A new synthetic entry to phosphinophosphinidene complexes. Synthesis and structural characterisation of the first side-on bonded and the first terminally bonded phosphinophosphinidene zirconium complexes [mu-(1,2:2-eta-tBu2P=P)[Zr(Cl)Cp2]2] and [[Zr(PPhMe2)Cp2](eta1)-P-PtBu2)

The reactions of lithiated diphosphanes with transition metal chlorides constitute a new general entry to phosphinophosphinidene complexes: the reaction of Cp2ZrCl2(Cp = C5H5) with tBu2P-P(SiMe3)Li (molar ratio approximately 1:1) yields [mu-(1,2:2-eta-tBu2P=P)[Zr(Cl)Cp2]2]; the reaction of Cp2ZrCl2 with tBu2P-P(SiMe3)Li (molar ratio approximately 1:2) and an excess of PPhMe2 in DME yields the first terminally bonded phosphinophosphinidene complex, [[Zr(PPhMe2)Cp2](eta1-P-PtBu2)].     

Five- and Six-Coordinate 2-Methyl-2-propanethiolato Complexes of Zirconium(IV): Synthesis and Structures of [Li(DME)(3)][Zr(SCMe(3))(5)] and [(THF)Li](2)Zr(SCMe(3))(6)

Five-coordinate and six-coordinate 2-methyl-2-propanethiolato complexes of zirconium, [Li(DME)(3)][Zr(SCMe(3))(5)] (1) and [(THF)Li](2)Zr(SCMe(3))(6) (2), were obtained from the ZrCl(4)/LiSCMe(3) reaction system. The control of the Zr coordination number, by the ether ligands, THF or DME, bound to Li, is demonstrated by the conversion of 2 into 1 upon dissolution in DME. 1 and 2 were crystallographically characterized. The structures are extensively disordered. Crystal data follow: 1, hexagonal P6(3)/m, a = b = 12.496(3) ?, c = 17.561(9) ?, Z = 2, V = 2375(1) ?(3), R = 5.0%, R(w) = 6.8%; 2, trigonal R32, a = b = 11.813(3) ?, c = 28.37(1) ?, Z = 3, V = 3428(1) ?(3), R = 5.2%, R(w) = 6.4%.     

Synthesis and group 4 complexes of tris(pyrrolyl-alpha-methyl)amine

The tetradentate, trianionic ligand tris(pyrrolyl-alpha-methyl)amine (H(3)tpa) is available in 84% yield in a single step by a triple Mannich reaction involving 3 equiv of pyrrole, 3 equiv of formaldehyde, and ammonium chloride. The new ligand is readily placed on titanium by transamination on Ti(NMe(2))(4), which generates Ti(NMe(2))(tpa) (1) in 73% yield. Treating 1 with 1 equiv of 1,3-dimethyl-2-iminoimidazolidine (H-imd) in toluene provided a rare example of a titanium 2-iminoimidazolidinide, which displays some interesting structural features. Of note is the Ti-N(imd) distance of 1.768(2) A, a typical Ti-N double to triple bond distance. Reaction of Zr(NMe(2))(4) with H(3)tpa gave a complex of variable composition, probably varying in the amount of labile dimethylamine retained. However, stable discreet compounds were available by addition of THF, pyridine, or 4,4'-di-tert-butyl-2,2'-bipyridine (Bu(t)bpy) to in situ generated Zr(NMe(2))(NHMe(2))(x)(tpa). Three chloro zirconium complexes were generated using three different strategies. Treating Zr(tpa)(NMe(2))(Bu(t)bpy) (5) with ClSiMe(3) afforded Zr(tpa)(Cl)(Bu(t)bpy) (6) in 92% yield. Reaction of Li(3)tpa with ZrCl(4)(THF)(2) in THF gave a 72% yield of ZrCl(tpa)(THF)(2) (7). In addition, treatment of ZrCl(NMe(2))(3) with H(3)tpa cleanly generated ZrCl(NHMe(2))(2)(tpa) (8) in 95% yield. An organometallic zirconium complex was generated on treatment of 6 with LiCtbd1;CPh; alkynyl Zr(Ctbd1;CPh)(tpa)(Bu(t)bpy) (9) was isolated in 62% yield. 1, Ti(imd)(tpa) (2), 6, and 9 were characterized by X-ray diffraction.     

