Mechanistic Investigation of Catalyst‐Transfer Suzuki–Miyaura Condensation Polymerization of Thiophene–Pyridine Biaryl Monomers with the Aid of Model Reactions

We have investigated the requirements for efficient Pd‐catalyzed Suzuki–Miyaura catalyst‐transfer condensation polymerization (Pd‐CTCP) reactions of 2‐alkoxypropyl‐6‐(5‐bromothiophen‐2‐yl)‐3‐(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)pyridine ( 12 ) as a donor–acceptor (D –A) biaryl monomer. As model reactions, we first carried out the Suzuki–Miyaura coupling reaction of X–Py–Th–X′ (Th=thiophene, Py=pyridine, X, X′=Br or I) 1 with phenylboronic acid ester 2 by using tBu₃PPd⁰ as the catalyst. Monosubstitution with a phenyl group at Th‐I mainly took place in the reaction of Br–Py–Th–I ( 1 b ) with 2 , whereas disubstitution selectively occurred in the reaction of I–Py–Th–Br ( 1 c ) with 2 , indicating that the Pd catalyst is intramolecularly transferred from acceptor Py to donor Th. Therefore, we synthesized monomer 12 by introduction of a boronate moiety and bromine into Py and Th, respectively. However, examination of the relationship between monomer conversion and the M_n of the obtained polymer, as well as the matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) mass spectra, indicated that Suzuki–Miyaura coupling polymerization of 12 with (o‐tolyl)tBu₃PPdBr initiator 13 proceeded in a step‐growth polymerization manner through intermolecular transfer of the Pd catalyst. To understand the discrepancy between the model reactions and polymerization reaction, Suzuki–Miyaura coupling reactions of 1 c with thiopheneboronic acid ester instead of 2 were carried out. This resulted in a decrease of the disubstitution product. Therefore, step‐growth polymerization appears to be due to intermolecular transfer of the Pd catalyst from Th after reductive elimination of the Th‐Pd‐Py complex formed by transmetalation of polymer Th–Br with (Pin)B–Py–Th–Br monomer 12 (Pin=pinacol). Catalysts with similar stabilization energies of metal–arene η²‐coordination for D and A monomers may be needed for CTCP reactions of biaryl D–A monomers.     

Investigation of catalyst‐transfer condensation polymerization for the synthesis of n‐type π‐conjugated polymer,poly(2‐dioxaalkylpyridine‐3,6‐diyl)

Kumada‐Tamao coupling polymerization of 6‐bromo‐3‐chloromagnesio‐2‐(3‐(2‐methoxyethoxy)propyl)pyridine 1 with a Ni catalyst and Suzuki‐Miyaura coupling polymerization of boronic ester monomer 2 , which has the same substituted pyridine structure, with ^tBu₃PPd(o‐tolyl)Br were investigated for the synthesis of a well‐defined n‐type π‐conjugated polymer. We first carried out a model reaction of 2,5‐dibromopyridine with 0.5 equivalent of phenylmagnesium chloride in the presence of Ni(dppp)Cl₂ and then observed exclusive formation of 2,5‐diphenylpyridine, indicating that successive coupling reaction took place via intramolecular transfer of Ni(0) catalyst on the pyridine ring. Then, we examined the Kumada‐Tamao polymerization of 1 and found that it proceeded homogeneously to afford soluble, regioregular head‐to‐tail poly(pyridine‐2,5‐diyl), poly(3‐(2‐(2‐(methoxyethoxy)propyl)pyridine) (PMEPPy). However, the molecular weight distribution of the polymers obtained with several Ni and Pd catalysts was very broad, and the matrix‐assisted laser desorption ionization time‐of‐flight mass spectra showed that the polymer had Br/Br and Br/H end groups, implying that the catalyst‐transfer polymerization is accompanied with disproportionation. Suzuki‐Miyaura polymerization of 2 with ^tBu₃PPd(o‐tolyl)Br also afforded PMEPPy with a broad molecular weight distribution, and the tolyl/tolyl‐ended polymer was a major product, again indicating the occurrence of disproportionation. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Influence of the Boron Moiety and Water on Suzuki–Miyaura Catalyst‐Transfer Condensation Polymerization

