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ABSTRACT: Treatment of Me(2)S·B(C(6)F(5))(n) H(3-n) (n=1 or 2) with ammonia yields the corresponding adducts. H(3)N·B(C(6)F(5))H(2) dimerises in the solid state through N-H···H-B dihydrogen interactions. The adducts can be deprotonated to give lithium amidoboranes Li[NH(2)B(C(6)F(5))(n)H(3-n)]. Reaction of the n=2 reagent with [Cp(2)ZrCl(2)] leads to disubstitution, but [Cp(2)Zr{NH(2)B(C(6)F(5))(2)H}(2)] is in equilibrium with the product of β-hydride elimination [Cp(2)Zr(H){NH(2)B(C(6)F(5))(2)H}], which proves to be the major isolated solid. The analogous reaction with [Cp(2)HfCl(2)] gives a mixture of [Cp(2)Hf{NH(2)B(C(6)F(5))(2)H}(2)] and the N-H activation product [Cp(2)Hf{NHB(C(6)F(5 )(2)H}]. [Cp(2)Zr{NH(2)B(C(6)F(5))(2)H}(2)]·PhMe and [Cp(2)Hf{NH(2)B(C(6)F(5))(2)H}(2)]·4(thf) exhibit β-B-agostic chelate bonding of one of the two amidoborane ligands in the solid state. The agostic hydride is invariably coordinated to the outside of the metallocene wedge. Exceptionally, [Cp(2)Hf{NH(2)B(C(6)F(5))(2)H}(2)]⋅PhMe has a structure in which the two amidoborane ligands adopt an intermediate coordination mode, in which neither is definitively agostic. [Cp(2)Hf{NHB(C(6)F(5))(2)H}] has a formally dianionic imidoborane ligand chelating through an agostic interaction, but the bond-length distribution suggests a contribution from a zwitterionic amidoborane resonance structure. Treatment of the zwitterions [Cp(2)MMe(μ-Me)B(C(6)F(5))(3)] (M=Zr, Hf) with Li[NH(2)B(C(6)F(5))(n)H(3-n)] (n=2) results in [Cp(2) MMe{NH(2)B(C(6)F(5))(2)H}] complexes, for which the spectroscopic data, particularly (1)J(B,H), again suggest β-B-agostic interactions. The reactions proceed similarly for the structurally encumbered [Cp''(2)ZrMe(μ-Me)B(C(6)F(5))(3)] precursor (Cp''=1,3-C(5)H(3)(SiMe(3))(2) , n=1 or 2) to give [Cp''(2)ZrMe{NH(2)B(C(6)F(5))(n)H(3-n)}], both of which have been structurally characterised and show chelating, agostic amidoborane coordination. In contrast, the analogous hafnium chemistry leads to the recovery of [Cp''(2)HfMe(2)] and the formation of Li[HB(C(6)F(5))(3)] through hydride abstraction.
Chemistry 06/2012; 18(28):8647-58. · 5.93 Impact Factor
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ABSTRACT: Treatment of TiCl(NMe(2))(3) with H(3)N·B(C(6)F(5))(3) results in N-H activation and ligand exchange to yield the structurally characterised salt [TiCl(NMe(2))(2)(NMe(2)H)(2)](+)[Ti[triple bond]NB(C(6)F(5))(3)(Cl)(2)(NMe(2)H)(2)](-). Cation exchange with [Me(4)N]Cl, [Ph(4)P]Cl and [(PhCH(2))Ph(3)P]Cl yields the respective ammonium and phosphonium salts of the [Ti[triple bond]NB(C(6)F(5))(3)(Cl)(2)(NMe(2)H)(2)](-) anion. X-ray crystallography reveals that the essential trigonal bipyramidal geometry and composition of the anion is retained in each of these salts despite some minor variations in the Ti-N-B angle and the nature of the interionic interactions. Electronic investigation by DFT calculations confirmed the Ti-N triple bond character implied by the experimentally determined bond length, with the HOMO and HOMO-1 having Ti-N π-bonding character. The dimethylamine ligands of the anion resist substitution by moderate bases but can be displaced by pyridine to give a pentacoordinate anion. In contrast, addition of 2,2'-bipyridyl gives a neutral octahedral complex. Treatment of the pyridine complex with TlCp results in the formation of a four coordinate anionic cyclopentadienyl complex.
