand containing metallocene catalysts are investigated. It is shown that active species with a local C s symmetric and enantiotopic coordination positions, in the general contest of the chain migratory insertion, behave syndioselective. However, the bilateral symmetry rule, central dogma of syndioselectivity, is not a catholic prerequisite and may be ignored by the C s systems whenever symmetric excess in steric bulk is present. An asymmetric excess of steric forces, on the other hand, will perturb the migratoy insertion process completely and induce a full tactic inversion in resulting C 1 symmetric catalysts. The findings also reveal that C 2 symmetry and helicity of homotopic catalysts, conditions thought to be essential for high isoselectivity, can be lifted in light of recent developments in high performance centrally chiral, C 1 symmetric enantiotopic catalysts.

The possibility of coupling lacunary polyoxometalates through a cationic center present in the vacancy by negatively charged organic ligands is demonstrated for the first time by single-crystal X-ray diffraction. The structure of the dimeric K12[{Yb(α-SiW11O39)(H2O)}2(μ-CH3COO)2]·38H2O complex, where two acetato ligands connect the ytterbium centers in a (η2, μ-1,1) fashion, is reported. Using gadolinium instead of ytterbium, both the isostructural dimeric compound K12[{Gd(α-SiW11O39)(H2O)}2(μ-CH3COO)2]·38H2O and the mononuclear sandwich complex [Gd(SiW11O39)2]13− can be selectively isolated, depending on the synthetic conditions. The magnetic properties of the dimeric gadolinium complex are presented. The influence of the nature of the rare-earth metal on the final compound is further highlighted by the fact that when praseodymium is used as the rare-earth element, only the sandwich compound can be obtained. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

A molecular approach to information storage employs redox-active molecules tethered to an electroactive surface. Attachment of the molecules to electroactive surfaces requires control over the nature of the tether (linker and surface attachment group). We have synthesized a collection of redox-active molecules bearing different linkers and surface anchor groups in free or protected form (hydroxy, mercapto, S-acetylthio, and Se-acetylseleno) for attachment to surfaces such as silicon, germanium, and gold. The molecules exhibit a number of cationic oxidation states, including one (ferrocene), two [zinc(II)porphyrin], three [cobalt(II)porphyrin], or four (lanthanide triple-decker sandwich compound). Electrochemical studies of monolayers of a variety of the redox-active molecules attached to Si(100) electrodes indicate that molecules exhibit a regular mode of attachment (via a Si-X bond, X = O, S, or Se), relatively homogeneous surface organization, and robust reversible electrochemical behavior. The acetyl protecting group undergoes cleavage during the surface deposition process, enabling attachment to silicon via thio or seleno groups without handling free thiols or selenols.

The reaction of [Ru(η3:η3-C10H16)Cl2]2 (1) with the Cp-linked phosphine ligands Ln (C5H5CH2CHRPR′2; R=H, R′=Ph, n=1; R=Ph, R′=Ph, n=2), in a 5:1 mixture of acetonitrile–ethanol and in the presence of Li2CO3 and KPF6 affords the cationic half-sandwich ruthenium(II) complexes [{η5-C5H4CH2CHRPR′2-κP}Ru(CH3CN)2]·[PF6] (4) and (5). Both complexes have been characterized in the solid state by an X-ray structure analysis. In contrast, the reaction between 1 and L3 (R=Ph, R′=o-xylyl) affords the cationic sandwich compound [{η5:η6-C5H4CH2CHPhPR′2}Ru]·[PF6] (7), in which one arene substituent of the phosphine is η6-coordinated to the metal and the phosphorus remains pendant. Treatment of 5 with tertiary phosphines (PR″3, R″=i-Pr, Ph, Cy) affords a mixture of the diastereomers [L2Ru(CH3CN)PR″3]+. The diastereoselectivity observed depends on the steric bulkiness of the phosphines and on the reaction conditions.

