Indenyl Ligand Research Articles

Synthesis, Electronic Structure, and Reactivity of Palladium(I) Dimers with Bridging Allyl, Cyclopentadienyl, and Indenyl Ligands

The synthesis of three new Pd(I) dimers, (μ-All)(μ-Cp){Pd(PEt3)}2 (All = C3H5, Cp = C5H5), (μ-All)(μ-Ind){Pd(PEt3)}2 (Ind = C7H9), and (μ-Cp)(μ-Ind){Pd(PEt3)}2, which contain a combination of bridging allyl, Cp, or indenyl ligands and are all supported by triethylphosphine as the ancillary ligand, is reported. The solid-state geometries, electronic structures, and reactivity of these new compounds have been compared with those of the dimers (μ-All)2{Pd(PEt3)}2 and (μ-Cp)2{Pd(PEt3)}2, which have previously been reported. This work establishes that there are many similarities in the solid-state and electronic structures of complexes containing bridging allyl, Cp, or indenyl ligands. For example, in all cases the bridging ligands bind through three carbon atoms to the two Pd atoms, with only the central carbon atom of the bridging group bound to both metal centers. However, there are also important differences based on the identity of the bridging ligand. As a result of different overlap between the metal ce...

Preparation and Reactivity of Stannyl Complexes of Ruthenium(II) Stabilized by an Indenyl Ligand

Trichlorostannyl complexes Ru(SnCl3)(η5-C9H7)(PPh3)L (1; L = P(OMe)3, P(OEt)3) were prepared by allowing chloro compounds RuCl(η5-C9H7)(PPh3)L to react with SnCl2·2H2O in ethanol. Treatment of compounds 1 with NaBH4 in ethanol yielded the tin trihydride derivatives Ru(SnH3)(η5-C9H7)(PPh3)L (2). The reaction of trichlorostannyl complexes 1 with MgBrMe in diethyl ether afforded the chlorodimethylstannyl derivatives Ru(SnClMe2)(η5-C9H7)(PPh3)L (3), whereas reaction with Li+C≡CPh– in THF yielded the trialkynylstannyl compounds Ru[Sn(C≡CPh)3](η5-C9H7)(PPh3)L (4). Treatment of the trihydridostannyl complexes 2 with the alkyl propiolate HC≡CCOOR led to the trivinylstannyl derivatives Ru[Sn{C(COOR)═CH2}3](η5-C9H7)(PPh3)L (5, 6; R = Me, Et). However, the reaction of [Ru]–SnH3 (2) with the propargylic alcohol HC≡CCPh2OH yielded the alkene H2C═C(H)CPh2OH and the hydride RuH(η5-C9H7)(PPh3)L (7). Treatment of tin trihydride complexes 2 with H2O led to the trihydroxostannyl derivatives Ru[Sn(OH)3](η5-C9H7)(PPh3)L (8). ...

Synthesis, Properties, and Reactivity of Palladium and Nickel NHC Complexes Supported by Combinations of Allyl, Cyclopentadienyl, and Indenyl Ligands

