Syntheses of polyfluorophenylcobalt(III) schiff base complexes using organothallium reagents

The complexes RCo(acacen) [R = C₆F₅, p-HC₆F₄, or o-HC₆F₄; H₂acacen = N,N′-ethylenebis(acetylacetonimine)] and RCo(salen) [R = C₆F₅ or p-HC₆F₄; H₂salen = N,N′-ethylenebis(salicylaldimine)] have been prepared by reaction between Co(acacen) or Co(salen) and the appropriate bromobis(polyfluorophenyl)thallium(III) compounds, and have been isolated as pyridinates. Spectroscopic evidence for formation of C₆F₅Co(salophen) [H₂salophen = _N,N′-o-phenylenebis(salicylaldimine)] has also been obtained. The reactivity of the thallium compounds increased in the sequence Ph₂TlBr ? (o-HC₆F₄)2TlBr < (p-HC₆F₄)₂TlBr < (C₆F₅)₂TlBr, and of the cobalt complexes in the sequence Co(salophen) < Co(salen) < Co(acacen). Possible mechanisms are discussed.     

The optical resolution of tris(pentane-2,4-dionato)metal(III) complexes

A facile large-scale optical resolution of neutral [M(pd)₃] complexes, M = Cr(III), Co(III), Ru(III), Rh(III) and Ir(III), through enantioselective complex formation with (2R, 3R)-(-)-dibenzoyltartaric acid, is described.     

Comparative study of hydroxo-fluoro and hydroxo-sulphido mixed ligand complexes of aluminum(III) and gallium(III)

The mixed ligand complex formation had been studied in the aluminate-fluoride, gallate-fluoride, aluminate-sulphide and gallate-sulphide systems by spectrophotometric as well as potentiometric methods using glass and sulphide selective electrodes. The formation of the species Al(OH)₃F^? and Ga(OH)₂S^? has been demonstrated and the equilibrium constants have been determined. Similar interaction could not be detected in the aluminate-sulphide and gallate-fluoride systems.The differences in behaviour of the metal ions to the characteristically hard fluoride and soft sulphide ligands can be interpreted in that the Ga³⁺ ion may form complexes with charged soft ligands too, its behaviour then differing from that of the typically hard Al³⁺ ion.     

Equilibrium study of the systems of aluminium(III), gallium(III) and indium(III) with mercaptoacetate, 3-mercaptopropionate and 2-mercaptobenzoate

Equilibrium studies were carried out by pH-potentiometry on the systems of aluminium(III), gallium(III) and indium(III) with mercaptoacetate (MerAc^2?), 3-mercaptopropionate (MerPr^2?) and 2-mercaptobenzoate (MerBe^2?). It was found that the complex-forming properties of the Al³⁺ ion towards these mercaptocarboxylic acid ligands differ from those of Ga³⁺ and Al³⁺. Under the conditions of the study, Al³⁺ forms only hydroxo complexes, while Ga³⁺ and In³⁺ form relatively stable complexes involving the simultaneous coordination of the carboxylate and the deprotonated mercapto group. In all cases the equilibrium systems can be described without the assumption of polynuclear complexes. The complexes Ga(MerAc)₂ and Ga(MerBe)₂ show marked stability; this was interpreted in terms of back-coordination and of interaction between the d¹⁰ electrons of the Ga³⁺ ion and the empty d orbitals of the S donor atom. Complexes of composition ML_i are not formed in the Ga³⁺-MerPr^2? system; this points to the importan roles of the number of atoms in the chelate ring and the higher stability of the Ga(III)-hydroxo complexes.     

