Structural diversity in bishydroxylamine complexes of gallium

Reactions of bishydroxylamines of the type HON(R)CH2CH2N(R)OH (R=Me, tBu) with trimethyl- and triisopropylgallium gave bicyclic metalla cages of the formula R'2GaO(R)NCH2CH2N(R)OGaR'2 [R'=Me, R=Me (), tBu (); R'=iPr, R=Me (), tBu ()] with six-membered Ga2O2N2-rings. While the complexes show the same core constitution in the solid state, NMR spectra reveal the steric influence of the isopropyl substituent of the compounds / on its behaviour in solution. The reaction of the sterically more demanding substituted tri-tert-butylgallium with HON(Me)CH2CH2N(Me)OH yielded a heterodimeric complex O'-[HON(Me)CH2CH2NH(Me)O(tBu2Ga)]-cyclo-(tBu2Ga)-O,N'-[ON(Me)CH2CH2N(Me)O] () with two gallium atoms of different surrounding and two different bishydroxylamine ligands, one doubly deprotonated and one protonated, but at one end in its tautomeric aminoxide form. Further condensation of was observed to give a tricyclic compound cyclo-[(tBuGa)ON(Me)CH2CH2N(Me)O]2 () with a central Ga2O2N2 ring resulting from two Ga-N donor-acceptor bonds.     

Base free lithium-organoaluminate and the gallium congener: potential precursors to heterometallic assemblies

The first examples of base free lithium-organoaluminate and the corresponding gallium compound [LM(Me)OLi]3 (M = Al (3), Ga (4); L = HC{C(Me)N-2,6-iPr2C6H3}2) have been prepared by the reaction of Li[N(SiMe3)2] with the corresponding metal hydroxides LM(Me)OH (M = Al (1), Ga(2)); the oxygen atom in the M-O-Li fragment exists as oxide ion and is involved in the central Li3O3 six-membered ring formation.     

Organoaluminium and -gallium compounds with N,N-diisopropylaminomethyl groups

The N,N-diisopropylaminomethyl aluminium compound [tBu2AlCH2NiPr2 x LiCl]2(1) and the gallium compounds Li[tBu2Ga(CH2NiPr2)2](2) and [tBu2GaCH2N(H)iPr2]Cl x tBu3Ga (3) were prepared by transmetallation of N,N-diisopropylaminomethyllithium LiCH2NiPr2 with di-tert-butylaluminium or -gallium chloride, and characterised by elemental analyses, multinuclear NMR spectroscopy (1H, 13C, 27Al, 7Li) and IR spectroscopy. The crystal structures have been determined by single crystal X-ray diffraction. Compound aggregates as a centrosymmetric dimer, with two Al-C-N units connected by a frame of two LiCl molecules [Al-Cl 2.367(1), Cl-Li 2.339(4) and 2.374(4), Li-N 1.977(4)A]. Compound 2 is a lithium organogallate with two weak LiN bonds [1.965(7) and 1.937(7)A]. Compound 3 contains two different moieties: tBu3Ga and a [tBu2GaCH2N(H)iPr2]+ cation, which are bridged by a Cl- anion [Ga-Cl 2.445(1) and 2.579(1), HCl 2.362(3)A].     

Group 13 β-ketoiminate compounds: gallium hydride derivatives as molecular precursors to thin films of Ga2O3

Bis(β-ketoimine) ligands, [R{N(H)C(Me)-CHC(Me)═O}(2)] (L(1)H(2), R = (CH(2))(2); L(2)H(2), R = (CH(2))(3)), linked by ethylene (L(1)) and propylene (L(2)) bridges have been used to form aluminum, gallium, and indium chloride complexes [Al(L(1))Cl] (3), [Ga(L(n))Cl] (4, n = 1; 6, n = 2) and [In(L(n))Cl] (5, n = 1; 7, n = 2). Ligand L(1) has also been used to form a gallium hydride derivative [Ga(L(1))H] (8), but indium analogues could not be made. β-ketoimine ligands, [Me(2)N(CH(2))(3)N(H)C(R')-CHC(R')═O] (L(3)H, R' = Me; L(4)H, R' = Ph), with a donor-functionalized Lewis base have also been synthesized and used to form gallium and indium alkyl complexes, [Ga(L(3))Me(2)] (9) and [In(L(3))Me(2)] (10), which were isolated as oils. The related gallium hydride complexes, [Ga(L(n))H(2)] (11, n = 3; 12, n = 4), were also prepared, but again no indium hydride species could be made. The complexes were characterized mainly by NMR spectroscopy, mass spectrometry, and single crystal X-ray diffraction. The β-ketoiminate gallium hydride compounds (8 and 11) have been used as single-source precursors for the deposition of Ga(2)O(3) by aerosol-assisted (AA)CVD with toluene as the solvent. The quality of the films varied according to the precursor used, with the complex [Ga(L(1))H] (8) giving by far the best quality films. Although the films were amorphous as deposited, they could be annealed at 1000 °C to form crystalline Ga(2)O(3). The films were analyzed by powder XRD, SEM, and EDX.     

