Lithium aluminates on a molecular titanium oxide

Lithium aluminates Li[Al(O-2,6-Me(2)C(6)H(3))R'(3)] (R' = Et, Ph) react with the μ(3)-alkylidyne oxoderivative ligands [{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-CR)] [R = H (1), Me (2)] to afford the aluminum-lithium-titanium cubane complexes [{R'(3)Al(μ-O-2,6-Me(2)C(6)H(3))Li}(μ(3)-O)(3){Ti(η(5)-C(5)Me(5))}(3)(μ(3)-CR)] [R = H, R' = Et (5), Ph (7); R = Me, R' = Et (6), Ph (8)]. Complex 7 evolves with the formation of a lithium dicubane species and a Li{Al(μ-O-2,6-Me(2)C(6)H(3))Ph(3)}(2)] unit.     

Construction of titanasiloxanes by incorporation of silanols to the metal oxide model [(Ti(eta 5-C5Me5)(mu-O))3(mu3-CR)]: DFT elucidation of the reaction mechanism

A family of novel titanasiloxanes containing the structural unit {[Ti(eta(5)-C(5)Me(5))O](3)} were synthesized by hydron-transfer processes involving reactions with equimolecular amounts of mu(3)-alkylidyne derivatives [{Ti(eta(5)-C(5)Me(5))(mu-O)}(3)(mu(3)-CR)] (R=H (1), Me (2)) and monosilanols, R(3)'Si(OH), silanediols, R(2)'Si(OH)(2), and the silanetriol tBuSi(OH)(3). Treatment of 1 and 2 with triorganosilanols (R'=Ph, iPr) in hexane affords the new metallasiloxane derivatives [{Ti(eta(5)-C(5)Me(5))(mu-O)}(3)(mu-CHR)(OSiR(3)')] (R=H, R'=Ph (3), iPr (4); R=Me, R'=Ph (5), iPr (6)). Analogous reactions with silanediols, (R'=Ph, iPr), give the cyclic titanasiloxanes [{Ti(eta(5)-C(5)Me(5))(mu-O)}(3)(mu-O(2)SiR'(2))(R)] (R=Me, R'=Ph (7), iPr (8); R=Et, R'=Ph (9), iPr (10)). Utilization of tBuSi(OH)(3) with 1 or 2 at room temperature produces the intermediate complexes [{Ti(eta(5)-C(5)Me(5)) (mu-O)}(3)(mu-O(2)Si(OH)tBu)(R)] (R=Me (11), Et(12)). Further heating of solutions of 11 or 12 affords the same compound with an adamantanoid structure, [{Ti(eta(5)-C(5)Me(5))(mu-O)}(3)(mu-O(3)SitBu)] (13) and methane or ethane elimination, respectively. The X-ray crystal structures of 3, 4, 6, 8, 10, 12, and 13 have been determined. To gain an insight into the mechanism of these reactions, DFT calculations have been performed on the incorporation of monosilanols to the model complex [{Ti(eta(5)-C(5)H(5))(mu-O)}(3)(mu(3)-CMe)] (2 H). The proposed mechanism consists of three steps: 1) hydron transfer from the silanol to one of the oxygen atoms of the Ti(3)O(3) ring, forming a titanasiloxane; 2) intramolecular hydron migration to the alkylidyne moiety; and 3) a mu-alkylidene ligand rotation to give the final product.     

Catalytic addition of amine N-H bonds to carbodiimides by half-sandwich rare-earth metal complexes: efficient synthesis of substituted guanidines through amine protonolysis of rare-earth metal guanidinates

Reaction of [Ln(CH(2)SiMe(3))(3)(thf)(2)] (Ln=Y, Yb, and Lu) with one equivalent of Me(2)Si(C(5)Me(4)H)NHR' (R'=Ph, 2,4,6-Me(3)C(6)H(2), tBu) affords straightforwardly the corresponding half-sandwich rare-earth metal alkyl complexes [{Me(2)Si(C(5)Me(4))(NR')}Ln(CH(2)SiMe(3))(thf)(n)] (1: Ln = Y, R' = Ph, n=2; 2: Ln = Y, R' = C(6)H(2)Me(3)-2,4,6, n=1; 3: Ln = Y, R' = tBu, n=1; 4: Ln = Yb, R' = Ph, n=2; 5: Ln = Lu, R' = Ph, n=2) in high yields. These complexes, especially the yttrium complexes 1-3, serve as excellent catalyst precursors for the catalytic addition of various primary and secondary amines to carbodiimides, efficiently yielding a series of guanidine derivatives with a wide range of substituents on the nitrogen atoms. Functional groups such as C[triple chemical bond]N, C[triple chemical bond]CH, and aromatic C--X (X: F, Cl, Br, I) bonds can survive the catalytic reaction conditions. A primary amino group can be distinguished from a secondary one by the catalyst system, and therefore, the reaction of 1,2,3,4-tetrahydro-5-aminoisoquinoline with iPrN==C==NiPr can be achieved stepwise first at the primary amino group to selectively give the monoguanidine 38, and then at the cyclic secondary amino unit to give the biguanidine 39. Some key reaction intermediates or true catalyst species, such as the amido complexes [{Me(2)Si(C(5)Me(4))(NPh)}Y(NEt(2))(thf)(2)] (40) and [{Me(2)Si(C(5)Me(4))(NPh)}Y(NHC(6)H(4)Br-4)(thf)(2)] (42), and the guanidinate complexes [{Me(2)Si(C(5)Me(4))(NPh)}Y{iPrNC(NEt(2))(NiPr)}(thf)] (41) and [{Me(2)Si(C(5)Me(4))(NPh)}Y{iPrN}C(NC(6)H(4)Br-4)(NHiPr)}(thf)] (44) have been isolated and structurally characterized. Reactivity studies on these complexes suggest that the present catalytic formation of a guanidine compound proceeds mechanistically through nucleophilic addition of an amido species, formed by acid-base reaction between a rare-earth metal alkyl bond and an amine N--H bond, to a carbodiimide, followed by amine protonolysis of the resultant guanidinate species.     