The synthesis of a series of Pd and Ni complexes containing combinations of 2-methylallyl (C4H7), cyclopentadienyl (C5H5, Cp), and indenyl (C7H9, Ind) ligands is reported. In all cases these complexes are supported by the electron-donating N-heterocyclic carbene ligand 1,3-bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene (IPr). The mixed Cp/2-methylallyl complexes (η1-Cp)(η3-2-methylallyl)Pd(IPr) (CpAllPd) and (η5-Cp)(η1-2-methylallyl)Ni(IPr) (CpAllNi) were synthesized through the reaction of IPr with (Cp)(2-methylallyl)M (M = Ni, Pd). The binding mode of the ligands is different in the two complexes, and as a result the total valence electron count around the metal is 18 for the Ni complex and only 16 for the Pd species. In the case of Pd, an analogue of CpAllPd containing an indenyl ligand, (η1-Ind)(η3-2-methylallyl)Pd(IPr) (IndAllPd), was synthesized through the reaction of (η3-Ind)Pd(IPr)Cl (IndClPd) with (2-methylallyl)magnesium chloride. The corresponding Ni complex (η5-Ind)(η1-2-methylallyl)Ni(IPr) (IndAllNi) could not be isolated. The binding modes of the ligands in the mixed indenyl/Cp complexes (η1-Ind)(η5-Cp)M(IPr) (M = Ni (IndCpNi), Pd (IndCpPd)) were the same for both Ni and Pd. IndCpPd was prepared through the reaction of IndClPd with NaCp, while IndCpNi was synthesized through the reaction of (η5-Cp)Ni(IPr)Cl (CpClNi) with lithium indenyl. Similarly, the structures of the bis(Cp) complexes (η5-Cp)(η1-Cp)Ni(IPr) (CpCpNi) and (η5-Cp)(η1-Cp)Pd(IPr) (CpCpPd) were identical for the two different metals. In contrast to CpCpPd, which is an 18-electron complex, the related bis(indenyl) Pd complex (η3-Ind)(η1-Ind)Pd(IPr) (IndIndPd) is a 16-electron species, while no Ni analogue of IndIndPd was characterized. Preliminary reactivity studies with electrophiles indicate that, in all systems with mixed ligands, the η1-ligand is nucleophilic and reacts selectively. The complexes CpAllPd, CpAllNi, CpCpPd, CpCpNi, IndClPd, IndAllPd, and IndIndPd were characterized by X-ray crystallography.

Synthesis and Characterisation of Sigma‐ and Pi‐Bonded Metallaphosphacarboranes

AbstractTwo new metallaphosphacarboranes have been synthesised from [7, 8‐nido‐CPB9H11]– by deprotonation followed by treatment with a metal fragment. Starting with [HNMe3][7, 8‐nido‐CPB9H11] deprotonation and reaction with a source of {(indenyl)Co}2+ affords the η‐bonded cobaltaphosphacarborane 3‐(η‐C9H7)‐3,1,2‐closo‐CoCPB9H10 (1) the first “half‐sandwich“ 3,1,2‐metallaphosphacarborane. The indenyl ligand conformation in 1 (cisoid between the indenyl bridgehead carbon atoms and cage heteroatoms, with the cage carbon atom lying below the indenyl C–C bond) reveals that the structural trans effect in a phosphacarborane ligand is weakest for carbon and therefore varies in the order B > P > C. Starting with [HNC5H11][7, 8‐nido‐CPB9H11] deprotonation and reaction with half an equivalent of [Ru(p‐cymene)Cl2]2 affords the σ‐bonded ruthenaphosphacarborane 8‐{Ru(p‐cymene)Cl(C5H11N)}‐7, 8‐nido‐CPB9H11 (2), the first example of a molecule with a phosphacarborane σ‐bonded to a metal to be crystallographically characterised.

Synthesis, characterization, and styrene polymerization catalysis of pyridyl-functionalized indenyl rare earth metal bis(silylamide) complexes

Amine elimination of rare earth metal tris(silylamide) complexes Ln[N(SiHMe2)2]3(THF)2 with 1 equiv of the pyridyl-functionalized indenyl ligand C9H7CMe2CH2C5H4N-α afforded the neutral mono-indenyl-ligated rare earth metal bis(silylamide) complexes (C9H6CMe2CH2C5H4N-α)Ln[N(SiHMe2)2]2 (Ln = Sc (1), Y (2), Nd (3)) in 70–82% isolated yields. These complexes were characterized by elemental analysis, FT-IR, NMR, and X-ray single crystal structural diffraction. X-ray determination showed that the metal centers are coordinated by one indenyl ring, one nitrogen atom from the pendent pyridyl group, and two amide groups to form a distorted tetrahedral geometry. In the presence of excess AliBu3 and on activation with 1 equiv of [Ph3C][B(C6F5)4] in toluene, 1–3 became active for syndiospecific polymerization of styrene in toluene at room temperature.

