Steric effects of the 2-(diphenylphosphino)pyridine bridging ligand in the synthesis of binuclear palladium(II) complexes

Treatment of [Pd{CH₂C(CH₃)CH₂}(Ph₂PPy)Cl] (Ph₂PPy = 2-(diphenylphosphino)pyridine) with cis-[Pd(^tBuNC)₂Cl₂] in dichloromethane affords the mixed isocyanide-tertiary phosphine complex cis-[Pd(^tBuNC)Ph₂PPy)Cl₂], in which the Ph₂PPy is a monodentate P-donor, and [{Pd[CH₂C(CH₃)CH₂]Cl}₂]. The steric effects of the Ph₂PPy bridging ligand in determining the reaction course is discussed. The complex cis-[Pd(^tBuNC)(Ph₂PPy)Cl₂] was crystallographically characterized: P2₁/n, a = 15.143(2), b = 9.527(1), c = 17.517(4) Å, β = 113.96(1)°, V= 2309.4(7) ų, Z = 4. The final R value was 0.044, R^w= 0.046 for the 3078 reflections with I > 3σ(I).     

Binuclear methyplatinum and phenylplatinum complexes with bis(dimethylphosphino)methane ligands

Reaction of cis-[Ptph₂(SMe₂)₂] with Me₂PCH₂PMe₂ (dmpm) gave cis-[PtPh₂(dmpm-P)₂] (1) or cis,cis-[Pt₂Ph₄(μ-dmpm)₂] (2) and reaction of 1 with [Pt₂Me₄(μ-SMe₂)₂] gave cis,cis-[Ph₂Pt(μ-dmpm)₂PtMe₂] (3). Reaction of 1 with trans-[PtClR(SMe₂)₂] gave cis,trans-[Ph₂Pt(μ-dmpm)₂PtClR], R = Me (5) or Ph (6), and in polar solvents, these isomerized to give [Ph₂Pt(μ-dmpm)₂PtR]⁺Cl⁻. When R = Me, further isomerization via the phenyl group transfer gave [PhMePt(μ-dmpm)₂PtPh]⁺Cl⁻. Oxidative addition of methyl iodide occurred reversibly at the cis-[PtMe₂P₂ unit of 3 to give cis,fac-[Ph₂Pt(μ-dmpm)₂PtIMe₃] but complex 2 failed to react with MeI. A comparison with similar known complexes of Ph₂PCH₂PPh₂ (dppm) is made and differences are attributed primarily to the lower steric hindrance of dmpm.     

New mesomorphic organocyclosiloxanes II. Thermal behaviour and mesophase structure of organocyclohexasiloxanes

Investigations of thermotropic phase transitions performed on organocyclosiloxanes [PhSi(O)OSiR]₆, where R is Me₃, Me₂(CH₂Cl) or Me₂(CH≃CH₂), have revealed that all these hexamers are mesomorphic compounds. The hexamers exhibit uncommon polymesomorphic behaviour forming two quite different mesomorphic structures. The molecular arrangement in the low temperature (LT) modification is characterized by two-dimensional (2D) long-range order with hexagonal packing. The X-ray diffraction pattern and peculiarities of molecular packing in the crystal lead us to suggest that the LT-mesophase is columnar, presumably of the Col_hd type. The LT-mesophase is formed by dimeric moieties, which associate with each other in column-like substructures, the ring planes not orthogonal to the stack axis. The high temperature (HT) mesophase is a plastic crystal (3D-order), where molecules take up positions in a face-centred cubic lattice. This is a very uncommon example of thermal behaviour for plastic crystals that provides a unique opportunity to bridge the gap between plastic crystalline and liquid crystalline mesomorphic behaviour. The thermal and structural properties of the mesophases depend upon the type of side groups of the hexamers. The size of the ring also affects the phase behaviour and the mesomorphic structure. This conclusion is consistent with data obtained by us earlier for cyclotetrasiloxanes.     