Synthesis and structures of selected benzamidinates of Li, Na, Al, Zr and Sn(II) using the C1-symmetric ligands [N(SiMe3)C(C6H4Me-4 or Ph)NPh]-

Several compounds based on the C(1)-symmetric ligands [N(R)C(Ar)NPh]- [abbreviated as B1 (Ar = C(6)H(4)Me-4) or B2 (Ar = Ph), R = SiMe(3)] are reported. They are the crystalline metal benzamidinates [Li(mu:kappa2-B1)(OEt2)](2) (1), [Al(kappa2-B1)2Me] (2), [Al(kappa2-B1)2X] [X = Cl/Me, 1 : 1 (3)], [Sn(kappa2-B1)2] (4), Zr(kappa2-B1)2Cl2 (5), [Zr(kappa2-B1)3Cl] (6), [Na(mu:kappa2-B1)(tmeda)]2 (7), K[B1] (8), Li(B2)(OEt2) (9) and Zr(kappa2-B1)3Cl (10) and the known benzamidine Z-H2NC(C6H4Me-4) = NPh (11). They were prepared by (i) insertion of the nitrile 4-MeC6H4CN (1, 7, 8, 11) or PhCN (9) into the appropriate M-N(R')Ph [R' = R and M = Li (1, 9), Na (7), K (8)] bond and subsequent hydrolysis for 11 [R' = H and M = Li], or (ii) a ligand transfer reaction using the lithium amidinate 1 and Al(Me)2Cl (2, 3), SnCl2 (4) or ZrCl4 (5, 6), or Li(B2) and ZrCl4 (10). The X-ray structures of 1, 2, 3, 4, 6b (i.e..3PhMe) 7, and 11 are presented. Exploratory polymerisation experiments are described, using 2, 5 or 6 as a procatalyst with methylaluminoxane (MAO) (Al : Zr ca. 500 : 1) as promoter. Thus toluene solutions were exposed to C2H4 under ambient conditions; while 2 was unresponsive, 5 and 6 showed modest activity in the formation of polyethylene.     

Enantioselective synthesis of ansa-zirconocenes

The reaction of the chiral chelated bis-amide complex Zr{(2R,4R)-PhNCHMeCH2CHMeNPh}Cl2(THF)2 (R,R-7) with lithium ansa-bis-indenyl reagents Li2[SBI](Et2O) (8a, SBI = (1-indenyl)2SiMe2) or Li2[EBI](Et2O) (8b, EBI = 1,2-(1-indenyl)2ethane) in THF affords the corresponding ansa-zirconocenes S,S-(SBI)Zr{(2R,4R)-PhNCHMeCH2CHMeNPh} (S,S,R,R-9a) or S,S-(EBI)Zr{(2R,4R)-PhNCHMeCH2CHMeNPh} (S,S,R,R-9b) in >95% isolated yield and >99% enantiomeric excess. Compound 9b was converted to the corresponding enantiomerically pure dichloride S,S-(EBI)ZrCl2 (S,S-10b) in 91% isolated yield by reaction with HCl in Et2O. The chiral diamine (2R,4R)-HPhNCHMeCH2CHMeNHPh (R,R-5) was recovered from this reaction.     

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.     

Coupling of coordinated 2-iminophosphorano-1-phosphaallyl leading to bridged iminophosphoranato complexes of zirconium and hafnium

Reaction of MCl4 (M = Zr, Hf) with 2 equiv of 2-iminophosphorano-1-phosphaallyl lithium [Li[P(Ph)C(=CHPh)P(Me)2=NSiMe3](THF)1.5] (1) affords ligand coupling complexes 3 and 4, respectively, while similar treatment of ZrCl4 with [Li[P(Ph)C(=C(SiMe2Bu(t))Ph)P(Me)2=NSiMe3](THF)2] (2) yields ligand transfer complex 5.     