Rare earth metal bis(silylamide) complexes bearing pyridyl-functionalized indenyl ligand: Synthesis, structure and performance in the living polymerization ofl-lactide and rac-lactide

Amine elimination of rare earth tris(silylamide) complexes Ln[N(SiHMe(2))(2)](3)(THF)(2) (Ln = La, Sm, Er, Lu) with 1 equiv. of the pyridyl-functionalized indenyl ligand C(9)H(7)CMe(2)CH(2)C(5)H(4)N-α afforded a series of neutral mono-indenyl-ligated rare earth metal bis(silylamide) complexes (C(9)H(6)CMe(2)CH(2)C(5)H(4)N-α)Ln[N(SiHMe(2))(2)](2) (Ln = La (1), Sm (2), Er (3), Lu (4)) in 83-87% isolated yields. Reaction of La[N(SiHMe(2))(2)](3)(THF)(2) with 2 equivalents of C(9)H(7)CMe(2)CH(2)C(5)H(4)N-α provided the neutral bis(indenyl) lanthanum mono(silylamide) complex (C(9)H(6)CMe(2)CH(2)C(5)H(4)N-α)(2)LaN(SiHMe(2))(2) (5). These complexes were characterized by elemental analysis, FT-IR and NMR (except for 3 for the strong paramagnetic property of the central metal). X-ray single crystal structural diffraction showed that 1-4 are isostructural and the central metals are four-coordinated by one indenyl ring, one nitrogen atom from the pendant pyridyl group, and two amide groups to form a distorted tetrahedral geometry; while the central metal in 5 is five-coordinated by two indenyl rings, two nitrogen atoms from the pendant pyridyl groups, and one amide group to adopt a distorted pyramidal geometry, if the indenyl ring is regarded as occupying an independent vertex. The monoanionic pyridyl-functionalized indenyl ligand is bonded to the central metal in η(5)/κ(1) constrained geometry configuration (CGC) mode. 1-4 are highly active for the ring-opening polymerization of L-lactide and rac-lactide. In the presence of 2 equivalents of benzyl alcohol, 1 shows high activity toward L-lactide and rac-lactide in a living fashion.

Structural and spin diversity of M(indenyl)2 transition-metal complexes: a DFT investigation

Full geometry optimization has been carried out for all the low-energy isomers of M(indenyl)2 (M = Sc–Ni, Y–Mo, Re, Ru–Pd). Depending on the electron-richness of the molecule, indenyl adopts various hapticities, some of them involving full or partial coordination of the C6 ring. Our results suggest that a judicious choice of substituents on the ligands should lead to the stabilization of η6-coordinated indenyl ligands. Indenyl is also shown to be quite flexible with respect to the spin ground state. Substituted iron and nickel bis-indenyl species should be characterizable in their triplet state. Thus, both from the point of view of coordination and the metal spin ground state, indenyl and cyclopentadienyl appear to behave quite differently.

Nine-Electron Donor Bridging Indenyl Ligands in Binuclear Iron Carbonyls

The recent (2011) discovery of two nine-electron donor bridging indenyl ligands in the cobalt sandwich complex {η5,η4-Me3Si)2C9H5}2Co2 makes of interest a search for structures of metal carbonyl derivatives with such indenyl ligands. In this connection, density functional theory studies on the binuclear iron carbonyls (C9H7)2Fe2(CO)n (n = 4, 3) predict structures having terminal pentahapto indenyl ligands similar to the experimentally known structures for their cyclopentadienyl analogues (C5H5)2Fe2(CO)n. Thus, the lowest-energy (C9H7)2Fe2(CO)4 structures are singlets with two bridging CO groups. Similarly, the lowest-energy (C9H7)2Fe2(CO)3 structures are triplets with three bridging CO groups and terminal pentahapto indenyl ligands. However, a nine-electron donor bridging indenyl ligand is found in the lowest-energy (C9H7)2Fe2(CO)2 structure, which has an Fe–Fe single bond and two terminal CO groups. Higher-energy (C9H7)2Fe2(CO)2 structures with terminal pentahapto indenyl ligands and short (∼2.1 A) Fe≡Fe...

