Unusual iron(III) ate complexes stabilized by Li-pi interactions

Several iron(III) complexes incorporating diamidoether ligands are described. The reaction between [Li(2)[RN(SiMe(2))](2)O] and FeX(3) (X=Cl or Br; R=2,4,6-Me(3)Ph or 2,6-iPr(2)Ph) form unusual ate complexes, [FeX(2)Li[RN(SiMe(2))](2)O](2) (2, X=Cl, R=2,4,6-Me(3)Ph; 3, X=Br, R=2,4,6-Me(3)Ph; 4, X=Cl, R=2,6-iPr(2)Ph) which are stabilized by Li-pi interactions. These dimeric iron(III)-diamido complexes exhibit magnetic behaviour characteristic of uncoupled high spin (S= 5/2 ) iron(III) centres. They also undergo halide metathesis resulting in reduced iron(II) species. Thus, reaction of 2 with alkyllithium reagents leads to the formation of iron(II) dimer [Fe[Me(3)PhN(SiMe(2))](2)O](2) (6). Similarly, the previously reported iron(III)-diamido complex [FeCl[tBuN(SiMe(2))](2)O](2) (1) reacts with LiPPh(2) to yield the iron(II) dimer [Fe[tBuN(SiMe(2))](2)O](2) but reaction with LiNPh(2) gives the iron(II) product [Fe(2)(NPh(2))(2)[tBuN(SiMe(2))](2)O] (5). Some redox chemistry is also observed as side reactions in the syntheses of 2-4, yielding THF adducts of FeX(2): the one-dimensional chain [FeBr(2)(THF)(2)](n) (7) and the cluster [Fe(4)Cl(8)(THF)(6)]. The X-ray crystal structures of 3, 5 and 7 are described.     

Osmabenzenes from the reactions of a dicationic osmabenzyne complex

Treatment of the osmabenzyne Os([triple bond]CC(SiMe(3))=C(Me)C(SiMe(3))=CH)Cl(2)(PPh(3))(2) (1) with 2,2'-bipyridine (bipy) and thallium triflate (TlOTf) produces the thermally stable dicationic osmabenzyne [Os([triple bond]CC(SiMe(3))=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)](OTf)(2) (2). The dicationic osmabenzyne 2 reacts with ROH (R = H, Me) to give osmabenzene complexes [Os(=C(OR)CH=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf, in which the metallabenzene ring deviates significantly from planarity. In contrast, reaction of the dicationic complex 2 with NaBH(4) produces a cyclopentadienyl complex, presumably through the osmabenzene intermediate [Os(=CHC(SiMe(3))=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf. The higher thermal stability of [Os(=C(OR)CH=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf relative to [Os(=CHC(SiMe(3))=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf can be related to the stabilization effect of the OR groups on the metallacycle. A theoretical study shows that conversion of the dicationic osmabenzyne complex [Os([triple bond]CC(SiMe(3))=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)](OTf)(2) to a carbene complex by reductive elimination is thermodynamically unfavorable. The theoretical study also suggests that the nonplanarity of the osmabenzenes [Os(=C(OR)CH=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf is mainly due to electronic reasons.     

Anisole-diphenoxide ligands and their zirconium dichloride and dialkyl complexes

Linear triphenol H3[RO3] (2,6-bis(3-tert-butyl-5-methyl-2-hydroxybenzyl)-4-R-phenol; R = Me, tBu) was found to undergo selective mono-deprotonation and mono-O-methylation. Deprotonation of H3[RO3] with 1 equiv of nBuLi resulted in the formation of Li{H2[RO3]}(Et2O)2 (R = Me (1a), tBu (1b)), in which the central phenol unit was lithiated. Treatment of H3[RO3] with methyl p-toluenesulfonate in the presence of K2CO3 in CH3CN gave the corresponding anisol-diphenol H2[RO2O] (2,6-bis(3-tert-butyl-5-methyl-2-hydroxybenzyl)-4-R-anisole; R = Me (2a), tBu (2b)). Reaction of H2[RO2O] with 2 equiv of nBuLi gave the dilithiated derivatives Li2[RO2O]. The lithium salts were reacted with ZrCl4 in toluene/THF to obtain the dichloride complex [RO2O]ZrCl2(thf) (R = Me (3a), tBu (3b)). 3b underwent dimerization along with a loss of THF to generate {[tBuO2O]ZrCl2}2 (4), whereas 4 was dissolved in THF to regenerate the monomer 3b. Alkylation of 3 with MeMgBr, PhCH2MgCl, and Me3SiCH2MgCl gave [MeO2O]ZrMe2(thf) (5), [RO2O]Zr(CH2Ph)2 (R = Me (6a), tBu (6b)), and [tBuO2O]Zr(CH2SiMe3)2 (7), respectively. Reaction of 3b with LiBHEt3 produced the hydride-bridged dimer [Li2(thf)4Cl]{[tBuO3]Zr}2(micro-H)3} (8), in which demethylation of the dianionic [tBuO2O] ligand took place to give the trianionic [tBuO3] ligand. The X-ray crystal structures of 1b, 2a, 3a, 4, 6a, and 7 were reported.     