Condition dependence of Zr electrochemical reactions and morphological evolution of Zr deposits in molten salt

This work presents a comprehensive study for the electrochemical behaviors of zirconium in LiCl-KCl eutectic.The effects of stirring,temperature and Zr concentration on the electrode reactions,the ZrCl_4 sublimation from the melt,microcosmic morphologies of Zr deposits(ZrCl and Zr)obtained at different potential and temperature have been investigated.The behaviors of Zr(Ⅳ),on a large concentration range from 0.13%to 2.28%in melt,show a multiple-step reaction involving Zr(Ⅳ),Zr(Ⅱ),ZrCl and Zr species.Temperature plays a crucial role on the changes of Zr(IV)reduction behavior on the solid electrode.The Zr(Ⅳ)/ZrCl couple is more easily observed at lower temperature and gradually diminishes with the increase of temperature.The Zr(Ⅳ)/Zr(Ⅱ)and Zr(Ⅱ)/Zr reactions are predominant on the W electrode at higher temperatures.At 673 K,a layered structure of insoluble ZrCl formed by potentiostatic electrolyses at 1.1 V was visualized by scanning electron microscopy-energy dispersive X-ray(SEM-EDS),while only Zr metal particles was observed at higher temperature than 773 K.An evolution of the Zr-based structure and size corresponding to the ZrCl and Zr metal based on different potentiostatic electrolysis was observed.The average particle size of the Zr metalparticles increases with the increase of temperature.     

Synthesis, Structure, and Reactivity of [Zr(6)Cl(18)H(5)](2)(-), the First Paramagnetic Species of Its Class

Reaction of [Zr(6)Cl(18)H(5)](3)(-) (1) with 1 equiv of TiCl(4) yields a new cluster anion, [Zr(6)Cl(18)H(5)](2)(-) (2), which can be converted back into [Zr(6)Cl(18)H(5)](3)(-) (1) upon addition of 1 equiv of Na/Hg. Cluster 2 is paramagnetic and unstable in the presence of donor molecules. It undergoes a disproportionation reaction to form 1, some Zr(IV) compounds, and H(2). It also reacts with TiCl(4) to form [Zr(2)Cl(9)](-) (4) and a tetranuclear mixed-metal species, [Zr(2)Ti(2)Cl(16)](2)(-) (3). The oxidation reaction of 1 with TiCl(4) is unique. Oxidation of 1 with H(+) in CH(2)Cl(2) solution results in the formation of [ZrCl(6)](2)(-) (5) and H(2), while in py solution the oxidation product is [ZrCl(5)(py)](-) (6). There is no reaction between 1 and TiI(4), ZrCl(4), [TiCl(6)](2)(-), [ZrCl(6)](2)(-), or CrCl(3). Compounds [Ph(4)P](2)[Zr(6)Cl(18)H(5)] (2a), [Ph(4)P](2)[Zr(2)Ti(2)Cl(16)] (3a), [Ph(4)P](2)[Zr(2)Cl(9)] (4a), [Ph(4)P](2)[ZrCl(6)].4MeCN (5a.4MeCN), and [Ph(4)P][ZrCl(5)(py)] (6a) were characterized by X-ray crystallography. Compound 2a crystallized in the trigonal space group R&thremacr; with cell dimensions (20 degrees C) of a = 28.546(3) ?, b = 28.546(3) ?, c = 27.679(2) ?, V = 19533(3) ?(3), and Z = 12. Compound 3a crystallized in the triclinic space group P&onemacr; with cell dimensions (-60 degrees C) of a = 11.375(3) ?, b = 13.357(3) ?, c = 11.336(3) ?, alpha = 106.07(1) degrees, beta = 114.77(1) degrees, gamma = 88.50(1) degrees, V = 1494.8(7) ?(3), and Z = 1. Compound 4a crystallized in the triclinic space group P&onemacr; with cell dimensions (-60 degrees C) of a = 12.380(5) ?, b = 12.883(5) ?, c = 11.000(4) ?, alpha = 110.39(7) degrees, beta = 98.29(7) degrees, gamma = 73.12(4) degrees, V = 1572(1) ?(3), and Z = 2. Compound 5a.4MeCN crystallized in the monoclinic space group P2(1)/c with cell dimensions (-60 degrees C) of a = 9.595(1) ?, b = 19.566(3) ?, c = 15.049(1) ?, beta = 98.50(1) degrees, V = 2794.2(6) ?(3), and Z = 2. Compound 6a crystallized in the monoclinic space group P2(1)/c with cell dimensions (20 degrees C) of a = 10.3390(7) ?, b = 16.491(2) ?, c = 17.654(2) ?, beta = 91.542(6) degrees, V = 3026.4(5) ?(3), and Z = 4.     

