Monomeric, one- and two-dimensional networks incorporating (2,6-Me2C6H3S)2Pb building blocks

The amine coordination of lead(II) has been examined through the preparation and structural analysis of Lewis base adducts of bis(thiolato)lead(II) complexes. Reaction of Pb(OAc)(2) with 2,6-dimethylbenzenethiol affords (2,6-Me(2)C(6)H(3)S)(2)Pb (6) in high yield. The solubility of 6 in organic solvents allows for the preparation of the 1:2 Lewis acid-base adduct [(2,6-Me(2)C(6)H(3)S)(2)Pb(py)(2)](7), and 1:1 adducts [(2,6-Me(2)C(6)H(3)S)(2)Pb(micro(2)-bipy)](infinity](8) and [(2,6-Me(2)C(6)H(3)S)(2)Pb(micro(2)-pyr)](infinity)(9)(where py = pyridine, bipy = 4,4'-bipyridyl and pyr = pyrazine) from reaction with an excess of the appropriate amine. In contrast to 7, reaction of (C(6)H(5)S)(2)Pb (1) with pyridine afforded the 2:1 adduct [(C(6)H(5)S)(4)Pb(2)(py)](infinity)(10). Compounds were characterized via elemental analysis, FT-IR, solution (1)H and (13)C[(1)H](6) NMR spectroscopy, and X-ray crystallography (7-10). The structures of 7-9 show the thiolate groups occupying two equatorial positions and two amine nitrogen atoms occupying axial coordination sites, yielding distorted see-saw coordination geometries, or distorted trigonal bipyramids if an equatorial lone pair on lead is considered. The absence of intermolecular contacts in 7 and 8 result in monomeric and one-dimensional polymeric structures, respectively. Weak Pb...S intermolecular contacts in 9 result in the formation of a two-dimensional macrostructure. In contrast, the structure of , shows extensive intermolecular Pb...S interactions, resulting in five- and six-coordinate bonding environments for lead(II), and a complex polymeric structure in the solid state. This demonstrates the ability of the 2,6-dimethylphenylthiolate ligand to limit intermolecular lead-sulfur interactions, while allowing the axial coordination of amine Lewis base ligands.     

Intramolecular hydrogen bonding controls 1,3-N,S- vs. 1,5-S,S'-coordination in Ni(II) complexes of N-thiophosphorylated thioureas RNHC(S)NHP(S)(OiPr)2

Reaction of the deprotonated N-thiophosphorylated thioureas RNHC(S)NHP(S)(OiPr)(2) (R = Ph, HL(I); 2-MeC(6)H(4)-, HL(II); 2,6-Me(2)C(6)H(3)-, HL(III); 2,4,6-Me(3)C(6)H(2)-, HL(IV); Me-, HL(V)) with Ni(II) leads to complexes of the formula [NiL(I-V)(2)]. The molecular structures of the thioureas HL(II-V) and the complexes [NiL(II-V)(2)] in the solid were elucidated by single-crystal X-ray diffraction analysis. In the complexes, the metal is found to be in a square planar trans-N(2)S(2) ([NiL(II-IV)(2)]) environment formed by the C=S sulfur atoms and the P-N nitrogen atoms, or in a square planar trans-S(2)S'(2) ([NiL(V)(2)]) environment formed by the C=S and P=S sulfur atoms of two deprotonated ligands. DFT calculations confirmed that the [Ni(L(II-IV)-N,S)(2)] isomers are more stable (by 16-21 kcal mol(-1)) than the corresponding [Ni(L(II-IV)-S,S')(2)] conformers. The main reason for higher stability of the 1,3-N,S vs. 1,5-S,S' isomers is the formation of intramolecular N-H···S=P hydrogen bonds. In solution the complexes [Ni(L(II-V)-N,S)(2)] have an exclusive 1,3-N,S coordination, while the compound [Ni(L(I)-N,S)(2)] exhibits two isomers in the (1)H and (31)P NMR spectra. The major species is assigned to the 1,3-N,S coordinated isomer, while the minor (～25%) signals are due to the 1,5-S,S' isomer. UV-Vis spectroscopic results are in line with this. The electrochemical measurements reveal reversible one-electron reduction and irreversible oxidations, both assigned to ligand-centred processes.     