Flexible coordination of the carboxylate ligand in tin(II) amides and a 1,3-diaza-2,4-distannacyclobutanediyl

A series of tin(II) amido complexes possessing m-terphenyl carboxylate ligands have been prepared. These complexes, namely [(Me(3)Si)(2)NSn(mu-O(2)CC(6)H(2)Ph(3))](2), [(Me(3)Si)(2)NSn(mu-O(2)CC(6)H(3)Mes(2))](2), and [(Me(3)Si)(2)NSn(mu-O(2)CC(6)H(2)Mes(2)Me)](2) [Mes = 2,4,6-trimethylphenyl], are the first structurally characterized examples of tin(II) carboxylate complexes exhibiting discrete Sn(2)O(4)C(2) heterocyclic cores. Initial reactivity studies led to the isolation of a 1,3-diaza-2,4-distannacyclobutanediyl, [(Mes(2)C(6)H(3)CO(2))Sn(mu-NSiMe(3))](2). This molecule possesses a Sn(2)N(2) heterocyclic core and it was crystallised as both the CH(2)Cl(2) and Et(2)O solvates. Although the tin atoms in this molecule have a formal oxidation state of 3+, preliminary computational studies on this molecule suggest that it is best described as a ground state singlet. Finally, the X-ray crystal structure of (CH(2)Cl)(Cl)Sn[N(SiMe(3))(2)](2), the product of oxidative addition of CH(2)Cl(2) to Sn[N(SiMe(3))(2)](2), is also presented herein.     

The synthesis, characterisation and reactivity of 2-phosphanylethylcyclopentadienyl complexes of cobalt, rhodium and iridium

2-Phosphanylethylcyclopentadienyl lithium compounds, Li[C(5)R'(4)(CH(2))(2)PR(2)] (R = Et, R' = H or Me, R = Ph, R' = Me), have been prepared from the reaction of spirohydrocarbons C(5)R'(4)(C(2)H(4)) with LiPR(2). C(5)Et(4)HSiMe(2)CH(2)PMe(2), was prepared from reaction of Li[C(5)Et(4)] with Me(2)SiCl(2) followed by Me(2)PCH(2)Li. The lithium salts were reacted with [RhCl(CO)(2)](2), [IrCl(CO)(3)] or [Co(2)(CO)(8)] to give [M(C(5)R'(4)(CH(2))(2)PR(2))(CO)] (M = Rh, R = Et, R' = H or Me, R = Ph, R' = Me; M = Ir or Co, R = Et, R' = Me), which have been fully characterised, in many cases crystallographically as monomers with coordination of the phosphorus atom and the cyclopentadienyl ring. The values of nu(CO) for these complexes are usually lower than those for the analogous complexes without the bridge between the cyclopentadienyl ring and the phosphine, the exception being [Rh(Cp'(CH(2))(2)PEt(2))(CO)] (Cp' = C(5)Me(4)), the most electron rich of the complexes. [Rh(C(5)Et(4)SiMe(2)CH(2)PMe(2))(CO)] may be a dimer. [Co(2)(CO)(8)] reacts with C(5)H(5)(CH(2))(2)PEt(2) or C(5)Et(4)HSiMe(2)CH(2)PMe(2) (L) to give binuclear complexes of the form [Co(2)(CO)(6)L(2)] with almost linear PCoCoP skeletons. [Rh(Cp'(CH(2))(2)PEt(2))(CO)] and [Rh(Cp'(CH(2))(2)PPh(2))(CO)] are active for methanol carbonylation at 150 degrees C and 27 bar CO, with the rate using [Rh(Cp'(CH(2))(2)PPh(2))(CO)] (0.81 mol dm(-3) h(-1)) being higher than that for [RhI(2)(CO)(2)](-) (0.64 mol dm(-3) h(-1)). The most electron rich complex, [Rh(Cp'(CH(2))(2)PEt(2))(CO)] (0.38 mol dm(-3) h(-1)) gave a comparable rate to [Cp*Rh(PEt(3))(CO)] (0.30 mol dm(-3) h(-1)), which was unstable towards oxidation of the phosphine. [Rh(Cp'(CH(2))(2)PEt(2))I(2)], which is inactive for methanol carbonylation, was isolated after the methanol carbonylation reaction using [Rh(Cp'(CH(2))(2)PEt(2))(CO)]. Neither of [M(Cp'(CH(2))(2)PEt(2))(CO)] (M = Co or Ir) was active for methanol carbonylation under these conditions, nor under many other conditions investigated, except that [Ir(Cp'(CH(2))(2)PEt(2))(CO)] showed some activity at higher temperature (190 degrees C), probably as a result of degradation to [IrI(2)(CO)(2)](-). [M(Cp'(CH(2))(2)PEt(2))(CO)] react with MeI to give [M(Cp'(CH(2))(2)PEt(2))(C(O)Me)I] (M = Co or Rh) or [Ir(Cp'(CH(2))(2)PEt(2))Me(CO)]I. The rates of oxidative addition of MeI to [Rh(C(5)H(4)(CH(2))(2)PEt(2))(CO)] and [Rh(Cp'(CH(2))(2)PPh(2))(CO)] are 62 and 1770 times faster than to [Cp*Rh(CO)(2)]. Methyl migration is slower, however. High pressure NMR studies show that [Co(Cp'(CH(2))(2)PEt(2))(CO)] and [Cp*Rh(PEt(3))(CO)] are unstable towards phosphine oxidation and/or quaternisation under methanol carbonylation conditions, but that [Rh(Cp'(CH(2))(2)PEt(2))(CO)] does not exhibit phosphine degradation, eventually producing inactive [Rh(Cp'(CH(2))(2)PEt(2))I(2)] at least under conditions of poor gas mixing. The observation of [Rh(Cp'(CH(2))(2)PEt(2))(C(O)Me)I] under methanol carbonylation conditions suggests that the rhodium centre has become so electron rich that reductive elimination of ethanoyl iodide has become rate determining for methanol carbonylation. In addition to the high electron density at rhodium.     

