Transformations of high spin MnII and FeII polymeric pivalates in reactions with pivalic acid and o-phenylenediamines

The thermolysis and reactions of the polymeric high spin Mn^II and Fe^II complexes [Mn(μ-OOCBu^t)₂(HOEt)]_n (1) and [Fe(μ-OOCBu^t)₂]_n (3) with pivalic acid and o-phenylenediamines 1,2-(NH₂)₂C₆H₂R₂ (R = H or Me) were studied. The synthesis of compound 1 performed with a deficiency of pivalate anions affords the antiferromagnetic chloropivalate polymer { (MeCN)(HOOCBu^t)(H₂O)Mn₅Cl(OH)(OOCBu^t)₈·MeCN}_n. The reaction of 1 with an excess of pivalic acid produces the antiferromagnetic polymer [Mn₄(OOCBu^t)₈(HOOCBu^t)₂]_n. The analogous reaction of pivalic acid with polymer 3 gives the mononuclear complex Fe(η ¹-OOCBu^t)₂(η¹-HOOCBu^t)₄ containing the high spin iron(II) atom as the major product. Study of the reactions of 3 with a deficiency (<1: 1) and an excess (>1: 1) of diamines demonstrated that the polymer {[(η²-(NH₂)₂C₆H₄)₂Fe(μ-OOCBu^t)₂][Fe₂(μ-OOCBu^t)₄] · · 2MeCN}_n is generated as the major product in the former case, whereas the mononuclear complexes Fe(η¹-OOCBu^t)₂[η¹-(NH₂)₂C₆H₄]₄ and Fe(η¹-OOCBu^t)₂[η²-(NH₂)₂C₆H₂Me₂][η¹-(NH₂)₂C₆H₂Me₂]₂ are predominantly obtained in the latter case. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 779–792, May, 2006.     

Pivalates with the M<Superscript>II</Superscript><Subscript>4</Subscript>O<Subscript>4</Subscript> cubane core (M = Co,Ni): synthesis,structure, magnetic properties,and solid-state thermolysis

Methods were developed for the controlled thermal synthesis of high-spin cubane-like pivalates {M^II ₄(μ₃−OR)₄} (M = Co or Ni; R = H or Me) starting from mono-and polynuclear complexes. The solid-state thermal decomposition of the known pivalate clusters [M^II ₄(μ₃−OMe)₄−(μ₂−OOCBu^t)₂(η²−OOCBu^t)₂(MeOH)₄] and the new clusters [M₄^II(μ₃)−OH₄(η¹−OOCBu^t)₃−(μ−(NH₂)₂C₆H₂Me₂)₃(η¹−(NH₂)₂C₆H₂Me₂)₃]⁺(OOCBu^t)− (M = Co or Ni) was studied by differential scanning calorimetry and thermogravimetry. The thermolysis of cubane-like CoII and NiII pivalates is a destructive process. The phase composition of the decomposition products is determined by the nature of coordinated ligands and the structural features of the metal core.     

Protonation and methylation of η-2,3,5,6-tetramethyl-1,4-benzoquinone(η-pentamethylcyclopentadienyl)cobalt

The preparation of the η⁴-4-2,3,5,6-tetramethyl-1,4-benzoquinonecomplex [CO(C₅Me₅)(C₁₀H₁₂O₂)] (I) is reported. Complex I undergoesreversible protonation to yield the 2-6-η-4-hydroxy-1-oxo-2,3,5,6-tetramethylcyclohexadienyl complex [Co(C₅Me₅)(C₁₀H₁₃O₂)BF₄ (II) and diprotonation to yield the η⁶-6-1,4-dihydroxy-2,3,5,6-tetramethylbenzene complex [Co(C₅Me₅)(C₁₀H₁₄O₂)] (BF₄)₂ (III). Methylation of complex I with MeI/AgPF₆ gives the 2---6-η-4-methoxy-1-oxo-2,3,5,6-tetramethylcyclohexadienyl complex [Co(C₅Me₅)(C₁₁H₁₅O₂])PF₆ (IV). In trifluoroacetic acid solution complex IV is protonated to form the η⁶-1-hydroxy-4-methoxy-2,3,5,6-tetramethylbenzene cation [Co(C₅Me₅)-(C₁₁H₁₆O₂)]²⁺     