Carbonyles tres decales par rapport a l'eclipse dans les aldehydes et les cetones aliphatiques satures: analyse conformationnelle theorique

The theoretical conformational analysis of two series of molecules HCOR, MeCOR is treated. Spectroscopic data [15] have indicated the existence of non-eclipsed conformations which become more important with increasing steric hindrance of the group R.All the methods used (semi-empirical quantum methods, P.C.I.L.O., I.N.D.O., C.N.D.O./2, and the Liquori empirical potential method) lead to the following stable conformations: with the carbonyl group exclusively eclipsed for slightly substituted R (R = Me, Et, tBu); with the carbonyl eclipsed and also staggered (? ? 60°) for moderately substituted compounds (MeCOPr, MeCOiBu, MeCOCiPr(Me)₂) (low rotational barriers permitting equilibria between eclipsed and staggered conformations); with the carbonyl exclusively staggered (? ? 60°) for more hindered compounds (MeCOCH₂tBu, MeCOCH(tBu)Me, MeCOC(Me),tBu, MeCOCH(tBu)₂).Contradictory results are obtained for certain compounds (iPrCOMe, tBuCH₂CHO for example) : the calculated changeover from eclipsed to staggered conformations differentiates the semi-empirical methods from the empirical potential method used.     

Reactivity of various four-coordinate aluminum alkyls towards dioxygen: evidence for spatial requirements in the insertion of an oxygen molecule into the AI-C bond

The interaction of dioxygen with various tetrahedral aluminum alkyls, (tBu)3Al.OEt2 (1), tBu2Al(mu-OtBu)2AltBu2 (6), (tBu)2Al(mesal) (2) [mesal=methyl salicylate anion], R2Al(mu-pz)2AlR2 [pz=deprotonated pyrazole, R= Me (3a), Et (3b), and tBu (3c)], R2Al(mu-3,5-Me2pz)2AIR2[3,5-Me2pz = deprotonated 3,5-dimethylpyrazole, R= Me (4a), and Et (4b)], and Et2B(mu-pz)2AlEt2 (5), has been investigated. We were particularly interested in the effect of steric hindrances both caused by the metal-bonded substituents and those that result from the nature of the bifunctional ligand used in the oxygenation reaction. In the reaction of 1 with O2, only the formation of the monoalkoxide compound6 was observed. The latter di-tert-butyl compound as well as all planar aluminapyrazoles, that is, the tert-butyl derivative 3c and lower alkylaluminum derivatives with the more demanding 3,5-dimethylpyrazoyl ligands 4a and 4b, are stable under an atmosphere of dry oxygen and ambient conditions. Inspection of the space-filling representation of these compounds has undoubtedly shown that the bulky tert-butyl groups or pyrazolyles ligands, respectively, provide steric protection for the metal center from the dioxygen attack. In contrast, the dialkylaluminum derivatives of pyrazole, 3a and 3b, and the diethylaluminum bis(1-pyrazolyl)borate complex 5, all with the metal center eclipsed with respect to the plane defined by the four nitrogen atoms, react smoothly with O2 to form the alkyl(alkoxy)aluminum complexes. In the reaction of 5 with O2 for example, the Et-B bonds remained intact, and the dimeric five-coordinate compound [Et2B(mu-pz)2 Al(mu-OEt)Et]2 (9) was isolated in good yield. The interaction of mononuclear di-tert-butyl chelate complex 2 with O2 at -15 degrees C gives (tBuOO)(tBuO)Al(mu-OtBu)2Al(mesal)2 (7) in high yield, and the presence of the alkylperoxo moiety is a particularly significant point in the resulting product. All the compounds have been characterized spectroscopically, and the structures of 3c, 4a, 6, 7, and 9 have been confirmed by X-ray crystallography. Structural features of 1-6 are discussed and are considered in relation to the possible approach pathways of the O2 molecule to the four-coordinate metal center. This analysis and the observed apparent dissimilarity in the reactions of model four-coordinate aluminum alkyls with O2 clearly show that the stereoelectronic prerequisites are responsible for the fundamentally different reactivity.     