Bimetallic fluorine-substituted anilido-aldimine zinc complexes for CO2/(cyclohexene oxide) copolymerization

Regioselective nucleophilic aromatic substitution of an o-fluorine occurs to afford fluorine-substituted o-phenylene-bridged bis(anilido-aldimine) compounds o-C6H4[(C6H2R2)N=CH-C6F4-(H)N(C6H3R'2)]2 when Li(H)N-C6H3R'2 (R' = iPr, Et, Me) is reacted with o-C6H4[(C6H2R2)N=CH-C6F5]2 (R = iPr, Et, Me) in a nonpolar solvent such as diethyl ether or toluene. Successive additions of Me2Zn and SO2 gas to the bis(anilido-aldimine) compounds afford quantitatively dinuclear mu-methylsulfinato zinc complexes o-C6H4[[(C6H2R2)N=CH-C6F4-N(C6H3R'2)-kappa2N,N]Zn(mu-OS(O)Me)]2 (R = iPr, R' = iPr, 3a; R = iPr, R' = Me, 3c; R = Et, R' = (i)Pr, 3d; R = Et, R' = Et, 3e; R = Et, R' = Me, 3f; R = Me, R' = iPr, 3g; R = Me, R' = Et, 3h; R = Me, R' = Me, 3i). The molecular structure of 3c was confirmed by X-ray crystallography. Fluorine-substituted complexes 3a-i show significantly higher TOF (turnover frequencies) than the unfluorinated analogues for CO2/(cyclohexene oxide) copolymerization. The TOF is highly sensitive to the substituents R and R', and the highest TOF (2480 h(-1)) is obtained with 3g (R = Me, R' = iPr). Complex 3g is less sensitive to the residual protic impurities present in the monomers and shows activity at such a low catalyst concentration as [Zn]:[cyclohexene oxide] = 1:50,000, at which the unfluorinated analogue is completely inactive. By realizing the activity at such an extremely low [Zn]:[cyclohexene oxide] ratio, we achieve a high TON (turnover number) up to 10,100. High-molecular-weight polymers (M(n), 100,000-200,000) are obtained with a rather broad molecular-weight distribution (M(w)/M(n), 1.3-2.5). The obtained polymers are not perfectly alternating, and variable carbonate linkages (65-85%) are observed depending on the N-aryl ortho substituents R and R' and the polymerization conditions.     

Tin-oxo clusters based on aryl arsonate anions

Reactions of Ph(3)SnOH or Ph3SnCl with aryl arsonic acids RAsO3H2, where R=C6H5 (1), 2-NH2C6H4 (2), 4-NH2C6H4 (3), 2-NO2C6H4 (4), 3-NO2C6H4 (5), 4-NO2C6H4 (6), 3-NO2-4-OHC6H3 (7), 2-ClC6H4 (8) and 2,4-Cl2C6H3 (9), gave 18 Sn-O cluster compounds. These compounds can be classified into four types: type A: [{(PhSn)3(RAsO3)3(mu3-O)(OH)(R'O)2}2Sn] (R=C6H5, 2-NH2C6H4, 4-NH2C6H4, 2-NO2C6H4, 3-NO2C6H4, 2-ClC6H4, 2,4-Cl2C6H3, and 3-NO2-4-OHC6H3; R'=Me or Et); type B: [{(PhSn)3(RAsO3)(2)(RAsO3H)(mu3-O)(R'O)2}2] (R=4-NO2C6H4, R'=Me); type C: [{(PhSn)3(RAsO3)3(mu3-O)(R'O)3}2Sn] (R=2,4-Cl2C6H3, R'=Me); type D: [{Sn3Cl3(mu3-O)(R'O)3}(2)(RAsO3)4] (R=2-NO2C6H4 and 4-NO2-C6H4; R'=Me or Et). Structures of types A and B contain [Sn3(mu3-O)(mu2-OR')2] building blocks, while in types C and D the stannoxane cores are built from two [Sn3(mu3-O)(mu2-OR')3] building blocks. The reactions proceeded with partial or complete dearylation of the triphenyltin precursor. These various structural forms are realized by subtle changes in the nature of the organotin precursors and aryl arsonic acids. The syntheses, structures, and structural interrelationship of these organostannoxanes are discussed.     