Although water promotes Suzuki–Miyaura coupling reaction, it also induces side reactions such as deboronation and dehalogenation. Therefore, Suzuki–Miyaura polymerization of triolborate halothiophene monomer 1 with ^tBu₃PPd(o‐tolyl)Br ( 2 ) in dry tetrahydrofuran (THF) is investigated. However, the resultant poly(3‐hexylthiophene) (P3HT) shows a broad molecular weight distribution and uncontrolled polymer ends. Model reactions of a number of boron reagents 3 with 2,5‐dibromothiophene ( 4 ) in the presence or absence of water indicate that intramolecular transfer of the catalyst is hardly affected by the boron moiety of 3 , whereas it is hindered in the absence of water. Indeed, polymerization of 1 with 2 in H₂O/THF affords P3HT with a narrower molecular weight distribution and controlled tolyl/H ends, as compared to the reaction in dry THF.

     

Investigation of Mizoroki‐Heck coupling polymerization as a catalyst‐transfer condensation polymerization for synthesis of poly(p‐phenylenevinylene)

Mizoroki‐Heck coupling polymerization of 1,4‐bis[(2‐ethylhexyl)oxy]‐2‐iodo‐5‐vinylbenzene ( 1 ) and its bromo counterpart 2 with a Pd initiator for the synthesis of poly(phenylenevinylene) (PPV) was investigated to see whether the polymerization proceeds in a chain‐growth polymerization manner. The polymerization of 1 with ^tBu₃PPd(Tolyl)Br ( 10 ) proceeded even at room temperature when 5.5 equiv of Cy₂NMe (Cy = cyclohexyl) was used as a base, but the molecular weight distribution of PPV was broad. The polymerization of 2 hardly proceeded at room temperature under the same conditions. In the polymerization of 1 , PPV with H at one end and I at the other was formed until the middle stage, and the polymer end groups were converted into tolyl and H in the final stage. The number‐average molecular weight (M_n) did not increase until about 90% monomer conversion and then sharply increased after that, indicating conventional step‐growth polymerization. The occurrence of step‐growth polymerization, not catalyst‐transfer chain‐growth polymerization, may be interpreted in terms of low coordination ability of H‐Pd(II)‐X(^tBu₃P) (X = Br or I), formed in the catalytic cycle of the Mizoroki‐Heck coupling reaction, to π‐electrons of the PPV backbone; reductive elimination of H‐X from this Pd species with base would take place after diffusion into the reaction mixture. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 543–551     

Reactions of tBu2P–PLi–PtBu2 with [(Et3P)2MCl2] (M = Ni,Pd, Pt). Synthesis and Properties of [(1,2‐η‐tBu2P=P–PtBu2)M(PEt3)Cl] (M=Ni,Pd)

^tBu₂P–PLi–P^tBu₂·2THF reacts with [cis‐(Et₃P)₂MCl₂] (M = Ni, Pd) yielding [(1,2‐η‐^tBu₂P=P–P^tBu₂)Ni(PEt₃)Cl] and [(1,2‐η‐^tBu₂P=P–P^tBu2)Pd(PEt₃)Cl], respectively. ^tBu₂P– PLi–P^tBu₂ undergoes an oxidation process and the ^tBu₂P–P–P^tBu₂ ligand adopts in the products the structure of a side‐on bonded 1,1‐di‐tert‐butyl‐2‐(di‐tert‐butylphosphino)diphosphenium cation with a short P–P bond. Surprisingly, the reaction of ^tBu₂P–PLi–P^tBu₂·2THF with [cis‐(Et₃P)₂PtCl₂] does not yield [(1,2‐η‐^tBu₂P=P–P^tBu₂)Pt(PEt₃)Cl].     