New mesomorphic organocyclosiloxanes I. Thermal behaviour and mesophase structure of organocyclotetrasiloxanes

cis-Cyclotetrasiloxanes of the formula cis-[PhSi(O)(OSiMe₂ R)]₄ with R = Me, CH₂Cl, CH CH₂ and cis-[ClC₆H₄Si(O)(OSiMe₃)]₄ were synthesized and investigated in terms of their thermotropic phase transitions. Two ordered phases were observed for the cis-cyclotetrasiloxanes, one at lower temperature exhibiting the properties of a crystal and one at higher temperature exhibiting the properties of a plastically crystalline (3D) mesophase. A detailed examination of the mesophase behaviour and mesophase structure of octaphenylcyclotetrasiloxane was also carried out. It was shown that the thermal properties and structural characteristics of the mesophase are influenced by the structural characteristics of the substituent attached at the silicon atom in the tetracyclosiloxane. The new mesomorphic cis-cyclotetrasiloxanes are by far the largest molecules reported to date as forming plastic crystals, and the temperature region of the mesophase is much broader than in other plastic crystals. All five cyclotetrasiloxanes studied were found to be isomorphous in the 3D-mesophase and the low temperature forms of the two cis-cyclotetrasiloxanes: PhSi(O)(OSiMe₂ R)₄ (R = Me, CH CH₂) were also isomorphous.     

Über dimere dimethylmetall-bis(trimethylgermyl)amide des aluminiums, galliums und indiums

The dimethylmetal bis(trimethylgermyl)amides of Al, Ga, and In have been prepared from Li[N(GeMe₃)₂] and Me₂MCl (Me = CH₃, M = Al, Ga) or Me₂MCN (M = Ga, In) in inert solvents. The NMR (¹H, ¹³C) and vibrational spectra (IR and Raman) of these dimeric compounds have been assigned and discussed. According to the X-ray structure determination [Me₂InN(GeMe₃)₂]₂ crystallizes in the monoclinic space group C2/c (Z = 4, R = 0.032) and is isomorphous with the bis(trimethylsilyl) homologue.     

Synthesis, structure and reactions of organometallic compounds of Groups 1–3 containing bulky silicon-substituted alkyl groups

Complexes trans-[PtX(L)(PPh₃)₂]A [1: X = CF₃; A = BF₄; L = NCNH₂, NCNMe₂, NCNEt₂, or NCNC(NH₂)₂. 2: X = Cl; A = BPh₄; L = NCNMe₂ or NCNEt₂] and cis-[PtCl(L)(PPh₃)₂][BPh₄] [3: L = NCNH₂ or NCNC(NH₂)₂], which appear to be the first cyanamide or cyanoguanidine complexes of platinum to be reported, have been prepared by treatment of trans-[PtBr(CF₃)(PPh₃)₂] (in CH₂Cl₂/acetone and in the presence of Ag[BF₄]) or of cis-[PtCl₂(PPh₃)₂] (in THF and in the presence of Na[BPh₄]), respectively, with the appropriate substrate. In KBr pellets or in solution 1 (L = NCNMe₂ or NCNEt₂) undergoes ready replacement of the organocyanamide (under the trans influence of CF₃) by bromide to regenerate trans-(PtBr(CF₃)(PPh₃)₂]. The X-ray structure of 1 (X = CF₃, A = BF₄, L = NCNEt₂) is also reported, and shows the presence of two apical intramolecular contacts of the metal with two ortho-hydrogen atoms of the phosphines, whereas the amine N atom of the diethylcyanamide is trigonal planar in the linear NCN framework with a delocalized π system.     

Syntheses, X-ray structures, and reactions of ruthenium carbonyl complexes containing 1,1-dithiolates