Expanding the scope of sulfur-centered Arbuzov rearrangement in diethyl/di-n-propyl sulfite for the synthesis of mixed-ligand di-n-butyltin alkanesulfonates

A one-pot reaction between di-n-butyltin oxide and diethyl/di-n-propyl sulfite in the presence of an equimolar amount of alkyl iodide proceeds via sulfur-centered Arbuzov rearrangement to afford the corresponding di-n-butyltin (alkoxy)alkanesulfonates n-Bu2Sn(OR')OS(O)2R [R = R' = Et (1), n-Pr (2); R = Me, R' = Et (3), n-Pr (4)]. The compounds 1 and 3 react with methylphosphonic acid under mild conditions to give [n-Bu2Sn(OS(O)2R)OP(O)(OH)Me]n [R = Et (5), Me (6), respectively].     

Amidoximes provide facile platinum(II)-mediated oxime-nitrile coupling

The nucleophilic addition of amidoximes R'C(NH(2))═NOH [R' = Me (2.Me), Ph (2.Ph)] to coordinated nitriles in the platinum(II) complexes trans-[PtCl(2)(RCN)(2)] [R = Et (1t.Et), Ph (1t.Ph), NMe(2) (1t.NMe(2))] and cis-[PtCl(2)(RCN)(2)] [R = Et (1c.Et), Ph (1c.Ph), NMe(2) (1c.NMe(2))] proceeds in a 1:1 molar ratio and leads to the monoaddition products trans-[PtCl(RCN){HN═C(R)ONC(R')NH(2)}]Cl [R = NMe(2); R' = Me ([3a]Cl), Ph ([3b]Cl)], cis-[PtCl(2){HN═C(R)ONC(R')NH(2)}] [R = NMe(2); R' = Me (4a), Ph (4b)], and trans/cis-[PtCl(2)(RCN){HN═C(R)ONC(R')NH(2)}] [R = Et; R' = Me (5a, 6a), Ph (5b, 6b); R = Ph; R' = Me (5c, 6c), Ph (5d, 6d), correspondingly]. If the nucleophilic addition proceeds in a 2:1 molar ratio, the reaction gives the bisaddition species trans/cis-[Pt{HN═C(R)ONC(R')NH(2)}(2)]Cl(2) [R = NMe(2); R' = Me ([7a]Cl(2), [8a]Cl(2)), Ph ([7b]Cl(2), [8b]Cl(2))] and trans/cis-[PtCl(2){HN═C(R)ONC(R')NH(2)}(2)] [R = Et; R' = Me (10a), Ph (9b, 10b); R = Ph; R' = Me (9c, 10c), Ph (9d, 10d), respectively]. The reaction of 1 equiv of the corresponding amidoxime and each of [3a]Cl, [3b]Cl, 5b-5d, and 6a-6d leads to [7a]Cl(2), [7b]Cl(2), 9b-9d, and 10a-10d. Open-chain bisaddition species 9b-9d and 10a-10d were transformed to corresponding chelated bisaddition complexes [7d](2+)-[7f](2+) and [8c](2+)-[8f](2+) by the addition of 2 equiv AgNO(3). All of the complexes synthesized bear nitrogen-bound O-iminoacylated amidoxime groups. The obtained complexes were characterized by elemental analyses, high-resolution ESI-MS, IR, and (1)H NMR techniques, while 4a, 4b, 5b, 6d, [7b](Cl)(2), [7d](SO(3)CF(3))(2), [8b](Cl)(2), [8f](NO(3))(2), 9b, and 10b were also characterized by single-crystal X-ray diffraction.     

Synthesis,structure, and reactivity of some sterically hindered (Silylamino)phosphines

A series of new (silylamino)phosphines that contain sterically bulky silyl groups on nitrogen were prepared by deprotonation/substitution reactions of the hindered disilylamines t-BuR(2)Si(Me(3)Si)NH (1, R = Me; 2, R = Ph) and (Et(3)Si)(2)NH (3). Sequential treatment of the N-lithio derivatives of 1-3 with PCl(3) or PhPCl(2) and MeLi gave the corresponding (silylamino)phosphines t-BuR(2)Si(Me(3)Si)NP(R')Me (5, R = Me, R' = Ph; 6, R = Ph, R' = Me) and (Et(3)Si)(2)NP(R)Me (11, R = Me; 12, R = Ph) in high yields. Two of the P-chloro intermediates t-BuR(2)Si(Me(3)Si)NP(Ph)Cl (7, R = Ph; 9, R = Me) were also isolated and fully characterized. Hydrolysis of 7 afforded the crystalline PH-substituted aminophosphine oxide t-BuPh(2)SiN(H)P(Ph)(=O)H (10). Thermal decomposition of 7 occurred with elimination of Me(3)SiCl and formation of a novel P(2)N(2) four-membered ring system (36) that contains both P(III) and P(V) centers. Reactions of the N-lithio derivatives of amines 1 and 2 with phosphorus trihalides afforded the thermally stable -PF(2) derivatives t-BuR(2)Si(Me(3)Si)NPF(2) (13, R = Me; 14, R = Ph) and the unstable -PCl(2) analogue 17 (R = Ph). Reduction (using LiAlH(4)) of the SiPh-substituted dihalophosphines 14 and 17 gave the unstable parent phosphine t-BuPh(2)Si(Me(3)Si)NPH(2) (15). The P-organo-substituted (silylamino)phosphines underwent oxidative bromination to afford high yields of the corresponding N-silyl-P-bromophosphoranimines t-BuR(2)SiN=P(R')(Me)Br (18, R = R' = Me; 19, R = Me, R' = Ph; 20, R = Ph, R' = Me) and Et(3)SiN=P(R)(Me)Br (23, R = Me; 24, R = Ph). Subsequent treatment of these reactive PBr compounds with lithium trifluoroethoxide or phenoxide produced the corresponding PO derivatives t-BuR(2)SiN=P(R')(Me)OR' ' (25 and 26, R' ' = CH(2)CF(3); 28-30, R' ' = Ph) and Et(3)SiN=P(R)(Me)OR' (31 and 33, R' = CH(2)CF(3); 32 and 34, R = Ph), respectively. Many of the new compounds containing the bulky tert-butyldiphenylsilyl group, t-BuPh(2)Si, were solids that gave crystals suitable for X-ray diffraction studies. Consequently, the crystal structures of three (silylamino)phosphines (6, 7, and 14), one (silylamino)phosphine oxide (10), one N-silylphosphoranimine (30), and the cyclic compound 36 were determined. Among the (silylamino)phosphines, the P-N bond distances [6, N-PMe(2), 1.725(3) A; 7, N-P(Ph)Cl, 1.68(1) A, 14, N-PF(2), 1.652(4) A] decreased significantly as the electron-withdrawing nature of the phosphorus substituents increased. The N-silylphosphoranimine t-BuPh(2)SiN=PMe(2)OPh (30), which is a model system for poly(phosphazene) precursors, had a much shorter P=N distance of 1.512(6) A and a wide Si-N-P bond angle of 166.4(3) degrees. A similar P=N bond distance [1.514(7) A] and Si-N-P angle [169.9(6) degrees ] were observed for the exocyclic P=N-Si linkage in the ring compound 36, while the phosphine oxide 10 had P-N and P=O distances of 1.637(4) and 1.496(3) A, respectively, and a Si-N-P angle of 134.3(2) degrees.     