Synthesis and structures of some heterometallic [(Li, Y)2, (M3, Ce) (M = Li or Na), (Li, Zr2) and (Li, Zr)4] oligomeric diamides derived from 1,2-bis(neopentylamino)benzene

The following crystalline, X-ray-characterised heterometallic oligomeric diamides have been prepared in good yield under mild conditions in diethyl ether from the dilithio or disodio derivative of the N,N'-dineopentyl-1,2-diaminobenzene [{N(H)(CH2Bu(t))}2C6H4-1,2] (abbreviated as H2L):[Y(L)(mu-Cl)2Li(OEt2)2]2 (1), [Li(OEt2)2Li(mu2-Cl)4(mu3-Cl)2{Zr(L)}2]2 (2), [Zr(L)2(mu-Cl){Li(OEt2)2}(mu2-Cl)2Zr(L)] (3), [Ce{(mu-L)M}3(OEt2)(1/2)] (3M = Li(1.82)Na(1.18)) (4), [Ce{(mu-L)Na}3(OEt2)] (5) and [Ce{(mu-L)Na}3] (6). Compounds 1-3 were obtained from Li2(L) and YCl3 (the colourless 1) or ZrCl4 (the red 2 and 3), while the red 4 and 5 were isolated from CeCl3 and M2(L) (3M = Li(1.82)Na(1.18)) (4) or Na2(L) (5). Attempted oxidation of 5 with Br2 in hexane yielded the black 6. The ligand is N,N'-chelating to each of the d- or f-block metals in 1-6; and in 4-6 L is also acting as a bridge between Ce and the alkali metal, to which L is thus also chelating.     

New complexes of zirconium(IV) and hafnium(IV) with heteroscorpionate ligands and the hydrolysis of such complexes to give a zirconium cluster

A series of zirconium and hafnium heteroscorpionate complexes have been prepared by the reaction of MCl4 (M = Zr, Hf) with the compounds [[Li(bdmpza)(H2O)](4)] [bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate], [[Li(bdmpzdta)(H2O)](4)] [bdmpzdta = bis(3,5-dimethylpyrazol-1-yl)dithioacetate], and (Hbdmpze) [bdmpze = 2,2-bis(3,5-dimethylpyrazol-1-yl)ethoxide] (the latter with the prior addition of Bu(n)Li). Under the appropriate experimental conditions, mononuclear complexes, namely, [MCl3(kappa3-bdmpzx)] [x = a, M = Zr (1), Hf (2); x = dta, M = Zr (3), Hf (4); x = e, M = Zr (5), Hf (6)], and dinuclear complexes, namely, [[MCl2(mu-OH)(kappa3-bdmpzx)]2] [x = a, M = Zr (7), Hf (8); x = dta, M = Zr (9); x = e, M = Zr (10)], were isolated. A family of alkoxide-containing complexes of the general formula [ZrCl2(kappa3-bdmpzx)(OR)] [x = a, R = Me (11), Et (12), iPr (13), tBu (14); x = dta, R = Me (15), Et (16), iPr (17), tBu (18); x = e, R = Me (19), Et (20), (i)Pr (21), (t)Bu (22)] was also prepared. Complexes 11-14 underwent an interesting hydrolysis process to give the cluster complex [Zr6(mu3-OH)8(OH)8(kappa2-bdmpza)8] (23). The structures of these complexes have been determined by spectroscopic methods, and the X-ray crystal structures of 7, 8, and 23 were also established.     

Direct synthesis of NNN-donor enantiopure scorpionate ligands by an efficient diastereoselective nucleophilic addition to imines

