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[(Me2S)Au]+ cations, generated from (Me2S)AuCl and AgSbF6 in dichloromethane at 0–20 °C, serve as sources of solvated Au+ (alongside unreactive [Au(SMe2)2]+), which reacts with the methyl-substituted arenes C6Me6–nHn (n = 0–2) with C–H bond cleavage to give the sulfonium salts [C6Me5–nHnCH2SMe2]+. There was no evidence for arene π coordination to Au+ or for the formation of σ-bonded Au–benzyl species. Surprisingly, the reaction of Au+ with CH2Ar2 leads to C–C bond cleavage (Ar = 2,4,6-C6H2Me3). The reactions are highly selective for benzylic C–H and C–C bonds, whereas metalation of the arene ring is not observed.

The borane dimethyl sulfide adduct H3B·SMe2 and the diethyl ether adduct of tris(pentafluorophenyl)borane, (C6F5)3B·OEt2, undergo facile exchange of hydride and pentafluorophenyl ligands, yielding (C6F5)2HB·SMe2 (1) and (C6F5)H2B·SMe2 (2) depending upon the ratio of reagents used. In the presence of excess dimethyl sulfide, both compounds can be isolated as colorless crystals, which have been structurally characterized.

The formation of cationic species relevant to olefin polymerization based on (SBI)HfCl2, Me2C(C5H4)(Flu)HfCl2, Ph2C(C5H4)(Flu)HfCl2, and L′HfCl2 activated by MAO, AlMe3/CPh3[B(C6F5)4], and AlBui3/CPh3[B(C6F5)4] (SBI = rac-Me2Si(Ind)2; L′ = C2H4(Flu)(5,6-C3H6-2-MeInd)) was studied by 1H, 13C, and 19F NMR spectroscopy. Thermally stable heterobinuclear intermediates of the type [LHf(μ-Me)2AlMe2]+[MeMAO]− and [LHf(μ-Me)2AlMe2]+[B(C6F5)4]− were identified when using MAO and AlMe3/CPh3[B(C6F5)4] as activators, respectively. The stability of these species explains the low productivity of hafnocene catalysts in the presence of AlMe3-containing activators, compared to zirconocenes. By contrast, in the ternary systems LHfCl2/AlBui3/CPh3[B(C6F5)4] hydride species were detected that must be responsible for the formation of the highly active sites in olefin polymerization. The ionic hydrido species differ significantly in stability. The formation of the mixed-alkyl complex L′Hf(Me)CH2SiMe3 proceeds with surprisingly h...

We report the first crystallographically characterized dimethylaniline complex of a group 4 metallocene. [(IPCF)ZrMe(NMe2Ph)][B(C6F5)4] shows strongly coordinated NMe2Ph which does not interchange in solution. DFT calculations suggest that the Zr-N bond is 23 kJ mol-1 stronger than the Zr-Me-Zr bond in [{(IPCF)ZrMe}2(µ-Me)][MeB(C6F5)3], the structure of which is also reported (IPCF = Me2C(C5H4)(fluorenyl)).

The mixed-alkyl metallocene complexes (IPCF)M(Me)(CH2SiMe3) (M = Zr, Hf; IPCF = Me2C(C5H4)(C13H8)) were synthesized by the reaction of (IPCF)M(Me)Cl (M = Zr, Hf) with Me3SiCH2MgCl. The crystal structures of (IPCF)Zr(CH2SiMe3)2, (IPCF)HfMe2, and (IPCF)Zr(Me)Cl were determined by X-ray diffraction. The kinetics of site epimerization of the ion pairs (IPCF)M(CH2SiMe3)(μ-Me)B(C6F5)3 and [(IPCF)MCH2SiMe3+···B(C6F5)4−] (M = Zr, Hf) were studied by variable-temperature NMR spectroscopy, while the solution ground-state structures of the ion pairs [LZrCH2SiMe3+···B(C6F5)4−] (L = SBI, IPCF; SBI = rac-Me2Si(Ind)2) were probed experimentally by 19F,1H HOESY NMR spectroscopy and theoretically by DFT and molecular dynamics calculations. They reveal differences in the strength of anion interactions between the SBI and IPCF systems which may be significant for their catalytic activity. The tetraarylborate salts are stabilized by agostic interactions to ligand Si−Me moieties, with Hf > Zr. The exchange rates of both the M...