Both amido-(cyclopentadienyl)boranes and bis(cyclopentadienyl)boranes of the types R 2 NB(C x H y ) (NR') and R 2 NB(C x H y ) 2 (R = alkyl, trimethylsilyl; R' = Ph; C x H y = C 5 H 5 (cyclopentadienyl), C 9 H 7 (indenyl), C 13 H 9 (fluorenyl)) were recently shown to form corresponding boron-bridged Group 4 metallocenes that exhibit high activities in Ziegler-Natta-type catalysed olefin polymerization. Here, the same boranes were utilized in the formation of metallocenes of ytterbium and zirconium, where the ligands selectively bind in a non-chelate fashion. The resulting complexes [Yb{η 5 -(C 5 H 4 )B(N i Pr 2 )NH t Bu} 2 {N(SiMe 3 ) 2 }] (2) and [Zr{η 5 -(C 9 H 6 )B(N(SiMe 3 ) 2 )(C 9 H 7 )}Cl 2 ] (4) allow studies on these ligands in a metal-bonded, though unstrained, environment. Furthermore, these complexes might find use as precursors in the formation of organometallic polymers, since they exhibit a readily available moiety for the coordination of further transition metal centres. Both complexes were fully characterized by multinuclear magnetic resonance spectroscopy and X-ray structure determination.

The interactions between the non-bonded atoms on adjacent units were assumed to be one of the major factors that hinder the exploration and advancement of macropolyhedral borane chemistry. In sandwich complexes involving boron as the bridging atom, the interaction between non-bonded atoms tends to be antibonding, but a closer analysis of various condensed systems shows that this cannot be generalized. The overlap populations (OPs) calculated for structures optimized at the B3LYP/6-31g* level [B 21 H 18 1- (5), B 20 H 16 (6), [Al(C 2 B 4 H 6 ) 2 ] 1- (7), B 12 H 10 2- (8), B 10 H 8 2- (9 and 14), B 11 H 13 (10), B 10 H 14 (11), C 2 B 8 H 12 (13) and B 20 H 18 2- (15)] indicate bonding interactions between the caps, except for 7 and 13. This is substantiated by a detailed extended Huckel-based molecular orbital (MO) study using B 10 H 14 as a model system to represent macropolyhedral boranes with higher fusions. An isolobal equivalent structure, [C 8 H 6 (Ru(CO) 2 Me) 2 ] (17), studied at the B3LYP/LANL2DZ level has weak RuRu interactions. An analysis of the nature of the MOs in B 10 H 14 (11) shows that there is no direct head on overlap of the cap orbitals that are antibonding; this is in contradiction to sandwiched molecules (7), where there are two occupied MOs with antibonding interactions. The m + n + o electron pair count (m is the number of cages involved in condensation, n is the number of vertices and o is the number of single vertex condensations) of sandwich complexes requires the filling of these two MOs. The negative OP between the carbon atoms in 13 is attributed to the greater electronegativity of carbon and is substantiated by a fragment MO analysis.

A general method for rapid construction of metallocene-based hosts is described. Treatment of polyether bridged bis(diphenylacetylenes) with a source of cyclopentadienyl cobalt at high temperature leads, via macrocyclization and capture of the intermediate cyclobutadiene, to macrocyclic systems tethered to an integral metallocene platform. Equal yields of the two possible structural isomers, the products of parallel or antiparallel cycloaddition of the precursor, are obtained. A combination of X-ray crystallography and NMR is employed to assign structures to the individual isomers and to assess the strength of lithium ion binding by the individual macrocycles.

In the title compounds, [Ru(C10H15)(C11H11)], (III), [Ru(C10H15)(C19H17)], (IV), and [Ru(C19H17)2], (V), respectively, the coordinating ring systems are planar and parallel, with the Ru atoms lying at perpendicular distances of Ru–Cp* 1.790 (1) A and Ru–indenyl 1.836 (1) A in (III), Ru–Cp* 1.791 (1) A and Ru–indenyl 1.837 (1) A in (IV), and Ru–indenyl 1.812 (1) A and 1.809 (1) A in (V) (Cp* is penta­methyl­cyclo­penta­dienyl). The ring conformations are eclipsed for (III), staggered for (IV) and intermediate for (V). All three compounds show short intermolecular contacts from C—H groups to some ring centroids; these could be regarded as C—H⋯π hydrogen bonds. The mol­ecules of each compound are thus connected via the 21 screw axis to form layers parallel to the xy plane.