Bis(dimethylphosphino)methane complexes of iron and ruthenium

The interaction of iron(II) acetate in presence of bis(dimethylphosphino)methane (dmpm) with dimethyl- and diethylmagnesium leads to cis-FeMe₂(     

Interaction of organic azides with methyl compounds of cobalt,rhodium, iridium,ruthenium and zirconium to give azido or 1,3-triazenido complexes. The crystal structures of tris-trimethylphosphineazido-dimethylcobalt(III) and bis(carbonyl)trimethylphosphineazidocobalt(I)

The interaction of azidotrimethylsilane with mer-CoMe₃(PMe₃)₃, fac-RhMe₃(PMe₃)₃, fac-IrMe₃(PMe₂Ph)₃, cis-RuMe₂(PMe₃)₄ and (η⁵-C₅H₅)₂ZrMe₂ gives tetramethylsilane and, respectively, the azido compounds MMe₂(N₃)(PMe₃)₃, M = Co, Rh, IrMe₂(N₃)(PMe₂Ph)₃, cis-Ru(N₃)₂(PMe₃)₄ and (η⁵-C₅H₅)₂ZrMe(N₃). The crystal structures of CoMe₂(N₃)(PMe₃)₃ and of the derived complex Co(N₃(CO)₂(PMe₃)₂ have been determined by X-ray diffraction.The dimethyl cobalt(III) compound has an octahedral structure with a mer arrangement of the three PMe₃ groups. The Co^III-N distance is rather long, at 2.071(4) Å. The cobalt(I) carbonyl compound has a trigonal bypyramidal structure with the two phosphines occupying the axial sites. The Co^I-N distance is 2.03(1) Å.The interaction of PhN₃ with (η⁵-C₅H₅)₂ZrR₂, R = Me, Ph, gives the 1,3-triazenido complexes (η⁵-C₅H₅)₂ZrR(RNNNPh) while mer-CoMe₃(PMe₃)₃ and p-MeC₆H₄N₃ react to give CoMe₂(MeNNNp-tol)(PMe₃)₂. In all three cases the triazenido group appears to be bidentate.     

Diamine platinum(II) complexes of 2,2′-diaminobiphenyl

Platinum(II) complexes of 2,2′-diaminobiphenyl, [Pt(R-pn)(dabp)]Cl₂ and [Pt(R,R-chxn)(dabp)]Cl₂, where R-pn is the R-1,2-diaminopropane, R,R-     

Trimethylphosphine complexes of tungsten(O) and (IV). X-ray crystal structures of trimethylphosphine tris (phenylacetylene) tungsten(O); bis(trimethylphosphine) tetrakis (methylisocyanide) tungsten(O), and oxodichlorotris (trimethylphosphine) tungsten (IV)

The reduction of WCl₄(PMe₃)₃ by sodium amalgam in presence of phenylacetylene gives W(PMe₃)(PhCCH)₃ (A). Reduction in presence of methylisocyanide gives W(PMe₃)₂(MeNC)₄ (B), while in presence of excess PMe₃ in tetrahydrofuran under hydrogen, WH₂Cl₂(PMe₃)₄ (C) is formed. The reaction of WCl₂(PMe₃)₄ with methanol in tetrahydrofuran gives mixtures of WH₂Cl₂(PMe₃)₄ and WOC1₂(PMe₃)₃ (D).The structures of A, B, and D have been determined by X-ray diffraction.     

Homogeneous catalysis: VI. Hydrosilylation using tris(pentanedionato)rhodium(III) or tetrakis(μ-acetato)dirhodium(II) as catalyst

The catalytic activity of tris(pentanedionato)rhodium(III), (or rhodium(III) acetylacetonate) (I) has been investigated for the hydrosilylation of a variety of organic substrates: alkenes, terminal or internal acetylenes, conjugated dienes, or α,β-unsaturated carbonyls or nitriles. With PhCHCH₂ or PhCH₂CHCH₂, ω-substitution was unexpectedly observed, as well as addition. Compound I is an active hydrosilylation catalyst in the absence of any added reducing agent, as is tetrakis(μ-acetato)dirhodium(II) (II) which does not, however, show any unusual catalytic activity due to the two metal atom cluster. Possible mechanisms are suggested.     

Synthesis of rhodium(II) pyrazolate complexes: Crystal structure of tetra-μ-3,5-dimethylpyrazolato dirhodium(II) bis-acetonitrile, (Rh-Rh)

The reaction of Rh₂(O₂CMe)₄ with the sodium salt of 3,5-dimethylpyrazole (3,5-Me₂pzH) in acetonitrile gives Rh₂(3,5-Me₂pz)₄ · 2MeCN. This yellow diamagnetic compound on heating gives Rh(3,5-Me₂pz)₄ which in turn forms adducts with different unidentate ligands, L, to give Rh₂(3,5-Me₂pz)₄ · 2L. The binuclear tetra bridged structure has been established for the acetonitrile complex by X-ray diffraction. The Rh-Rh distance is 2.353(3) Å and the Rh-N (acetonitrile) distance is 2.202(5) Å. Some unsubstituted pyrazolates have been made.     