Reactions of tetrakis(dimethylamide)-titanium, -zirconium and -hafnium with silanes: synthesis of unusual amide hydride complexes and mechanistic studies of titanium-silicon-nitride (Ti-Si-N) formation

M(NMe(2))(4) (M = Ti, Zr, Hf) were found to react with H(2)SiR'Ph (R' = H, Me, Ph) to yield H(2), aminosilanes, and black solids. Unusual amide hydride complexes [(Me(2)N)(3)M(mu-H)(mu-NMe(2))(2)](2)M (M = Zr, 1; Hf, 2) were observed to be intermediates and characterized by single-crystal X-ray diffraction. [(Me(2)N)(3)M(mu-D)(mu-NMe(2))(2)](2)M (1-d(2), 2-d(2)) were prepared through reactions of M(NMe(2))(4) with D(2)SiPh(2). Reactions of (Me(2)N)(3)ZrSi(SiMe(3))(3) (5) with H(2)SiR'Ph were found to give aminosilanes and (Me(2)N)(2)Zr(H)Si(SiMe(3))(3) (6). These reactions are reversible through unusual equilibria such as (Me(2)N)(3)ZrSi(SiMe(3))(3) (5) + H(2)SiPh(2) right arrow over left arrow (Me(2)N)(2)Zr(H)Si(SiMe(3))(3) (6) + HSi(NMe(2))Ph(2). The deuteride ligand in (Me(2)N)(2)Zr(D)Si(SiMe(3))(3) (6-d(1)) undergoes H-D exchange with H(2)SiR'Ph (R' = Me, H) to give 6 and HDSiR'Ph. The reaction of Ti(NMe(2))(4) with SiH(4) in chemical vapor deposition at 450 degrees C yielded thin Ti-Si-N ternary films containing TiN and Si(3)N(4). Ti(NMe(2))(4) reacts with SiH(4) at 23 degrees C to give H(2), HSi(NMe(2))(3), and a black solid. HNMe(2) was not detected in this reaction. The reaction mixture, upon heating, gave TiN and Si(3)N(4) powders. Analyses and reactivities of the black solid revealed that it contained -H and unreacted -NMe(2) ligands but no silicon-containing ligand. Ab initio quantum chemical calculations of the reactions of Ti(NR(2))(4) (R = Me, H) with SiH(4) indicated that the formation of aminosilanes and HTi(NR(2))(3) was favored. These calculations also showed that HTi(NH(2))(3) (3b) reacted with SiH(4) or H(3)Si-NH(2) in the following step to give H(2)Ti(NH(2))(2) (4b) and aminosilanes. The results in the current studies indicated that the role of SiH(4) in its reaction with Ti(NMe(2))(4) was mainly to remove amide ligands as HSi(NMe(2))(3). The removal of amide ligands is incomplete, and the reaction thus yielded "=Ti(H)(NMe(2))" as the black solid. Subsequent heating of the black solid and HSi(NMe(2))(3) may then yield TiN and Si(3)N(4), respectively, as the Ti-Si-N materials.     