Treatment of [Ru₂(CO)₄(MeCN)₆][BF₄]₂ or [Ru₂(CO)₄(μ-O₂CMe)₂(MeCN)₂] with uni-negative 1,1-dithiolate anions via potassium dimethyldithiocarbamate, sodium diethyldithiocarbamate, potassium tert-butylthioxanthate, and ammonium O,O′-diethylthiophosphate gives both monomeric and dimeric products of cis-[Ru(CO)₂(η²-(SS))₂] ((SS)⁻=Me₂NCS₂⁻ (1), Et₂NCS₂⁻ (2), ^tBuSCS₂⁻ (3), (EtO)₂PS₂⁻ (4)) and [Ru(CO)(η²-(Me₂NCS₂))(μ,η²-Me₂NCS₂)]₂ (5). The lightly stabilized MeCN ligands of [Ru₂(CO)₄(MeCN)₆][BF₄]₂ are replaced more readily than the bound acetate ligands of [Ru₂(CO)₄(μ-O₂CMe)₂(MeCN)₂] by thiolates to produce cis-[Ru(CO)₂(η²-(SS))₂] with less selectivity. Structures 1 and 5 were determined by X-ray crystallography. Although the two chelating dithiolates are cis to each other in 1, the dithiolates are trans to each other in each of the {Ru(CO)(η²-Me₂NCS₂)₂} fragment of 5. The dimeric product 5 can be prepared alternatively from the decarbonylation reaction of 1 with a suitable amount of Me₃NO in MeCN. However, the dimer [Ru(CO)(η²-Et₂NCS₂)(μ,η²-Et₂NCS₂)]₂ (6), prepared from the reaction of 2 with Me₃NO, has a structure different from 5. The spectral data of 6 probably indicate that the two chelating dithiolates are cis to each other in one {Ru(CO)(η²-Et₂NCS₂)₂}fragment but trans in the other. Both 5 and 6 react readily at ambient temperature with benzyl isocyanide to yield cis-[Ru(CO)(CNCH₂Ph)(η²-(SS))₂] ((SS)=Me₂NCS₂⁻ (7) and Et₂NCS₂⁻ (8)). A dimerization pathway for cis-[Ru(CO)₂(η²-(SS))₂] via decabonylation and isomerization is proposed.     

Synthesis and electrochemical behaviour of the cyanamide-isocyanide complexes of rhenium, trans-[ReL(CNR)(Ph2PCH2CH2PPh2)2] ( L = NCNH2 or NCNH)

Reaction of trans-[ReCl(CNR)(dppe)₂] (R = Me (Ia) or ^tBu (Ib); DPPE = Ph₂PCH₂CH₂PPh₂) in CH₂Cl₂ with cynamide in the presence of TlBF₄ forms the new cynamide-isocyanide complexes trans-[Re(CNR)(NCNH₂)(dppe)₂][BF₄] (R = Me (IIa) or ^tBu (IIb)), which upon treatment by ^tBuOK or Et₃N give trans-[Re(NCNH)(CNR)(dppe)₂] (R = Me (IIIa) or ^tBu (IIIb)). The electrochemical behaviour of these species was studied by cyclic voltammetry and controlled potential electrolysis at a Pt electrode in an aprotic solvent, and cathodic reduction of II results in the formation of III.     

Highly stereoselective reduction of methyl ketone complexes of the chiral Lewis acid [(η-C5H5)Re(NO)(PPh3)] by K(s-C4H9)3BH; synthesis of optically active secondary alcohols and derivatives

Reaction of optically active ketone complexes (+)-(R)-[(η⁵-C₅H₅)Re(NO)-(PPh₃)(η¹-O=C(R)(CH₃)]⁺ BF₄⁻ (R = CH₂CH₃, CH(CH₃)₂m C(CH₃)₃, C₆H₅) with K(s-C₄H₉)₃BH gives alkoxide complexes (+)-(RS)-(η⁵-C₅H₅)Re(NO)(PPh₃)-(OCH(R)CH₃) (73–90%) in 80–98% de. The alkoxide ligand is then converted to Mosher esters (93–99%) of 79–98% de.     

Equilibrium constants and kinetics of carbon monoxide insertion in alkyl complexes of ruthenium(II)

The equilibrium constants of the reaction of cis, trans-[Ru(CO)₂(PMe₃)₂(CH₃)I] (Mc) with carbon monoxide to give cis, trans[Ru(CO)₂(PMe₃)₂ (COMe)i] (Ac) and trans, trans[Ru(CO)₂(PMe₃)₂(COMe)I] (At) were measured at various temperatures in toluene. The thermodynamic parameters are compared with those obtained for the isoelectronic complexes of iron, and the trend is discussed. The kinetics of the carbonylation reaction of Mc, as well as those of the inverse decarbonylation reaction of At were measured. The kinetics of the carbonylation of the new complex trans, trans-[Ru(CO)₂(PMe₃)₂(CH₃)I] (Mt) were also investigated. All the results afford further support to the previously proposed CO insertion mechanism occurring via methyl migration. The comparison of these kinetic results with those of isoelectronic complexes of iron indicates that ruthenium is more reactive than iron, which is reflected by its greater aptitude to act as catalyst in many processes.     