第ⅢA族金属叠氮多聚体结构和性质的理论研究

在DFT-B3LYP/SDD水平上计算研究了第A族金属叠氮多聚体(Me₂MN₃)_n(n=1～3,M=Ga,Al)的结构和性质.多聚体(Me₂MN₃)₂,3的各优化构型均为环状,通过一子体系叠氮基的α-N和另一子体系的金属Ga或Al相连.二聚体(Me₂MN₃)₂中含M2N2平面四元环结构,三聚体(Me₂MN₃)₃具有结合能相近的扭船式和椅式两种构象,均含M₃N₃六元环结构.与单体相比,多聚体的几何参数变化较大.报道了它们在不同温度下的热力学性质,发现叠氮二甲基镓和铝体系以二聚体形式存在.     

Synthesis of Al complexes containing phenoxy-imine ligands and their use as the catalyst precursors for efficient living ring-opening polymerisation of epsilon-caprolactone

Al complexes containing phenoxy-imine ligands of type, Me2Al[O-2-R1-6-(R2N=CH)C6H3] [R1 = Me, R2 = 2,6-iPr2C6H3 (1a), tBu (1b); R1 = tBu, R2 = 2,6-iPr2C6H3 (2a), tBu (2b), cyclohexyl (2c), adamantyl (2d), C6H5 (2e), 2,6-Me2C6H3 (2f), C6F5 (2g)] have been prepared in high yields from AlMe3 by treating with 1.0 equiv. of 2-R1-6-(R2N=CH)C6H3OH in n-hexane. Structures for 1a, 1b, 2a-e and 2g were determined by X-ray crystallography, and these complexes have a distorted tetrahedral geometry around Al; both the Al-O and the Al-N bond distances were influenced by substituents in both the aryloxo and the imino groups. Me2Al[mu2-O-2-(R2N=CH)C6H4](AlMe3) [R2 = 2,6-iPr2C6H3 (3a), tBu (3b)] were prepared exclusively by reaction of AlMe3 with 2-(R2N=CH)C6H4OH, and these complexes form a distorted tetrahedral geometry around each Al centre with additional AlMe3 coordinating to the oxygen in the phenoxy-imine ligand. Complexes 1a, 1b and 2a-g were tested as catalyst precursors for ring-opening polymerisation (ROP) of epsilon-caprolactone (CL) in the presence of (n)BuOH (1.0 equiv. to Al), and their catalytic activities were strongly influenced by the imino substituent (R2). The efficient ROP has been achieved using the C6F5 analogue (2g), with the ROP taking place in a living manner.     

Iminoacylation. 3. Formation of platinum(IV)-based metallaligands due to facile one-end addition of vic-dioximes to coordinated organonitriles

The reaction of vic-dioximes with the organonitrile platinum(IV) complexes trans-[PtCl4(RCN)2] (R = Me, CH2Ph, Ph, vic-dioxime = dimethylglyoxime; R = Me, vic-dioxime = cyclohexa-, cyclohepta-, and cyclooctanedione dioximes) proceeds rapidly under relatively mild conditions and affords products of one-end addition of the dioximes to the nitrile carbon, i.e. [PtC4(NH=C(R)ON=[spacer]=NOH)2] (1-6) (R = Me, CH2Ph, Ph, spacer = C(Me)C-(Me) for dimethylglyoxime; R = Me, spacer = C[C4H8]C, C[C5H10]C, C[C6H12]C for the other dioximes), giving a novel type of metallaligand. All addition compounds were characterized by elemental analyses (C, H, N, C1, Pt), FAB mass spectrometry, and IR and 1H, 13C[1H], and 195Pt NMR spectroscopy. X-ray structure determination of the dimethylformamide bis-solvate [PtCl4(NH=C(Me)ON=C(Me)C(Me)=NOH)2] x 2DMF (la) disclosed its overall trans geometry with the dimethylglyoxime part in anti configuration and the amidine one-end (rather than N,N-bidentate) coordination mode of the N-donor ligands. When a mixture of cis- and trans-[PtC4(MeCN)2] in MeCN was treated with dimethylglyoxime, the formation of, correspondingly, cis- and trans-[PtCl4(NH=C(Me)ON=C(Me)C(Me)=NOH)2] (1) was observed and cis-to-trans isomerization in DMSO-d6 solution was monitored by 1H, 2D [1H,15N] HMQC, and 195Pt NMR spectroscopies. Although performed ab initio calculations give evidence that the trans geometry is the favorable one for the iminoacylated species [PtCl4-(ligand)2], the platinum(IV) complex [PtCl4(NH=C(Me)ON=C[C4Hs]C=NOH)2] (4) was isolated exclusively in cis configuration with the two metallaligand "arms" held together by intramolecular hydrogen bonding between the two peripheral OH groups, as it was proved by single-crystal X-ray diffractometry. The classic substitution products, e.g. [PtC12(N,N-dioximato)2] (12-15), are formed in the addition reaction as only byproducts in minor yield; two of them, [PtCl2(C7H11N2O2)2] (14) and [PtCl2(C8H13N2O2)2] (15), were structurally characterized. Complexes (12-15) were also prepared by reaction of the vic-dioximes with [PtCl4L(Me2SO)] (L = Me2SO, MeCN), but monoximes (Me2C=NOH, [C4H8]C=NOH, [C5H10]C=NOH, PhC(H)=NOH, (OH)C6H4C(H)= NOH) react differently adding to [PtCl4(MeCN)(Me2SO)] to give the corresponding iminoacylated products [PtCl4(NH=C(Me)ON=CRR')(Me2SO)](7-11).     