Study of the Lithiated Phenylacetonitrile Monoanions and Dianions Formed According to the Lithiated Base Used (LHMDS, LDA, or n-BuLi). 2. Alkylation and Deuteriation Mechanism Study by Vibrational and NMR Spectroscopy and Quantum Chemistry Calculations

Mechanisms of alkylation by PhCH(2)Cl or CH(3)I in THF and of deuteriation by DCl (4 N in D(2)O) in THF or THF-toluene of lithiated phenylacetonitrile monoanions and dianions obtained with LHMDS, LDA, or n-BuLi are studied by vibrational and NMR spectroscopy and quantum chemistry calculations. Dialkylation of the three dilithio dianions generated with n-BuLi (2.0-2.7 equiv, THF-hexane) depends on their structure: N-lithio (PhCCNLi)(-)Li(+) and (C,N)-dilithio PhCLiCNLi dianions afford PhCR(2)CN (R = PhCH(2), CH(3)) from the intermediate N-lithio monoalkylated monoanion PhCRCNLi 10; C-lithio dianion (PhCLiCN)(-)Li(+) leads to a carbenoid species, the C-lithio monoalkylated nitrile PhCLiRCN 11, which either eliminates carbene Ph-C?-R and different LiCN species or isomerizes to PhCRCNLi in the presence of LiX (X = Cl, I). Dialkylation or dideuteriation of monoanions (monomers, dimers, and heterodimers [PhCHCNLi·LiR'], R' = (SiMe(3))(2)N, (i-Pr)(2)N) obtained with LHMDS or LDA (2.4 equiv, THF) proceeds via a sequential mechanism involving monometalation-monoalkylation (or monodeuteriation) reactions. Some carbene and (LiCNLi)(+) are also observed, and explained by another mechanism implying the C-lithio monoalkylated monoanion PhCLiRCN 9 in the presence of LiX. These results show the ambiphilic behavior of PhCLiRCN as a carbenoid (11) or a carbanion (9) and the importance of LiX formed in situ in the first alkylation step.     

Synthesis, structure and catalytic activity of alkali metal-free bent-sandwiched lanthanide amido complexes with calix[4]-pyrrolyl ligands

Simple silylamine elimination reactions of calix[4]-pyrrole [R(2)C(C(4)H(2)NH)](4) (R = Me (1), {-(CH(2))(5)-}(0.5) (2)) with 2 equiv. of [(Me(3)Si)(2)N](3)Ln(μ-Cl)Li(THF)(3) (Ln = Nd, Sm, Dy) in reflux toluene, afforded the novel dinuclear alkali metal-free trivalent lanthanide amido complexes (η(5):η(1):η(5):η(1)-R(8)-calix[4]-pyrrolyl){LnN(SiMe(3))(2)}(2) (R = Me, Ln = Nd (3), Sm (4), Dy (5); R = {-(CH(2))(5)-}(0.5), Ln = Nd (6), Sm(7)). The complexes were fully characterized by elemental analyses, spectroscopic analyses and single-crystal X-ray analyses. X-ray diffraction studies showed that each lanthanide metal was supported by bispyrrolyl anions in an η(5) fashion and along with three nitrogen atoms from N(SiMe(3))(2) and two other pyrroyl rings in η(1) modes formed the novel bent-sandwiched lanthanide amido bridged trivalent lanthanide amido complexes, similar to ansa-cyclopentadienyl ligand-supported lanthanide amides with respect to each metal center. The catalytic activities of these organolanthanide complexes as single component l-lactide polymerization catalysts were studied.     