New enantiopure imines (1-9) with a chiral substrate to control the stereochemistry of a newly created stereogenic center have been synthesized by reaction of the commercially available (1R)-(-)-myrtenal and different primary amines. The diastereomerically enriched lithium-scorpionate compounds [Li(κ(3)-mobpza)(THF)] (10) (mobpza = N-p-methylphenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide), [Li(κ(3)-mobpza)(THF)] (11) (mobpza = N-p-methoxyphenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide), [Li(κ(3)-fbpza)(THF)] (12) (fbpza = N-p-fluorophenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide), and [Li(κ(3)-clbpza)(THF)] (13) (clbpza = N-p-chlorophenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide) were obtained by a diastereoselective 1,2-addition of an organolithium reagent to imines in good yield and with good diastereomeric excess (ca. 80%). The complexes [LiCl(κ(2)-R,R-fbpzaH)(THF)] (14) and [LiCl(κ(2)-R,R-clbpzaH)(THF)] (15) were obtained in enantiomerically pure form by the treatment of THF solutions of 12 or 13 with NH(4)Cl. The enantiomerically pure amines (R,R-mbpzaH) (16), (R,R-mobpzaH) (17), (R,R-fbpzaH) (18), and (R,R-clbpzaH) (19) were obtained by hydrolysis of the lithium-scorpionate compounds 10-13 with H(2)O. The lithium compound 12 was reacted with [TiCl(4)(THF)(2)] or [ZrCl(4)] to give the enantiopure complexes [MCl(3)(κ(3)-R,R-fbpza)] [M = Ti (20), Zr (21)]. The amine compound 18 reacted with [MX(4)] (M = Ti, X = O(i)Pr, OEt; M = Zr; X = NMe(2)) to give the complexes [MX(3)(κ(3)-R,R-fbpza)] (22-24). The reaction of Me(3)SiCl with [Zr(NMe(2))(3)(κ(3)-R,R-fbpza)] (24) in different molar ratios led to the halide-amide-containing complexes [ZrCl(NMe(2))(2)(κ(3)-R,R-fbpza)] (25) and [ZrCl(2)(NMe(2))(κ(3)-R,R-fbpza)] (26) and the halide complex 21. The isolation of only one of the three possible diastereoisomers of complexes 25 and 26 revealed that chiral induction from the ligand to the zirconium center took place. The structures of these compounds were elucidated by (1)H and (13)C{(1)H} NMR spectroscopy, and the X-ray crystal structures of 5, 12, 14, 15, and 24 were also established.     

Synthesis and structure of asymmetric zirconium-substituted silicotungstates, [Zr6O2(OH)4(H2O)3(beta-SiW10O37)3]14- and [Zr4O2(OH)2(H2O)4(beta-SiW10O37)2]10-

The reaction of ZrCl4 with [gamma-SiW10O36]8- in a potassium acetate buffer results in two different products depending on the reactant ratios. The trimeric species [Zr6O2(OH)4(H2O)3(beta-SiW10O37)3]14- (1) consists of three beta23-SiW10O37 units linked by an unprecedented Zr6O2(OH)4(H2O)3 cluster with C1 point group symmetry. The dimeric species [Zr4O2(OH)2(H2O)4(beta-SiW10O37)2]10- (2) consists of beta22- and beta12-SiW10O37 units sandwiching a Zr4O2(OH)2(H2O)4 cluster, which also has C1 symmetry. Polyanion 1 contains more zirconium centers than any other polyoxometalate known to date.     

Amido/amine triazacyclononane-based zirconium complexes: syntheses, reactivity, and structures

The reactions of [Zr(NMe2)4]2 with triamido-triazacyclonane ligand precursors, {NH(Ph)SiMe2}3tacn (H3N3[9]N3) and {NH(C6H4F)SiMe2}3tacn (H3N3-F[9]N3), led to the formation of complexes [Zr(NMe2)2{N(Ph)SiMe2}2{NH(Ph) SiMe2}tacn], 1, and [Zr(NMe2)2{N(o-C6H4F)SiMe2}2{NH(o-C6H4F)SiMe2} tacn], 2, where the zirconium is coordinated to two remaining dimethylamido ligands and to a dianionic tacn-based ligand, [{N(Ph')SiMe2}2{NH(Ph')SiMe2}tacn]2-, that formed from deprotonation of two amine pendent arms of the ligands' precursors. The third pendent arm of H3N3[9]N3 and H3N3-F[9]N3 remains neutral and not bonded to the zirconium. Treatment of 1 with NaH led to the synthesis of [Zr(NMe2){N(Ph)SiMe2}2tacn], 3, that results from the cleavage of the N-Si bond of the original neutral pendent arm. Complexes [ZrCl{N(Ph')SiMe2}2tacn] (Ph' = C6H5, 4, and C6H4F, 5) have been obtained by reactions of ZrCl4 with {MN(Ph')SiMe2}3tacn.2THF (M = Li, Na). Reactions of 4 and 5 with LiC triple bond CPh led to the syntheses of [Zr(CCPh){N(Ph')SiMe2}2tacn] (Ph' = C6H5, 6, and C6H4F, 7). The solid-state structure of 3 shows a chiral metal center.     