Transfer hydrogenation processes to mu(3)-alkylidyne groups on the organotitanium oxide [Ti(3)Cp*O(3)

The photochemical treatment of mu(3)-alkylidyne complexes [[TiCp*(mu-O)](3)(mu(3)-CR)] (R=H (1), Me (2), Cp*=eta(5)-C(5)Me(5)) with the amines (2,6-Me(2)C(6)H(3))NH(2), Et(2)NH, and Ph(2)NH and the imine Ph(2)C=NH leads to the partial hydrogenation of the alkylidyne moiety that is supported on the organometallic oxide, [Ti(3)Cp*O(3)], and the formation of new oxoderivatives [[TiCp*(3)(mu-CHR)(R'NR")] (R"=2,6-Me(2)C(6)H(3), R'=H, R=H (3), Me (4); R'=R"=Et, R=H (5), Me (6); R'=R"=Ph, R=H (7), Me (8)) and [[TiCp*(mu-O)](3)(mu-CHR)(N=CPh(2))] (R=H (9), R=Me (10)), respectively. A sequential transfer hydrogenation process occurs when complex 1 is treated with tBuNH(2), which initially gives the mu-methylene [[TiCp*(mu-O)](3)(mu-CH(2))(HNtBu)] (11) complex and finally, the alkyl derivative [[TiCp*(mu-O)](3)(mu-NtBu)Me] (12). Furthermore, irradiation of solutions of the mu(3)-alkylidyne complexes 1 or 2 in the presence of diamines o-C(6)H(4)(NH(2))(2) and H(2)NCH(2)CH(2)NH(2) (en) affords [[TiCp*(mu-O)](3)(mu(3)-eta(2)-NC(6)H(4)NH)] (13) and [[TiCp*(mu-O)](3)(mu(3)-eta(2)-NC(2)H(4)NH)] (14) by either methane or ethane elimination, respectively. In the reaction of 1 with en, an intermediate complex [[TiCp*(mu-O)](3)(mu-CH(2))(NHCH(2)CH(2)NH(2))] (15) is detected by (1)H NMR spectroscopy. Thermal treatment of the complexes 4-10 quantitatively regenerates the starting mu(3)-alkylidyne compounds and the amine R'(2)NH or the imine Ph(2)C=NH; however, heating of solutions of 3 or 4 in [D(6)]benzene or a equimolecular mixture of both at 170 degrees C produces methane, ethane, or both, and the complex [[TiCp*(mu-O)](3)[mu(3)-eta(2)-NC(6)H(3)(Me)CH(2)]] (16). The molecular structure of 8 has been established by single-crystal X-ray analysis.     

Syntheses of Group 4 ansa-trovacene complexes and conversion of [1]silatrovacenophanes into paramagnetic metallopolymers by ring-opening polymerization

An improved protocol for the selective dilithiation of [V(η(5)-C(5)H(5))(η(7)-C(7)H(7))] has been developed, which afforded [V(η(5)-C(5)H(4)Li)(η(7)-C(7)H(6)Li)]·PMDTA (5; PMDTA=N,N,N',N',N'-pentamethyldiethylenetriamine) in almost quantitative yield (98%). In the solid state, the species features a dimeric structure with two terminal and two bridging lithium atoms, with the latter connecting both sandwich subunits. Reaction with suitable Group 4 dihalide compounds enabled the isolation of highly strained silicon- and germanium-bridged [1]trovacenophanes 6 and 7. Similarly, reaction of 5 with Cl(2)Sn(2)tBu(4) afforded the rather unstrained complex [V(η(5)-C(5)H(4))(η(7)-C(7)H(6))Sn(2)tBu(4)] (8), which together with 7 represent the first trovacenophanes to incorporate heavier analogues of silicon in the ansa-bridge. Ring-opening polymerization reactions of [V(η(5)-C(5)H(4))(η(7)-C(7)H(6))SiRR'] (2a: R=R'=Me; 6: R=Me, R'=iPr) were performed by heating in a solution of toluene in the presence of the Karstedt catalyst, which resulted in the formation of the corresponding soluble poly(trovacenylsilanes) in yields of 41 and 33%, respectively. As estimated by gel permeation chromatography (GPC), the macromolecules possess molecular weights of M(n)=10,010 and 5580 g mol(-1) with polydispersity indices of 2.31 and 1.64 for 9 and 10, respectively. ESR spectroscopic studies on 9 and 10 revealed only a single broad resonance in each case without any identifiable (51)V hyperfine coupling.     

Reactions of amides with organoaluminum compounds: factors affecting the coordination mode of aluminum amidates

Factors affecting the coordination mode of an amidato group on aluminum will be presented. The reaction of N-tert-butylalkylacetamide ((t)BuNHCR([double bond]O)) with 1.1 molar equiv of Me(3)Al in refluxing hexane affords a pentacoordinated, dimeric compound [Me(2)Al[eta(2)-(t)BuNC(R)(mu(2)-O)]](2) (3, R = p-(t)Bu-C(6)H(4); 4, R = 2,6-F,F-C(6)H(3); 5, R = Me; 6, R = CF(3); 7, R = p-F(3)C-C(6)H(4)). However, in the presence of 2.2 molar equiv of Me(3)Al, N-tert-butyl-4-tert-butylbenzamide ((t)BuNHC(p-(t)Bu-C(6)H(4))([double bond]O in refluxing hexane gives [Me(2)Al[eta(2)-(t)BuNC(p-(t)Bu-C(6)H(4))(mu(2)-O)]AlMe(3)], 8. In contrast, the reaction of R'NHCR' '([double bond]O) with 1 molar equiv of R(3)Al at room temperature produces tetracoordinated, dimeric, eight-membered ring aluminum compounds [R(2)Al[mu,eta(2)-R'NC(R' ')O]](2) (9, R = Me, R' = 2,6-(i)Pr, (i)()Pr-C(6)H(3), R' ' = Ph; 10, R = Me, R' = (i)Bu, R' ' = Ph; 11, R = Et, R' = Bn, R' ' = Ph; 12, R = Me, R' = Ph, R' ' = CF(3); 13, R = Me, R' = Bn, R' ' = CF(3)). On the other hand, 4'-chlorobenzanilide ((p-Cl-C(6)H(4))NHCPh([double bond]O)) reacts with R(3)Al to produce trimeric, twelve-membered ring aluminum compounds [R(2)Al[mu, eta(2)-(p-Cl-C(6)H(4))NC(Ph)O]](3) (14, R = Me; 15, R = Et). Furthermore, the reaction of 2'-methoxybenzanilide with 1 molar equiv of Me(3)Al in hexane yields a dinuclear aluminum complex [Me(2)Al(o-OMe-Ph)NC(Ph)(O)AlMe(3)], 16.     