Dalton Transactions 03/2012; 41(18):5599-609. · 3.84 Impact Factor
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ABSTRACT: [(Me2S)Au]+ cations, generated from (Me2S)AuCl and AgSbF6 in dichloromethane at 0-20°, 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 obsd. [on SciFinder(R)]
Organometallics 01/2012; 31(7):2534-2537. · 3.96 Impact Factor
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ABSTRACT: Treatment of the tris(pyrazolyl)borate metal triamides Tp'M(NMe(2))(3), where Tp' = (C(3)H(3)N(2))(3)BH (Tp) or (3,5-Me(2)C(3)HN(2))(3)BH (Tp*) and M = Ti, Zr and Hf, with the Brønsted acidic Lewis adduct (C(6)F(5))(3)B·NH(3) in toluene solution leads to the formation of Tp'M(NMe(2))(2){NH(2)B(C(6)F(5))(3)} complexes. The exception to this was the attempted preparation of Tp*Ti(NMe(2))(2){NH(2)B(C(6)F(5))(3)} which was unsuccessful. Where Tp' = Tp and M = Ti and Zr and where Tp' = Tp* and M = Zr the complexes have been characterized by single crystal X-ray diffraction methods, revealing the first examples of octahedral amidoborane complexes of the group 4 metals. Attempts to drive the reactions to completion resulted in competing preferential hydrolysis of the amidoborane group, regenerating (C(6)F(5))(3)B·NH(3).
Dalton Transactions 06/2011; 40(28):7434-41. · 3.84 Impact Factor
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ABSTRACT: Treatment of Cp(2)HfCl(2) with two equivalents of LiNH(2)BH(C(6)F(5))(2) in toluene solution yields Cp(2)Hf{NHBH(C(6)F(5))(2)}, which has been crystallographically characterised. The otherwise base-free [NHBH(C(6)F(5))(2)] complex is stabilised by an agostic interaction.
Chemical Communications 05/2011; 47(20):5870-2. · 6.17 Impact Factor
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ABSTRACT: Compounds of the new tetrafluorophthalimido anion, [C(6)F(4)(CO)(2)N](-), are readily accessible by treatment of tetrafluorophthalimide with either LiNPr(i)(2) or mixtures of NEt(3) and Me(3)ECl (E = Si or Sn), to give C(6)F(4)(CO)(2)N-X (X = Li 3, SiMe(3)4, and SnMe(3)5). The reaction of the trimethylsilyl derivative 4 with AgF leads cleanly to the ion pair complex [Ag(NCMe)(2)][Ag(N(CO)(2)C(6)F(4))(2)] (6·2MeCN), which contains a linear [Ag{N(CO)(2)C(6)F(4)}(2)](-) anion and a tetracoordinate Ag(+) cation. Compound 6 reacts with iodine to give the N-iodo compound C(6)F(4)(CO)(2)NI 7, which crystallises as an acetonitrile adduct. Treatment of 6 with LAuCl affords LAu{N(CO)(2)C(6)F(4)} (L = Ph(3)P 8a, Cy(3)P 8b, or THT 9), whereas the reaction with AuCl in acetonitrile affords the heterobinuclear compound [Ag(MeCN)(2)][Au{N(CO)(2)C(6)F(4)}(2)]·MeCN (10·3MeCN). The tetrafluorophthalimido ligand is not readily displaced by donor ligands; however, the addition of B(C(6)F(5))(3)(Et(2)O) to a diethyl ether solution of 8a leads to the salt [Au(PPh(3))(2)][N{COB(C(6)F(5))(3)}(2)C(6)F(4))] 11. The analogous reaction of (THT)Au{N(CO)(2)C(6)F(4)} with B(C(6)F(5))(3) in toluene in the presence of excess norbornene (nb) gives [Au(nb)(3)][N{COB(C(6)F(5))(3)}(2)C(6)F(4))] 12. Compounds 11 and 12 contain a new non-coordinating phthalimido-bridged diborate anion with O-bonded boron atoms. The crystal structures of compounds 2-11 are reported.