Reactions of [(eta(6)-arene)RuCl(2)](2) with Aromatic Phosphines Containing Methoxy Groups in 2,6-Positions

Reactions of [(eta(6)-arene)RuCl(2)](2) 1 (arene = p-cymene (a), 1,2,3,4-Me(4)C(6)H(2) (b), 1,2,3-Me(3)C(6)H(2) (c)) with tris(2,6-dimethoxyphenyl)phosphine (TDMPP) led to loss of two molecules of CH(3)Cl to give (eta(6)-arene)Ru[{2-O-C(6)H(3)-6-OMe}(2){C(6)H(3)(OMe)(2)-2,6}], 2a-c, which contains a trihapto ligand (eta(3)-P,O,O) derived from TDMPP, whereas the 1,3,5-Me(3)C(6)H(3) (1d), 1,2,3,5-Me(4)C(6)H(2) (1e), and C(6)Me(6) (1f) complexes did not react with TDMPP. The structures of 2a and 2b were confirmed by X-ray analyses: for 2a, a = 11.691(2) ?, b = 15.228(2) ?, c = 10.320(1) ?, alpha = 95.93(1) degrees, beta = 113.783(9) degrees, gamma = 83.86(1) degrees, triclinic, P&onemacr;, Z = 2, R = 0.051; for 2b, a = 17.79(2) ?, b = 15.43(1) ?, c = 20.93(1) ?, beta = 91.25(8) degrees, monoclinic, P2(1)/n, Z = 8, R = 0.056. Bis(2,6-dimethoxyphenyl)phenylphosphine (BDMPP) reacted with 1a, 1b, and 1d at room temperature to give (eta(6)-arene)RuCl[PPh(2-O-C(6)H(3)-6-OMe){C(6)H(3)(OMe)(2)-2,6}], 3a,b,d, which contains a dihapto (eta(2)-P,O) ligand derived from BDMPP by an X-ray analysis of 3a: a = 12.33(1) ?, b = 14.246(8) ?, c = 11.236(9) ?, alpha = 91.47(8) degrees, beta = 117.28(6) degrees, gamma = 111.70(6) degrees, triclinic, P&onemacr;, Z = 2, R = 0.040. A similar reaction with 1f recovered the starting materials, but that in refluxing MeCN produced [(eta(6)-C(6)Me(6))Ru[PPh(2-O-C(6)H(3)-6-OMe}(2)], 4f, containing a trihapto (eta(3)-P,O,O) ligand derived from BDMPP. Complex 1d reacted with BDMPP at reflux in MeCN/CH(2)Cl(2) and resulted in a loss of an arene ring to give a five-coordinate complex, Ru[eta(2)-P,O-PPh(2-O-C(6)H(3)-6-OMe){C(6)H(3)(OMe)(2)-2,6}](2)(MeCN), 5. Treatment of (2,6-dimethoxyphenyl)diphenylphosphine (MDMPP) with 1f gave (eta(6)-C(6)Me(6))RuCl[eta(2)-P,O-PPh(2)(2-O-C(6)H(3)-6-OMe)],6f, and that with 1b gave (eta(6)-1,2,3,4-Me(4)C(6)H(2))RuCl[eta(2)-P,O-PPh(2)(2-O-C(6)H(3)-6-OMe}], 6b, and (eta(6)-1,2,3,4-Me(4)C(6)H(2))RuCl(2)[eta(1)-P-PPh(2){C(6)H(3)(OMe)(2)-2,6}],7b. The phosphine ligand of 6b acted as a bidentate ligand derived from MDMPP: a = 8.074(4) ?, b = 16.816(3) ?, c = 18.916(4) ?, beta = 94.05(3) degrees, monoclinic, P2(1)/n, Z = 4, R = 0.051. Transformation of 7b to 6b readily occurred accompanying an elimination of MeCl. Reaction of 1a with MDMPP eliminated an arene ring to give the octahedral compound RuCl(2)[eta(2)-P,OMe-PPh(2){C(6)H(3)(MeO)(2)-2,6}](2), 8. An X-ray analysis of 8 showed that two MDMPP ligands were in a cis-position: a = 10.596(14) ?, b = 27.586(12) ?, c = 13.036(8) ?, beta = 108.17(7) degrees, monoclinic, P2(1)/n, Z = 4, R = 0.035.     