Synthesis and structural studies of germyl and germyl/stannyl substituted tungstenocenes

One-pot reactions of [WCp2(H)2] and [WCp2(H)(SnMe3)] with "BuLi followed by an equivalent of GeMe2Cl2 afford mono(germyl) substituted tungstenocenes [WCp2(H)(GeMe2Cl)] (1) and [WCp2(SnMe3)(GeMe2Cl)] (7). Reactions of the products with tin halides in the presence NEt3 afford the mixed complexes [WCp2(SnR2X)(GeMe2Y)] (X, Y = Cl, Br, R = Me, Et), which were further converted to moderately stable compounds [WCp2(SnR2H)(GeMe2H)] (R = Me (10), Et (11)). A number of asymmetric mono(halo)-substituted germyl/stannyl tungstenocenes [WCp2(SnMe2X)(GeMe2H)] (X = Cl (12), Br (13)) and [WCp2(SnEt2Y)(GeMe2H)] (Y = Br (14), I (15)) were prepared by selective halogenation of the Sn-H bond in 10 and 11. X-Ray studies of [WCp2(H)(GeMe2Cl)] (1), [WCp2(SnEt2Br)(GeMe2Cl)] (4), and [WCp2(SnEt2Br)(GeMe2H)] (14) established classical structures of these compounds. X-Ray study of complex [WCp2(SnMeCl)(GeMe2Cl)] (3) revealed the presence of interligand Ge-Cl...Sn-Cl interactions in a highly Ge/Sn disordered structure. Analyses of molecular parameters of 1, 4, and 14 suggest the presence of a negative hyperconjugation between metal lone pairs and the sigma*-orbital of the E-X bond, which is stronger in bromo substituted complexes in comparison with chloro substituted ones.     

Bimetallic anilido-aldimine zinc complexes for epoxide/CO2 copolymerization

Acyclic o-phenylene-bridged bis(anilido-aldimine) compounds, o-C(6)H(4){C(6)H(2)R(2)N=CH-C(6)H(4)-(H)N(C(6)H(3)R'(2))}(2) and related 30-membered macrocyclic compounds, o-C(6)H(4){C(6)H(2)R'(2)N=CH-C(6)H(4)-(H)N-C(6)H(2)R(2)}(2) (o-C(6)H(4)) are prepared. Successive additions of Me(2)Zn and SO(2) gas to the bis(anilido-aldimine) compounds afford quantitatively dinuclear mu-methylsulfinato zinc complexes, o-C(6)H(4){(C(6)H(2)R(2)N=CH-C(6)H(4)-N(C(6)H(3)R'(2))-kappa(2)-N,N)Zn(mu-OS(O)Me)}(2) (R = iPr and R' = iPr, 29; R = Et and R' = Et, 30; R = Me and R'= Me, 31; R = Me and R' = iPr, 32; R = Et and R' = Me, 33; R = Et and R' = iPr, 34; R = iPr and R' = Et, 35) and o-C(6)H(4){C(6)H(2)R'(2)N=CH-C(6)H(4)-N-C(6)H(2)R(2)-kappa(2)-N,N)Zn(mu-OS(O)Me)}(2) (o-C(6)H(4)) (R = Et and R'= Et, 36; R = Me and R' = Me, 37; R = iPr and R' = Me, 38; R = Et and R' = Me, 39; R = Me and R'= iPr, 40). Molecular structures of 34 and 40 are confirmed by X-ray crystallography. Complexes 30-35 show high activity for cyclohexene oxide/CO(2) copolymerization at low [Zn]/[monomer] ratio (1:5600), whereas the complex of mononucleating beta-diketiminate {[(C(6)H(3)Et(2))N=C(Me)CH=C(Me)N(C(6)H(3)Et(2))]Zn(mu-OS(O)Et)}(2) shows negligible activity in the same condition. Activity is sensitive to the N-aryl ortho substituents and the highest activity is observed with 32. Turnover number up to 2980 and molecular weight (M(n)) up to 284 000 are attained with 32 at such a highly diluted condition as [Zn]/[monomer] = 1:17 400. Macrocyclic complexes 36-40 show negligible activity for copolymerization.     

Synthesis and spectroscopic and X-ray structural characterization of R2Sn(IV)-oxydiacetate and -iminodiacetate complexes

Seven novel R2Sn(IV)-oxydiacetate (oda) and -iminodiacetate (ida) compounds of the form [R2Sn(oda)(H2O)]2 (R = Me, nBu, and Ph) (1-3), [(R2SnCl)2(oda)(H2O)2]n (R = Et, iBu, and tBu) (4-6), and [Me2Sn(ida)(MeOH)]2 (7) have been synthesized and characterized by IR, 1H, 13C, and 119Sn NMR (solution), solid-state 119Sn CPMAS NMR, and (119m)Sn M?ssbauer spectroscopy. The crystal structure of [Me2Sn(oda)(H2O)]2, 1, shows it to be dinuclear (centrosymmetric), with two seven-coordinated tin atoms, bridged by one arm of the carboxylate group from each oda. By contrast, the crystal structure of [(Et2SnCl)2(oda)(H2O)2]n, 4, comprises a zigzag polymeric assembly containing a pair of different alternating subunits, {Et2SnCl(H2O)} and {Et2SnCl(H2O)(oda)}, which are connected by way of bridging oda carboxylates, thus giving seven-coordinate tin centers in both components. Finally, the structure of [Me2Sn(ida)(MeOH)]2, 7, also centrosymmetric dinuclear, is comprised of a pair of mononuclear units with seven-coordinate tin. The 119Sn solid-state CPMAS NMR and (119m)Sn Mossbauer suggest the presence of seven-coordinate Sn metal atoms in some derivatives and the existence of two different tin sites in the [(R2SnCl)2(oda)(H2O)2]n compounds.     