Synthesis and structural investigation of N,N',N' '-trialkylguanidinato-supported zirconium(IV) complexes

The addition of 2 equiv of N,N',N' '-triisopropylguanidine (guanH(2)) to Zr(CH(2)Ph)(4) produced the bis(guanidinato)bis(benzyl)zirconium complex [((i)PrNH)C(N(i)Pr)(2)](2)Zr(CH(2)Ph)(2) (1). The mono(guanidinato) complex [((i)PrN)(2)C(NH(i)Pr)]ZrCl(3) (2) was accessible by the reaction of 2 equiv of guanH(2) with ZrCl(4). Guanidinium hydrochloride, [C(NH(i)Pr)(3)]Cl, is a byproduct of this reaction. When crystallized from THF, complex 2 was isolated as the THF adduct [((i)PrNH)C(N(i)Pr)(2)]ZrCl(3)(THF) (2-THF). The mixed cyclopentadienyl guanidinato complex [eta(5)-1,3-(Me(3)Si)(2)C(5)H(3)][((i)PrNH)C(N(i)Pr)(2)]ZrCl(2) (3) was prepared by treatment of [1,3-(Me(3)Si)(2)C(5)H(3)]ZrCl(3) with the in situ generated lithium triisopropylguanidinate salt. The reaction of guanH(2) with [1,3-(Me(3)Si)(2)C(5)H(3)]ZrMe(3) affords the dimethyl derivative [eta(5)-1,3-(Me(3)Si)(2)C(5)H(3)][((i)PrNH)C(N(i)Pr)(2)]ZrMe(2) (4). Definitive evidence for the molecular structures of these products is provided through single-crystal X-ray characterization of 1, 2-THF, and 3, which are presented. The extent of pi delocalization within the guanidinato ligand is discussed in the context of the metrical parameters obtained from these structural studies.     

Syntheses and structures of the first terminal phosphanylphosphido complex of hafnium [Cp2Hf(Cl){η(1)-(Me3Si)P-P(NEt2)2}] and the first zirconocene-phosphanylphosphinidene dimer [Cp2Zr{μ(2)-P-P(NEt2)2}2ZrCp2

Reactions of (Et(2)N)(2)P-P(SiMe(3))Li with [Cp(2)MCl(2)] (M = Zr, Hf) in toluene or pentane yield the related terminal phosphanylphosphido complexes [Cp(2)M(Cl){η(1)-(Me(3)Si)P-P(NEt(2))(2)}]. The solid state structure of [Cp(2)Hf(Cl){η(1)-(Me(3)Si)P-P(NEt(2))(2)}] was established by single crystal X-ray diffraction. The reaction of (Et(2)N)(2)P-P(SiMe(3))Li with [Cp(2)ZrCl(2)] in THF or DME solutions leads to the formation of deep red crystals of the first neutral diamagnetic zirconocene-phosphanylphosphinidene dimer [Cp(2)Zr{μ(2)-P-P(NEt(2))(2)}(2)ZrCp(2)]. The molecular structure of this compound was confirmed by X-ray diffraction. The reactions of (R(2)N)(2)P-P(SiMe(3))Li with [CpZrCl(3)] yield the related tetraphosphetanes R(2)NP(μ(2)-PSiMe(3))(2)PNR(2), which apparently are formed as a result of a transfer of NR(2) groups from a P atom to the Zr atom.     