Flexibility of an Open Indenyl Ligand in Iron(II) Complexes

[FeI2(thf)2] was sequentially treated with Li(C5Me5) and the potassium salt of the phenylmethallyl (“open indenyl”) ligand oIndMe, leading to selective formation of the half-open ferrocene [(η5-C5Me5)Fe(η5-oIndMe)] (1). A variable-temperature NMR study revealed a barrier of ca. 12 kcal mol–1 for the rotation of the phenyl group. The apparent lability and susceptibility of the oIndMe ligand in 1 to undergo η5–η3 interconversion allowed the preparation of the complexes [(η5-C5Me5)Fe(η3-oIndMe)(L)] (2, L = CO; 3, L = IMe; 4, L = PMe3) by addition of carbon monoxide, 1,3,4,5-tetramethylimidazolin-2-ylidene (IMe), and trimethylphosphine, respectively. The η3-bound phenylmethallyl ligand in these complexes initially adopts an anti orientation with regard to the relative positions of the phenyl and methyl substituents, followed by anti-to-syn isomerization. For L = CO, both isomers could be isolated, and the conversion of anti-2 into syn-2 was monitored by NMR spectroscopy at 35, 50, 65, and 80 °C, affording an ...

Synthesis and Reactivity Studies of Benzo-Substituted Bis(indenyl) Iron and Zirconium Complexes: The Difference a Methyl Group Can Make

The synthesis of the sterically hindered 1,3,4,7-tetrasubstituted indenyl ligand 1,3-(CHMe2)2-4,7-Me2-C9H3 is accomplished via initial preparation of 4,7-dimethylindene and subsequent installation of isopropyl groups on the five-membered ring. Synthesis of the corresponding bis(indenyl) iron complex (η5-C9H3-1,3-(CHMe2)2-4,7-Me2)2Fe (3) and comparison to a bis(indenyl) iron analogue devoid of benzo substituents, (η5-C9H5-1,3-(CHMe2)2)2Fe (4), through variable-temperature NMR studies and electrochemistry, establishes the new ligand as both more sterically demanding and slightly more electron rich. Alkali-metal reduction of (η5-C9H3-1,3-(CHMe2)2-4,7-Me2)2ZrCl2 (5) yields an equilibrium mixture of the η5,η9 sandwich complex 7 and the cyclometalated hydride 8, indicating both that benzo binding is still possible when the six-membered ring is substituted and that ligand activation can be modulated by the choice of substituents, as the η5,η9 zirconium sandwich 9, which lacks methyl groups on the benzo ring, does not cyclometalate under ambient conditions. The reactivity of 8 was explored, demonstrating that the cyclometalated species can act as a source of both Zr(II), via ligand-induced reductive elimination, and Zr(IV), through insertion or σ bond metathesis, depending on the added reagent. Addition of H2 to 8 gives (η5-C9H3-1,3-(CHMe2)2-4,7-Me2)2ZrH2 (17), which upon prolonged thermolysis results in benzo C═C bond insertion into the Zr hydride. The reaction rate in comparison to that of the bis(indenyl) zirconium dihydride analogue 19, without benzo substituents, suggests that the methyl groups on the six-membered ring significantly reduce the rate of intramolecular insertion. These studies show that benzo substitution accomplishes both major intended goals: destabilizing the interaction of the benzo ring with low-valent metals while reducing the rate of insertion of a benzo C═C bond into a metal hydride in high-oxidation-state complexes.