Ni(II) and Fe(II) complexes based on bis(imino)aryl pincer ligands: synthesis, structural characterization and catalytic activities

Bis(imino)aryl NCN pincer Ni(II) complexes 2,6-(ArN=CH)(2)C(6)H(3)NiBr (1: Ar = 2,6-Me(2)C(6)H(3); 2: Ar = 2,6-Et(2)C(6)H(3); 3: Ar = 2,6-(i)Pr(2)C(6)H(3)) were prepared via the oxidative-addition of Ni(0)(Ph(3)P)(4) with bis(N-aryl)-2-bromoisophthalaldimine. These nickel complexes were characterized by NMR and elemental analyses. Their solid molecular structures were established by X-ray diffraction analyses. The nickel metal centers adopt distorted square planar geometries with the bromine atoms acting as one coordinate ligands. The NCN pincer Fe(II) complexes 2,6-(ArN=CH)(2)C(6)H(3)Fe(μ-Cl)(2)Li(THF)(2) (4: Ar = 2,6-Me(2)C(6)H(3); 5: Ar = 2,6-Et(2)C(6)H(3); 6: Ar = 2,6-(i)Pr(2)C(6)H(3)) were synthesized by lithium salt metathesis reactions of the ligand lithium salts with FeCl(2). X-ray structure analyses of 4 and 5 revealed that the Fe(II) complexes are hetero-dinuclear with the iron atoms in trigonal bipyramidal environments. When activated with MAO, the nickel complexes are active for norbornene vinyl polymerization but are inert for butadiene polymerization. The Fe(II) complexes show moderate activities in butadiene polymerization when activated with alkylaluminium, affording the cis-1,4 enriched polymer.     

Structure and Properties of [Fe(4)S(4){2,6-bis(acylamino)benzenethiolato-S}(4)](2)(-) and [Fe(2)S(2){2,6-bis(acylamino)benzenethiolato-S}(4)](2)(-): Protection of the Fe-S Bond by Double NH.S Hydrogen Bonds

Iron-sulfur clusters containing a singly or doubly NH.S hydrogen-bonded arenethiolate ligand, [Fe(4)S(4)(S-2-RCONHC(6)H(4))(4)](2)(-) (R = CH(3), t-Bu, CF(3)), [Fe(4)S(4){S-2,6-(RCONH)(2)C(6)H(3)}(4)](2)(-), [Fe(2)S(2)(S-2-RCONHC(6)H(4))(4)](2)(-) (R = CH(3), t-Bu, CF(3)), and [Fe(2)S(2){S-2,6-(RCONH)(2)C(6)H(3)}(4)](2)(-), were synthesized as models of bacterial [4Fe-4S] and plant-type [2Fe-2S] ferredoxins. The X-ray structures and IR spectra of (PPh(4))(2)[Fe(4)S(4){S-2,6-(CH(3)CONH)(2)C(6)H(3)}(4)].2CH(3)CN and (NEt(4))(2)[Fe(2)S(2){S-2,6-(t-BuCONH)(2)C(6)H(3)}(4)] indicate that the two amide NH groups at the o,o'-positions are directed to the thiolate sulfur atom and form double NH.S hydrogen bonds. The NH.S hydrogen bond contributes to the positive shift of the redox potential of not only (Fe(4)S(4))(+)/(Fe(4)S(4))(2+) but also (Fe(4)S(4))(2+)/(Fe(4)S(4))(3+) in the [4Fe-4S] clusters as well as (Fe(2)S(2))(2+)/(Fe(2)S(2))(3+) in the [2Fe-2S] clusters. The doubly NH.S hydrogen-bonded thiolate ligand effectively prevents the ligand exchange reaction by benzenethiol because the two amide NH groups stabilize the thiolate by protection from dissociation.     

Terphenyl ligand stabilized lead(II) derivatives: steric effects and lead-lead bonding in diplumbenes