Promoting Difficult Carbon–Carbon Couplings: Which Ligand Does Best?

A Pd complex, cis‐[Pd(C₆F₅)₂(THF)₂] ( 1 ), is proposed as a useful touchstone for direct and simple experimental measurement of the relative ability of ancillary ligands to induce C?C coupling. Interestingly, 1 is also a good alternative to other precatalysts used to produce Pd⁰L. Complex 1 ranks the coupling ability of some popular ligands in the order P^tBu₃>o‐TolPEWO‐F≈tBuXPhos>P(C₆F₅)₃≈PhPEWO‐F>P(o‐Tol)₃≈THF≈tBuBrettPhos?Xantphos≈PhPEWO‐H?PPh₃ according to their initial coupling rates, whereas their efficiency, depending on competitive hydrolysis, is ranked tBuXPhos≈P^tBu₃≈o‐TolPEWO‐F>PhPEWO‐F>P(C₆F₅)₃?tBuBrettPhos>THF≈P(o‐Tol)₃>Xantphos>PhPEWO‐H?PPh₃. This “meter” also detects some other possible virtues or complications of ligands such as tBuXPhos or tBuBrettPhos.     

Promoting Difficult Carbon–Carbon Couplings: Which Ligand Does Best?

A Pd complex, cis‐[Pd(C₆F₅)₂(THF)₂] ( 1 ), is proposed as a useful touchstone for direct and simple experimental measurement of the relative ability of ancillary ligands to induce C−C coupling. Interestingly, 1 is also a good alternative to other precatalysts used to produce Pd⁰L. Complex 1 ranks the coupling ability of some popular ligands in the order P^tBu₃>o‐TolPEWO‐F≈tBuXPhos>P(C₆F₅)₃≈PhPEWO‐F>P(o‐Tol)₃≈THF≈tBuBrettPhos≫Xantphos≈PhPEWO‐H≫PPh₃ according to their initial coupling rates, whereas their efficiency, depending on competitive hydrolysis, is ranked tBuXPhos≈P^tBu₃≈o‐TolPEWO‐F>PhPEWO‐F>P(C₆F₅)₃≫tBuBrettPhos>THF≈P(o‐Tol)₃>Xantphos>PhPEWO‐H≫PPh₃. This “meter” also detects some other possible virtues or complications of ligands such as tBuXPhos or tBuBrettPhos.     

Reactions of Lithium Salts of Triphosphanes tBu2P–PLi–PtBu2 and tBu2P–PLi–P(NEt2)2 with Metal Complexes [(R3P)2MCl2] (M = Ni,Pd, Pt,R3P = Et3P,pTol3P,Ph2EtP,iPr3P)

tBu₂P–PLi–PtBu₂ · 2THF reacts with [(R₃P)₂MCl₂] (M = Pt, Pd, Ni; R₃P = Et₃P, pTol₃P, Ph₂EtP, iPr₃P) to yield isomers of [(1,2‐η‐tBu₂P=P–PtBu₂)M(PR₃)Cl], in which the tBu₂P–P–PtBu₂ ligand adopts the arrangement of a side‐on bonded 1,1‐di‐tert‐butyl‐2‐(di‐tert‐butylphosphanyl)diphosphenium cation. tBu₂P–PLi–P(NEt₂)₂ · 2THF reacts with [(R₃P)₂MCl₂] but does not form complexes with a tBu₂P–P–P(NEt₂)₂ moiety, however, splitting of a P–P(NEt₂)₂ bond of the parent triphosphane takes place.     