Chelate-controlled synthesis of racemic ansa-zirconocenes

The reaction of Zr[PhN(CH(2))(3)NPh]Cl(2)(THF)(2) (5) with lithium ansa-bis-indenyl reagents Li(2)[XBI](Et(2)O) (XBI = (1-indenyl)(2)SiMe(2) (SBI, 7a), (2-methyl-1-indenyl)(2)SiMe(2) (MSBI, 7b), (2-methyl-4,5-benz-1-indenyl)(2)SiMe(2) (MBSBI, 7c), (2-methyl-4-phenyl-1-indenyl)(2)SiMe(2) (MPSBI, 7d), and 1,2-(1-indenyl)(2)ethane (EBI, 7e)) affords rac-(XBI)Zr[PhN(CH(2))(3)NPh] (8a-e) in high yield. The meso isomers were not detected by (1)H NMR. X-ray crystallographic studies show that the Zr[PhN(CH(2))(3)NPh] rings in 5, 8a, 8c, and (C(5)H(5))(2)Zr[PhN(CH(2))(3)NPh] (10) adopt twist conformations that position the N-Ph groups on opposite sides of the N-Zr-N plane. This conformation complements the metallocene structures of rac-8a-e but would destabilize the corresponding meso isomers. It is proposed that the Zr[PhN(CH(2))(3)NPh] ring adopts a similar twist conformation in the stereodetermining transition state for addition of the second indenyl ring in these reactions, which leads to a preference for rac products. The results of metallocene syntheses from other Zr amide precursors support this proposal. 8a-e are converted to the corresponding rac-(XBI)ZrCl(2) complexes (9a-e) by reaction with HCl.     

C3-chiral tripodal amido complexes

A comprehensive study into the coordination chemistry of two C3-chiral tripodal amido ligands has been carried out. The amido ligands contain a trisilylmethane backbone and chiral peripheral substituents. The amine precursors. HC(SiMe2NH[(S)-1-phenylethyl]]3 (1) and HC[SiMe2NH[(R)-1-indanyl]]3 (2) were found to be in equilibrium in solution with the cyclic diamines HC[SiMe2N[(S)-1-phenylethyl]2](SiMe2NH-[(S)-1-phenylethyl]] (3) and HC[SiMe2NH[(R)-1-indanyl]][SiMe2NH[(R)-1-indanyl]) (4), which are generated upon ejection of one molecule of the chiral primary amine. Reaction of these equilibrium mixtures with three molar equivalents of butyllithium instantaneously gave the trilithium triamides HC[SiMe2N(Li)[(S)-1-phenylethyl]]3 (5) and HC[SiMe2N(Li)[(R)-1-indanyl]]3 (6), both of which were characterised by an X-ray diffraction study. Both lithium compounds possess a central heteroadamantane core, in which the two-coordinate Li atoms are additionally weakly solvated by the three aryl groups of the chiral peripheral substituents, the Li-C contacts being in the range of 2.65-2.73 A. Reaction of 5 and 6 with [TiCl4(thf)2] and ZrCl4 gave the corresponding amido complexes [TiCl-[HC[SiMe2N[(S)-1-phenylethyl]]3]] (7), [TiCl(HC[SiMe2N[(R)-1-indanyl]]3]] (8), [ZrCl[HC[SiMe2N[(S)-1-phenylethyl]]3]] (9) and [ZrCl[HC[SiMe2N[(R)-1-indanyl]]3]] (10), respectively. Of these, compound 7 was structurally characterised by X-ray structure analysis and was shown to possess a C3-symmetrical arrangement of the tripod ligand. The chiral anionic dinuclear complex [Li-(OEt2)4][Zr2Cl3[HC[SiMe2N[(S)-1-phenylethyl]]3]2] (11) was isolated from reaction mixtures leading to 9. An X-ray diffraction study established its dimeric structure, in which the chiral amido ligands cap the two metal centres, which are linked through three symmetrically arranged, bridging chloro ligands. Reaction of 9 and 10 with a series of alkyl Grignard and alkyllithium reagents yielded the corresponding alkylzirconium complexes. X-ray structure analyses of [Zr(CH3)[HC[SiMe2N[(S)-1-phenylethyl]]3]] (12) and [Zr(CH3)-[HC[SiMe2N)[(R)-1-indanyl]]3]] (20) established their detailed molecular arrangements. While the reaction of 12 with the aryl ketones PhC(O)R (R = CH = CHPh, iPr, Et) gave the corresponding C-O insertion products, which contain an additional chiral centre in the alkoxy group, with low stereoselectivity (0-40% de). The corresponding conversions with several aryl aldehydes yielded the alkoxo complexes with high stereoselectivity. Upon hydrolysis, the chiral alcohols were isolated and shown to have enantiomeric excesses between 68 and 82%. High stereodiscrimination was also observed in the insertion reactions of several chiral ketones and aldehydes. However, this was shown to originate primarily from the chirality of the substrate. In analogous experiments with carbonyl compounds, the ethyl- and butyl-zirconium analogues of 12 did not undergo CO insertion into the metal-alkyl bond. Instead, beta-elimination and formal insertion into the metal-hydride bond occurred. It was found that the elimination of the alkene was induced by     