The reaction of PbBr(2) with the lithium reagents LiC(6)H(3)-2,6-(C(6)H(3)-2,6-Pr(i)(2))(2) (LiArPr(i)(2)) and Et(2)O.LiC(6)H(3)-2,6-(2,6-Pr(i)-4-Bu(t)C(6)H(2))(2) (Et(2)O.LiArPr(i)(2)Bu(t)) furnished the bromide bridged organolead(II) halides [Pb(mu-Br)ArPr(i)(2)](2) (1) and[Pb(mu-Br)ArPr(i)(2)Bu(t)](2) (2) as orange crystals. Treatment of 1 with a stoichiometric amount of methylmagnesium bromide resulted in the "diplumbene" Pr(i)(2)Ar(Me)PbPb(Me)ArPr(i)(2) (3). The addition of 1 equiv of 4-tert-butylphenylmagnesium bromide to 1 afforded the feebly associated, Pb-Pb bonded species [Pb(C(6)H(4)-4-Bu(t))ArPr(i)(2)](2) (4), whereas the corresponding reaction of tert-butylmagnesium chloride and 1 afforded the monomer Pb(Bu(t))ArPr(i)(2) (5). The reaction of the more crowded aryl lead(II) bromide [Pb(mu-Br)ArPr(i)(3)](2) (Ar = C(6)H(3)-2,6(C(6)H(2)-2,4,6-Pr(i)(3))(2)) with 4-isopropyl-benzylmagnesium bromide or LiSi(SiMe(3))(3) yielded the monomers 6, [Pb(CH(2)C(6)H(4)-4-Pr(i))ArPr(i)(3)], or 7, [Pb(Si(SiMe(3))(3))ArPr(i)(3)]. All compounds were characterized with use of X-ray crystallography, (1)H, (13)C, and (207)Pb NMR (3-7), and UV-vis spectroscopy. The dimeric Pb-Pb bonded (Pb-Pb = 3.1601(6) A) structure of 3 may be contrasted with the previously reported monomeric structure of Pb(Me)ArPr(i)(3), which differs from 3 only in that it has para Pr(i) substituents on the flanking aryl rings. The presence of these groups is sufficient to prevent the weak Pb-Pb bonding seen in 3. The dimer 4 displays a Pb-Pb distance of 3.947(1) A, which indicates a very weak lead-lead interaction, and it is possible that this close approach could be caused by packing effects. The monomeric structures of 6 and 7 are attributable to steric effects and, in particular, to the large size of ArPr(i)(3).     

Synthesis of triamidoamine ligands of the type (ArylNHCH(2)CH(2))(3)N and molybdenum and tungsten complexes that contain an [ArylNCH(2)CH(2))(3)N]3- ligand

Aryl bromides react with (H(2)NCH(2)CH(2))(3)N in a reaction catalyzed by Pd(2)(dba)(3) in the presence of BINAP and NaO-t-Bu to give the arylated derivatives (ArylNHCH(2)CH(2))(3)N [Aryl = C(6)H(5) (1a), 4-FC(6)H(4) (1b), 4-t-BuC(6)H(4) (1c), 3,5-Me(2)C(6)H(3) (1d), 3,5-Ph(2)C(6)H(3) (1e), 3,5-(4-t-BuC(6)H(4))(2)C(6)H(3) (1f), 2-MeC(6)H(4) (1g), 2,4,6-Me(3)C(6)H(2) (1h)]. Reactions between (ArNHCH(2)CH(2))(3)N (Ar = C(6)H(5), 4-FC(6)H(4), 3,5-Me(2)C(6)H(3), and 3,5-Ph(2)C(6)H(3)) and Mo(NMe(2))(4) in toluene at 70 degrees C lead to [(ArNHCH(2)CH(2))(3)N]Mo(NMe(2)) complexes in yields ranging from 64 to 96%. Dimethylamido species (Ar = 4-FC(6)H(4), 3,5-Me(2)C(6)H(3)) could be converted into paramagnetic [(ArNHCH(2)CH(2))(3)N]MoCl species by treating them with 2,6-lutidinium chloride in tetrahydrofuran (THF). The "direct reaction" between 1a-f and MoCl(4)(THF)(2) in THF followed by 3 equiv of MeMgCl yielded [(ArNHCH(2)CH(2))(3)N]MoCl species (3a-f) in high yield. If 4 equiv of LiMe instead of MeMgCl are employed in the direct reaction, then [(ArNHCH(2)CH(2))(3)N]MoMe species are formed. Tungsten species, [(ArNHCH(2)CH(2))(3)N]WCl, could be prepared by analogous "direct" methods. Cyclic voltammetric studies reveal that MoCl complexes become more difficult to reduce as the electron donating ability of the [ArylNCH(2)CH(2))(3)N]3- ligand increases, and the reductions become less reversible, consistent with ready loss of chloride from ([(ArNHCH(2)CH(2))(3)N]MoCl)(-). Tungsten complexes are more difficult to reduce, and reductions are irreversible on the CV time scale.     