Treatment of (C6F5)2Zn(toluene) with 2 equiv of a series of benzonitrile or pyridine derivatives yielded the complexes (C6F5)2Zn(L)2 (where L = benzonitrile, 4-(phenyl)benzonitrile, 4-(N-pyrrolyl)benzonitrile, pyridine, 4-(phenyl)pyridine, and 4-(N-pyrrolyl)pyridine). The four-coordinate solution-phase nature of these complexes was confirmed by a series of variable-temperature 19F NMR experiments and comparison to (C6F5)2Zn(2,2′-bipy). The solvent-free solid-state structures of each of the four-coordinate adducts and the toluene solvate of (C6F5)2Zn(NCC6H4C6H5)2 were determined by single-crystal X-ray diffraction and have distorted tetrahedral geometries. Analysis of the crystal packing revealed a preponderance of offset face-to-face homo−aryl and embrace-like interactions over the hetero−aryl, pentafluorophenyl−phenyl, interaction. These aryl−aryl synthons serve to assemble paired, one- and three-dimensional supramolecular architectures.

A series of eight adducts of the form (RR‘R‘ ‘N)2·Zn(C6F5)2 have been prepared through treatment of the Lewis acid Zn(C6F5)2 with 2 equiv of the corresponding amine (R = tBu or CH2Ph, R‘ = R‘ ‘ = H; R = R‘ = Me or CH2Ph, R‘ ‘ = H; R = Me, R‘ = CH2Ph, R‘ ‘ = H; RR‘ = cyclo-C4H8 or cyclo-C5H10, R‘ ‘ = H; R = R‘ = Me, R‘ ‘ = CH2Ph). The solid-state structures of all eight compounds have been elucidated by single-crystal X-ray diffraction. In each case the geometry about the zinc atom is essentially tetrahedral. However, there is considerable variation in the supramolecular architectures in the solid state. A number of types of noncovalent interactions are observed including phenyl−pentafluorophenyl stacking, X−H···F−C contacts, and offset face-to-face contacts between pentafluorophenyl rings, giving rise to one-, two-, and three-dimensional supramolecular structures. In our examples we find that no one intermolecular interaction predominates.

Reactive intermediates in living olefin polymerization over homogeneous catalysts based on bis[N-(3-tert-butylsalicylidene)-2,3,4,5,6-pentafluoroanilinato]titanium(IV) dichloride (L2TiCl2) have been studied. Outer sphere ion pairs [L2TiMe(S)]+[Me-MAO]- and [L2TiMe(S)]+[B(C6F5)4]- (S = solvent molecule), formed by activation of L2TiCl2 with MAO or with AlMe3/[CPh3]+[B(C6F5)4]-, and reactions of these ion pairs with ethene to afford chain-propagating species [L2TiP]+[Me-MAO]- and [L2TiP]+[B(C6F5)4]- (P = growing polymeryl chain) have been characterized by 1H, 13C, and 19F NMR spectroscopy.