Synthesis,Structure, and Reactivity of RuII Complexes with Trimethylsilylethinylamidinate Ligands

The mononuclear amidinate complexes [(η⁶‐cymene)‐RuCl( 1a )] ( 2 ) and [(η⁶‐C₆H₆)RuCl( 1b )] ( 3 ), with the trimethylsilyl‐ethinylamidinate ligands [Me₃SiC≡CC(N‐c‐C₆H₁₁)₂]^– ( 1a^– ) and[Me₃SiC≡CC(N‐i‐C₃H₇)₂]^– ( 1b^– ) were synthesized in high yields by salt metathesis. In addition, the related phosphane complexes[(η⁵‐C₅H₅)Ru(PPh₃)( 1b )] ( 4a ) [(η⁵‐C₅Me₅)Ru(PPh₃)( 1b )] ( 4b ), and [(η⁶‐C₆H₆)Ru(PPh₃)( 1b )](BF₄) ( 5 ‐BF₄) were prepared by ligand exchange reactions. Investigations on the removal of the trimethyl‐silyl group using [Bu₄N]F resulted in the isolation of [(η⁶‐C₆H₆)Ru(PPh₃){(N‐i‐C₃H₇)₂CC≡CH}](BF₄) ( 6 ‐BF₄) bearing a terminal alkynyl hydrogen atom, while 2 and 3 revealed to yield intricate reaction mixtures. Compounds 1a / b to 6 ‐BF₄ were characterized by multinuclear NMR (¹H, ¹³C, ³¹P) and IR spectroscopy and elemental analyses, including X‐ray diffraction analysis of 1b , 2 , and 3 .     

“Constrained geometry” catalysts of the rare-earth metals for the hydrosilylation of olefins

A series of yttrium and lutetium alkyl complexes [Ln(η⁵-C₅Me₄ZNR′-κN)(CH₂SiMe₃)(THF)_n] (Ln = Y, Lu) was prepared by reacting the tris(trimethylsilylmethyl) precursor [Ln(CH₂SiMe₃)₃(THF)₂] with different linked amino-cyclopentadienes of the type (C₅Me₄H)ZNHR′ (Z = SiMe₂, CH₂SiMe₂; R′ = tBu, Ph, C₆H₄-tBu-4, C₆H₄-nBu-4). The catalytic activity of these alkyl complexes in the hydrosilylation of 1-decene and styrene using PhSiH₃ as reagent was examined under standard conditions. A significant influence of the ligand structure on the catalytic property (turnover frequency, regioselectivity) was observed with the yttrium complex [Y(η⁵-C₅Me₄CH₂SiMe₂NtBu-κN)(CH₂SiMe₃)(THF)] being the most active for 1-decene hydrosilylation.     

Diimido‐, Imido(oxo)‐, Dioxo‐ und Imido(alkyliden)‐Halbsandwich‐Verbindungen über selektive Hydrolyse und α—H‐Abstraktion an Organylkomplexen des sechswertigen Molybdäns und Wolframs