Chromium complexes supported by phenanthrene-imine derivative ligands: synthesis, characterization and catalysis on isoprene cis-1,4 polymerization

Reactions of CrCl(2)(THF)(2) with N-aryl-9,10-iminophenanthraquinone in CH(2)Cl(2) give the monoimine chromium complexes (Ar)IPQCrCl(2)(THF)(2) (1, Ar = 2,6-Me(2)C(6)H(3); 2, Ar = 2,6-Et(2)C(6)H(3); 3, Ar = 2,6-(i)Pr(2)C(6)H(3)). Molecular structures of 1 and 3 were revealed to be monomeric with the chromium atoms in distorted octahedral geometries. Similar reactions of CrCl(2)(THF)(2) with N,N-bis(arylimino)phenanthrene ligands afford the diimine complexes (Ar1,Ar2)BIPCrCl(μ-Cl)(3)Cr(THF)(Ar1,Ar2)BIP (4, Ar(1) = Ar(2) = 2,6-Me(2)C(6)H(3); 5, Ar(1) = Ar(2) = 2,6-Et(2)C(6)H(3); 6, Ar(1) = Ar(2) = 2,6-(i)Pr(2)C(6)H(3); 7, Ar(1) = 2,6-Me(2)C(6)H(3), Ar(2) = 2,6-(i)Pr(2)C(6)H(3)). The X-ray diffraction analysis shows that 4, 5, and 7 are chlorine-bridged dimers with each chromium atom in a distorted octahedral geometry. Upon activation with MAO, all these complexes exhibit good catalytic activities for isoprene polymerization affording polyisoprene with predominantly a cis-1,4 unit.     

In(8)(C(6)H(3)-2,6-Mes(2))(4) (Mes=C(6)H(2)-2,4,6-Me(3)): A Metal-Rich Main-Group Cluster with a Distorted Cubane Structure

A distorted In(8) cubane core (see picture) is present in the novel indium cluster In(8)(C(6)H(3)-2,6-Mes(2))(4) (Mes=C(6)H(2)-2,4,6-Me(3)), which was synthesized by the reaction of LiC(6)H(3)-2,6-Mes(2) with InCl. It has an average In-In bond length of 2.92 ? and represents a new addition to the range of heavier Group 13 element clusters.     

Quasi-isomeric gallium amides and imides GaNR2 and RGaNR (R = organic group): reactions of the digallene, Ar'GaGaAr' (Ar' = C6H3-2,6-(C6H3-2,6-Pri2)2) with unsaturated nitrogen compounds

Reactions of the "digallene" Ar'GaGaAr'(1) (Ar' = C(6)H(3)-2,6-(C(6)H(3)-2,6-Pr(i)(2))(2)), which dissociates to green :GaAr' monomers in solution, with unsaturated N-N-bonded molecules are described. Treatment of solutions of :GaAr' with the bulky azide N(3)Ar(#) (Ar(#) = C(6)H(3)-2,6-(C(6)H(2)-2,6-Me(2)-4-Bu(t))(2)), afforded the red imide Ar'GaNAr(#) (2). Addition of the azobenzenes, ArylNNAryl (Aryl = C(6)H(4)-4-Me (p-tolyl), mesityl, and C(6)H(3)-2,6-Et(2)) yielded the 1,2-Ga(2)N(2) ring compound Ar'GaN(p-tolyl)N(p-tolyl)GaA' (3) or the products MesN=NC(6)H(2)-2,4-Me(2)-6-Ga(Me)Ar' (4) and 2,6-Et(2)C(6)H(3)N=NC(6)H(3)-2-Et-6-Ga(Et)Ar' (5). Reaction of GaAr' with N(2)CPh(2) yielded the 1,3-Ga(2)N(2) ring compound Ar'Ga(mu:eta(1)-N(2)CPh(2))(2)GaAr' (6), which is quasi-isomeric to 3. Calculations on simple model isomers showed that the Ga(I) amide GaNR(2) (R = Me) is much more stable than the isomeric Ga(III) imide RGaNR. This led to the synthesis of the first stable monomeric Ga(I) amide, GaN(SiMe(3))Ar' ' (8) (Ar' ' = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-Me(3))(2) from the reaction of LiN(SiMe(3))Ar' ' (7) and "GaI". Compound 8 is also the first one-coordinate gallium species to be characterized in the solid state. The reaction of 8 with N(3)Ar' ' afforded the amido-imide derivative Ar' 'NGaN(SiMe(3))Ar' ' (9), a gallium nitrogen analogue of an allyl anion. All compounds were spectroscopically and structurally characterized. In addition, DFT calculations were performed on model compounds of the amide, imide, and cyclic 1,2- and 1,3-species to better understand their bonding. The pairs of compounds 2 and 8 as well as 3 and 6 are rare examples of quasi-isomeric heavier main group element compounds.     