New and versatile routes to zirconium imido dichloride compounds

Reactions of zirconium dialkyl- or bis(amido)-dichloride complexes "[Zr(CH2SiMe3)2Cl2(Et2O)2]" or [Zr(NMe2)2Cl2(THF)2] with primary alkyl and aryl amines are described. Reaction of "[Zr(CH2SiMe3)2Cl2(Et2O)2]" with RNH2 in THF afforded dimeric [Zr2(mu-NR)2Cl4(THF)4](R=2,6-C6H3iPr2 (1), 2,6-C6H3Me2 (2) or Ph (3)), [Zr2(mu-NR)2Cl4(THF)3](R=tBu (5), iPr (6), CH2Ph (7)), or the "ate" complex [Zr2(mu-NC6F5)2Cl6(THF)2{Li(THF)3}2](4, the LiCl coming from the in situ prepared "[Zr(CH2SiMe3)2Cl2(Et2O)2]"). With [Zr(NMe2)2Cl2(THF)2] the compounds [Zr2(mu-NR)2Cl4(L)x(L')y](R=2,6-C6H3iPr2 (8), 2,6-C6H3Me2 (9), Ph (10) or C6F5 (11); (L)x(L')y=(NHMe2)3(THF), (NHMe2)2(THF)2 or undefined), [Zr2(mu-NtBu)2Cl4(NHMe2)3] (12) and insoluble [Zr(NR)Cl2(NHMe2)]x(R=iPr (13) or CH2Ph (14)) were obtained. Attempts to form monomeric terminal imido compounds by reaction of or with an excess of pyridine led, respectively, to the corresponding dimeric adducts [Zr2(mu-2,6-C6H3Me2)2Cl4(py)4] (15) and [Zr2(mu-NtBu)2Cl4(py)3] (16). The X-ray structures of 1, 2, 4, 8, 12 and 15 have been determined.     

Zur reaktion von metall-koordiniertem kohlenmonoxid mit yliden: XI. Einige neuartige η1-vinyl-komplexe des eisens durch deprotonierung kationischer carbenkomplexe mit trimethyl(methylen)phosphoran

Novel η¹-vinyl complexes of the type Cp(CO)(L)FeC(OMe)C(R)R′ (R = R′ = H, Me; R = H, R′ = Me; L = Me₃P, Ph₃P) are obtainied via methylation of the acyl complexes Cp(CO)(L)FeC(O)R (R = Me, Et, i-Pr) with MeOSO₂F and subsequent deprotonation of the resulting carbene complexes [Cp(CO)(L)FeC(OMe)R]SO₃F with the phosphorus ylide Me₃PCH₂. The same procedure can be applied for the synthesis of the pentamethylcyclopentadienyl derivative C₅Me₅(CO)(Me₃P)FeC(OMe)CH₂, while treatment of the hydroxy or siloxy carbene complexes [Cp(CO)(L)FeC(OR)Me]X (R = H, Me₃Si; X = SO₃CF₃) with Me₃CH₂ results in the transfer of the oxygen bound electrophile to the ylidic carbon. Some remarkable spectroscopic properties of the new complexes are reported.     

Vanadium complexes of the N(CH2CH2S)3(3-) and O(CH2CH2S)2(2-) ligands with coligands relevant to nitrogen fixation processes