Aryl Phosphine Nickel(II) and Palladium(II) Complexes with N,O‐Amino‐carboxylate Chelate Ligands [(Aryl)(R3P)M(N,O‐α‐aminocarboxylate)](M = Ni,Pd). Catalysts for the Polymerization of Olefins

The title complexes [(Aryl)(R₃P)M(N,O‐α‐aminocarboxylate)] (M = Ni, Pd) were synthesized by reaction of [(o‐tolyl)(Ph₃P)₂NiBr] or of [(p‐Me₃CC₆H₄)(o‐tolyl₃P)Pd(μ‐Br)]₂ with the anions of α‐amino acids. The spectroscopic data indicate that the nickel complexes are formed as mixtures of isomers, whereas for the palladium complexes only one isomer is observed. The complex [(o‐tolyl)(Ph₃P)Ni(glycinate)] is – in the presence of AlEt₃ – a highly active catalyst for the polymerization of ethylene [up to 1800 kg PE / (mol Ni·h)] and gives polymers with remarkably high molecular weights (up to 900.000 g/mol) and with few branchings.     

Reaction of Frustrated Lewis Pairs with Ketones and Esters

The frustrated Lewis pair (FLP) Mes₂PCH₂CH₂B(C₆F₅)₂ ( 1 ) reacts with an enolizable conjugated ynone by 1,4‐addition involving enolate tautomerization to give an eight‐membered zwitterionic heterocycle. The conjugated endione PhCO‐CH?CH‐COPh reacts with the intermolecular FLP tBu₃P/B(C₆F₅)₃ by a simple 1,4‐addition to an enone subunit. The same substrate undergoes a more complex reaction with the FLP 1 that involves internal acetal formation to give a heterobicyclic zwitterionic product. FLP 1 reacts with dimethyl maleate by selective overall addition to the C?C double bond to give a six‐membered heterocycle. It adds analogously to the triple bond of an acetylenic ester to give a similarly structured six‐membered heterocycle. The intermolecular FLP P(o‐tolyl)₃/B(C₆F₅)₃ reacts analogously with acetylenic ester by trans‐addition to the carbon–carbon triple bond. An excess of the intermolecular FLP tBu₃P/B(C₆F₅)₃, which contains a more nucleophilic phosphane, reacts differently with acetylenic ester examples, namely by O? C(alkyl) bond cleavage to give the {R‐CO₂[B(C₆F₅)₃]₂^?}[alkyl‐PtBu₃⁺] salts. Simple aryl or alkyl esters react analogously by using the borane‐stabilized carboxylates as good leaving groups. All essential products were characterized by X‐ray diffraction.     

Synthesis and solid‐state structures of t‐Bu3Ga–EPh3 Lewis acid–base adducts

Three Lewis acid–base adducts t‐Bu₃Ga–EPh₃ (E = P 1 , As 2 , Sb 3 ) were synthesized by reactions of Ph₃E and t‐Bu₃Ga and characterized by heteronuclear NMR (¹H, ¹³C (³¹P)) and IR spectroscopy, elemental analysis and single crystal X‐ray diffraction. Their structural parameters are discussed and compared to similar t‐Bu₃Ga adducts. The strength of the donor‐acceptor interactions within 1 – 3 was investigated in solution by temperature‐dependent ¹H NMR spectroscopy and by quantum chemical calculations.     

Über Bildung und Reaktionen der CH2Li‐Derivate von tBu2P–P=P(CH3)tBu2 und (Me3Si)tBuP–P=P(CH3)tBu2