Diimido, Imido Oxo, Dioxo, and Imido Alkylidene Halfsandwich Compounds via Selective Hydrolysis and α—H Abstraction in Molybdenum(VI) and Tungsten(VI) Organyl Complexes Organometal imides [(η⁵‐C₅R₅)M(NR′)₂Ph] (M = Mo, W, R = H, Me, R′ = Mes, tBu) 4 — 8 can be prepared by reaction of halfsandwich complexes [(η⁵‐C₅R₅)M(NR′)₂Cl] with phenyl lithium in good yields. Starting from phenyl complexes 4 — 8 as well as from previously described methyl compounds [(η⁵‐C₅Me₅)M(NtBu)₂Me] (M = Mo, W), reactions with aqueous HCl lead to imido(oxo) methyl and phenyl complexes [(η⁵‐C₅Me₅)M(NtBu)(O)(R)] M = Mo, R = Me ( 9 ), Ph ( 10 ); M = W, R = Ph ( 11 ) and dioxo complexes [(η⁵‐C₅Me₅)M(O)₂(CH₃)] M = Mo ( 12 ), M = W ( 13 ). Hydrolysis of organometal imides with conservation of M‐C σ and π bonds is in fact an attractive synthetic alternative for the synthesis of organometal oxides with respect to known strategies based on the oxidative decarbonylation of low valent alkyl CO and NO complexes. In a similar manner, protolysis of [(η⁵‐C₅H₅)W(NtBu)₂(CH₃)] and [(η⁵‐C₅Me₅)Mo(NtBu)₂(CH₃)] by HCl gas leads to [(η⁵‐C₅H₅)W(NtBu)Cl₂(CH₃)] 14 und [(η⁵‐C₅Me₅)Mo(NtBu)Cl₂(CH₃)] 15 with conservation of the M‐C bonds. The inert character of the relatively non‐polar M‐C σ bonds with respect to protolysis offers a strategy for the synthesis of methyl chloro complexes not accessible by partial methylation of [(η⁵‐C₅R₅)M(NR′)Cl₃] with MeLi. As pure substances only trimethyl compounds [(η⁵‐C₅R₅)M(NtBu)(CH₃)₃] 16 ‐ 18 , M = Mo, W, R = H, Me, are isolated. Imido(benzylidene) complexes [(η⁵‐C₅Me₅)M(NtBu)(CHPh)(CH₂Ph)] M = Mo ( 19 ), W ( 20 ) are generated by alkylation of [(η⁵‐C₅Me₅)M(NtBu)Cl₃] with PhCH₂MgCl via α‐H abstraction. Based on nmr data a trend of decreasing donor capability of the ligands [NtBu]^2— > [O]^2— > [CHR]^2— ? 2 [CH₃]^— > 2 [Cl]^— emerges.     

Chirale Halbsandwich‐Pentamethylcyclopentadienyl‐Rhodium(III)‐ und Iridium(III)‐Komplexe mit Schiff‐Basen aus Salicylaldehyd und α‐Aminosäureestern [1]

Chiral Half‐sandwich Pentamethylcyclopentadienyl Rhodium(III) and Iridium(III) Complexes with Schiff Bases from Salicylaldehyde and α‐Amino Acid Esters [1] A series of diastereoisomeric half‐sandwich complexes with Schiff bases from salicylaldehyde and L‐α‐amino acid esters including chiral metal atoms, [(η⁵‐C₅H₅)(Cl)M(N,O‐Schiff base)], has been obtained from chloro bridged complexes [(η⁵‐C₅Me₅)(Cl)M(μ‐Cl)]₂ (M = Rh, Ir). Abstraction of chloride from these complexes with Ag[BF₄] or Ag[SO₃CF₃] affords the highly sensitive compounds [(η⁵‐C₅Me₅)M(N,O‐Schiff base]⁺X^? (M = Rh, Ir; X = BF₄, CF₃SO₃) to which PPh₃ can be added under formation of [(η⁵‐C₅Me₅)M(PPh₃)(N,O‐Schiff base)]⁺X^?. The diastereoisomeric ratio of the complexes ( 1 ‐ 7 and 11 ‐ 12 ) has been determined from NMR spectra.     