Dalton Transactions 02/2011; 40(5):1079-90. · 3.84 Impact Factor
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ABSTRACT: 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.
04/2010;
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ABSTRACT: The phosphinoborane adduct H(3)P x B(C(6)F(5))(3) can be deprotonated using LiN(SiMe(3))(2) to give the phosphidoborate salt Li[H(2)PB(C(6)F(5))(3)], which was converted to the phosphidodiborates Li[H(2)P{B(C(6)F(5))(3)}(2)] and Li[H(2)P{B(C(6)F(5))(3)}{BH(3)}] by treatment with an equivalent of B(C(6)F(5))(3) or Me(2)S.BH(3), respectively. A series of anions of the form [RR'P{M(C(6)F(5))(3)}{BH(3)}](-), where R = R' = Ph or R= (t)Bu, R' = H, and M = B or Al, were prepared (through treatment of salts Li[RR'P(BH(3))] with the corresponding Lewis acid) and characterized using multinuclear NMR, elemental analysis and X-ray crystallography. The solid state structures of [Li(Et(2)O)(x)][Ph(2)P{M(C(6)F(5))(3)}{BH(3)}] exhibit eta(2)-bonding of the BH(3) group to the cationic lithium center. The attempted preparation of an analogous series with amide cores of the form [R(2)N{B(C(6)F(5))(3)}{BH(3)}](-) proved unsuccessful; among the competing reaction pathways hydride abstraction occurred preferentially to yield Li[HB(C(6)F(5))(3)] and dimers or higher oligomers with the composition (R(2)NBH(2))(n).
Inorganic Chemistry 10/2009; 48(23):11474-82. · 4.60 Impact Factor
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ABSTRACT: The Grignard reagent Ar(F)'MgBr (Ar(F)' = 4-(C(6)F(5))C(6)F(4)) reacts with Me(3)SiCl, Me(2)SiCl(2) and Me(3)SnCl to give the 4-nonafluorobiphenyl group 14 complexes Ar(F)'Me(3)Si, (Ar(F)')(2)Me(2)Si and Ar(F)'Me(3)Sn respectively. Ar(F)'Me(3)Sn undergoes only methyl group exchange when treated with BBr(3), yielding Ar(F)'Me(2)SnBr. The solid state structures of Ar(F)'Me(3)Sn and Ar(F)'Me(2)SnBr have been determined and exhibit the expected distorted tetrahedral geometries at tin. The reaction between three equivalents of Ar(F)'MgBr and BF(3) was not selective, while one equivalent of Ar(F)'MgBr and (Ar(F))(2)BF (Ar(F) = C(6)F(5)) reacted cleanly to give (Ar(F))(2)Ar(F)'B. Treatment of BCl(3) with three equivalents of Ar(F)'Li, prepared at low temperature from the reaction between Ar(F)'Br and n-BuLi, yielded (Ar(F)')(3)B. The molecular structures of the acetonitrile adducts of (Ar(F))(2)Ar(F)'B and (Ar(F)')(3)B closely resemble that of (Ar(F))(3)B.NCMe. During the course of the boron investigations, reaction with adventitious water led to the structural characterization of (Ar(F)')(2)BOH.OH(2) as a hydrogen-bonded dimer. The Grignard reagent reacts selectively with ZnCl(2) in diethyl ether giving first [(Ar(F)')Zn(micro-Cl)(OEt(2))](2) then (Ar(F)')(2)Zn(OEt(2))(2), both of which have been characterised by X-ray diffraction. The corresponding reaction with HgCl(2) requires the use of tetrahydrofuran as the solvent and yields (Ar(F)')(2)Hg(THF)(2).