Transition-metal complexes of two valence tautomers of a bulky phenoxide, 2,6-Bu-t2-4-MeC6H2O− (ArO−); preparation and crystal and molecular structure of a phenoxytitanium(III) and a cyclohexadienonylrhodium(I) complex, [Ti(η-C5H5)2 OAr] and [Rh(ArO-η5)(PPh3)2]

The 2,6-di-t-butyl-4-methylphenoxo ligand (ArO^?) is ambidentate, giving rise to the O-bonded 15-electron d¹ [Ti(η-C₅H₅)₂OAr] and the η⁵ -[C(2)-C(6)]-bonded 18-electron d⁸ complex [Rh(ArO-η⁵)(PPh₃)₂], obtained from [{Ti(η-C₅H₅)₂Cl}₂]-LiO Ar and [Rh{N(SiMe₃)₂}(PPh₃)₂]-ArOH, respectively; the average TiC(η) distance is 2.362(10) Å, TiO 1.892(2) Å, and O:C(of Ar) 1.352(3) Å, and TiOC 142.3(2)°; in the Rh^I complex, C(2)C(6) are coplanar (with CC(av.) 1.38(2) Å). C(1)O 1.28 Å, and Rh to C(2) C(6) bond lengthsare in the range 2.19–2.65 Å.     

Allyl complexes of dicyclopentadienyl-niobium(III) and -tantalum(III)

The synthesis and the properties of the complexes Cp₂TaCl₂, Cp₂M(allyl), Cp₂M(1-methylallyl) and Cp₂M(2-methylallyl) with M  Nb, Ta are described. The complex Cp₂TaCl₂ has one unpaired electron per tantalum atom, while the allyl complexes are diamagnetic. The IR and PMR spectra indicate that the allyl group is π-bonded to the metal. The mass spectra of the complexes are discussed; the thermal stability of the Cp₂Nb- and Cp₂Ta-(allyl) complexes was investigated by differential thermal analysis. The properties of the niobium and tantalum complexes are compared with those of the corresponding titanium complexes.     

An examination of the relationship between the x-ray diffraction-derived molecular structure of chloro (1,11-diamino-3,6,9-trithiaundecane)cobalt(III) cation and its inner sphere reduction by iron(II)

The crystal structure of racemic [Co(NSSSN)Cl](ClO₄)Cl was determined by X-ray diffraction methods. It crystallizes in the monoclinic system, space group P2₁/c, with cell constants of a = 9.795(3), b = 10.412(3) and c = 16.323(8) Å, and β = 93.87(4)°; V = 1661 ųd (meas.; flotation) = 1.85 gm-cm^?3, d (calc.; Z = 4 molecules/unit cell) = 1.88 gm-cm^?3. The molecules, a racemic mixture, have the absolute configurations λλδλ or δδλδ at each of the four five-membered rings and resemble, in general, the so called αα conformer already described by Snow¹ in his study of the Co(tetraen)Cl²⁺ cation. However, the torsional angles at C2, C3 and C8, C9 in the two terminal C-C-NH₂ fragments are quite different in the two systems. For Co(tetraen)Cl²⁺ they are 44.7° and ?20.2° respectively, whereas for Co(NSSSN)C²⁺ the values –52.3° and –44.6° obtain. Also, the ring Co-S1-C3-C2-N1 does not have the classical, low energy conformation found in Co(tetraen)Cl²⁺. The presence of the larger Co-S bonds causes the two terminal -NH₂ groups to be pushed toward each other, and to minimize steric hindrance between adjacent -NH₂ hydrogens and ligand twists C2 down and staggers the terminal hydrogens. We visualize the propagation of these distortion effects in solution as being transferred from one side to the other across the entire ligand chain with concomittant effects on the activation of the precursor complex in electron transfer reactions, resulting in ~10⁷ rate enhancement over the Co(tetraen)Cl² system. Kinetic data for the reduction of Co(NSSSN)X²⁺ and Co(NSNSN)X²⁺ (X = Cl^?, Br^?) by Fe(II) is also presented and discussed.     