Isomerisation of α-pinene oxide in the presence of indenyl allyl dicarbonyl molybdenum(II) and tungsten(II) complexes

Abstract The indenyl complexes IndM( η 3 -C 3 H 5 )(CO) 2 (M = Mo ( 1 ), W ( 2 )), (IndMe)Mo( η 3 -C 3 H 5 )(CO) 2 ( 3 ) and (IndSiMe 3 )Mo( η 3 -C 3 H 5 )(CO) 2 ( 4 ) display catalytic activity for the isomerisation of α-pinene oxide. Conversion reached 97% after 3 h at 35 °C in the presence of 1 and 1,2-dichloroethane as solvent, giving campholenic aldehyde in 56% yield. Solvent polarity and basicity appear to affect the reaction rate. Whereas the type of substituent on the indenyl ligand does not appear to have a strong impact on catalytic performance, changing the metal centre from Mo ( 1 ) to W ( 2 ) gave a significantly more active catalyst.

How big is a Cp? Cycloheptatrienyl zirconium complexes with bulky cyclopentadienyl and indenyl ligands

A combination of phase-transfer and traditional alkylation strategies has been employed to synthesise sterically encumbered 1,3-di(cyclohexyl) and 1,3-di(tert-butyl) substituted indenes in multi-gram quantities. These indenyl ligands and sterically demanding alkyl cyclopentadienyl ligands have been used to prepare a series of [(η(7)-C(7)H(7))Zr(η(5)-L)] (L = Cp and Ind) complexes by straightforward salt metathesis between [(η(7)-C(7)H(7))ZrCl(tmeda)] and the corresponding sodium indenide or cyclopentadienide. All of these Zr complexes have been characterized by elemental analysis, NMR spectroscopy and single crystal X-ray diffraction. The structural information derived from these studies was employed to evaluate the steric demand of these ligands in a realistic manner.

Complexes of manganese, iron and cobalt with sterically demanding indenyl ligands

A series of manganese, iron and cobalt complexes bearing sterically demanding 1,3-disubstituted indenyl ligands, 1,3-(Me(3)C)(2)C(9)H(5) (Ind(tBu)) (1) and 1,3-(C(6)H(11))(2)C(9)H(5) (Ind(cHexyl)) (2), has been prepared. These complexes have been fully characterised by various spectroscopic techniques, elemental analysis, and X-ray diffraction experiments. In addition the electronic and steric properties of these ligands have been evaluated. Although the cone angles and electronic properties are similar to 1,2,4-(Me(3)C)(3)C(5)H(2) (Cp'), indenyl iron half-sandwich complexes are only stable at low temperature. This has been demonstrated for 1-FeI using suitable trapping experiments such as CO or NaCp' addition to yield 1-Fe(CO)(2)I and 1-FeCp', respectively. Overall the metal-ligand bonds in these indenyl compounds are weaker than in the corresponding cyclopentadienyl derivatives. In addition, the bis(indenyl)manganese complexes, 1-Mn and 2-Mn, are high-spin, as established by solid state magnetic susceptibility studies in the temperature range 2-300 K.

Photocatalytic properties of new cyclopentadienyl and indenyl rhodium(I) carbonyl complexes with water-soluble 1,3,5-triaza-7-phosphaadamantane (PTA) and tris(2-cyanoethyl)phosphine

Reactions of [( η 5-R)Rh(CO) 2] (R = cp, ind) with water-soluble phosphines (L = 1,3,5-triaza-7-phosphaadamantane and tris(2-cyanoethyl)phosphine) give the new rhodium(I) complexes of the types [Rh( η 5-cp)(CO)(PTA)] ( 1), [Rh( η 5-cp)(CO)(P(CH 2CH 2CN) 3)] ( 2), [Rh( η 5-ind)(CO)(PTA)] ( 3) and [Rh( η 5-ind)(CO)(P(CH 2CH 2CN) 3)] ( 4) in isolated yields of 52–75%. All these compounds have been fully characterized by IR, 1H, 31P{ 1H} and 13C{ 1H} NMR, FAB-MS spectroscopies and elemental analyses. Reactivity for the substitution of phosphine is greater for [( η 5-ind)Rh(CO)(L)] comparing to [( η 5-cp)Rh(CO)(L)] because of a flexibility of the indenyl ligand to undergo facile η 5– η 3 coordinative isomerizations. The obtained complexes are active catalyst precursors for the dehydrogenation of propan-2-ol, octane and cyclooctane under photoassisted conditions without any organic hydrogen transfer acceptors, giving TOFs of 26–56 using 3 as precatalyst.