Allylstannation V. cis-stereoconvergent sysnthesis of homoallylic alcohols and 4-chloro-2,6-dialkyl-3-methyltetrahydro-pyrans by the addition reaction of 1-buten-3-yldichloro-n-butyltin and aldehydes

1-Buten-3-yl-n-butyldichlorotin, generated in situ by redistribution of (E/Z)-2-butenyltri-n-butyltin and BuSnCl₃, reacts readily with neat RCHO (R = CH₃, C₂H₅, (CH₃)₂CH) at 25°C to give linear alcohols RCH(OH)CH₂CH---CHCH₃ and/or 2,3,4,6-tetrasubstituted tetrahydropyrans, CH₂CH(R)OCH(R)CH(CH₃)CH-(Cl), which are mainly in the cis-configuration with respect to the CH(CH₃)-CH(Cl) bond. When R = (CH₃)₃C and C₆H₅, only the homoallylic alcohols are obtained. These cis-stereoconvergent syntheses are explained in terms of kinetic control of the formation of adducts obtained by insertion of one or two aldehyde molecules into the organotin substrate.     

Synthesis, characterization, and X-ray crystal structures of W(VI) alkyl complexes with chelating diamide and imido co-ligands

The complex W(NPh)Cl₂[o-(NSiMe₃)₂C₆H₄] 3 was synthesized from PhN = WCl₄ · OEt₂ and N,N′-(Li₂[o-(NSiMe₃)₂C₆H₄] and reacts with Lewis bases to form the adducts W(NPh)Cl₂[o-(NSiMe₃)₂C₆H₄](L) (L = PMe₃, THF, 3-picoline, ^tBuNC, MeCN) 4a–e. Crystals of 4a are triclinic, space group P1¯, with a = 9.562(1), b = 10.277(1), c = 14.920(2) Å, = 82.15(1), β = 80.18(1), γ = 80.41(1)°, and Z = 2. The structure was solved by the heavy atom method and refined to R = 0.0408 for 4224 observed (I > 2σ(I)) reflections. The dialkyl complexes W(NPh)R₂[o-(NSiMe₃)₂C₆H₄] (R = Me, Et, CH₂Ph, CH₂CMe₃, CH₂CMe₂Ph) 5–9 are formed through subsequent reactions of 3 with the corresponding Grignard reagent. Crystals of complex 5 are monoclinic, space group P2(1)/n, with a = 10.3545(2), b = 17.9669(1), c = 13.3168(1) Å, β = 103.826(1)°, and Z = 4. The structure of complex 5 was solved by direct methods in SHELXTL5 and refined to R = 0.0247 for 4572 observed reflections. Compound 5 has a square pyramidal geometry in which the imido ligand occupies the apical position and reacts with PMe₃ to form the adduct W(NPh)Me₂[o-(NSiMe₃)₂C₆H₄](PMe₃) 5a. Crystals of complex 5a are monoclinic, space group C2/m, with a = 13.5336(1), b = 14.4291(1), c = 15.3785(1) Å, β = 110.365(1)°, and Z = 4. The structure of compound 5a was solved by direct methods in shelxtl5 and refined to R = 0.0272 for 3057 observed reflections. Crystals of the bis-neopentyl complex 8 are monoclinic, space group P2(1)/n, with a = 10.6992(4), b = 18.3144(7), c = 16.0726(6) Å, β = 92.042(1)°, and Z = 4. The structure of 8 was solved by direct methods in shelxtl5 and refined to R = 0.0261 for 5881 observed reflections. Complex 8 has a trigonal bipyramidal geometry with both neopentyl groups and one amido nitrogen in the equatorial plane.     

Synthesis, characterization and catalytic activity in Heck-type reactions of orthometallated Pd and Pt complexes derived from (1R,2R)-1,2-diaminocyclohexane