Pd(II) complexes of Schiff bases and their application as catalysts in Mizoroki–Heck and Suzuki–Miyaura cross‐coupling reactions

Schiff bases of 2‐(phenylthio)aniline, (C₆H₅)SC₆H₄N?CR (R = (o‐CH₃)(C₆H₅), (o‐OCH₃)(C₆H₅) or (o‐CF₃)(C₆H₅)), and their palladium complexes (PdLCl₂) were synthesized. The compounds were characterized using ¹H NMR and ¹³C NMR spectroscopy and micro analysis. Also, electrochemical properties of the ligands and Pd(II) complexes were investigated in dimethylformamide–LiClO₄ solution with cyclic and square wave voltammetry techniques. The Pd(II) complexes showed both reversible and quasi‐reversible processes in the ?1.5 to 0.3 V potential range. The synthesized Pd(II) complexes were evaluated as catalysts in Mizoroki–Heck and Suzuki–Miyaura cross‐coupling reactions. Copyright © 2015 John Wiley & Sons, Ltd.     

Structure and bonding in haloarylgallyl complexes of iron, ruthenium and osmium [(η-C5H5)(CO)2M{Ga(X)(Ph)}]: A theoretical study

Density Functional Theory calculations have been performed for the halophenylgallyl complexes of iron, ruthenium and osmium [(η⁵-C₅H₅)(CO)₂M(Ga(X)Ph)] (M = Fe, Ru, Os; X = Cl, Br, I) at the DFT/BP86/TZ2P/ZORA level of theory. The calculated geometry of iron complexes [(η⁵-C₅H₅)(CO)₂Fe(Ga(Cl)Ph)] and [(η⁵-C₅H₅)(CO)₂Fe(Ga(I)Ph)] is in excellent agreement with structurally characterized complexes [(η⁵-C₅H₅)(CO)₂Fe(Ga(Mes^∗)Cl)], [(η⁵-C₅Me₅)(CO)₂Fe(Ga(Mes^∗)Cl)] and [(η⁵-C₅Me₅)(CO)₂Fe(Ga(Mes)I)] (Mes = C₆H₂Me₃-2,4,6; Mes^∗ = C₆H₂^tBu₃-2,4,6). The M-Ga bond distances as well as Mayer bond order of the M-Ga bonds suggest that the M-Ga bonds in these complexes are nearly M-Ga single bond. The π-bonding component of the total orbital contribution is significantly smaller than that of σ-bonding. Thus, in these complexes the Ga(X)Ph ligand behaves predominantly as a σ-donor. The contributions of the electrostatic interaction terms ΔE_elstat are significantly smaller in all gallyl complexes than the covalent bonding ΔE_orb term. The absolute values of the ΔE_Pauli, ΔE_int and ΔE_elstat contributions to the M-Ga bonds increase in both sets of complexes via the order Fe < Ru < Os. In the complexes [(η⁵-C₅H₅)(Me₃P)₂Fe(Ga(X)Ph)] (X = Cl, Br, I), interaction energy as well as bond dissociation energy decrease upon going from X = Cl to X = I.     

Cu(I) and Ru(II) complexes with elemental phosphorus as ligand: Synthesis and properties

New complexes of Cu(I) and Ru(II) with elemental (white) phosphorus (P₄), [Cu(C₅H-i-Pr₄)(η²-P₄)], [Cu(C₅H-i-Pr₄)(μ,η^2:1-P₄)Cu(C₅H-i-Pr₄)], and [Ru(C₅Me₅)(PCy₃)(η²-P₄)Cl], are synthesized with tetraphosphorus molecule as bidentate η²-ligand. The complexes are obtained by reacting elemental phosphorus with the Cu carbonyl(tetraisopropylcyclopentadienyl) complex [Cu(C₅H-i-Pr₄)(CO)] or with Ru(II) (pentamethylcyclopentadienyl)(tricyclohexylphosphine) chloride, [Ru(C₅Me₅)(PCy₃)Cl]. The structures and compositions of the obtained complexes are studied by ¹H, ³¹P NMR method and elemental analysis. The P₄ molecule is connected to Cu(I) and Ru(II) fragments through the P-P edge due to a side coordination.     