Dalton Transactions 04/2009; · 3.84 Impact Factor
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ABSTRACT: The ammonia adduct of tris(pentafluorophenyl)boron, (C6F5)3B.NH3, is a potentially tri-functional hydrogen-bond donor. Co-crystallisation with the bases acetonitrile, pyridine, tetrahydrofuran, tetramethylethylenediamine, 15-crown-5, 1,4-diazabicyclo[2.2.2]octane (DABCO), pyrazine and 4,4'-bipyridine results, not in donor exchange, but in the formation of supermolecules assembled through hydrogen bonding to second coordination sphere acceptors. The complexes have been characterised by elemental analysis, multinuclear NMR and single-crystal diffraction methods. The solid-state architectures range in complexity, from the hydrogen bonded pairing of (C6F5)3B.NH3, with a single monodentate acceptor molecule (e.g. MeCN to form (C6F5)3B.NH3.NCMe), through complexation with all three N-H groups to the macrocycle 15-crown-5, to the formation of infinite one-dimensional chains with pyrazine and DABCO, and to two-dimensional networks with the divergent acceptor 4,4'-bipyridine.
Dalton Transactions 01/2009; · 3.84 Impact Factor
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ABSTRACT: The crystalline ion-pair [TiCl(NMe(2))(2)(NMe(2)H)(2)](+)[TiCl(2){NB(C(6)F(5))(3)}(NMe(2)H)(2)](-), in which the anion has a triply bonded nitridoborate ligand, is formed through the multiple activation of H(3)N x B(C(6)F(5))(3) when treated with [Ti(NMe(2))(3)Cl].
Chemical Communications 12/2008; · 6.17 Impact Factor
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ABSTRACT: 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 high diastereoselectivity; the sterically more hindered isomer is produced preferentially. It reacts with CPh3[B(C6F5)4] to afford the ion pair [L′Hf-CH2SiMe3]+[B(C6F5)4]− as two diastereomers that exist in dynamic equilibrium. The rates of site epimerization of this ion pair indicate only small energy differences between the two isomers.
10/2008;
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ABSTRACT: 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)).
Organometallics 10/2008; 27(23):6371-6374. · 3.96 Impact Factor
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ABSTRACT: 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 MeB(C6F5)3− and the B(C6F5)4− compounds increase with increasing ion pair concentration. This acceleration is also seen on addition of excess [Ph3C][B(C6F5)4]. Pulsed-field gradient spin−echo (PGSE) NMR measurements indicated that both [(IPCF)ZrCH2SiMe3+···B(C6F5)4−] and [(SBI)ZrCH2SiMe3+···B(C6F5)4−] were present mainly as ion quadruples in toluene-d8/1,2-F2C6H4 (8/2 in volume) at millimolar concentrations and, notably, their aggregation increased to a similar extent with the addition of an excess of [Ph3C][B(C6F5)4]. The results demonstrate the formation of mixed-ion aggregates of the type {[(L)MR+···X−][CPh3+···X−]n}. However, whereas the site epimerization rates kex of the system (SBI)ZrMe(CH2SiMe3)/[Ph3C][B(C6F5)4] continue to increase linearly with the total ion concentration, for (IPCF)ZrMe(CH2SiMe3)/[Ph3C][B(C6F5)4] mixtures kex reaches a plateau at ca. 400 s−1 (at 20 °C). Measurement of site epimerization rates as a function of ion pair concentration [(A+)x(B+)1−xX−] therefore provides evidence for the existence of a rate-limiting barrier in the IPCF system, while it is absent in others.