The chiral bis-imine (1R,2R)-C₆H₁₀-[E---N=CH---C₆H₃---3,4-(OMe)₂]₂ 1 (LH) reacts with [Pd(OAc)₂] (1:1 molar ratio; OAc=acetate) giving the orthometallated [Pd(OAc)(C₆H₂---4,5-(OMe)₂---2-CH=N-(1R,2R)-C₆H₁₀---N=CH---C₆H₃-3′,4′-(OMe)₂-κ-C,N,N)] 2 (abbreviated as [Pd(OAc)(L-κ-C,N,N)]), through C---H bond activation on only one of the aryl rings and N,N-coordination of the two iminic N atoms. 2 reacts with an excess of LiCl to give [Pd(Cl)(L-κ-C,N,N)] 3. The reaction of 3 with AgClO₄ and neutral or anionic ligands L′ (1:1:1 molar ratio) affords [Pd(L-κ-C,N,N)(L′)](ClO₄) (L′=PPh₃ 4a, NCMe 5, pyridine 6, p-nitroaniline 7) or [Pd(I)(L-κ-C,N,N)] 8. Complex 4a reacts with wet CDCl₃ giving [Pd(C₆H₂---4,5-(OMe)₂---2-CH=N-(1R,2R)---C₆H₁₀---NH₂-κ-C,N,N)(PPh₃)](ClO₄) 4b as a result of the hydrolysis of the C=N bond not involved in the orthometallated ring. The molecular structure of 4b·CH₂Cl₂ has been determined by X-ray diffraction methods. Cleavage of the Pd---N bond trans to the C_aryl atom can be accomplished by coordination of strongly chelating ligands, such as acetylacetonate (acac) or bis(diphenylphosphino)ethane (dppe), forming [Pd(acac-O,O′)(L-κ-C,N)] 9 and [Pd(L-κ-C,N)(dppe-P,P′)](ClO₄) 12, while classical N,N′-chelating ligands such as 1,10-phenantroline (phen) or 2,2′-bipyridyl (bipy) behave as monodentate N-donor ligands yielding [Pd(L-κ-C,N,N)(κ¹-N-phen)](ClO₄) 10 and [Pd(L-κ-C,N,N)(κ¹-N-bipy)](ClO₄) 11. Treatment of 1 with PtCl₂(DMSO)₂ (1:1 molar ratio) in refluxing 2-methoxyethanol gives Cl₂Pt[(NH₂)₂C₆H₁₀---N,N′] 13a and [Pt(Cl)(C₆H₂---4,5-(OMe)₂---2-CH=N-(1R,2R)---C₆H₁₀---NH₂-κ-C,N,N)] 13b, while [Pt(Cl)(L-κ-C,N,N)] 14 can be obtained by reaction of [Pt(μ-Cl)(η³-2-Me---C₃H₄)]₂ with 1 in refluxing CHCl₃. Complexes 2 and 3 catalyzed the arylation of methyl acrylate giving good yields of the corresponding methyl cinnamates and TON up to 847 000. Complex 3 also catalyzes the hydroarylation of 2-norbornene, but with lower yields and without enantioselectivity.     

Heterobimetallic Mo---Sn complexes. Reactions of [Mo(CO)3(CH3CN)2(Cl)(SnRCl2)] (R = Me, Ph) with 4(4-XC6H4)3 (X = Cl, F, H, Me, MeO)

Three families of heterobimetallic compounds were obtained by reaction of [Mo(CO)₃(CH₃CN)₂(Cl)(SnRCl₂)] (R = Ph, Me) with P(4-XC₆H₄)₃ (X = Cl, F, H, Me, MeO). The type of compound obtained dependent on the solvent and concentration of the starting compound. So, [Mo(CO)₂(CH₃COCH₃)₂(PPh₃)(Cl)(SnRCl₂)]·nCH₃COCH₃ (R = Ph, n = 0.5; R = Me, n = 1) (type I) and [Mo(CO)₃{P(4-XC₆H₄)₃}(μ-Cl)(SnRCl₂)]₂ (R = Ph, X = Cl, F, H, Me, MeO; R = Me, X = Cl, F) (type II) were isolated from acetone solution in ca 0.05 M and 0.1 M concentrations, respectively. However, [Mo(CO)₃(CH₃CN) {P(4-XC₆H₄)₃}(Cl)(SnRCl₂)] (R = Ph, X = H; R = Me, X = Cl, F, H) (type III) were obtained from dichloromethane solution independently of the concentration used. All new complexes showed a seven-coordinate environment at molybdenum, containing Mo---Cl and Mo---Sn bonds. Mössbauer spectra indicated a four-coordination at tin for type III complexes.     