Molecularly nonstoichiometric crystals in phosphorus compounds

Molecularly nonstoichiometric crystals obtained as a result of differential occupation of sites with oxygen atom/phosphorus lone pair of electrons or with sulfur/selenium in three sets of phosphorus compounds are described. These are formed by a combination of (a) [CH2(6-t-Bu-4-MeC6H2O)2]PNMe2 (11) and [CH2(6-t-Bu-4-MeC6H2O)2]P(O)NMe2 (13), (b) [CH2(6-t-Bu-4-MeC6H2O)2]P(S)NMe2 (14) and [CH2(6-t-Bu-4-MeC6H2O)2]P(Se)NMe2 (15), and (c) [(2,6-Me2C6H3O)(O)P-micro-N-t-Bu]2 (16) and (2,6-Me2C6H3O)(O)P(micro-N-t-Bu)2P(O-2,6-Me2C6H3) (17). In the case of c, three different types of crystals with varying stoichiometry of 16 and 17 (1:9, 1:1.5, and 1:0.43) are obtained. The results are substantiated by the combined use of 31P NMR spectroscopy and X-ray crystallography. These observations suggest that we should be cautious with regards to the purity of samples when syntheses involving the oxidation of P(III) systems are reported. It is also emphasized that the apparent P-X distances in some of these crystals cannot actually be taken as true bond lengths.     

Synthesis, structural characterization, reactivity, and thermal stability of [eta(5):sigma-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2)

Reaction of [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]TiCl(NMe2) (1) with 1 equiv of PhCH2K, MeMgBr, or Me3SiCH2Li gave corresponding organotitanium alkyl complexes [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2) (R = CH2Ph (2), CH2SiMe3 (4), or Me (5)) in good yields. Treatment of 1 with 1 equiv of n-BuLi afforded the decomposition product {[eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti}2(mu-NMe)(mu:sigma-CH2NMe) (3). Complex 5 slowly decomposed to generate a mixed-valence dinuclear species {[eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti}2(mu-NMe2)(mu:sigma-CH2NMe) (6). Complex 1 reacted with 1 equiv of PhNCO or 2,6-Me2C6H3NC to afford the corresponding monoinsertion product [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(Cl)[eta(2)-OC(NMe2)NPh] (7) or [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(Cl)[eta(2)-C(NMe2)=N(2,6-Me2C6H3)] (8). Reaction of 4 or 5 with 1 equiv of R'NC gave the titanium eta(2)-iminoacyl complexes [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(NMe2)[eta(2)-C(R)=N(R')] (R = CH2SiMe3, R' = 2,6-Me2C6H3 (9) or tBu (10); R = Me, R' = 2,6-Me2C6H3 (11) or tBu (12)). The results indicated that the unsaturated molecules inserted into the Ti-N bond only in the absence of the Ti-C(alkyl) bond and that the Ti-C(cage) bond remained intact. All complexes were fully characterized by various spectroscopic techniques and elemental analyses. Molecular structures of 2, 3, 6-8, and 10-12 were further confirmed by single-crystal X-ray analyses.     

Synthesis, characterization, and hydrolysis of aluminum(III) compounds bearing the C6F5-substituted beta-diketiminate HC[(CMe)(NC6F5)]2 (L) ligand

A series of Al(III) compounds containing the C6F5-substituted beta-diketiminate ligands LAlMeCl (2), LAlMe2 (3), LAlMeI (4), and LAlBr2 (5) (L = HC[(CMe)(NC6F5)]2) were synthesized and characterized. The hydrolysis of 2 and 4 in the presence of 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene as the hydrogen halide acceptor both lead to (LAlMe)2(mu-O) (6), a methylalumoxane derivative, which is the first hydrolysis product with the general formula of (RAlMe)(n)O. A comparison of the hydrolysis products of 2 and 4 with that of L'AlMeCl (L' = HC[(CMe)(NAr)]2, Ar = 2,6-iPr2C6H3) shows that with the C6F5-substituted beta-diketiminate ligand, it was not possible to generate LAlMe(OH). This is obviously due to the stronger Br?nsted acidity of the proton and the smaller size of the C6F5 group in this compound compared to that of the corresponding 2,6-iPr2C6H3 derivative.     