Thermal decomposition of dinuclear complexes LM(μ-OOCR)<Subscript>4</Subscript>ML (L is α-substituted pyridine)

The solid-state thermal decomposition of the dinuclear pivalate complexes LM(μ-OOCR)₄ML, both those synthesized earlier (M = Mn^II, Fe^II, or Co^II; L = 2,6-(NH₂)₂C₅H₃N)) and new complexes (M = Cu^II; L = 2,6-(NH₂)₂C₅H₃N or (2-NH₂)(6-CH₃)C₅H₃N), was studied by differential scanning calorimetry and thermogravimetry. The decomposition of the Co^II complexes is accompanied by the aggregation to form the volatile octanuclear complex Co₈(μ₄-O)₂(μ_n-OOCCMe₃)₁₂ (n = 2 or 3), whereas the thermolysis of the Mn^II, Fe^II, and Cu^II complexes is destructive, the phase composition of the decomposition products being substantially dependent on the nature of metal and the α substituent R in the apical organic ligand.     

[Co(g5‐Me5C5)(g3‐tBu2PPCH–CH3)] aus [Co(g5‐Me5C5)(g2‐C2H4)2] und tBu2P–P=P(Me)tBu2

Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes. XVII [1] [Co(g⁵‐Me₅C₅)(g³‐^tBu₂PPCH–CH₃)] from [Co(g⁵‐Me₅C₅)(g²‐C₂H₄)₂] and ^tBu₂P–P=P(Me)^tBu₂ [Co(η⁵‐Me₅C₅)(η³‐^tBu₂PPCH–CH₃)] 1 is formed in the reaction of [Co(η⁵‐Me₅C₅)(η²‐C₂H₄)₂] 2 with ^tBu₂P–P 4 (generated from ^tBu₂P–P=P(Me)^tBu₂ 3 ) by elimination of one C₂H₄ ligand and coupling of the phosphinophosphinidene with the second one. The structure of 1 is proven by ³¹P, ¹³C, ¹H NMR spectra and the X‐ray structure analysis. Within the ligand ^tBu₂P¹P²C¹H–CH₃ in 1 , the angle P1–P2–C1 amounts to 90°. The Co, P1, P2, C1 atoms in 1 look like a „butterfly”︁. The reaction of 2 with a mixture of ^tBu₂P–P=P(Me)^tBu₂ 3 and ^tBu–C?P 5 yields [Co(η⁵‐Me₅C₅){η⁴‐(^tBuCP)₂}] 6 and 1 . While 6 is spontaneously formed, 1 appears only after complete consumption of 5 .     

Übergangsmetall-substituierte acylphosphane und phosphaalkene: XI. Phosphaalkenyl-, disilylphosphido- und diacylphosphidokomplexe des dicarbonylpentamethylcyclopentadienylosmium. Zur kenntnis von [(η5-C5Me5)Os(CO)2]2

The reaction of Os₃(CO)₁₂ with C₅Me₅H in boiling decalin gives the complexes (η⁵-C₅Me₅)(CO)₂OsH and [(η⁵-C₅Me₅)(CO)₂Os]₂. Both compounds were converted into (η⁵-C₅Me₅)(CO)₂OsP(SiMe₃)₂ (III) via the intermediate form (η⁵-C₅-Me₅)(CO)₂OsBr. Complex III was treated with ArC(O)Cl (Ar = Ph, 2,4,6-Me₃C₆H₂) to give mixtures of the phosphaalkenyl complexes (η⁵-C₅Me₅)(CO)₂OsPC(OSiMe₃)(Ar) (IVa, b) and the diacylphosphido complexes (η⁵-C₅Me₅)(CO)₂-OsP[C(O)Ar]₂ (Va, b). Pivaloyl chloride underwent reaction with III to give complex Vc as the only product. The synthesis of the complexes IVa, b includes an E/Z isomerization process.     