Formation and Reactions of the CH₂Li‐Derivatives of ^tBu₂P–P=P(CH₃)^tBu₂ and (Me₃Si)^tBuP–P=P(CH₃)^tBu₂ With ⁿBuLi, (Me₃Si)^tBuP–P=P(CH₃)^tBu₂ ( 1 ) and ^tBu₂P–P=P(CH₃)^tBu₂ ( 2 ) yield (Me₃Si)^tBuP–P=P(CH₂Li)^tBu₂ ( 3 ) and ^tBu₂P–P=P(CH₂Li)^tBu₂ ( 4 ), wich react with Me₃SiCl to give (Me₃Si)^tBuP–P=P(CH₂–SiMe₃)^tBu₂ ( 5 ) and ^tBu₂P–P=P(CH₂–SiMe₃)^tBu₂ ( 6 ), respectively. With ^tBu₂P–P(SiMe₃)–P^tBuCl ( 7 ), compound 3 forms 5 as well as the cyclic products [H₂C–P(^tBu)₂=P–P(^tBu)–P^tBu] ( 8 ) and [H₂C–P(^tBu)₂=P–P(P^tBu₂)–P(^tBu)] ( 9 ). Also 3 forms 8 with ^tBuPCl₂. The cleavage of the Me₃Si–P‐bond in 1 by means of C₂Cl₆ or N‐bromo‐succinimide yields (Cl)^tBuP–P=P(CH₃)^tBu₂ ( 10 ) or (Br)^tBuP–P=P(CH₃)^tBu₂ ( 11 ), resp. With LiP(SiMe₃)₂, 10 forms (Me₃Si)₂P–P(^tBu)–P=P(CH₃)^tBu₂ ( 12 ), and Et₂P–P(^tBu)–P=P(CH₃)^tBu₂ ( 13 ) with LiPEt₂. All compounds are characterized by ³¹P NMR Data and mass spectra; the ylide 5 and the THF adduct of 4 additionally by X‐ray structure analyses.     

Reaktionen von tBu2P–P=P(Me)tBu2 mit (Et3P)2NiCl2 und [{η2‐C2H4}Ni(PEt3)2]

Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes. XXIII. Reactions of ^tBu₂P–P=P(Me)^tBu₂ with (Et₃P)₂NiCl₂ and [{η²‐C₂H₄}Ni(PEt₃)₂] ^tBu₂P–P=P(Me)^tBu₂ ( 1 ) forms with (Et₃P)₂NiCl₂ ( 2 ) and Na(Nph) the [μ‐(1,3 : 2,3‐η‐^tBu₂P₄^tBu₂){Ni(PEt₃)Cl}₂] ( 3 ) as main product. Using Na/Hg instead as reducing agent the Ni⁰ compounds [{η²‐^tBu₂P–P}Ni(PEt₃)₂] ( 4 ), [{η²‐^tBu₂P–P=P–P^tBu₂}Ni(PEt₃)₂] ( 5 ) and [(Et₃P)Ni(μ‐P^tBu₂)]₂ ( 6 ) with four‐membered Ni₂P₂ ring result. [{η²‐C₂H₄}Ni(PEt₃)₂] yields with 1 also 4 . The compounds were characterized by ¹H and ³¹P{¹H} NMR investigations and 3 also by a single crystal X‐ray analysis. It crystallizes triclinic in the space group P 1 with a = 1129.4(2), b = 1256.8(3), c = 1569.5(3) pm, α = 72.44(3)°, β = 70.52(3)° and γ = 74.20(3)°.     

Zum Einfluß der PR3‐Liganden auf Bildung und Eigenschaften der Phosphinophosphiniden‐Komplexe [{η2‐tBu2P–P}Pt(PR3)2] und [{η2‐tBu2P1–P2}Pt(P3R3)(P4R′3)]

Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes XXI The Influence of the PR₃ Ligands on Formation and Properties of the Phosphinophosphinidene Complexes [{η²‐^tBu₂P–P}Pt(PR₃)₂] and [{η²‐^tBu₂P¹–P²}Pt(P³R₃)(P⁴R′₃)] (R₃P)₂PtCl₂ and C₂H₄ yield the compounds [{η²‐C₂H₄}Pt(PR₃)₂] (PR₃ = PMe₃, PEt₃, PPhEt₂, PPh₂Et, PPh₂Me, PPh₂ⁱPr, PPh₂^tBu and P(p‐Tol)₃); which react with ^tBu₂P–P=PMe^tBu₂ to give the phosphinophosphinidene complexes [{η²‐^tBu₂P–P}Pt(PMe₃)₂], [{η²‐^tBu₂P–P}Pt(PEt₃)₂], [{η²‐^tBu₂P–P}Pt(PPhEt₂)₂], [{η²‐^tBu₂P–P}Pt(PPh₂Et)₂], [{η²‐^tBu₂P–P}Pt(PPh₂Me)₂], [{η²‐^tBu₂P–P}Pt(PPh₂ⁱPr], [{η²‐^tBu₂P–P}Pt(PPh₂^tBu)₂] and [{η²‐^tBu₂P–P}Pt(P(p‐Tol)₃)₂]. [{η²‐^tBu₂P–P}Pt(PPh₃)₂] reacts with PMe₃ and PEt₃ as well as with ^tBu₂PMe, PⁱPr₃ and P(c‐Hex)₃ by substituting one PPh₃ ligand to give [{η²‐^tBu₂P¹–P²}Pt(P³Me₃)(P⁴Ph₃)], [{η²‐^tBu₂P¹–P²}Pt(P³Ph₃)(P⁴Me₃)], [{η²‐^tBu₂P¹–P²}Pt(P³Et₃)(P⁴Ph₃)], [{η²‐^tBu₂P¹–P²}Pt(P³Me^tBu₂)(P⁴Ph₃)], [{η²‐^tBu₂P¹–P²}Pt(P³ⁱPr₃)(P⁴Ph₃)] and [{η²‐^tBu₂P¹–P²}Pt(P³(c‐Hex)₃)(P⁴Ph₃)]. With ^tBu₂PMe, [{η²‐^tBu₂P–P}Pt(P(p‐Tol)₃)₂] forms [{η²‐^tBu₂P¹–P²}Pt(P³Me^tBu₂)(P⁴(p‐Tol)₃)]. The NMR data of the compounds are given and discussed with respect to the influence of the PR₃ ligands.     

Komplexchemie P‐reicher Phosphane und Silylphosphane. XXV. Bildung und Struktur des [{cyclo‐P3(PtBu2)3}{Ni(CO)2}{Ni(CO)3}]

Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes. XXV. Formation and Structure of [{ cyclo ‐P₃(P^tBu₂)₃}{Ni(CO)₂}{Ni(CO)₃}] ^tBu₂P–P=P(R)^tBu₂ (R = Br, Me) reacts with [Ni(CO)₄] yielding [{cyclo‐P₃(P^tBu₂)₃}{Ni(CO)₂}{Ni(CO)₃}]. The two cis‐^tBu₂P substituents of the cyclotriphosphane, which results from the trimerization of the phosphinophosphinidene ^tBu₂P–P, are coordinating to a Ni(CO)₂ unit forming a five‐membered P₄Ni chelate ring. The trans‐^tBu₂P group is linked to a Ni(CO)₃ unit. The compound crystallizes in the orthorhombic space group Pbca (No. 61) with a = 933.30(5), b = 2353.2(1) and c = 3474.7(3) pm.     

Bildung und Strukturen von [{η2‐tBu2P–P=P–PtBu2}Pt(PR3)2]

Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes. XVIII. Syntheses and Structures of [{η²‐^tBu₂P–P=P–P^tBu₂}Pt(PR₃)₂] ^tBu₂P–P=P(Me)^tBu₂ reacts with [{η²‐C₂H₄} · Pt(PR₃)₂] as well as with [{η²‐^tBu₂P–P}Pt(PR₃)₂] yielding [{η²‐^tBu₂P–P=P–P^tBu₂}Pt(PR₃)₂]; PR₃ = PMe₃ 3 a , PEtPh₂ 3 b , 1/2 dppe 3 c , PPh₃ 3 d , P(p‐Tol)₃ 3 e . All compounds are characterized by ¹H and ³¹P NMR spectra, for 3 b and 3 d also crystal structure determinations were performed. 3 b crystallizes in the triclinic space group P1 (No. 2) with a = 1212.58(7), b = 1430.74(8), c = 1629.34(11) pm, α = 77.321(6), β = 70.469(5), γ = 87.312(6)°. 3 d crystallizes in the triclinic space group P1 (No. 2) with a = 1122.60(9), b = 1355.88(11), c = 2025.11(14) pm, α = 83.824(9), β = 82.498(9), γ = 67.214(8)°.     