Primary amido substituted diborane4 compounds and imidodiborate4 anions

Treatment of the diborane(4) compound B(2)(NMe(2))(4) with aniline or 2,6-dimethylaniline results in the primary amido compounds B(2)(NHR)(4)(R = Ph, 2,6-Me(2)C(6)H(3)); subsequent treatment with n-BuLi in toluene in each case affords the first examples of anionic imidodiborates namely Li(4)(thf)(6)B(2)(NPh)(4) and Li(4)(thf)(4)B(2)(N-2,6-Me(2)C(6)H(3))(4); all complexes have been characterised crystallographically.     

Synthesis and structural characterization of two-coordinate low-valent 14-group metal complexes bearing bulky bis(amido)silane ligands

A series of germylene, stannylene and plumbylene complexes [η(2)(N,N)-Me(2)Si(DippN)(2)Ge:] (3a), [η(2)(N,N)-Ph(2)Si(DippN)(2)Ge:] (3b), [η(2)(N,N)-Me(2)Si(DippN)(2)Sn:] (4), [η(2)(N,N)-Me(2)Si(DippN)(2)Pb:](2) (5a), and [η(2)(N,N)-Ph(2)Si(DippN)(2)Pb:] (5b) (Dipp = 2,6-iPr(2)C(6)H(3)) bearing bulky bis(amido)silane ligands were readily prepared either by the transamination of M[N(SiMe(3))(2)](2) (M = Sn, Pb) and [Me(2)Si(DippNH)(2)] or by the metathesis reaction of bislithium bis(amido)silane [η(1)(N),η(1)(N)-R(2)Si(DippNLi)(2)] (R = Me, Ph) with the corresponding metal halides GeCl(2)(dioxane), SnCl(2), and PbCl(2), respectively. Preliminary atom-transfer chemistry involving [η(2)(N,N)-Me(2)Si(DippN)(2)Ge:] (3a) with oxygen yielded a dimeric oxo-bridged germanium complex [η(2)(N,N)-Me(2)Si(DippN)(2)Ge(μ-O)](2) (6). All complexes were characterized by (1)H, (13)C, (119)Sn NMR, IR, and elemental analysis. X-ray single crystal diffraction analysis revealed that the metal centres in 3b, 4, and 5b are sterically protected to prevent interaction between the metal centre and the nitrogen donors of adjacent molecules while complex 5a shows a dimeric feature with a strong intermolecular Pb···N interaction.     

New titanium complexes with symmetric or asymmetric cis-9,10-dihydrophenanthrenediamide ligands formed through sequential intramolecular C-C bond-forming reactions

A series of new titanium(IV) complexes with symmetric or asymmetric cis-9,10-dihydrophenanthrenediamide ligands, cis-9,10-PhenH(2)(NR)(2)Ti(O(i)Pr)(2) [PhenH(2) = 9,10-dihydrophenanthrene, R = 2,6-(i)Pr(2)C(6)H(3) (2a), 2,6-Et(2)C(6)H(3) (2b), 2,6-Me(2)C(6)H(3) (2c)], cis-9,10-PhenH(2)(NR(1))(NR(2))Ti(O(i)Pr)(2) [R(1) = 2,6-(i)Pr(2)C(6)H(3), R(2) = 2,6-Et(2)C(6)H(3) (2d); R(1) = 2,6-(i)Pr(2)C(6)H(3), R(2) = 2,6-Me(2)C(6)H(3) (2e)], and [cis-9,10-PhenH(2)(NR(1))(2)][o-C(6)H(4)(CH=NR(2))]TiO(i)Pr [R(1) = 2,6-(i)Pr(2)C(6)H(3), R(2) = 2,6-Et(2)C(6)H(3) (3a); R(1) = 2,6-(i)Pr(2)C(6)H(3), 2,6-Me(2)C(6)H(3) (3b)], have been synthesized from the reactions of TiCl(2)(O(i)Pr)(2) with o-C(6)H(4)(CH=NR)Li [R = 2,6-(i)Pr(2)C(6)H(3), 2,6-Et(2)C(6)H(3), 2,6-Me(2)C(6)H(3)]. The symmetric complexes 2a-2c were obtained from the reactions of TiCl(2)(O(i)Pr)(2) with 2 equiv of the corresponding o-C(6)H(4)(CH=NR)Li followed by intramolecular C-C bond-forming reductive elimination and oxidative coupling processes, while the asymmetric complexes 2d-2e were formed from the reaction of TiCl(2)(O(i)Pr)(2) with two different types of o-C(6)H(4)(CH=NR)Li sequentially. The complexes 3a and 3b were also isolated from the reactions for complexes 2d and 2e. All complexes were characterized by (1)H and (13)C NMR spectroscopy, and the molecular structures of 2a, 2b, 2e, and 3a were determined by X-ray crystallography.     