1,4-Bis(diphenylphosphanyl)butane-κ2P,P′]chlorido(η5-indenyl)ruthenium(II)

Facile ligand substitution is observed when the ruthenium chloride complex [Ru(η5-C9H7)Cl(PPh3)2] is treated with 1,4-bis­(diphenyl­phosphan­yl)butane in refluxing toluene yielding the title compound, [Ru(C9H7)Cl(C28H28P2)]. The RuII atom has a typical piano-stool coordination, defined by the indenyl ligand, one Cl atom and two phosphanyl P atoms. The Ru—P bond lengths are 2.2502 (9) and 2.2968 (8) Å.

Indenyl Ligands as Supports for Reactive, Low-Valent Cobalt(I) Fragments

Alkali-metal reduction of (η5-C9H5-1,3-(SiMe3)2)2Co (1) in the presence of vinyltrimethylsilane affords the unusual indenyl cobalt(I) dimer 3, where interligand η4-benzo coordination is achieved. Though an aggregate, 3 serves as a ready source of a 14-electron indenyl cobalt(I) equivalent, on the basis of competition experiments between 3 and (η5-C9H5-1,3-(SiMe3)2)Co(COD) (2) with carbon monoxide. The enhanced reactivity of 3 brought about by benzo coordination, relative to a typical donor-ligated source of Co(I), suggests the compound may serve as a promising platform for small-molecule activation and functionalization.

Reaction of Spiro[2.4]hepta-4,6-diene with Molybdenum(II) Indenyl Compounds: Effects of Substitution in the Indenyl Ligand

The series of molybdenum indenyl compounds [(Ind′)Mo(CO)2(NCMe)2][BF4] was prepared, and their reactivity toward spiro[2.4]hepta-4,6-diene was studied. It was observed that the spiro[2.4]hepta-4,6-diene ring opening could be blocked through substitution in the indenyl ring. Hence, the 2-substituted compound [(η5-C9H6Me)Mo(CO)2(NCMe)2][BF4] and 1,3-disubstituted compound [(η5-C9H5tBu2)Mo(CO)2(NCMe)2][BF4] do not produce the usual ansa-compounds but the compounds with η4-bonded spiro[2.4]hepta-4,6-diene [(Ind′)(η4-C5H4(CH2)2)Mo(CO)2][BF4]. The use of 1-substituted compounds [(η5-C9H6R)Mo(CO)2(NCMe)2][BF4] (R = Ph, tBu) or compounds with less sterically demanding substituents in the 1,3-positions [(η5-C9H5Ph2)Mo(CO)2(NCMe)2][BF4] does not block the ring-opening reaction. These compounds give ansa-molybdenocenes [(Ind′)(η5-C5H4CH2-η1-CH2)Mo(CO)][BF4] in a manner similar to that for the unsubstituted analogue. The reaction products were characterized by NMR and IR spectroscopy. Structures of [(η5-C9H5Ph2)Mo(η3...

Synthesis and Crystal Structure of Rare Earth Metal Chlorides Bearing Bridged‐Indenyl Ancillary Ligand

AbstractTwo new rare earth metal chloride complexes supported by a bridged‐indenyl ancillary ligand, [C9H6SiMe2‐ (CH2)2SiMe2C9H6]Ln(µ‐Cl)2Li(TMEDA) [Ln=Y (1), Lu (2)], were synthesized via salt metathesis reaction. Reaction of C9H7SiMe2(CH2)2SiMe2C9H7 with 2 equiv. of n‐butyllithium in hexane at room temperature afforded [C9H6SiMe2‐ (CH2)2SiMe2C9H6]Li2 as white powder in 95% isolated yield. Further treatment of [C9H6SiMe2(CH2)2SiMe2‐ C9H6]Li2 with anhydrous LnCl3 in 1:1 molar ratio in THF/TMEDA at room temperature provided the bridged‐indenyl rare earth metal chlorides 1 and 2 in 86%–89% isolated yields. Both complexes were characterized by FT‐IR spectroscopy, NMR spectroscopy, elemental analysis, and X‐ray single crystal structure analysis. The central metals in both complexes are eight‐coordinated by two indenyl ligands in η5‐fashion, and two chlorine atoms to adopt a distorted tetrahedral geometry.