tBuP(NH2)2--a reactive synthon for the synthesis of molecular imidophosphinates of group 13 metals

Reactions of tBuP(NH(2))(2) with Group 13 trialkyls MR(3) (M=Al, Ga, In; R=Me, tBu) were investigated in detail. According to variable-temperature (VT) NMR investigations, the reaction proceeds stepwise with the initial formation of aminophosphane adducts, which subsequently react to give iminophosphorane adducts and finally the heterocyclic metallonitridophosphinates. BP86/TZVPP (DFT) calculations were performed to verify this reaction pathway, to elucidate the influence of the central Group 13 element on the stability of the reaction intermediates and the heterocycles, as well as to assess the thermodynamics of their formation. The relative stability of free and complexed aminophosphane RP(NH(2))(2) and iminophosphorane R(H(2)N)(H)P=NH (adducts) with P(III) and P(V) centers was studied in more detail with DFT and MP2 methods. In addition, the influence of the substituent R was investigated by variation of R from H to Me, tBu, F, and NH(2). In general, the aminophosphane form was found to be favored for the free ligand, however, upon complexation with MR(3) (M=Al, Ga; R=alkyl) both forms are almost equal in energy.     

Synthesis of MII[N(SiMe3)2][Me3SiNC(tBu)NSiMe3] (M = Sn,Ge) from amidinate precursors: active catalysts for phenyl isocyanate cyclization

Mixed amidinato amido complexes [Me3SiNC(tBu)NSiMe3]M[N(SiMe3)2] (M = Sn 2, Ge 3) were prepared by the reaction of [Me3SiNC(tBu)NSiMe3]Li (1a) with SnCl2 and GeCl2(dioxane) in ether. The N(SiMe3)2 ligand in these compounds is derived from the rearrangement of the [Me3SiNC(tBu)NSiMe3]- anion with extrusion of tBuCN. The susceptibility of [Me3SiNC(tBu)NSiMe3]- to rearrangement appears to be dependent on reaction solvent and on the coordinated metal center. Single-crystal X-ray diffraction studies of 2 and 3 are presented. Replacement of Me for tBu in the ligand allowed [Me3SiNC(Me)NSiMe3]2SnII (4) to be isolated, and an X-ray structure of this compound is reported. The isolation of 4 indicates that steric factors also play a role in the stability of [Me3SiNC(tBu)NSiMe3]-. Compounds 2 and 3 are outstanding catalysts for the cyclotrimerization of phenyl isocyanates to perhydro-1,3,5-triazine-2,4,6-triones (isocyanurates) at room temperature. In contrast, complex 4 catalytically reacts with phenyl isocyanate to produce isocyanate dimer and trimer in a 52:35 ratio.     