Co‐catalyst effects on the thermal stability/activity of N,N,N‐Co ethylene polymerization Catalysts Bearing Fluoro‐Substituted N‐2,6‐dibenzhydrylphenyl groups

The unsymmetrical bis (arylimino)pyridines, 2‐[CMeN{2,6‐{(4‐FC₆H₄)₂CH}₂–4‐t‐BuC₆H₂}]‐6‐(CMeNAr)C₅H₃N (Ar = 2,6‐Me₂C₆H₃ L1 , 2,6‐Et₂C₆H₃ L2 , 2,6‐i‐Pr₂C₆H₃ L3 , 2,4,6‐Me₃C₆H₂ L4 , 2,6‐Et₂–4‐MeC₆H₂ L5 ), each containing one N‐aryl group bedecked with ortho‐substituted fluorobenzhydryl groups, have been employed in the preparation of the corresponding five‐coordinate cobalt (II) chelates, LCoCl₂ ( Co1 – Co5 ); the symmetrical comparator [2,6‐{CMeN(2,6‐(4‐FC₆H₄)₂CH)₂–4‐t‐BuC₆H₂}₂C₅H₃N]CoCl₂ (Co6) is also reported. All cobaltous complexes are paramagnetic and have been characterized by ¹H/¹⁹F NMR spectroscopy, FT‐IR spectroscopy and elemental analysis. The molecular structures of Co3 and Co6 highlight the different degrees of steric protection given to the metal center by the particular N‐aryl group combination. Depending on the aluminoxane co‐catalyst employed to activate the cobalt precatalyst, distinct variations in thermal stability and activity of the catalyst towards ethylene polymerization were exhibited. In particular with MAO, the resultant catalysts reached their optimal performance at 70 °C delivering high activities of up to 10.1 × 10⁶ g PE (mol of Co)^?1 h^?1 with Co1  >  Co4  >  Co2  >  Co5  >  Co3 >>  Co6 . On the other hand, using MMAO, the catalysts operate most effectively at 30 °C but are by comparison less productive. In general, the polyethylenes were highly linear, narrowly disperse and displayed a wide range of molecular weights [M_w range: 18.5–58.7 kg mol^?1 (MAO); 206.1–352.5 kg mol^?1 (MMAO)].     

Indenylvanadium(V)‐Verbindungen. Darstellung,Struktur und NMR‐spektroskopische Untersuchungen

Indenylvanadium(V) Compounds Synthesis, Structure, and NMR Spectroscopic Studies Syntheses of the indenylvanadium(V)compounds are described: ^tC₄H₉N = V(η⁵‐C₉H₇)Cl₂ ( 1 ), ^tC₄H₉N = V(η⁵‐C₉H₇)Br₂ ( 2 ), ^tC₄H₉N = V(η⁵‐C₉H₇)(O^tC₄H₉)Cl ( 3 ), ^tC₄H₉N = V(η¹‐C₉H₇)(O^tC₄H₉)₂ ( 4 ), ^tC₄H₉N = V(η¹‐C₉H₇)₂(O^tC₄H₉) ( 5 ), ^tC₄H₉N = V(η¹‐C₉H₇)(η⁵‐C₅H₅) · (O^tC₄H₉) ( 6 ), ^tC₄H₉N = V(η¹‐C₉H₇)(η⁵‐C₅H₅)(NH^tC₄H₉) ( 7 ). All compounds were totally characterized by spectroscopic methods (MS; ¹H, ¹³C, ⁵¹V NMR), 3 by single crystal X‐ray diffraction. For 6 the presence of the diastereomeres RR/SS and RS/SR was shown by NMR spectroscopy. The chlorovanadate (IV) complex [NHC₄H₉]₂⁺[(^tC₄H₉N)₇V₇ · (μ‐Cl)₁₄Cl₂]^2– has been obtained by decomposition of 1 in solution; the crystal structure indicates a wheel structure with hydrogen bonds between the tert‐butylammonium cations and the complex anion.     