The synthesis and structural characterization of the complex [Ru(η6-C6H6)(η6-C6H4(CH3)COOCH3)] [BF4]2 (2) and of its precursor [Ru(η6-C6H4(CH3)COOCH3)Cl2]2 (1) are reported. Compound (2) has been characterized in two polymorphic modifications (2a and 2b) and the molecular organization in the solid state has been investigated. The complex [Ru(η5-C5H5)(η6-C6H5OH)][PF6] (3) has also been investigated; it has been shown to possess a disorder similar to that observed in the high temperature phase of related systems such as [Ru(η5-C5H5)(η6-C6H6)][PF6].

(R)-(+)-1,1′-Bi-2-naphthol [(R)-(+)-(HOC10H6C10H6OH)] has been used as a chiral building block in the construction of chiral organo-organometallic crystals. The reaction of the neutral molecule with [Co(η5-C5H5)2] in diethyl ether yields the supramolecular salts [CoIII(η5-C5H5)2][(R)-(+)-(HOC10H6C10H6O)]·[(R)-(+)-(HOC10H6C10H6OH)] (1) and [CoIII(η5-C5H5)2][(R)-(+)-(HOC10H6C10H6O)]·[(R)-(+)-(HOC10H6C10H6OH)]0.5 (2), depending on the stoichiometric ratios between the binaphthol and the organometallic sandwich compound. Molecular aggregation is achieved ia a combination of neutral and charge-assisted O–H···O bonds between the binaphthol and binaphtholate components and ia weaker interactions of the C–H···O and C–H···π types involving the [CoIII(η5-C5H5)2]+ cation. The same reaction with racemic 1,1′-bi-2-naphthol in diethyl ether, followed by recrystallisation from nitromethane, yields the solvate species [CoIII(η5-C5H5)2][(R,S)-(HOC10H6C10H6O)]·[(R,S)-(HOC10H6C10H6OH)][MeNO2]1.5 (3). For comparison, the alkali salts Cs[(R,S)-(HOC10H6C10H6O)]·[(R,S)-(HOC10H6C10H6OH)] (4) and Rb[(R,S)-(HOC10H6C10H6O)]· [(R,S)-(HOC10H6C10H6OH)] (5) have also been prepared by treating [(R,S)-(HOC10H6C10H6OH)] with the Cs and Rb hydroxides. Both organometallic and alkali salts show how the cations tend to be encapsulated within a niche formed by the folding of hydrogen-bonded naphthol–naphtholate chains.

The reactions of [MCp * (η 6 -C 6 Me 6 )][PF 6 ], M = Fe: 1 , Ru: 2 , Cp * = η 5 -C 5 Me 5 , with KOH (in DME) or tert -BuOK (in THF) and methyl iodide, allyl bromide or benzyl bromide are regioselective on the arene ligand only for 2 , giving the complexes [RuCp * {η 6 -C 6 (CH 2 R) 6 }][PF 6 ], R = methyl ( 3 ), allyl ( 4 ) or benzyl ( 5 ), although some formations of C-C bonds also occur on the Cp * ligand in the case of the reactions of allyl and benzyl bromides. This contrasts with the complete lack of regioselectivity formerly observed with the iron analogue 1 , and is best taken into account by the difference of steric effects which are less marked in 2 than in 1 .

The structure of a mono-substituted ferrocene derivative of which the flexible spacer is located between the ferrocenyl and mesogenic groups, ω-[4-(4-methoxyphenoxycarbonyl)phenoxycarbonyl]propyl 4-ferrocenylbenzoate was determined by the X-ray diffraction method. It was found that the two cyclopentadienyl rings in the ferrocene and the—C3H6—chain introduced as a flexible spacer exhibited a very interesting conformation. The two cyclopentadienyl rings are a staggered conformation rather than an eclipsed one. This staggered conformation is an unusual structure in mono-substituted ferrocene derivatives, in general. Also, the—C3H6—chain includes two gauche conformations and makes a bent molecular feature rather than a rod-like one. As a result, the title compound does not exhibit liquid crystallinity.