Functionalization of aminophosphanes: synthesis and X-ray crystal structure of novel dilithium and trilithium complexes containing silicon-fused heteronuclear SiN2PLi five-membered rings

A first structurally characterized primary aminophosphane (Ar 2PNH 2 ( 2); Ar = 2,4,6- iPr 3C 6H 2) that is a stable solid at room temperature without decomposition by self-condensation is reported. Reactions of N-phosphanyllithium amide ( tBu 2PNHLi ( 3)) with Me 2SiCl 2 and MeSiCl 3 in Et 2O result in the formation of Me 2Si(NHP tBu 2) 2 ( 4) and MeSi(NHP tBu 2) 3 ( 5), respectively. Subsequent treatment of 4 and 5 with 2 and 3 equiv of nBuLi gave the dilithium ( 6) and trilithium ( 7) complexes, respectively. Further treatment of 5 with 3 equiv of AlMe 3 yielded the trialuminum complex MeSi[N(AlMe 2)P tBu 2] 3 ( 8). These three complexes were investigated by microanalysis and multinuclear NMR spectroscopy. The dilithium complex [Me 2Si(NLiP tBu 2) 2.3THF] ( 6) and the trilithium complex [MeSi(NLiP tBu 2) 3.3Et 2O] ( 7) were further characterized by single-crystal X-ray structural analysis.     

Accessing low denticity coordination modes of a high denticity tripodal ligand to complete its coordinative repertoire

New coordination complexes of the neutral tripodal tetra-amine Me(6)TREN with tBu(3)Ga or tBu(2)Zn have been synthesised and studied with their molecular structures revealing, for the first time, coordination to metal centres via an η(1) or η(2) mode, adding to previously reported η(3) and η(4) ligated examples.     

Tuning the redox potentials of dinuclear tungsten oxo complexes [(Cp*W(4,4'-R,R-2,2'-bpy)(mu-O))2][PF6]2 toward photochemical water splitting

A series of novel dinuclear tungsten(IV) oxo complexes with disubstituted 4,4'-R,R-2,2'-bipyridyl (R(2)bpy) ligands of the type [(Cp*W(R(2)bpy)(mu-O))(2)][PF(6)](2) (R=NMe(2), tBu, Me, H, Cl) was prepared by hydrolysis of the tungsten(IV) trichloro complexes [Cp*W(R(2)bpy)Cl(3)]. Cyclic voltammetry measurements for the tungsten(IV) oxo compounds provided evidence for one reversible oxidation and two reversible reductions leading to the oxidation states W(V)W(IV), W(IV)W(III) and W(III)W(III). The corresponding complexes [(Cp*W(R(2)bpy)(mu-O))(2)](n+) [PF(6)](n) (n=0 for R=Me, tBu, and 1, 3 for both R=Me) could be isolated after chemical oxidation/reduction of the tungsten(IV) oxo complexes. The crystal structures of the complexes [(Cp*W(R(2)bpy)(mu-O))(2)][BPh(4)](2) (R=NMe(2), tBu) and [(Cp*W(Me(2)bpy)(mu-O))(2)](n+)[PF(6)](n) (n=0, 1, 2, 3) show a cis geometry with a puckered W(2)O(2) four-membered ring for all compounds except [(Cp*W(Me(2)bpy)(mu-O))(2)] which displays a trans geometry with a planar W(2)O(2) ring. Examining the interaction of these novel tungsten oxo complexes with protons, we were able to show that the W(IV)W(IV) complexes [(Cp*W(R(2)bpy)(mu-O))(2)][PF(6) (-)](2) (R=NMe(2), tBu) undergo reversible protonation, while the W(III)W(III) complexes [(Cp*W(R(2)bpy)(mu-O))(2)] transfer two electrons forming the W(IV)W(IV) complex and molecular hydrogen.     

Synthesis and characterization of calcium complexes containing eta 2-pyrazolato ligands

Treatment of calcium bromide with 3,5-di-tert-butylpyrazolatopotassium (2 equiv) in tetrahydrofuran afforded Ca(tBu2pz)2(THF)2 (69%). The reaction of this compound with pyridine (3 equiv), tetramethylethylenediamine (TMEDA, 1 equiv), N,N,N',N',N"-pentamethyldiethylenetriamine (PMDETA, 1 equiv), triglyme (1 equiv), and tetraglyme (1 equiv) yielded Ca(tBu2pz)2(py)3 (51%), Ca(tBu2pz)2(TMEDA) (74%), Ca(tBu2pz)2(PMDETA) (50%), Ca(tBu2pz)2(triglyme) (73%), and Ca(tBu2pz)2(tetraglyme) (57%), respectively. Treatment of the tetrahydrofuran adduct of Ca(Me2pz)2, generated in situ, with PMDETA (1 equiv), triglyme (1 equiv), and tetraglyme (1 equiv) afforded Ca(Me2pz)2(PMDETA) (65%), Ca(Me2pz)2(triglyme) (54%), and Ca(Me2pz)2(tetraglyme) (40%), respectively. The X-ray crystal structures of Ca(tBu2pz)2(py)3, Ca(tBu2pz)2(TMEDA), Ca(tBu2pz)2(PMDETA), Ca(tBu2pz)2(triglyme), and Ca(Me2pz)2(PMDETA) revealed six-, seven-, or eight-coordinate calcium centers with eta 2-pyrazolato ligands. Ca(tBu2pz)2(triglyme) sublimes at 160 degrees C (0.1 mmHg). The potential utility of these complexes as source compounds for chemical vapor deposition processes is discussed.     