Di-tert-butylcyclopentadienyl complexes of europium and ytterbium: synthesis and crystal structures of (1,3-But 2C5H3)2 Eu·THF, (1,3-But 2C5H3)(C5Me5)Yb·THF, and\left( {1,3 - Bu^t _2 C_5 H_3 } \right)_2 Yb(\mu _2 - Cl)_2 Li(THF)_2

The (1,3-Bu^t ₂C₅H₃)₂Eu·THF complex was prepared by the reaction of 1,3-Bu^t ₂C₅H₃Na with Eul₂ in tetrahydrofuran. The mixed-ligand (1,3-Bu^t ₂C₅H₃)(C₅Me₅)Yb·THF complex was obtained by the reaction of YbI₂ with C₅Me₅Na and 1,3-Bu^t ₂C₅H₃Na. The reaction of 1,3-Bu^t ₂C₅H₃Li with YbCl₃ afforded the ( $\left( {1,3 - Bu^t _2 C_5 H_3 } \right)_2 Yb(\mu _2 - Cl)_2 Li(THF)_2 $ )ate-complex. The structures of the title compounds were established by X-ray diffraction analysis.     

Synthesis, characterization and catalytic behaviour of ansa-zirconocene complexes containing tetraphenylcyclopentadienyl rings: X-ray crystal structures of [Zr{Me2Si(η-C5Ph4)(η-C5H3R)}Cl2] (R = H, Bu)

The ansa-bis(cyclopentadiene) compounds, Me₂Si(C₅HPh₄)(C₅H₄R) (R = H (2); Bu^t (3)), have been prepared by the reaction of C₅HPh₄(SiMe₂Cl) (1) with Na(C₅H₅) or Li(C₅H₄Bu^t), respectively, and transformed to the di-lithium derivatives, Li₂{Me₂Si(C₅Ph₄)(C₅H₃R)} (R = H (4); Bu^t (5)), by the action of n-butyllithium. The ansa-zirconocene complexes, [Zr{Me₂Si(η⁵-C₅Ph₄)(η⁵-C₅H₃R)}Cl₂] (R = H (6); Bu^t (7)), were synthesized from the reaction of ZrCl₄ with 4 or 5, respectively. Compounds 6 and 7 have been tested in the polymerization of ethylene and compared with their methyl-substituted analogues, [Zr{Me₂Si(η⁵-C₅Me₄)(η⁵-C₅H₃R)}Cl₂] (R = H (8); Bu^t (9)). Whilst 8 and 9 are catalytically active, the tetraphenyl-substituted complexes 6 and 7 proved to be inactive in the polymerization of ethylene. This phenomenon has been explained by DFT calculations based on the reaction intermediates in the polymerization processes involving 6 and 7, which showed that the extraction of a methyl group from the zirconocene complex to form the cationic active specie is endothermic and therefore unfavourable.     

Protonation and methylation of η4-2,3,5,6-tetramethyl-1,4-benzoquinone(η5-pentamethylcyclopentadienyl)cobalt

The preparation of the η⁴-4-2,3,5,6-tetramethyl-1,4-benzoquinonecomplex [CO(C₅Me₅)(C₁₀H₁₂O₂)] (I) is reported. Complex I undergoesreversible protonation to yield the 2-6-η-4-hydroxy-1-oxo-2,3,5,6-tetramethylcyclohexadienyl complex [Co(C₅Me₅)(C₁₀H₁₃O₂)BF₄ (II) and diprotonation to yield the η⁶-6-1,4-dihydroxy-2,3,5,6-tetramethylbenzene complex [Co(C₅Me₅)(C₁₀H₁₄O₂)] (BF₄)₂ (III). Methylation of complex I with MeI/AgPF₆ gives the 26-η-4-methoxy-1-oxo-2,3,5,6-tetramethylcyclohexadienyl complex [Co(C₅Me₅)(C₁₁H₁₅O₂])PF₆ (IV). In trifluoroacetic acid solution complex IV is protonated to form the η⁶-1-hydroxy-4-methoxy-2,3,5,6-tetramethylbenzene cation [Co(C₅Me₅)-(C₁₁H₁₆O₂)]²⁺     