The Fe-57 Mossbauer Effect was used to study a solution (0.2% by Weight) of 1,1′-diacetylferrocene (DAF) in the liquid crystalline material p-n-hexyloxy-benzylidene-p-toluidine (HBT). The DAF contained enriched Fe-57. The Mossbauer Effect parameters were determined for the temperature range 100–300K in the crystalline solid phase and 100–200K in the cold smectic s phase of HBT. Here “cold” means the smectic glass and the supercoded smectic phase. The Ln recoil-free intensity (f) vs T data exhibited linear Debye behavior for the solid phase over the entire temperature range. The low temperature (T < 190) portion of the cold smectic Inf vs T data also exhibited Debye behavior, and the smectic glass gave a Mossbauer-Debye temperature (θ lc ) about 30 K. lower than the crystalline phase. The smectic glass-super cooled smectic transition was determined to be Tg = 190 K from the deviation of the Inf vs T data from linear behavior. Above Tg , the deviation from linear Debye behavior followed a (T-Tg)2 d...

Synthesis, spectral, and structural studies of the first examples of porphyrins substituted at the meso positions with sterically hindered η(5)-CpCo(η(4)-C4Ph4) cobalt sandwich units are described. The novel dipyrromethane derived cobalt sandwich compound {η(5)-[(C4H4N)2CH]C5H4}Co(η(4)-C4Ph4) 1, as well as its parent aldehyde, η(5)-[C5H4(CHO)]Co(η(4)-C4Ph4), were used in the synthesis of porphyrins having one or two η(5)-CpCo(η(4)-C4Ph4) groups at their meso positions. 1,9-Diformyldipyrromethane derived η(5)-CpCo(η(4)-C4Ph4) 2 was synthesized using dipyrromethane 1 under Vilsmeier conditions. A reaction of 2 with unsubstituted dipyrromethane under basic conditions in the presence of Pd(C6H5CN)2Cl2 yielded an A-type palladium coordinated porphyrin 3 [where A = η(5)-CpCo(η(4)-C4Ph4)]. A similar reaction of 2 with meso aryl and ferrocenyl-substituted dipyrromethanes yielded trans-AB type palladium coordinated porphyrins 4-6 [where A = η(5)-CpCo(η(4)-C4Ph4) and B = 4-tert-butylphenyl 4, ferrocenyl 5, and pentafluorophenyl 6]. Reactions of 2 with 5-ferrocenyl dipyrromethane under the same reaction conditions in the presence of Ni(acac)2 and Zn(OAc)2 gave the trimetallic nickel(II) and zinc(II) complexed trans-AB type porphyrins 7 and 8 having both cobalt and iron sandwich units at the meso positions. Crystal structure of the Pd(II) porphyrin 5 and nickel(II) porphyrin 7 showed nonplanar structures having distinct ruffle type distortion of the porphyrin ring. Demetalation of the zinc(II) trans-AB type porphyrin 8 in the presence of trifluoroacetic acid gave the metal free base porphyrin 9. Reactions of the cobalt sandwich aldehyde [(η(5)-C5H4(CHO)]Co(η(4)-C4Ph4) with sterically hindered dipyrromethane derivatives under acid-catalyzed condensation reactions gave trans-A2B2 type porphyrins [where A = η(5)-CpCo(η(4)-C4Ph4) and B = pentafluorophenyl, 10 mesityl 11]. In contrast, reactions of [η(5)-C5H4(CHO)]Co(η(4)-C4Ph4) with sterically unhindered meso-4-tert-butylphenyl dipyrromethane resulted in both AB3 12 and cis-A2B2 13 type porphyrins [where A = η(5)-CpCo(η(4)-C4Ph4) and B = (4-tert-butylphenyl] as a result of scrambling. The new porphyrin derivatives have been structurally characterized, and their spectral and electrochemical features were determined.

Molecules of ferrocene-1,1′-diylbis(2-phenylethanedione), [Fe(C13H9O2)2], lie across twofold rotation axes. One of the oxygen atoms in each diketone unit acts as a bis-acceptor of inter­molecular C-H⋯O hydrogen bonds. Hydrogen bonds employing cyclopentadienyl C-H bonds as donors generate spirals of molecules around 31 axes, while those employing phenyl C-H bonds as donors generate two-dimensional sheets.