Vanadium(III) and vanadium(V) complexes derived from the tris(2-thiolatoethyl)amine ligand [(NS3)3-] and the bis(2-thiolatoethyl)ether ligand [(OS2)2-] have been synthesized with the aim of investigating the potential of these vanadium sites to bind dinitrogen and activate its reduction. Evidence is presented for the transient existence of (V(NS3)(N2)V(NS3), and a series of mononuclear complexes containing hydrazine, hydrazide, imide, ammine, organic cyanide, and isocyanide ligands has been prepared and the chemistry of these complexes investigated. [V(NS3)O] (1) reacts with an excess of N2H4 to give, probably via the intermediates (V(NS3)(NNH2) (2a) and (V(NS3)(N2)V(NS3) (3), the V(III) adduct [V(NS3)(N2H4)] (4). If 1 is treated with 0.5 mol of N2H4, 0.5 mol of N2 is evolved and green, insoluble [(V(NS3))n] (5) results. Compound 4 is converted by disproportionation to [V(NS3)(NH3)] (6), but 4 does not act as a catalyst for disproportionation of N2H4 nor does it act as a catalyst for its reduction by Zn/HOC6H3Pri2-2,6. Compound 1 reacts with NR1(2)NR2(2) (R1 = H or SiMe3; R2(2) = Me2, MePh, or HPh) to give the hydrazide complexes [V(NS3)(NNR2(2)] (R2(2) = Me2, 2b; R2(2) = MePh, 2c; R2(2) = HPh, 2d), which are not protonated by anhydrous HBr nor are they reduced by Zn/HOC6H3Pri2-2,6. Compound 2b can also be prepared by reaction of [V(NNMe2)(dipp)3] (dipp = OC6H3Pri2-2,6) with NS3H3. N2H4 is displaced quantitatively from 4 by anions to give the salts [NR3(4)][V(NS3)X] (X = Cl, R3 = Et, 7a; X = Cl, R3 = Ph, 7b; X = Br, R3 = Et, 7c; X = N3, R3 = Bu(n), 7d; X = N3, R3 = Et, 7e; X = CN, R3 = Et, 7f). Compound 6 loses NH3 thermally to give 5, which can also be prepared from [VCl3(THF)3] and NS3H3/LiBun. Displacement of NH3 from 6 by ligands L gives the adducts [V(NS3)(L)] (L = MeCN, nu CN 2264 cm-1, 8a; L = ButNC, nu NC 2173 cm-1, 8b; L = C6H11NC, nu NC 2173 cm-1, 8c). Reaction of 4 with N3SiMe3 gives [V(NS3)(NSiMe3)] (9), which is converted to [V(NS3)(NH)] (10) by hydrolysis and to [V(NS3)(NCPh3)] (11) by reaction with ClCPh3. Compound 10 is converted into 1 by [NMe4]OH and to [V(NS3)NLi(THF)2] (12) by LiNPri in THF. A further range of imido complexes [V(NS3)(NR4)] (R4 = C6H4Y-4 where Y = H (13a), OMe (13b), Me (13c), Cl (13d), Br (13e), NO2 (13f); R4 = C6H4Y-3, where Y = OMe (13g); Cl (13h); R4 = C6H3Y2-3,4, where Y = Me (13i); Cl (13j); R4 = C6H11 (13k)) has been prepared by reaction of 1 with R4NCO. The precursor complex [V(OS2)O(dipp)] (14) [OS2(2-) = O(CH2CH2S)2(2-)] has been prepared from [VO(OPri)3], Hdipp, and OS2H2. It reacts with NH2NMe2 to give [V(OS2)(NNMe2)(dipp)] (15) and with N3SiMe3 to give [V(OS2)(NSiMe3)(dipp)] (16). A second oxide precursor, formulated as [V(OS2)1.5O] (17), has also been obtained, and it reacts with SiMe3NHNMe2 to give [V(OS2)(NNMe2)(OSiMe3)] (18). The X-ray crystal structures of the complexes 2b, 2c, 4, 6, 7a, 8a, 9, 10, 13d, 14, 15, 16, and 18 have been determined, and the 51V NMR and other spectroscopic parameters of the complexes are discussed in terms of electronic effects.     

Synthetic and structural studies of donor-functionalized alkoxy derivatives of gallium

The synthesis of a range of alkyl/chloro-gallium alkoxide and amido/alkoxide compounds was achieved via a series of protonolysis and alcoholysis steps. The initial reaction involved the synthesis of [Me(Cl)Ga{N(SiMe(3))(2)}](2) (1) via methyl group transfer from the reaction of GaCl(3) with two equivalents of LiN(SiMe(3))(2). Reaction of 1 with varying amounts of ROH resulted in the formation of [Me(Cl)Ga(OR)](2) (2, R = CH(2)CH(2)OMe; 3, CH(CH(3))CH(2)NMe(2)), [Me(Cl)Ga{N(SiMe(3))(2)}(μ(2)-OR)Ga(Cl)Me] (4, R = CH(2)CH(2)NMe(2)), or [MeGa(OR)(2)] (5, R = CH(CH(3))CH(2)NMe(2)). Compound 4 represents an intermediate in the formation of dimeric complexes, of the type [Me(Cl)Ga(OR)](2), when formed from compound [Me(Cl)Ga{N(SiMe(3))(2)}](2). A methylgallium amido/alkoxide complex [MeGa{N(SiMe(3))(2)}(OCH(2)CH(2)OMe)](2) (6) was isolated when 2 was further reacted with LiN(SiMe(3))(2). In addition, reaction of 2 with HO(t)Bu resulted in a simple alcohol/alkoxide exchange and formation of [Me(Cl)Ga(O(t)Bu)](2) (7). In contrast to the formation of 1, the in situ reaction of GaCl(3) with one equivalent of LiN(SiMe(3))(2) yielded [Cl(2)Ga{N(SiMe(3))(2)}](2) in low yield, where no methyl group transfer has occurred. Reaction of alcohol with [Cl(2)Ga{N(SiMe(3))(2)}](2) was then found to yield [Cl(2)Ga(OR)](2) (8, R = CH(2)CH(2)NMe(2)), and further reaction of 8 with LiN(SiMe(3))(2) yielded the gallium amido alkoxide complex, [ClGa{N(SiMe(3))(2)}(OR)](2) (9, R = CH(2)CH(2)NMe(2)), similar to 6. The structures of compounds 4, 5, 7, and 8 have been determined by single-crystal X-ray diffraction.     