Study of half-sandwich platinum group metal complexes bearing dpt-NH2 ligand

A quite general approach for the preparation of η⁵-and η⁶-cyclichydrocarbon platinum group metal complexes is reported. The dinuclear arene ruthenium complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ (arene = C₆H₆, C₁₀H₁₄ and C₆Me₆) and η⁵-pentamethylcyclopentadienyl rhodium and iridium complexes [(η⁶-C₅Me₅)M(μ-Cl)Cl]₂ (M = Rh, Ir) react with 2 equiv. of 4-amino-3,5-di-pyridyltriazole (dpt-NH₂) in presence of NH₄PF₆ to afford the corresponding mononuclear complexes of the type [(η⁶-arene)Ru(dpt-NH₂)Cl]PF₆ {arene = C₁₀H₁₄ (1), C₆H₆ (2) and C₆Me₆ (3)} and [(η⁶-C₅Me₅)M(dpt-NH₂)Cl]PF₆ {M = Rh (4), Ir (5)}. However, the mononuclear η⁵-cyclopentadienyl analogues such as [(η⁵-C₅H₅)Ru(PPh₃)₂Cl], [(η⁵-C₅H₅)Os(PPh₃)₂Br], [(η⁵-C₅Me₅)Ru(PPh₃)₂Cl] and [(η⁵-C₉H₇)Ru(PPh₃)₂Cl] complexes react in presence of 1 equiv. of dpt-NH₂ and 1 equiv. of NH₄PF₆ in methanol yielded mononuclear complexes [(η⁵-C₅H₅)Ru(PPh₃)(dpt-NH₂)]PF₆ (6), [(η⁵-C₅H₅)Os(PPh₃)(dpt-NH₂)]PF₆ (7), [(η⁵-C₅Me₅)Ru(PPh₃)(dpt-NH₂)]PF₆ (8) and [(η⁵-C₉H₇)Ru(PPh₃)(dpt-NH₂)]PF₆ (9), respectively. These compounds have been totally characterized by IR, NMR and mass spectrometry. The molecular structures of 4 and 6 have been established by single crystal X-ray diffraction and some of the representative complexes have also been studied by UV–Vis spectroscopy.     

Stable N‐Heterocyclic Carbene Adducts of Arylchlorosilylenes and Their Germanium Homologues

The first N‐heterocyclic carbene adducts of arylchlorosilylenes are reported and compared with the homologous germanium compounds. The arylsilicon(II) chlorides SiArCl(Im‐Me₄) [Ar=C₆H₃‐2,6‐Mes₂ (Mes=C₆H₂‐2,4,6‐Me₃), C₆H₃‐2,6‐Trip₂ (Trip=C₆H₂‐2,4,6‐iPr₃)] were obtained selectively on dehydrochlorination of the arylchlorosilanes SiArHCl₂ with 1,3,4,5‐tetramethylimidazol‐2‐ylidene (Im‐Me₄). The analogous arylgermanium(II) chlorides GeArCl(Im‐Me₄) were prepared by metathetical exchange of GeCl₂(Im‐Me₄) with LiC₆H₃‐2,6‐Mes₂ or addition of Im‐Me₄ to GeCl(C₆H₃‐2,6‐Trip₂). All compounds were fully characterized. Density functional calculations on ECl(C₆H₃‐2,6‐Trip₂)(Im‐Me₄), where E=Si, Ge, at different levels of theory show very good agreement between calculated and experimental bonding parameters, and NBO analyses reveal similar electronic structures of the two aryltetrel(II) chlorides. The low gas‐phase Gibbs free energy of bond dissociation of SiCl(C₆H₃‐2,6‐Trip₂)(Im‐Me₄) (Δ${G{{{\circ}\hfill \atop {\rm calcd}\hfill}}}$ =28.1 kJ mol^?1) suggests that the carbene adducts SiArCl(Im‐Me₄) may be valuable transfer reagents of the arylsilicon(II) chlorides SiArCl.