Catalyst behaviour for 1-pentene and 4-methyl-1-pentene polymerisation for C2-, Cs- and C1-symmetric zirconocenes

1-Pentene and 4-methyl-1-pentene (4M1P) have been polymerised using several C2-symmetric ansa-zirconocene catalysts rac-X(2-R1,4-R2-Ind)2ZrCl2 [X = C2H4, R1 = R2 = H (1); X = SiMe2, R1 = R2 = H (2); X = SiMe2, R1 = Me, R2 = H (3); X = SiMe2, R1 = H, R2 = Ph (4); X = SiMe2, R1 = Me, R2 = Ph (5)] with MAO as cocatalyst. The effects of polymerisation conditions as well as substituents on the indenyl ligand were studied. Except for the poly-1-pentenes synthesized with 3 and 5 at low temperatures, low molecular weight isotactic polymers were generally obtained. Compared to their behaviour in propylene polymerisation, the relative activity and selectivity of catalysts 1–5 are considerably different for 1-pentene and 4M1P polymerisation. Of the five catalysts, 1 and 4 showed the highest activities for both 1-pentene and 4M1P polymerisation, while 5 resulted in the lowest activities, especially for 4M1P polymerisation. Subsequently, a Cs- and several C1-symmetric zirconocenes, (R1)2C(3-R2-Cp)(2,7,-R3-Flu)ZrCl2 (R1 = Me, R2 = R3 = H (6); R1 = R2 = Me, R3 = H (7); R1 = Me, R2 = t-Bu, R3 = H (8); R1 = Me, R2 = R3 = t-Bu (9); R1 = Ph, R2 = t-Bu, R3 = H (10); R1 = Ph, R2 = R3 = t-Bu (11), were tested in 1-pentene and 4M1P polymerisation with MAO as cocatalyst. The effect of substituents on the bridge, the cyclopentadienyl (Cp) and fluorenyl (Flu) ligand, was studied relative to the polymerisation temperature and type of monomer. The molecular weights of the polymers were considerably higher than those of the poly-1-pentenes and P4M1Ps obtained with C2-symmetric zirconocenes (1–5). The catalytic activities and polymer molecular weights strongly depend on the fluorenyl substituent and the bridge, while the type of substituent on the Cp ligand has a strong influence on the tacticity of the polymers.

New cyclopentadienylethylphosphane chelate complexes with unsymmetrical phosphane substitution

The syntheses, characterization, and some reactions of (phosphanylethyl)cyclopentadienyl chelate complexes of cobalt, rhodium, iridium, nickel, and chromium with unsymmetrical substitution at the phosphorus atom are described. The ligand systems were prepared by nucleophilic ring opening of spiro[2.4]hepta-4,6-diene with lithium tert-butylphenylphosphide or lithium tert-butylcyclohexylphosphide. The anionic ligands give the respective chelate complexes by treatment with metal halide reagents. In three cases it was possible to obtain X-ray crystal structure analyses. The cobalt chelate complex undergoes oxidative addition with a dihydrosilane, the reaction results in the formation of products with three stereogenic centers at phosphorus, cobalt, and silicon, which show dynamic behavior as indicated by VTNMR. The rhodium chelate complex undergoes oxidative addition of iodomethane with diastereoselective formation of the respective Rh(III) chelate. While diastereoselectivity caused by a planar chiral indenyl ligand or by a stereogenic carbon center in the chelate backbone has earlier been observed, this is the first case of a stereoinduction by the stereogenic phosphorus ligand. Activation energies for the rotation of cobalt and rhodium chelates have also been determined by VTNMR.