Synthesis and Crystal Structure of an Ionic Compound [Fe(CN)_6·(PhCH_2NC_9H_7)_4]·12H_2O

A novel ionic compound [Fe(CN)6(PhCH2NC9H7)4]·12H2O (C70H80FeN10O12, Mr = 1309.29) has been synthesized and its structure was characterized by IR, elemental analysis and X-ray diffraction. The compound crystallizes in triclinic, space group P1, with a = 10.968(7), b = 11.466(7), c = 14.077(8) , α = 87.014(7), β = 78.124(7), γ = 72.708(7)o, V = 1654.1(17) 3, Z = 1, Dc = 1.314 g·cm–3, F(000) = 692, μ = 0.298 mm–1, the final R = 0.0519 and wR = 0.1355. The building unit of the title compound consists of four (PhCH2N+C9H7) ions, one [Fe(CN)6]4– anion, and a dozen water molecules. According to the structural analysis, [Fe(CN)6]4– ions are linked together by O–H···O and O–H···N hydrogen bonds, while (PhCH2N+C9H7) and [Fe(CN)6]4– ions interact with each other by electrostatic force to form an ionic compound.     

Deprotonation reactions of zirconium and hafnium amide complexes H2N-M[N(SiMe3)2]3 and subsequent silyl migration from amide -N(SiMe3)2 to imide =NH ligands

Ammonolysis of previously reported Cl-M[N(SiMe3)2]3 (M = Zr, 1a; Hf, 1b) leads to the formation of peramides H2N-M[N(SiMe3)2]3 (M = Zr, 2a; Hf, 2b) which upon deprotonation by LiN(SiMe3)2 or Li(THF)3SiPh2But yields imides Li+(THF)n{HN(-)-M[N(SiMe3)2]3} (M = Zr, 3a; Hf, 3b). One -SiMe3 group in 3a-b undergoes silyl migration from a -N(SiMe3)2 ligand to the imide =NH ligand to give Li+(THF)2{Me3SiN(-)-M[NH(SiMe3)][N(SiMe3)2]2} (M = Zr, 4a; Hf, 4b) containing an imide =N(SiMe3) ligand. The kinetics of the 3a --> 4a conversion was investigated between 290 and 315 K and was first-order with respect to 3a. The activation parameters for this silyl migration are DeltaH++ = 13.3(1.3) kcal/mol and DeltaS++ = -34(3) eu in solutions of 3a (in toluene-d8 with 1.07 M THF) prepared in situ. THF in the mixed solvent promoted the 3a --> 4a reaction. The effect of THF on the rate constants of the conversion has been studied, and the kinetics of the reaction was 3.4(0.6)th order with respect to THF. Crystal and molecular structures of H2N-Zr[N(SiMe3)2]3 (2a) and 4a-b have been determined.     

Synthesis and structural characterization of alkaline-earth-metal bis(amido)silane and lithium oxobis(aminolato)silane complexes

Several of alkaline-earth-metal complexes [(η(2):η(2):μ(N):μ(N)-Li)(+)](2)[{η(2)-Me(2)Si(DippN)(2)}(2)Mg](2-) (4), [η(2)(N,N)-Me(2)Si(DippN)(2)Ca·3THF] (5), [η(2)(N,N)-Me(2)Si(DippN)(2)Sr·THF] (6), and [η(2)(N,N)-Me(2)Si(DippN)(2)Ba·4THF] (7) of a bulky bis(amido)silane ligand were readily prepared by the metathesis reaction of alkali-metal bis(amido)silane [Me(2)Si(DippNLi)(2)] (Dipp = 2,6-i-Pr(2)C(6)H(3)) and alkaline-earth-metal halides MX(2) (M = Mg, X = Br; M = Ca, Sr, Ba, X = I). Alternatively, compounds 5-7 were synthesized either by transamination of M[N(SiMe(3))(2)](2)·2THF (M = Ca, Sr, Ba) and [Me(2)Si(DippNH)(2)] or by transmetalation of Sn[N(SiMe(3))(2)](2), [Me(2)Si(DippNH)(2)], and metallic calcium, strontium, and barium in situ. The metathesis reaction of dilithium bis(amido)silane [Me(2)Si(DippNLi)(2)] and magnesium bromide in the presence of oxygen afforded, however, an unusual lithium oxo polyhedral complex {[(DippN(Me(2)Si)(2))(μ-O)(Me(2)Si)](2)(μ-Br)(2)[(μ(3)-Li)·THF](4)(μ(4)-O)(4)(μ(3)-Li)(2)} (8) with a square-basket-shaped core Li(6)Br(2)O(4) bearing a bis(aminolato)silane ligand. All complexes were characterized using (1)H, (13)C, and (7)Li NMR and IR spectroscopy, in addition to X-ray crystallography.     