Studies in the flexibility of macrocyclic ligands. Crystal and molecular structure of 2,13-dimethy1-3,6,9,12,18-pentaazabicyclo (12.3.1) octadeca-(18),14,16-triene-dichloroion (III) hexafluorophosphate

The crystal structure of the title compound [FeL²Cl₂] [PF₆] is reported. Crystals are monoclinic with a = 11.747(9), b = 16.051(11), c = 11.964(10)Å, β = 98.1(1)°, Z = 4, Spacegroup P2₁/n. 1173 independent reflections above background have been refined to R 0.09. The coordination geometry around the Fe(III) ion is pentagonal bipyramidal with the two chlorine atoms in axial positions [Fe-Cl 2.348(7), 2.354(7)Å]. The five donor nitrogen atoms of the macrocycle form a pentagonal girdle with lengths in the range 2.20(2)–2.25(2)Å. The macrocycle conformation is compared to that found in [CuL²]²⁺ and [CoL²Cl]²⁺ where the 5N donor set provides respectively trigonal bipyramidal and square pyramidal environments and also to that found in the comparable 7-coordinate [FeL¹(NCS)₂]⁺ where L¹ is the related pentaene.     

Reaction of dichloromanganese(IV) Schiff-base complexes with water as a model for water oxidation in photosystem II

The dichloromanganese(IV) Schiff-base complexes Mn(N-R-3-NO₂ sal)₂Cl₂ (R = n-C₃H₇, n-C₄H₉, n-C₆H₁₃,     

Some trimethylphosphineoxide complexes of lanthanide and indium tris-(bis-trimethylsilylamides)

The reactions of the 3-coordinated metal tris-(bis-trimethylsilylamides) M[N(SiMe₃)₂]₃ (ML₃; where M = La, Pr, Eu, Gd and In) with trimethylphosphineoxide Me₃PO(L′) have been studied. All of these metals gave 1:1 complexes ML₃(L′) which dissociated on heating in vacuo. The Pr and Eu complexes gave interesting pseudo-contact shifted ¹H NMR spectra which are qualitatively in accord with the expected molecular structure. Variable temperature NMR measurements proved the restricted rotation of the silylamide (L) ligands occurs around the M–N axes. Evidence is also presented for unstable 5-coordinated complexes ML₃(L′)₂. The gadolinium 1:1 complex gave a very broad NMR spectrum and its ESR spectrum is being investigated.     

Iron carbonyl complexes of 2,3,5,6-tetrakis(methylene)-7-oxabicyclo[2.2.1]heptane. Crystal and molecular structure of (C10H10O)Fe(CO)3 and (C9H10CO)Fe2(CO)6

The reaction of 2,3,5,6-tetrakis(methylene)-7-oxabicyclo[2.2.1]heptane (I) with iron carbonyls in various solvents yields the (η⁴-1,3-diene)Fe(CO)₃ isomers (II: exo; III: endo) and the bimetallic isomers bis[(η⁴-1,3-diene)Fe(CO)₃] (IV: bis(exo); V: endo,exo). In weakly coordinating solvents, a parallel rearrangement of I occurs through CO bond cleavage of the allylic ether by Fe₂(CO)₉ yielding an unsaturated ketone (VI) bonded to two Fe(CO)₃ groups through a trimethylenemethane and a 1,3-diene system, respectively. The geometries of III and VI have been ascertained by X-ray crystal structure determinations.     