Über dimere dimethylmetall-bis(trimethylgermyl)amide des aluminiums, galliums und indiums

The dimethylmetal bis(trimethylgermyl)amides of Al, Ga, and In have been prepared from Li[N(GeMe₃)₂] and Me₂MCl (Me = CH₃, M = Al, Ga) or Me₂MCN (M = Ga, In) in inert solvents. The NMR (¹H, ¹³C) and vibrational spectra (IR and Raman) of these dimeric compounds have been assigned and discussed. According to the X-ray structure determination [Me₂InN(GeMe₃)₂]₂ crystallizes in the monoclinic space group C2/c (Z = 4, R = 0.032) and is isomorphous with the bis(trimethylsilyl) homologue.     

Understanding the reactivity of strained sandwich compounds with aluminum or gallium in bridging positions: experiments and DFT calculations

The aluminum and gallium dichlorides (Mamx)ECl(2)1a (E = Al; 82%) and 1b (E = Ga; 79%) (Mamx = 2,4-di-tert-butyl-6-[(dimethylamino)methyl]phenyl) reacted with dilithioferrocene or dilithioruthenocene to give [1]ferrocenophanes (2a, 2b) and [1]ruthenocenophanes (3a, 3b), respectively. The galla[1]ruthenocenophane 3b could be isolated from the reaction mixture through precipitation into hexane (50%), while 2a, 2b, and 3a underwent ring-opening polymerization under the reaction conditions of their formation reactions to give metallopolymers (M(w) (DLS) between 8.07 and 106 kDa). Monomer 3b was polymerized using Karstedt's catalyst resulting in an M(w) of 28.6(±6.3) kDa. In order to get an indication of the structure of polymers, bis(ferrocenyl) compounds (Mamx)EFc(2) (E = Al (4a), 51%; E = Ga (4b), 49%) were prepared and characterized by single crystal X-ray analysis. DFT calculations shed some light on the unexpected high reactivity of these new strained sandwich species. Optimized geometries of known aluminum and gallium-bridged [1]ferrocenophanes (Al(Pytsi) (6a), Ga(Pytsi) (6b); Pytsi = [dimethyl(2-pyridyl)silyl]bis(trimethylsilyl)methyl) and [1]ruthenocenophanes (Al(Me(2)Ntsi) (7a), Ga(Me(2)Ntsi) (7b); Me(2)Ntsi = [(dimethylamino)dimethylsilyl]bis(trimethylsilyl)methyl) matched very well with experimental molecular structures. Geometries of species 2a, 2b, 3a, and 3b were optimized (BP86/TZ2P) and the structural influence of the tBu group of the Mamx ligand in ortho position was evaluated by optimizing molecular structures of the four unknown species where the ortho-tBu group was replaced by an H atom (2a(H), 2b(H), 3a(H), and 3b(H)). The most pronounced structural effect was seen as a change of the orientation of the bridging moiety with respect to the sandwich unit. As the tBu group was removed, the aromatic ligand moved toward the freed-up space. The energetics (ΔE, ΔH(298K), and ΔG(298K)) accompanied by the structural changes were evaluated by a hydrogenolysis reaction of strained species resulting in Cp(2)M (M = Fe, Ru) and respective aluminum and gallium dihydrides. This nonisodesmic reaction showed that [1]metallocenophanes equipped with the ortho-tBu group were on average 5.5 kcal/mol higher strained (ΔH(298K)) than species where the tBu group was lacking. The investigation of the isodesmic reaction between strained species and Cp(2)M yielding bis(metallocenyl) compounds revealed that the ortho-tBu group sterically interacts with one of the metallocenyl units. The bis(metallocenyl) compounds are model compounds for the respective metallopolymers and one can conclude that even though the ortho-tBu group imposes additional strain on the starting metallocenophanes, this effect cancels out in ROPs because the ortho-tBu group imposes a similar strain on the resulting polymers. The uncovered steric repulsion between the ortho-tBu group and the sandwich moieties probably causes the ortho-tBu to act as an unusually sensitive NMR probe of the tacticity of the polymers.     