[O(S),O=P]型配体修饰的单氯单茂锆催化剂的高温乙烯聚合

以Ph3CB(C6F5)4/iBu3Al作为助催化体系,研究了单氯半茂型催化剂,ClCp′Zr[X-2-R1-4-R2-6-(Ph2P=O)C6H2]2(Cp′=C5H5,a:X=O,R1=Ph,R2=H;b:X=O,R1=F,R2=H;c:X=O,R1=tBu,R2=H;d:X=O,R1=R2=tBu;e:X=O,R1=SiMe3,R2=H;f:X=S,R1=SiMe3,R2=H;Cp′=C5Me5;g:X=O,R1=SiMe3,R2=H)的乙烯高温（50~125 ℃）聚合行为。 结果表明,催化剂a~d可在高温(50~100 ℃)下高效引发乙烯聚合,最佳反应温度为75 ℃。 适当增大R1取代基的位阻或引入吸电子取代基均有利于提高催化活性。 三甲基硅烷基取代的催化剂[WTHZ]e[WTBZ]耐高温性能较催化剂a~d大大提升,在100 ℃时,乙烯聚合活性可达5628 kg/(mol Zr·h)。 金属中心的配位原子及茂环上取代基团的改变对催化活性和聚合物的相对分子质量分布有一定的影响。     

Oxido-bridged di-, tri-, and tetra-nuclear iron complexes bearing bis(trimethylsilyl)amide and thiolate ligands

A series of di-, tri-, and tetra-nuclear iron-oxido clusters with bis(trimethylsilyl)amide and thiolate ligands were synthesized from the reactions of Fe{N(SiMe(3))(2)}(2) (1) with 1 equiv of thiol HSR (R = C(6)H(5) (Ph), 4-(t)BuC(6)H(4), 2,6-Ph(2)C(6)H(3) (Dpp), 2,4,6-(i)Pr(3)C(6)H(2) (Tip)) and subsequent treatment with O(2). The trinuclear clusters [{(Me(3)Si)(2)N}Fe](3)(μ(3)-O){μ-S(4-RC(6)H(4))}(3) (R = H (3a), (t)Bu (3b)) were obtained from the reactions of 1 with HSPh or HS(4-(t)BuC(6)H(4)) and O(2), while we isolated a tetranuclear cluster [{(Me(3)Si)(2)N}(2)Fe(2)(μ-SDpp)](2)(μ(3)-O)(2) (4) as crystals from an analogous reaction with HSDpp. Treatment of a tertrahydrofuran (THF) solution of 1 with HSTip and O(2) resulted in the formation of a dinuclear complex [{(Me(3)Si)(2)N}(TipS)(THF)Fe](2)(μ-O) (5). The molecular structures of these complexes have been determined by X-ray crystallographic analysis.     

A new class of binuclear and trinuclear iron-sulfur clusters derived from bis[bis(trimethylsilyl)amido]iron(II)