The title compound, tetra-μ-iodo-bis[(η5-pentamethylcyclopentadienyl)molybdenum](Mo-Mo) tetraiodoferrate(III) di-μ-iodo-μ-oxo-bis[iodo(η5-pentamethylcyclopentadienyl)molybdenum](Mo-Mo), forms as a by-product of the thermal decarbonylation of [(η5-C5Me5)MoI3(CO)2] in tetrahydrofuran. The source of the iron is an impurity in the [(η5-C5Me5)2Mo2(CO)3]2 starting material used to make the triiodide compound. The structure consists of three independent species, namely a [(η5-C5Me5)2Mo2(μ-I)4]+ cation with two pentamethylcyclopentadienylmolybdenum moieties bridged by four iodide ligands, a tetrahedral [FeI4]− anion and a neutral dinuclear species comprising two pentamethylcyclopentadienyliodomolybdenum units bridged by two iodide and an oxo ligand. All three fragments sit on crystallographic mirror planes in the monoclinic space group P21/m.

The syntheses of the η-lutidine(η-allyl)molybdenum compounds [Mo(2,6-lutidine)(η-C3H5)Cl]2 1, Mo(η-2,6-lutidine)(η-C3H5)(η2-O2CR)] (2: R = CH3, 3: R = C(CH3)3) and [Mo(η-2,6-lutidine)(η-C3H5)2] 4 are described. The sandwich compound [Mo(η-2,6-lutidine)2] undergoes facile ligand displacement giving zero-valent compounds MoL6, where L = CO, CNR, and Mo(diene)3, where diene = 2,3-dimethyl-1,3-butadiene. The crystal structure of compound 1 has been determined.

A sandwich compound of cyclooctatetraendiyl (COT)2− samarium-potassium was synthesized and analyzed using a flexible calix[4]arene dianion. This compound, [p-tBu-calix[4]-(OMe)2(O)2]arenediyl-samarium-(η8-cyclooctatetraendiyl)-potassium (tetrahydrofurane)3, is constructed as a linear sequence L-Sm--K-, where L, , and are specific ligands with L = O,O-dimethyl-calix[4]arene2−, = cyclo-octatetraendiyl, and = tetrahydrofurane templates.

The reactivity of the organosamarium(II) indenyl complex (C 9 H 7 ) 2 Sm(THF) x , 1, has been compared with that of (C 5 Me 5 ) 2 Sm(THF) 2 , 2, and (C 5 Me 5 ) 2 Sm, 3, by examination of characteristic organosamarium(II) reactions which form trivalent oxide, iodide, cyclooctatetraenyl and azobenzene complexes. Complex 1 reacts with excess N 2 O to form [(C 9 H 7 ) 2 Sm(THF)] 2 (μ-O), 4, and (C 9 H 7 ) 3 Sm(THF), 5, as the major products. Two equivalents of 1 react with one equivalent of 1,2-diiodoethane in THF to give (C 9 H 7 )SmI 2 (THF) 2 , 6, as well as 5. Complex 1 reacts with 1,3,5,7-cyclo-octatetraene in a 2 :1 ratio in THF to form 5 and (C 9 H 7 )Sm(C 8 H 8 )(THF) x , 7, which has been fully characterized as the 2,2'-bipyridine adduct (C 9 H 7 )Sm(C 8 H 8 )(C 10 H 8 N 2 ), 7a. The reaction of 1 with azobenzene in a 2 :1 ratio forms [(C 9 H 7 )Sm(N 2 Ph 2 )(THF)] x , 8, and 5. Complexes 4-6 and 7a have been definitively identified by X-ray crystallography. Complex 4 crystallizes from THF in space group P1 [C i 1 ; No. 2] with unit cell parameters at 163 K of a = 8.072(2) A, b = 9.502(2) A, c = 12.250(3) A, α=101.42(2)°, β=90.71(2)°, γ=102.50(2)°, V= 897.7(4) A 3 and Z = 1 for D calcd = 1.704 Mg m -3 . Least-squares refinement of the model based on 3924 reflections (|F 0 | >3.0 σ (|F 0 |)) converged to a final R F = 2.4%. The geometry around each Sm atom is a distorted tetrahedron and the Sm-O-Sm angle is 180°. Complex 5 crystallizes from THF/hexanes at -35 °C in space group P6 3 [C 6 6 ; No. 173] with unit cell parameters at 163 K of a=11.7370(14) A, c= 10.1994(12) A, V=1216.8(3) A 3 and Z=2 for D calcd = 1.550 Mg m -3 . Least-squares refinement of the model based on 976 reflections (|F 0 | > 3.0σ (|F 0 |) converged to a final R F =2.3%. The three ring centroids and the THF oxygen atom define a distorted tetrahedron around samarium with a (ring centroid)-Sm-(ring centroid) angle of 116.0°. Complex 6 crystallizes from THF/hexanes as the trisolvate (C 9 H 7 )SmI 2 (THF) 3 , 6a, in space group P2 1 /n [C 5 2h ; No. 14] with unit cell parameters at 163K of a = 8.3969(12) A. b = 17.165(5) A, c= 33.592(7) A, β=96.468(15)°, V=4811(2) A 3 and Z=8 for D calcd =2.031 Mg m -3 . Least-squares refinement of the model based on 5664 reflections (|F 0 | > 2.0 σ (|F 0 |)) converged to a final R F = 3.3%. The six ligands around Sm in 6a describe a distorted octahedron. The iodide ligands are trans to each other with a 153.8(1)° I-Sm-I angle. Adduct 7a crystallizes from hot THF/toluene in space group P1 [C i 1 ; No. 2] with a unit cell parameters at 163 K of a = 7.886(7) A, b = 16.72(2) A, c = 17.48(2) A, α = 62.96(7)°, β=85.17(7)°, γ= 85.23(9)°, V=2042(3)A 3 and Z=4. The cyclooctatetraenyl and indenyl ligands generate a bent metallocene structure for 7a which contains a chelating bipyridyl group in the plane bisecting the two rings