Stereoelectronic influence of the type of bifunctional ansa-monocyclopentadienyldimethylsilylamido ligand on the molecular structures displayed by zirconium dichloride and 1,4-diphenylbutadiene complexes

A series of organozirconium dichloride and 1,4-diphenylbutadiene complexes featuring a dianionic bifunctional ligand with a cyclopentadienyl-type functionality and an appended amido N donor have been prepared and structurally characterized. [(C(5)H(4))SiMe(2)(N-t-Bu)]ZrCl(2), 1, [(C(9)H(6))SiMe(2)(N-t-Bu)]ZrCl(2), 2, and [(C(5)Me(4))SiMe(2)(N-i-Pr)]ZrCl(2), 3, were prepared in two steps, with ligand chelation accomplished by an amine elimination reaction followed by treatment of the diamido Zr intermediate with an excess of SiMe(3)Cl. X-ray structural analyses reveal that in the solid state 2 is monomeric, whereas 1 and 3 are centrosymmetric dimers linked by a pair of bridging chlorides. The level of asymmetry displayed by the central Zr(2)(micro-Cl)(2) moiety is indicated by the variation in the pair of independent bridging Zr-Cl bond distances, which are 2.618(1) and 2.657(1) A in 1 and 2.542(1) and 2.745(1) A in 3, respectively. The metathetical reactions of [Mg(C(4)H(4)Ph(2))(THF)(3)](n)() with 1, 2, 3, and [(C(5)Me(4))SiMe(2)(N-t-Bu)]ZrCl(2) proceed to afford the corresponding 1,4-diphenylbutadiene derivatives 4, 5, 6, and 7, respectively. Solution NMR data show that 6 is obtained exclusively as the supine isomer, whereas compounds 4, 5, and 7 exist as >20:1, 6:1, and 2:1 mixtures of the supine and prone isomers at ambient temperature. The molecular structures of the supine forms of 4, 5, 6, and 7 are appreciably folded (70-80 degrees ) along the line of intersection between the plane containing the Zr and the two terminal butadiene carbons and the plane of the cis-butadiene fragment. An increase in the folding is accompanied by a decrease in the difference between the average Zr-C(terminal) and Zr-C(internal) bond distances and leads to a more pronounced long-short-long C-C bond sequence within the coordinated butadiene.     

Deactivation pathways of ethylene polymerization catalysts derived from titanium and zirconium 1,3-bis(furyl)-1,1,3,3-tetramethyldisilazide complexes

The stoichiometric reaction between the previously described lithium amide salts, LiN(SiMe2R)2 [Li{i}, R = furyl, Li{ii}, R = 2-methylfuryl] and titanium(iv)chloride at low temperature afforded the mono-amide compounds Ti{i}Cl3 (1a) and Ti{ii}Cl3 (1b). The analogous zirconium derivatives Zr{i}Cl3 (3a) and Zr{ii}Cl3 (3b) were accessed via the reaction of excess trimethylsilylchloride with the mixed tetra-amide species, Zr{i}(NMe2)3 (2a) and Zr{ii}(NMe2)3 (2b). The bis-amide complexes Ti{ii}2Cl2 (4b), Zr{i}2Cl2 (5a) and Zr{ii}2Cl2 (5b) were synthesized in a straightforward salt metathesis reaction employing two equivalents of Li{i} or Li{ii} with the metal salts, MCl4(THF)2. The reactivity of the halide compounds 1 and 3-5 with a variety of alkylating agents was studied, with ligand transfer from the transition-element to the main group metal-alkyl reagent being the predominant reaction pathway. The reaction of 4b with MeLi was, however, partially successful affording the titanium(III) complex, Ti{ii}2X (X = Cl/Me, 6b'); this compound was subsequently made as the pure chloride from the reaction of two equivalents of Li{iii} with TiCl3(THF)3. The targeted dialkyl species, Ti{ii}Me2 (7b), was successfully isolated from the reaction between the dichloride 4b and dimethylmagnesium. The molecular structures of 1a, 1b, [3a]2 [3b]2, 4b, 5b and 6b have been solved using single-crystal X-ray diffraction techniques, indicating varying nuclearity of the complexes and hapticities for the amide ligands in the solid-state. The catalytic activity of selected complexes in the polymerization of ethylene is reported.