The compound Fe[N(SiMe 3) 2] 2 is shown to be a useful precursor to dinuclear and trinuclear iron-sulfur-silylamido complexes by reaction with thiols or thiols and sulfur in tetrahydrofuran (THF) or toluene. Reaction with 1 equiv of p-tolylthiol affords [Fe 2(mu 2-S- p-tol) 2(N(SiMe 3) 2) 2(THF) 2] ( 1); with 0.5 equiv of adamantane-1-thiol, [Fe 2(mu 2-S-1-Ad)(mu 2-N(SiMe 3) 2)(N(SiMe 3) 2) 2] ( 2) is formed. The clusters [Fe 3(mu 3-Q)(mu 2-SR) 3(N(SiMe 3) 2) 3] are available by three methods: (i) self-assembly in the systems Fe[N(SiMe 3) 2] 2/RSH/S or Se [Q = S, R = p-tol ( 3) and 1-Ad ( 5)]; (ii) reaction of 1 with Q = S or Se to yield 3 or [Fe 3Se(S- p-tol) 3(N(SiMe 3) 2) 3] ( 4); (iii) reaction of 2 with 1-AdSH and S to give 5. Structures of 1- 5 are presented. Complexes 1 and 2 contain planar Fe 2S 2 and Fe 2SN rhombs. Clusters 3- 5 contain a mixed-valence Fe 3Q(SR) 3 core with trigonal (cuboidal) geometry. Of known iron-sulfur clusters, these most closely resemble previously reported [Fe 3S(S-R-S) 3] (2-) stabilized by bidentate thiolate ligands. Complexes 1- 5, together with a small set of recently described clusters of nuclearities 2, 4, and 8, constitute a new class of iron-sulfur-silylamido clusters. Complexes 3- 5 constitute a new structure type of mixed-valence iron-sulfur clusters.     

Diversity of new structural types in polynuclear iron chemistry with a tridentate N,N,O ligand

The syntheses, crystal structures, and magnetochemical characterization of four new iron clusters [Fe7O4(O2CPh)11(dmem)2] (1), [Fe7O4(O2CMe)11(dmem)2] (2), [Fe6O2(OH)4(O2CBut)8(dmem)2] (3), and [Fe3O(O2CBut)2(N3)3(dmem)2] (4) (dmemH=Me2NCH2CH2N(Me)CH2CH2OH)=2-{[2-(dimethylamino)ethyl]methylamino}ethanol) are reported. The reaction of dmemH with [Fe3O(O2CR)6(H2O)3](NO3) (R=Ph (1), Me (2), and But (3)) gave 1, 2, and 3, respectively, whereas 4 was obtained from the reaction of 3 with sodium azide. The complexes all possess rare or novel core topologies. The core of 1 comprises two [Fe4(mu3-O)2]8+ butterfly units sharing a common body Fe atom. The core of 2 consists of a [Fe3O3] ring with each doubly bridging O2- ion becoming mu3 by also bridging to a third, external Fe atom; a seventh Fe atom is attached on the outside of this core via an additional mu3-O2- ion. The core of 3 consists of a [Fe4(mu3-O)2]8+ butterfly unit with an Fe atom attached above and below this by bridging O atoms. Finally, the core of 4 is an isosceles triangle bridged by a mu3-O2- ion with a rare T-shaped geometry and with the azide groups all bound terminally. Variable-temperature, solid-state dc, and ac magnetization studies were carried out on complexes 1-4 in the 5.0-300 K range. Fitting of the obtained magnetization (M) vs field (H) and temperature (T) data by matrix diagonalization and including only axial anisotropy (zero-field splitting) established that 1, 2, and 4 each possess an S=5/2 ground state spin, whereas 3 has an S=5 ground state. As is usually the case, good fits of the magnetization data could be obtained with both positive and negative D values. To obtain more accurate values and to determine the sign of D, high-frequency EPR studies were carried out on single crystals of representative complexes 1.4MeCN and 3.2MeCN, and these gave D=+0.62 cm-1 and |E|>or=0.067 cm-1 for 1.4MeCN and D=-0.25 cm-1 for 3.2MeCN. The magnetic susceptibility data for 4 were fit to the theoretical chiM vs T expression derived by the use of an isotropic Heisenberg spin Hamiltonian and the Van Vleck equation, and this revealed the pairwise exchange parameters to be antiferromagnetic with values of Ja=-3.6 cm-1 and Jb=-45.9 cm-1. The combined results demonstrate the ligating flexibility of dmem and its usefulness in the synthesis of a variety of Fex molecular species.     

Alkyl-eta2-alkene niobocene and tantalocene complexes with the allyldimethylsilyl-eta5-cyclopentadienyl ligand: synthesis, NMR studies and DFT calculations