The new mixed-alkyl metallocene complexes (SBI)M(Me)CH2SiMe3 (M = Zr, Hf) are accessible by the successive treatment of (SBI)MCl2 with Me3SiCH2MgCl and MeMgCl in toluene (SBI = rac-Me2Si(1-Ind)2). Reaction with B(C6F5)3 or CPh3+[B(C6F5)4]- in toluene or toluene/difluorobenzene affords (SBI)Mδ+(CH2SiMe3)(μ-Me)Bδ-(C6F5)3 and the ion pairs [(SBI)MCH2SiMe3+···B(C6F5)4-], respectively. Both types of compounds are thermally stable in aromatic solvents at ambient temperature. Whereas in the MeB(C6F5)3- complexes the alkyl ligand points away from the metal and tight anion coordination forms the familiar inner-sphere ion pair, in the B(C6F5)4- salts the alkyl ligand adopts a conformation that enables agostic bonding to a γ-CH3 group. Here, and by implication in M-polymeryl species of similar steric requirements, agostic interactions are preferred over anion coordination, leading to an outer-sphere ion pair structure. This alkyl bonding mode retards the −SiMe3 rotation, which for M = Hf is slow on the NMR time scal...

The Schiff base N,N‘-o-phenylenebis(3,5-di-tert-butyl-salicylideneimine) (1; tBu4salophenH2) reacts with 1 equiv of Zr(η5-C5H5)Cl3·DME in the presence of 2.2 equiv of NEt3 in pentane to give the monocyclopentadienyl bis(phenoxo-imino) monochloro zirconium derivative Zr(η5-C5H5)[C6H4-1,2-{NCH(3,5-tBu2C6H2-2-O)}2]Cl (2). Moreover, 2 equiv of the monolithiated reagent derived from 3-tert-butyl-N-ethylsalicylaldimine by reaction with LinBu in hexane reacts at −78 °C with 1 equiv of Zr(η5-C5H5)Cl3·DME in THF to yield the corresponding monocyclopentadienyl bis(phenoxo-imino) monochloro zirconium complex Zr(η5-C5H5)[CH3CH2NCH{(3-tBuC6H3-2-O)}]2Cl (5) after elimination of LiCl. Methylation of 2 with MgClMe in pentane or toluene at −78 °C affords Zr(η5-C5H5)[1,2-C6H4{NCH(3,5-tBu2C6H2-2-O)}{NCH(Me)(3,5-tBu2C6H2-2-O)}] (3) as a result of the reduction of one of the CN bonds of the coligand. The hydrolysis of 3 gives the new organic compound [C6H4{NCH(3,5-tBu2C6H2-2-OH)}{NCH(Me)(3,5-tBu2C6H2-2-OH)}] (4), which was al...

The ansa-borane complex (Me2S)(C6H5)B(C5H4)2ZrCl2 ( 1 ) reacts selectively with 2 equiv of LiC6F5 to give (Me2S)(C6H5)B(C5H4)2Zr(C6F5)2 ( 2 ) and with 3 equiv LiC6F5 to form the borato-bridged complex [Li(Et2O)3][(C6F5)(C6H5)B(C5H4)2Zr(C6F5)2] ( 3a ). The C6F5 groups are exchanged for Me by reaction with AlMe3 to form [Li(Et2O)x][(C6F5)(C6H5)B(C5H4)2ZrMe2] ( 4 ). Treatment of BCl3 with (SiMe3)(SnMe3)C5H4 affords BCl(C5H4SiMe3)2 ( 5 ), which undergoes a dehalosilylation reaction with ZrCl4(Me2S)2 to give Cl(Me2S)B(C5H4)ZrCl2 ( 6 ). The reaction of 6 with LiC6F5 proceeds in a fashion similar to that of 2 , leading first to (Et2O)ClB(C5H4)2Zr(C6F5)2 ( 7 ) and with 5 equiv of LiC6F5 to [Li(Et2O)4][(C6F5)2B(C5H4)2Zr(C6F5)2] ( 9a ) in 28% yield. The yield is improved through the use of C6F5MgBr at 60 °C. The C6F5 groups are readily exchanged for Me through reaction with LiMe to give [Li(Et2O)4][(C6F5)2B(C5H4)2ZrMe2] ( 10a ). Complexes 3 , 9 , and 10 are catalysts for ethene polymerization when activated with MAO or AlBui3/[CPh3][B(C6F5)4].