Investigation of Suzuki–Miyaura catalyst‐transfer polycondensation of AB‐type fluorene monomer using coordination‐saturated aryl Pd(II) halide complexes as initiators

Novel triarylamine‐based coordination‐saturated aryl Pd(II) halide complexes ligated by PEt₃, PCy₃, and P(o‐tol)₃ were successfully synthesized by direct oxidative addition of aryl halide to the corresponding Pd(0) precursors. Suzuki–Miyaura coupling polymerization of 2‐(7‐halide‐9,9‐dioctylfluoren‐2‐yl)?1,3,2‐dioxaborinane with these Pd(II) complexes as initiators was investigated for the synthesis of poly(fluorene)s with triarylamine end group. Pd(II) complexes with PCy₃ or P(o‐tol)₃ exhibited catalytic activity and realized the catalyst‐transfer polycondensation at 75 °C and room temperature, respectively, while the polymerization using Pd(II) catalyst ligated by PEt₃ did not proceed, which indicated that the bulky phosphine ligands could facilitate the reductive elimination and further promote the polymerization. In addition, the dimeric Pd(II) complex with P(o‐tol)₃ can convert into monomeric Pd(II) intermediate with an open coordination site, which had a higher activity. The end groups of the afforded polyfluorene were analyzed by matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) mass spectrometry, in which the Ar/H end groups are indicative of the catalyst‐transfer polymerization. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1457–1463     

[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 .     

1‐Azaallyl Complexes of NiII,PdII, and TiIII

The metal complexes [Ni{N(Ar)C(R)C(H)Ph}₂) ( 2 ) (Ar = 2,6‐Me₂C₆H₃, R = SiMe₃), [Ti(Cp₂){N(R)C(Bu^t)C(H)R}] ( 3 ), M{N(R)C(Bu^t)C(H)R}I [M = Ni ( 4 a ) or Pd ( 4 b )] and [M{N(R)C(Bu^t)C(H)R}I(PPh₃)] [M = Ni ( 5 a ) or Pd ( 5 b )] have been prepared from a suitable metal halide and lithium precursor of ( 2 ) or ( 3 ) or, alternatively from [M(LL)₂] (M = Ni, LL = cod; M = Pd, LL = dba) and the ketimine RN = C(Bu^t)CH(I)R ( 1 ). All compounds, except 4 were fully characterised, including the provision of X‐ray crystallographic data for complex 5 a .     

Polymerization of norbornene with a pendent sulfonyl fluoride group catalyzed by palladium complex bearing tBu3P ligand

The combination of palladium complex (^tBu₃P)Pd(Me)Cl ( 1 ) and NaB[3,5‐(CF₃)₂C₆H₃]₄ (NaBAr₄) catalyzed homopolymerization of a novel monomer, norbornene (NB) with a pendent 2‐fluorosulfonyltetrafluoroethoxymethyl chain (NBSF). Catalytic activities of 1 /NaBAr₄ were higher than those of previously reported palladium or nickel catalysts, probably, because the palladium center with electron donative ^tBu₃P ligand was barely poisoned by the sulfonyl fluoride coordination. Thus, 1 /NaBAr₄ is the current best catalyst system for NBSF polymerization. The catalyst system also gave copolymers of NB with NBSF. The obtained copolymers have high sulfonyl‐fluoride incorporation and a narrow molecular weight distribution. Present catalyst system could control incorporation ratio of NBSF by changing a feed monomer ratio with slow addition of NB solution. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5133–5141, 2008