Interaction of tertiary phosphines with lignin-type, alpha,beta-unsaturated aldehydes in water

To learn more about the bleaching action of pulps by (hydroxymethyl)phosphines, lignin chromophores, such as the alpha,beta-unsaturated aromatic aldehydes, sinapaldehyde, coniferylaldehyde, and coumaraldehyde, were reacted with the tertiary phosphines R2R'P [R = R' = Me, Et, (CH2)3OH, iPr, cyclo-C6H11, (CH2)2CN; R = Me or Et, R' = Ph; R = Ph, R' = Me, m-NaSO3-C6H4] in water at room temperature under argon. In all cases, initial nucleophilic attack of the phosphine occurs at the activated C=C bond to form a zwitterionic monophosphonium species. With the phosphines PR3 [R = Me, Et, (CH2)3OH] and with R2R'P (R = Me or Et, R' = Ph), the zwitterion undergoes self-condensation to give a bisphosphonium zwitterion that can react with aqueous HCl to form the corresponding dichloride salts (as a mixture of R,R- and S,S-enantiomers); X-ray structures are presented for the bisphosphonium chlorides synthesized from the Et3P and Me3P reactions with sinapaldehyde. With the more bulky phosphines, iPr3P, MePPh2, (cyclo-C6H11)3P, and Na[Ph2P(m-SO3-C6H4)], only an equilibrium of the monophosphonium zwitterion with the reactant aldehyde is observed. The weakly nucleophilic [NC(CH2)2]3P does not react with sinapaldehyde. An analysis of some exceptional 1H NMR data within the prochiral phosphorus centers of the bisphosphonium chlorides is also presented.     

Quenched gas-phase reactions of tetraborane(10), B4H10, with substituted alkynes: new nido-dicarbapentaboranes and arachno-monocarbapentaboranes

New alkyl derivatives of the nido-dicarbapentaborane, 1,2-C(2)B(3)H(7), and arachno-carbapentaborane, 1-CB(4)H(10), have been identified as the main volatile carbaborane products in quenched gas-phase reactions of tetraborane(10), B(4)H(10), with alkyl-substituted ethynes RC[triple bond]CR' (R = Me, Et, (n)Pr or (t)Bu, R' = H; R = Me or Et, R' = Me). The gaseous mixtures were heated at 70 degrees C, and monitored by gas-phase mass spectrometry. Each reaction was quenched when the ethyne was used up. The quenched gas-phase reaction of B(4)H(10) and Me(3)SiC[triple bond]CH gave a single volatile carbaborane product, 1-Me(3)Si-1,2-C(2)B(3)H(6).     

Organozinc hydroxylamides: on the bulk-dependent interplay of nuclearity, structure and dynamics

The reactions of zinc dialkyls, R(2)Zn (1a-d; R = Me (a), Et (b), iPr (c) and tBu (d)), with N,N-dialkylhydroxylamines, HO-NR'(2) (2a-c; R' = Me (a), Et (b) and iPr (c)), afford organozinc hydroxylamides under alkane extrusion. Species of different nuclearity are observed, depending on the hydroxylamine 2 employed. The smaller 2a and 2b give pentanuclear complexes of the general formula Zn(RZn)(4)O-NR'(2))(6) (R = Me, Et, iPr and tBu; R' = Me and Et), whereas the derivatives of 2c are tetramers of the general formula (RZn)(4)(O-NR'(2))(4) (R = Me, Et and iPr; R' = iPr) as governed by bulk issues about the N-donor. Due to the ability of the double-donor unit O-NR(2) to change its bridging mode, two coordination isomers exist for both types of compounds. The pentanuclear species crystallise either in a heterofenestrane or an octahedroid motif. For these species, the central Zn atom exhibits either coordination number 4 or 6; in solution, a rapid change between coordination isomers is observed. Due to the absence of a central Zn atom in the tetranuclear species, these aggregate in heterocubane geometries or such derived thereof. They display the O-N units in either κ(3)O or κ(2)O;κ(1)N mode. The tetranuclear species are also yielded with the less sterically encumbered precursors under thermodynamic conditions (i.e. reflux), as exemplified by the reaction of Me(2)Zn (1a) with HO-NEt(2) (2b). They are non-dynamic in solution, showing that a central cation is mandatory for the fluxional behaviour observed for the pentanuclear derivatives. DFT studies on the O-NMe(2) series reveal that the relative energies of the pentazinc isomers become more similar with increasing RZn group size; possible conversions of these to their tetrazinc counterparts were also scrutinised. Two κ(3)O-bridged degradation products of hydroxylamide complexes could be structurally characterised. They were formed either by partial product hydrolysis, or by in situ oxygenation of the starting zinc dialkyl.