Syntheses, spectroscopic characteristics and thermolytic rearrangements of bis-[(trimethylgermyl)methyl]platinum(II) and bis-[(trimethylstannyl)methyl]platinum(II) complexes

The preparations and spectroscopic characteristics are reported of a series of (trimethylgermyl)methyl- and (trimethylstannyl)methylplatinum(II) complexes with diene and P-donor ancillary ligands, cis-Pt(CH₂GeMe₃)₂L₂ (L = PPh₃ or PPh₂Me; L₂ = dppe or cod) and cis-Pt(CH₂SnMe₃)₂L₂ (L = PPh₃; L₂ =cod). Thermolysis of toluene solutions of cis-Pt(CH₂GeMe₃)₂(PPh₃)₂ leads to cis-Pt(Me)(CH₂GeMe₂CH₂GeMe₃)(PPh₃)₂ via β-alkyl migration, after (non-rate-limiting) phosphine dissociation. Estimated activation parameters (ΔH_{298 K}^‡ = 126 ± 3 kJ mol⁻¹, ΔS^‡ = + 17 ± 7 J mol⁻¹ K⁻¹ and hence Δ_{298 K}^‡ = 121 ± 5 kJ mol⁻¹) suggest that this system is more migration labile than its silicon analogue, primarily as a result of a lower activation enthalpy. While cis-Pt(CH₂GeMe₃)₂(PPh₂Me)₂ reacts similarly but less readily, Pt(CH₂GeMe₃)₂(dppe)₂ is inert at operable temperatures. Thermolysis of Pt(CH₂GeMe₃)₂(cod) generates 1,1,3,3,-tetramethyldi-1,3-germacyclobutane as the major organogermanium product, while from cis-Pt(CH₂SnMe₃)₂(PPh₃)₂, 1,1,3,3-tetramethyldi-1,3-stannacyclobutane predominates. Mechanistic implications are discussed.     

Synthesis, characterization and the unpleasantly disordered crystal structure of Ir(Ome)(CO)(PPh3)2(SO4)

The adducts of O₂ and SO₂ with trans-MeOIr(CO)(PPh₃)₂ are formed in equilibria and have been characterized. Reaction of the SO₂ adduct, Ir(OMe)(SO₂)(CO)(PPh₃)₂ with dioxygen leads to the sulfato complex, Ir(Ome)(CO)(PPh₃)₂(SO₄), the structure of which has been determined. Ir(Ome)(CO)(PPh₃)₂(SO₄) crystallizes in the monoclinic system with a 11.958(2), b 14.163(3), c 12.231(2) Å, β 118.365(12)°, V 1822.7(6) ų and Z = 2. Diffraction data for 2θ = 4.5–45.0° (Mo-K) were collected with a Syntex P2₁ diffractometer and the structure was solved (assuming space group P2₁/m and an unpleasant 2-fold disordered model) and refined to R = 4.8% for all 2512 independent data (R = 3.5% for those 2042 data with ¦F_O¦ > 6σ(¦F¦)). The iridium(III) atom has a distorted octahedral coordination sphere with trans PPh₃ ligands and a cis-chelating bidentate O,O′-SO₄ group; the structure is completed by mutually cis OMe and CO ligands.     

Reactivity of ruthenium complexes with uninegative (X,S)-donor ligands (X = S,P)—II. Phosphine substitution in [Ru(S,S)2(PR3)2] derivatives. Crystal structure of trans-bis(O-ethyldithiocarbonate)bis(dimethylphenylphosphine)-ruthenium(II)

The complexes [Ru(S,S)₂(PPh₃)₂] [S,S = EtCOCS₂⁻, (CH₂)₄NCS₂⁻] react with a variety of tertiary phosphines with the substitution of triphenylphosphine and the formation of [Ru(S,S)₂(PR₃)₂]. The reaction occurs with the formation ofthe cis isomer, except for the complex with PMe₂Ph that gives rise to the trans isomer as the crystal structure shows. The effect of the different phosphines on the ruthenium complex is analysed in terms of the spectroscopic and electrochemical properties of the isolated compounds. The cyclic voltammetric studies of the cis complexes show that isomerization to the trans isomer occurs on oxidation. This isomerization is not observed in the trans-[Ru(S,S)₂(PMe₂Ph)₂] complexes that give rise to stable trans-ruthenium(II)/ruthenium(III) couples. In a similar way the diphosphine complexes afford a quasi-reversible cis-ruthenium(II)/ruthenium(III) process.     