Exploiting thiacalix4arene and sulfur-bridged bisphenolates as ligands for bioinorganic studies involving iron(III) requires the prior development of synthetic routes (varying substituents and reaction conditions) to construct complexes with low nuclearities and accessible coordination sites, which was in the focus of this investigation. Treating p-tert-butylthiacalix4arene (H4TC) and 1, 4-dimethyl-p-tert-butylthiacalix4arene (Me2H2TC) with Fe[N(SiMe3)2]3 yielded in the formation of the iron(III) complexes [(Me3SiTC)2Fe2] (1) and [(Me2TC)3Fe2] (3), respectively. While 1 is a sandwich compound, in 3 one [Me2TC]2– unit is bridging two [Me2TCFe]+ moieties. Employing thiobisphenolates as ligands it turned out, that in dependence on the residues R and the preparation method it is possible to selectively access sandwich, anionic or neutral complexes, which were shown to contain central high-spin iron(III) atoms. The syntheses, structures, and electronic properties of three iron(III) bisphenolate complexes, [ClL2Fe]NEt3H (4), [MeLFeCl2]NEt3H (5), and [tBuLFeCl(thf)] (7) are discussed.

The Ru II atom is located symmetrically between the two arene rings forming a sandwich-type complex. There are two BF 4 − counterions per molecule and the cations pack as canted stacks in the lattice. Many of the structural features of the coordinated fluorene ligand resemble those observed in the X-ray crystal structure of free fluorene. The arene ligands adopt an eclipsed conformation and are separated at a distance of 3.450 A

1,2-Bis(dimethylamino)-1,2-di-9-fluorenyldiborane(4) (1) is doubly metallated with group 1 and 2 metals to yield metal 1,2-bis(dimethylamino)-1,2-di-9-fluorenyldiborate(4) 2-Li to 2-Ba. The conformations of these compounds in solution are investigated by NMR spectroscopy, and the solid-state structures of 2-Li · 5 THF, 2-K · 4 THF, 2-K · 2 DME, and 2-Ca · 2 THF are determined by X-ray diffraction. All four structures can be described as main group metallocenes. The potassium derivatives form contact ion pairs, leading to polymeric chain-like structures. In contrast, 2-Li · 5 THF exhibits the rare combination of a contact ion pair with a solventseparated ion pair, giving the monomeric structure [Li(THF)4][(fl2B2(NMe2)2)Li · THF]. 2-Ca · 2 THF, which is also monomeric, adapts a severely distorted geometry.