Ligand effects in the syntheses and structures of novel heteroleptic and homoleptic bismuth(III) formamidinate complexes

Metathesis reactions of the alkali metal formamidinates M(RNC(H)NR), M = Li or K; R = C(6)H(3)-2,6-Pr(i)(2) (L(1)), C(6)H(3)-2,6-Et(2) (L(2)); C(6)H(2)-2,4,6-Me(3) (L(3)), C(6)H(3)-2,6-Me(2) (L(4)) or C(6)H(4)-2-Ph (L(5)), with BiX(3) (X = Cl or Br) gave a range of bismuth(iii) formamidinate complexes [Bi(L)Br(micro-Br)(thf)](2) (L = L(1), L(4)), [{Bi(L(1))Cl(2)(thf)}(2)Bi(L(1))Cl(2)], [Bi(L)(2)X] (L = L(2), L(5), X = Br; L = L(1), X = Cl), and [Bi(L)(3)] (L = L(2), L(3)). An analogous organometallic complex Bi(L(1))(2)Bu(n) was also isolated as a side product in one instance. Structural characterisation of the di-halide complexes show symmetrical dimers for X = Br, with two bromide bridges, and a coordinated thf molecule on each Bi atom, whereas for X = Cl a thf deficient species was crystallised, and has a weakly associated trinuclear array with two coordinated thf molecules per three Bi atoms. Complexes of the form Bi(L)(2)X (X = Br, Cl, Bu(n)) and Bi(L)(3) all have monomeric structures but the Bi(L)(3) species show marked asymmetry of the formamidinate binding, suggesting that they have reached coordination saturation.     

Synthesis and Characterization of Ge(II), Sn(II), and Pb(II) Monoamides with -NH2 Ligands

The synthesis and characterization of the first divalent germanium, tin, and lead monoamide derivatives of the parent amide group -NH(2) are presented. They have the general formula (ArMNH(2))(2) (M = Ge, Ar = Ar'(C(6)H(3)-2,6-Pr(i)(2)) or Ar* (C(6)H(3)-2,6(C(6)H(2)-2,4,6-Pr(i)(3))); M = Sn, Ar = Ar*; M = Pb, Ar = Ar*). For germanium and tin, they were obtained by reacting the corresponding terphenyl halides of the group 14 elements with liquid ammonia in diethyl ether. The lead amide derivative (Ar*PbNH(2))(2) was synthesized by reaction of LiNH(2) with Ar*PbBr in diethyl ether. The compounds were characterized by IR and multinuclear NMR spectroscopies and by X-ray crystallography in the case of the (Ar'GeNH(2))(2) or (Ar*SnNH(2))(2) derivatives. They possess dimeric structures with two -NH(2) groups bridging the germanium and tin centers. For lead, the reaction with ammonia led to isolation of a stable ammine complex of formula Ar*PbBr(NH(3)) which was characterized by IR and NMR spectroscopies and by X-ray crystallography. It is the first structural characterization of a divalent lead ammine complex.     

Synthesis and characterisation of cyanodithioimidocarbonate [C2N2S2]2- complexes

[PPh4]2[M(C2N2S2)2](M = Pt, Pd) and [Pt(C2N2S2)(PR3)2](PR3= PMe2Ph, PPh3) and [Pt(C2N2S2)(PP)](PP = dppe, dppm, dppf) were all obtained by the reaction of the appropriate metal halide containing complex with potassium cyanodithioimidocarbonate. The dimeric cyanodithioimidocarbonate complexes [[Pt(C2N2S2)(PR3)]2](PR3 = PMe2Ph), [M[(C2N2S2)(eta5-C5Me5)]2](M = Rh, Ir)and [[Ru(C2N2S2)(eta6-p-MeC6H4iPr)]2] have been synthesised from the appropriate transition metal dimer starting material. The cyanodithioimidocarbonate ligand is S,S and bidentate in the monomeric complexes with the terminal CN group being approximately coplanar with the CS2 group and trigonal at nitrogen thus reducing the planar symmetry of the ligand. In the dimeric compound one of the sulfur atoms bridges two metal atoms with the core exhibiting a cubane-like geometry.