Paramagnetische organothalliumverbindungen in lösung: I. Esr-untersuchungen von diphenyl-thallium(III)-tonenpaaren mit brenzcatefechinen,pyrogallolen und 1,2-diketonen

Diphenylthallium hydroxide reacts very smoothly in organic solvents with catechols, pyrogallols and 1,2-diketones to stable paramagnetic diphenylthalliumsemiquinone and diphenylthalliumsemidione complexes respectively. This reaction has been investigated with 43 different ligands in numerous solvents. Therefore its general application is proofed.The ESR-spectra of these solutions show the hydrogen hyperfine structure of the ligands and an unusual large coupling which we assign to magnetic interaction of the free electron with the ²⁰³Tl and ²⁰⁵Tl nuclei. The thallium splittings observed depend remarkably on the ligands used. We refer this to different solvation phenomena.Semiquinones of the pyrogallol type show on principle two different radical types. Small concentrations of diphenylthallium hydroxide produce $\text{1}\text{1}$ complexes. These can be converted into $\text{1}\text{2}$ complexes by addition of further amounts of diphenyl thallium hydroxide.The ESR-spectra of the semiquinone-and the semidione-thallium complexes exhibit an unusually strong solvent dependence of the thallium coupling and of the g-factor. It is possible to explain both variations uniformly by the different donor ability of the solvents used.All complexes investigated indicate remarkable temperature dependence of the thallium splitting and the g-factor. The thallium couplings show a positive temperature gradient whereas the g-factor decrease with increasing temperature as expected.Based on the sum of the observed effects, we assume that the radicals observed by us are ion pairs in which a diphenylthallium cation interacts with the semiquinone- or semidione-anion, respectively.     

Regioselective addition of protic acids to tricarbonyliron complexes of 2,3,5,6-tetrakis(methylene)-7-oxabicyclo[2.2.1]heptane. Crystal structure of (C10H10O)Fe2(CO)6

The main product of the thermal reaction between the title oxatetraene (I) and Fe₂(CO)₉ in ether/pentane is the bimetallic complex (C₁₀H₁₀O)Fe₂(CO)₆-diexo (II), which has C_2υ symmetry both in the solid state (X-ray analysis) and in solution. Whereas the protonation of the free ligand leads usually to polymerisation, the addition of a protic acid such as CF₃CO₂H to II proceeds cleanly at 0°C giving first a (η 3-allyl)Fe(CO)₃O₂CCF₃ complex (III). The intermediate III adds a second equivalent of acid in a slower step (k₂/k₁ = 0.1, CF₃CO₂D/CHCl₃, 0°C) giving the trans-bis(η³-allyl) isomer IV with high regioselectivity. The addition of CF₃CO₂D yields the corresponding deuteriomethylallyliron tricarbonyl trifluoroacetates III′ and IV′. No further deuterium incorporation is observed at 0°C, thus confirming the kinetic control of the regioselective double addition of protic acid to II.     

Stereospecific functionalisations of iron carbonyl complexes of 5,6,7,8-tetrakis(methylene)bicyclo[2.2.2]oct-2-ene. Crystal and molecular structure of (C12H12)Fe2(CO)6

When the reaction between an excess of Fe₂(CO)₉ and the pentaene 5,6,7,8-tetrakis(methylene)bicyclo[2.2.2]oct-2-ene(I) is carried out in hexane/methanol the endo,exo-bis(tetrahaptotricarbonyliron) isomer (C₁₂H₁₂)Fe₂(CO)₆(IIa)is the major product. The structure of this complex has been determined by X-ray diffraction.The asymmetric positions of the two Fe(CO)₃ groups with respect to the roof-shaped organic skeleton was used to induce either stereo-specific functionalisation of the uncoordianted endocyclic CC double bond or stereo-and regiospecific functionalisation of one of the two coordinated s-cis-butadiene groups of the pentaene. Thus, hydroboration/oxidation of Ila gave the endo-exo-bis(tetrahaptotricarbonyliron)isomer of 5,6,7,8-tetrakis(methylene)bicyclo[2.2.2]octane-2-ol (IV). cis deuteration of the exocyclic double bond was achieved by treating IIa with D₂/PtO₂ in n-hexane.Protonation of IIa by HCl/AlCl₃/CH₂Cl₂ to give the η⁴-diene : η²-ene : η³-dienyl cationic complex Va, followed by quenching of Va with NaHCO₃/CH₃OH, resulted in a 1,4-addition of methanol to one coordinated s-cis-butadiene system. In contrast, quenching with NaOCH₃/CH₃OH resulted in the corresponding 1,2-addition of methanol. This gave the η⁴-1,3-diene : η⁴-1,4-diene complex VIIIa in which, suprisingly, one Fe(CO)₃ group is coordinated to two CC double bonds in gauche positions with respect to each other.