Synthesis and molecular structure of the optically active organoaluminium dimer (S)-(—)-(S)-(—)- [(C6H5)CH(CH3)NHA1(CH3)2]2

Reaction of the optically active primary amine (S)-(—)--methylbenzylamine with trimethylaluminium in heptane affords the crystalline organoaluminium dimer (S)-(—)-(S)-(—)-[(C₆H₅)CH(CH₃)NHA1(CH₃)₂]₂. Isolated as large, colourless, extremely air-sensitive prismatic crystals, the title compound crystallizes in the orthorhombic space group P2₁2₁2₁ with unit cell parameters a = 8.406(3), b = 15.505(4), c = 17.547(5) Å, V = 2287 ų and p = 1.03 g cm⁻³ for Z = 4. Least-squares refinement based on 1477 observed reflections converged at R = 0.056, R_w = 0.058. Methane was eliminated during the course of the reaction due to cleavage of A1---C and N---H bonds resulting in an asymmetric A1₂N₂ fragment at the core of the organoaluminium dimer. The mean A1---C bond distance in the dimethylaluminium units is 1.930(8), while the mean A1---N bond distance is 1.950(5) Å. Specific rotation ([]_D²⁵ in CH₂C1₂)of the dimer is determined to be - 20.6°.     

Synthesis and characterization of planarly chiral nonbridged bis(1-R-indenyl) zirconium dichloride complexes and X-ray structure of rac-[(η-C9H6-1-C(CH3)2---o-C6H4---OCH3)2ZrCl2]·THF

Reactions of the lithium salts of 3-substituted indenes 1, 2 with ZrCl₄(THF)₂ gave two series of nonbridged bis(1-substituted)indenyl zirconocene dichloride complexes. Fractional recrystallization from THF–petroleum ether furnished the pure racemic and mesomeric isomers of [(η⁵-C₉H₆-1-C(R¹)(R²)---o-C₆H₄---OCH₃)₂ZrCl₂]·nTHF (R¹=R²=CH₃, n=1, rac-1a and meso-1b; R¹=CH₃, R²=C₂H₅; n=0.5 or 0, rac-2a and meso-2b), respectively. Complex 1a was further characterized by X-ray diffraction to have a C₂ symmetrically racemic structure, where the six-member rings of the indenyl parts are oriented laterally and two o-CH₃O---C₆H₄---C(CH₃)₂--- substituents are oriented to the open side of the metallocene (Ind: bis-lateral, anti; Substituent: bis-central, syn). The four zirconocene complexes are highly symmetrical in solution as characterized by room temperature ¹H-NMR, however ¹H–¹H NOESY of meso-1b shows that some of the NOE interactions arise from the two separated indenyl parts of the same molecule, which can only be well explained by taking into account the torsion isomers in solution.     

Synthesis of mer-[RuCl3(DMSO)(bpy)], reactivity and electrochemistry of mer-[RuCl3(DMSO)(bpy)] and mer-[RuCl3(TMSO)(bpy)] complexes

[H(DMSO)₂][trans-RuCl₄(DMSO)₂] (1) reacts with 2,2′-bipyridine in ethanol at room temperature resulting in the formation of a major compound, mer-[RuCl₃(DMSO)(bpy)] (bpy = 2,2′-bipyridine) 3 and a known minor compound, cis-[RuCl₂(DMSO)₄] (4). The compounds 3 and 4 are formed via an anticipated intermediate mer-[RuCl₃(DMSO)₃] (2). The reaction of 3 and mer-[RuCl₃(TMSO)(bpy)] (5) with small molecules like imidazole, carbon monoxide and KSCN yield, mer-[RuCl₃(bpy)(im)] · 2DMSO (im = imidazole) (6) and cis-[RuCl₂(TMSO)(CO)(bpy)] (7), cis-[RuCl₂(DMSO)(CO)(bpy)] (8) and K[RuCl₃(bpy)(SCN)] (9), respectively. The formations of 3, 6 and 7 have been authenticated by single crystal structure determinations. Compound 6 is formed by the substitution of DMSO or TMSO from 3 and 5, respectively, whereas 7 and 8 are formed by unprecedented one-electron reductions of 5 and 3. The reactions of 3 and 5 with KSCN resulted in the same compound, K[RuCl₃(NCS)(bpy)] (9). DFT calculations were performed to distinguish whether the thiocyanate ligand is bound to ruthenium through S or N. In the ruthenium bipyridine systems, the HOMO contains ruthenium d-orbitals and the LUMO is typically π^*-orbitals of the bipyridine ring. Complexes 3, 6 and 7 are redox active in acetone and DMSO solvent showing prominent a reduction peak and corresponding oxidation peak.