Organometallics 09/2008; 27(21):5474–5487. · 3.96 Impact Factor
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ABSTRACT: 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.
03/2008;
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ABSTRACT: The title ionic solid, [Ti(C(2)H(6)N)3(C(2)H(7)N)2][Ti(C(18)BF(15)N)(C(18)H(2)BF(15)N)Cl(C(2)H(7)N)(2)].C(7)H(8), (I), comprises a cation with three dimethylamide ligands in the equatorial plane and two dimethylamine ligands positioned axially in a trigonal-bipyramidal geometry about the central Ti(IV) atom. The anion has a highly distorted octahedral structure. The two dimethylamine ligands are coordinated mutually trans. The chloride is trans to the tris(pentafluorophenyl)boron-amide, while the sixth coordination site is occupied by an ortho-F atom of the tris(pentafluorophenyl)boron-amide group in a trans disposition with respect to the tris(pentafluorophenyl)boron-nitride ligand. The most significant feature of the anion is the presence of an unprecedented terminal Ti[triple-bond]N moiety [1.665 (2) A], stabilized by coordination to B(C(6)F(5))(3), with a Ti[triple-bond]N-B angle of 169.50 (19) degrees.
Acta Crystallographica Section C Crystal Structure Communications 10/2007; 63(Pt 9):m401-4. · 0.52 Impact Factor
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Journal of the American Chemical Society 09/2007; 129(30):9282-3. · 9.91 Impact Factor
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ABSTRACT: Treatment of the homoleptic titanium amides [Ti(NR(2))(4)] (R=Me or Et) with the Brønsted acidic reagent H(3)NB(C(6)F(5))(3) results in the elimination of one molecule of amine and the formation of the four-coordinate amidoborate complexes [Ti(NR(2))(3){NH(2)B(C(6)F(5))(3)}], the identity of which was confirmed by X-ray crystallography. The reaction with [Zr(NMe(2))(4)] proceeds similarly but with retention of the amine ligand to give the trigonal-bipyramidal complex [Zr(NMe(2))(3){NH(2)B(C(6)F(5))(3)}(NMe(2)H)]. Cyclopentadienyl (Cp) amidoborate complexes, [MCp(NR(2))(2){NH(2)B(C(6)F(5))(3)}] (M=Ti, R=Me or Et; M=Zr, R=Me) can be prepared from [MCp(NR(2))(3)] and H(3)NB(C(6)F(5))(3), and exhibit greater thermal stability than the cyclopentadienyl-free compounds. H(3)NB(C(6)F(5))(3) reacts with nBuLi or LiN(SiMe(3))(2) to give LiNH(2)B(C(6)F(5))(3), which complexes with strong Lewis acids to form ion pairs that contain weakly coordinating anions. The attempted synthesis of metallocene amidoborate complexes from dialkyl or diamide precursors and H(3)NB(C(6)F(5))(3) was unsuccessful. However, LiNH(2)B(C(6)F(5))(3) does react with the highly electrophilic reagents [MCp(2)Me(mu-Me)B(C(6)F(5))(3)] to give [MCp(2)Me(mu-NH(2))B(C(6)F(5))(3)] (M=Zr or Hf). Comparison of the molecular structures of the Group 4 amidoborate complexes reveals very similar B--N, Ti--N and Zr--N bond lengths, which are consistent with a description of the bonding as a dative interaction between an {M(L)(n)(NH(2))} fragment and the Lewis acid B(C(6)F(5))(3). Each of the structures has an intramolecular hydrogen-bonding arrangement in which one of the nitrogen-bonded hydrogen atoms participates in a bifurcated FHF interaction to ortho-F atoms.
Chemistry 02/2007; 13(16):4535-47. · 5.93 Impact Factor
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Berichte der deutschen chemischen Gesellschaft 09/2006; 2006(20):4037 - 4041. · 2.94 Impact Factor
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ABSTRACT: 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.
07/2006;