Ligand-tetrahydrofuran coupling in chelated aluminum phosphinates

When the reagents LAlMe (L = N,N'-(alkylene or arylene)bis(3,5-di-tert-butyl)salicylideneimine (alkylene = ethylene (Salen(tBu))(1), propylene (Salpen(tBu))(2), and butylene (Salben(tBu)) (3); arylene = phenylene (Salophen(tBu) (4), 3,4-dimethylphenylene (Salomphen(tBu) (5)) are combined with Ph(H)P(O)OH in tetrahydrofuran (thf) the unique aluminophosphinate compounds, [L(tBu)Al[O(2)P(H)Ph]](n) with L, n = Salen,(infinity)(6), Salpen, 2 (7), Salben, 2 (8), Salophen, (infinity)(9) and Salomphen, (infinity)(10) are produced. The yields for the latter two reactions are low, and it was subsequently found that the unique thf-coupled compounds appear in the thf filtrates of the original reaction mixture. These compounds are, [L-thf(tBu)Al[O(2)P(H)Ph]](2), L = Salophen (13) and Salomphen (14). The thf connects through an alpha-carbon to only one of the two possible imine carbons of the ligand. While trying to determine how this coupling proceeds, the six-coordinate, solution-state species LAlMe(thf) (L = Salophen (11) and Salomphen (12) were discovered and implicated as intermediates. All of the compounds are characterized by melting point, NMR, IR, and X-ray analyses for 5-8, 13, and 14. A possible mechanism for the thf coupling event is presented.     

Synthesis and characterization of HC[C(Me)N(C(6)H(3)-2,6-i-Pr(2))](2)MX(2) (M = Al, X = Cl, I; M = Ga, In, X = Me, Cl, I): sterically encumbered beta-diketiminate group 13 metal derivatives

A series of group 13 metal complexes featuring the beta-diketiminate ligand [[(C(6)H(3)-2,6-i-Pr(2))NC(Me)](2)CH](-) (i.e., [Dipp(2)nacnac](-), Dipp = C(6)H(3)-2,6-i-Pr(2)) have been prepared and spectroscopically and structurally characterized. The chloride derivatives Dipp(2)nacnacMCl(2) (M = Al (3), Ga (5), In (8)) were isolated in good yield by the reaction of 1 equiv of Dipp(2)nacnacLi.Et(2)O (2) and the respective metal halides. The iodide derivatives Dipp(2)nacnacMI(2) (M = Al (4), Ga (6), In (9)), which are useful for reduction to afford M(I) species, were made by a variety of routes. Thus, 4 was obtained by treatment of the previously reported Dipp(2)nacnacAlMe(2) with I(2), whereas the gallium analogue 6 was obtained as a product of the reaction of "GaI" with Dipp(2)nacnacLi.Et(2)O, and 9 was obtained by direct reaction of InI(3) and the lithium salt. The methyl derivatives Dipp(2)nacnacMMe(2) (M = Ga (7), In (10)), which are analogous to the previously reported Dipp(2)nacnacAlMe(2), were synthesized by the reaction of GaMe(3) with Dipp(2)nacnacH (1) or by reaction of the indium chloride derivative 8 with 2 equiv of MeMgBr in diethyl ether. The compounds 3-10 exist as colorless, air- and moisture-sensitive crystalline solids. Their X-ray crystal structures feature nearly planar C(3)N(2) arrays in the Dipp(2)nacnac ligand backbone with short C-C and C-N distances that are consistent with a delocalized structure. However, there are large dihedral angles between the C(3)N(2) plane and the N(2)M metal coordination plane which have been attributed mainly to steric effects. The relatively short M-N distances are consistent with the coordination numbers of the metals and the normal/dative character of the nitrogen ligands. The compounds were also characterized by (1)H and (13)C NMR spectroscopy. (1)H NMR data for 7 revealed equivalent methyl groups whereas the spectrum of 10 displayed two In-Me signals which indicated that ring wagging was slow on the (1)H NMR time scale.     