The (borylcyclopentadienyl)titanium complex (Cp-B)TiCl3 (1; Cp-B = eta(5)-C5H4B(C6F5)(2)) reacts with LiC5H5 (LiCp), LiC5H4SiMe3 (LiCP'), and LiC9H7 (LiInd) to give the titanocene complexes (Cp-B)CpTiCl2 (2), (Cp-B)Cp'TiCl2 (3), and (Cp-B)(Ind)TiCl2 (4), respectively. In contrast to 1, which possesses piano stool geometry with an uncoordinated, trigonal-planar borg moiety, the -B(C6F5)(2) substituents in 2-4 act as intramolecular Lewis acids by coordinating to chloride ligands, with formation of B-Cl-Ti bridges that have relatively short B-Cl and elongated Ti-Cl bonds. The compounds are fluxional, with the -B(C6F5)(2) moiety switching rapidly from one chloride ligand to the other (2: Delta G(double dagger) = 37 kJ mol(-1) (200 K)). Recrystallization of 2 in the presence of traces of moisture afforded (Cp-B)CpTi(mu-OH)Cl (5), with a rigid B-O-Ti chelate arrangement. Treatment of 1 with 1 or 2 equiv of LiHNCMe3 gives the binuclear titanium imido complexes [(Cp-B)TiCl(mu-NCMe3)](2) (7) and [(Cp-B)TiCl(mu-NCMe3). H2NCMe3](2) (8), respectively. These complexes are based on Ti2N2 rings but show no boron-imide interactions. In contrast, the reaction of 2 with LiNHCMe3 affords (Cp-B)CpTi(mu-NHCMe3)Cl (9), which exhibits a constrained-geometry type Cp-B-N arrangement. The crystal structures of 4, 5, 8, and 9 have been determined.

Bis(pentafluorophenyl)boron fluoride (C6F5)2BF·OEt2 (1), readily accessible from BF3·OEt2 and 2 equiv of C6F5MgBr, reacts with fluorenyllithium to give (Flu)B(C6F5)2 (4), while the reaction with indenyllithium leads to the regioisomers 1- and 2-IndB(C6F5)2 5 and 6, which are separated by fractional crystallization. 4 and 5 form crystalline adducts with tert-butylamine. The trimethylsilyl derivatives Flu(SiMe3)B(C6F5)2 (9) and Ind(SiMe3)B(C6F5)2 (10) are similarly prepared. Heating (C6F5)2BF·OEt2 leads to ether cleavage and formation of (C6F5)2BOEt. Treatment of 5 and 6 with Zr(NMe2)4 at room temperature gives indenylzirconium amido half-sandwich complexes; however, the reaction is accompanied by the unexpected exchange of one boron-C6F5 substituent by NMe2, to form 1- and 2-{C9H6B(C6F5)(NMe2)}Zr(NMe2)3. Reaction with SiClMe3 affords the trichlorides 1- and 2-{C9H6B(C6F5)(NMe2)}ZrCl3. The NMe2 substituent reduces the Lewis acidity of boron, so that donor ligands such as THF or DME coordinate exclusively to...

The reaction between NaNH2 and B(C6F5)3 affords the amidodiborate anion [H2N{B(C6F5)3}2]-, the structure of which shows multiple intramolecular NH···F hydrogen bonding. Reaction with HCl affords [H(OEt2)2][H2N{B(C6F5)3}2], while treatment of zirconocene dimethyls with [CPh3][H2N{B(C6F5)3}2] gives highly active alkene polymerization catalysts.

Cation exchange of [Li(THF)4]+[C5H5B(C6F5)3]- with [NEt4][BF4] gives the stable, ether-free salt [NEt4][C5H5B(C6F5)3], which reacts cleanly with Zr(NMe2)4 to afford [NEt4][{C5H4B(C6F5)3}Zr(NMe2)3] in good yield. The triamide is readily converted into the crystallographically characterized dimeric trichloride [NEt4]2[{C5H4B(C6F5)3}Zr(μ-Cl)Cl2]2.