Group 5 metal complexes [M(eta5-C5H5)[eta5-C5H4SiMe2(CH2-eta]2-CH=CH2)]X] (M = Nb, X = Me, CH2Ph, CH2SiMe3; M = Ta, X = Me, CH2Ph) and [Ta(eta5-C5Me5)[eta5-C5H4SiMe2(CH2-eta2-CH=CH2)]X] (X = Cl, Me, CH2Ph, CH2SiMe3) containing a chelating alkene ligand tethered to a cyclopentadienyl ring have been synthesized in high yields by reduction with Na/Hg (X = Cl) and alkylation with reductive elimination (X = alkyl) of the corresponding metal(iv) dichlorides [M(eta5-Cp)[eta5-C5H4SiMe2(CH2CH=CH2)]Cl2] (Cp = C5H5, M = Nb, Ta, Cp = C5Me5, M = Ta). These chloro- and alkyl-alkene coordinated complexes react with CO and isocyanides [CNtBu, CN(2,6-Me2C6H3)] to give the ligand-substituted metal(III) compounds [M(eta5-Cp)[eta5-C5H4SiMe2(CH2CH=CH2)]XL] (X = Cl, Me, CH2Ph, CH2SiMe3). Reaction of the chloro-alkene tantalum complex with LiNHtBu results in formation of the imido hydride derivative [Ta(eta5-C5Me5)[eta5-C5H4SiMe2(CH2CH=CH2)]H(NtBu)]. NMR studies for all of the new compounds and DFT calculations for the alkene-coordinated metal complexes are compared with those known for related group 4 metal cations.     

Bimetallic complexes from amphoteric group 13/15 ligands: syntheses and X-ray crystal structures

Bimetallic, pentel-bridged complexes of the type [(dmap)Me2M-E(SiMe3)2-M'(CO)n] (M=Al, Ga; E=P, As, Sb; M'=Cr, Fe, Ni; DMAP=4-(dimethylamino)pyridine) are formed by reactions of DMAP-coordinated monomeric Group 13/15 compounds [(dmap)Me2M-E(SiMe3)2] with the transition metal complexes [(Me3N)Cr(CO)5], [Fe3(CO)12], and [Ni(CO)4]. For the first time, this reaction offers a general pathway to compounds containing a Group 13 metal and a transition metal bridged by a pentel atom. Complexes prepared in this way were characterized by IR and multinuclear NMR spectroscopy and by single-crystal X-ray structure analysis. Their electronic and structural properties are discussed in detail. The Group 13/15 ligands are very weak acceptors, which is likely to be due to the electropositive Group 13 metal, and the complexes feature comparatively long pentel-transition metal bonds. In addition, the synthesis and structural characterization of the parent DMAP-coordinated gallanes [(dmap)Me2Ga-E(SiMe3)2] (E=P, As) are reported.     

Synthesis and structures of heteroleptic silylenes

The reaction of benzamidinato silicon trichloride [{PhC(NR)2}SiCl3] [R = Bu(t) (1), SiMe3 (2)] with 2 equiv of potassium in THF afforded mononuclear chlorosilylene [{PhC(NBu(t))2}SiCl] (3) and [{PhC(NSiMe3)2}2SiCl2] (4), respectively. Compound 4 was formed by the disproportionation of unstable [{PhC(NSiMe3)2}SiCl]. The reaction of [{PhC(NBu(t))2}SiCl3] (1) with 1 equiv of LiR (R = NMe2, OBu(t), OPr(i), PPr(i)2) in THF yielded [{PhC(NBu(t))2}SiCl2R] [R = NMe2 (5), OBu(t) (6), OPr(i) (7), PPr(i)2 (8)]. Treatment of 5-8 with 2 equiv of potassium in THF resulted in the novel heteroleptic silylene [{PhC(NBu(t))2}SiR] [R = NMe2 (9), OBu(t) (10), OPr(i) (11), PPr(i)2 (12)]. Compounds 4, 9, and 12 have been analyzed by X-ray crystallography.     

Reaction of the stable silylene Si[(NCH2But)2C6H4-1,2] with lithium amides

The thermally stable silylene Si[(NCH2But)2C6H4-1,2] 1 undergoes oxidative addition reactions with the lithium amides LiNRR'(R = SiMe3, R' = But; R = SiMe3, R' = C6H3Me2-2,6; R = R' = Me or R = R' = Pri) to afford the new lithium amides Li(THF)2[N(R)Si(SiMe3){(NCH2But)2C6H4-1,2}][R = But2 or R = C6H3Me2-2,6 (3a)] or the new tris(amino)functionalised silyllithiums Li(THF)x[Si{(NCH2But)2C6H4-1,2}NRR'][R = SiMe3, R' = C6H3Me2-2,6, x = 2 (3); R = R'= Me, x = 3 (4) or R = R' = Pri, x = 3 (5)]. Compounds 4 and 5 are stable at ambient temperature but compound 3 is thermally labile and converts into 3a upon heating. The pathway for the formation of 2 and 3 is discussed and the X-ray structures of 2-5 are presented.