Synthesis and reactivity of calix[4]arene-supported group 4 imido complexes

New mononuclear titanium and zirconium imido complexes [M(NR)(R'(2)calix)] [M=Ti, R'=Me, R=tBu (1), R=2,6-C(6)H(3)Me(2) (2), R=2,6-C(6)H(3)iPr(2) (3), R=2,4,6-C(6)H(2)Me(3) (4); M=Ti, R'=Bz, R=tBu (5), R=2,6-C(6)H(3)Me(2) (6), R=2,6-C(6)H(3)iPr(2) (7); M=Zr, R'=Me, R=2,6-C(6)H(3)iPr(2) (8)] supported by 1,3-diorganyl ether p-tert-butylcalix[4]arenes (R'(2)calix) were prepared in good yield from the readily available complexes [MCl(2)(Me(2)calix)], [Ti(NR)Cl(2)(py)(3)], and [Ti(NR)Cl(2)(NHMe(2))(2)]. The crystallographically characterised complex [Ti(NtBu)(Me(2)calix)] (1) reacts readily with CO(2), CS(2), and p-tolyl-isocyanate to give the isolated complexes [Ti[N(tBu)C(O)O](Me(2)calix)] (10), [[Ti(mu-O)(Me(2)calix)](2)] (11), [[Ti(mu-S)(Me(2)calix)](2)] (12), and [Ti[N(tBu)C(O)N(-4-C(6)H(4)Me)](Me(2)calix)] (13). In the case of CO(2) and CS(2), the addition of the heterocumulene to the Ti-N multiple bond is followed by a cycloreversion reaction to give the dinuclear complexes 11 and 12. The X-ray structure of 13.4(C(7)H(8)) clearly establishes the N,N'-coordination mode of the ureate ligand in this compound. Complex 1 undergoes tert-butyl/arylamine exchange reactions to form 2, 3, [Ti(N-4-C(6)H(4)Me)(Me(2)calix)] (14), [Ti(N-4-C(6)H(4)Fc)(Me(2)calix)] (15) [Fc=Fe(eta(5)-C(5)H(5))(eta(5)-C(5)H(4))], and [[Ti(Me(2)calix)](2)[mu-(N-4-C(6)H(4))(2)CH(2)]] (16). Reaction of 1 with H(2)O, H(2)S and HCl afforded the compounds [[Ti(mu-O)(Me(2)calix)](2)] (11), [[Ti(mu-S)(Me(2)calix)](2)] (12), and [TiCl(2)(Me(2)calix)] in excellent yields. Furthermore, treatment of 1 with two equivalents of phenols results in the formation of [Ti(O-4-C(6)H(4)R)(2)(Me(2)calix)] (R=Me 17 or tBu 18), [Ti(O-2,6-C(6)H(3)Me(2))(2)(Me(2)calix)] (19) and [Ti(mbmp)(Me(2)calix)] (20; H(2)mbmp=2,2'-methylene-bis(4-methyl-6-tert-butylphenol) or CH(2)([CH(3)][C(4)H(9)]C(6)H(2)-OH)(2)). The bis(phenolate) compounds 17 and 18 with para-substituted phenolate ligands undergo elimination and/or rearrangement reactions in the nonpolar solvents pentane or hexane. The metal-containing products of the elimination reactions are dinuclear complexes [[Ti(O-4-C(6)H(4)R)(Mecalix)](2)] [R=Me (23) or tBu (24)] where Mecalix=monomethyl ether of p-tert-butylcalix[4]arene. The products of the rearrangement reaction are [Ti(O-4-C(6)H(4)Me)(2) (paco-Me(2)calix)] (25) and [Ti(O-4-C(6)H(4)tBu)(2)(paco-Me(2)calix)] (26), in which the metallated calix[4]arene ligand is coordinated in a form reminiscent of the partial cone (paco) conformation of calix[4]arene. In these compounds, one of the methoxy groups is located inside the cavity of the calix[4]arene ligand. The complexes 24, 25 and 26 have been crystallographically characterised. Complexes with sterically more demanding phenolate ligands, namely 19 and 20 and the analogous zirconium complexes [Zr(O-4-C(6)H(4)Me)(2)(Me(2)calix)] (21) and [Zr(O-2,6-C(6)H(3)Me(2))(2)(Me(2)calix)] (22) do not rearrange. Density functional calculations for the model complexes [M(OC(6)H(5))(2)(Me(2)calix)] with the calixarene possessing either cone or partial cone conformations are briefly presented.