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The limited knowledge on low-coordinate zero-valent transition-metal species has intrigued great synthetic efforts in developing ligand sets for their stabilization. While the combined ligand set of N-heterocyclic carbene (NHC) with vinylsilanes was the only known ligand system amenable to the stabilization of three-coordinate formal zero-valent cobalt, iron, and manganese complexes, the exploration on other ligands has proved that the ligand set of NHCs with styrene is equally effective in stabilizing three-coordinate formal zero-valent metal complexes in the form of (NHC)M(η2-CH2CHPh)2 (NHC = IPr, IMes; M = Co, Fe, Mn). These styrene complexes can be prepared by the one-pot reactions of MCl2 with styrene, NHC and KC8, and have been characterized by various spectroscopic methods. Preliminary reactivity study indicated that the interaction of [(IMes)Fe(η2-CH2CHPh)2] with DippN3 produces the iron(IV) bisimido complex [(IMes)Fe(NDipp)2] and styrene, which hints at the utility of these zero-valent metal styene complexes as synthons of the mono-coordinate species (NHC)M(0).

Four iron complexes {[PhN(CH2)2NH(SiMe3)]4FeLi·Et2O (1), [PhN(CH2)3NSiMe3]2FeLi(Et2O) (2), [PhN(CH2)2NCH(Ph)NSiMe3]2FeLi(Et2O)2 (3), and [PhN(CH2)3NCH(Ph)NSiMe3]2FeLi(Et2O)2 (4)} with polydentate nitrogen ligands were synthesized and structurally characterized by X-ray crystallography. The X-ray structures of complexes 1–4 show that they crystallize in three different systems. The magnetic properties of 1–4 were investigated. The magnetization trends of magnetic field intensity show the curves of Type-S, illustrating those complexes 1–4 are superparamagnetic.

The dimer lithium complex 3 and zirconium complexes 4–6 were synthesized and characterized. Monomer/dimer zirconium complexes 4–6 were synthesized by changing the molar ratio of ZrCl4 : ligand. Their structures were confirmed by X-ray diffraction analysis, which showed a distorted octahedral geometry. Complexes 5 and 6 were zirconium trichloride compounds, while complex 4 was not a zirconium chloride species. The catalytic behaviors of complexes 4–6 were investigated in the presence of MAO as a cocatalyst. It was found that the catalytic activities of these zirconium complexes toward ethylene polymerization were closely related to the bonding patterns (η3:η1, η3 or η1), the number of chlorine atoms in the procatalysts and the availability of the coordination site in the molecule. Zirconium trichloride complex 5 showed the highest catalytic activity mainly because of its η1 bonding pattern.

Two chiral bisferrocenyl-modified bis(acyl-thiourea) enantiomers, (1R,2R)-bis(ferrocenylcarbonylthioureido)cyclohexane (1) and (1S,2S)-bis(ferrocenylcarbonylthioureido)cyclohexane (2), were synthesized by the reactions of 2.2 equivalents of ferrocenoyl isothiocyanate with (1R,2R) and (1S,2S)-1,2-diaminocyclohexane (1,2-DACH) via a nucleophilic addition reaction, respectively. The two new compounds were fully characterized by 1H NMR, 13C NMR, IR, UV-Vis, elemental analyses and single-crystal X-ray diffraction. The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) experiments of compounds 1 and 2 showed roughly similar single reversible redox waves when using nBu4NClO4 (TBAP) as the supporting electrolyte, whereas two CV and DPV waves were observed when using nBu4NBArF4 [ArF4 = 3,5-bis(trifluoromethyl)phenyl]. Furthermore, both compounds 1 and 2 displayed potential antitumor activity against human HepG2 cells. When compounds 1 and 2 were crystallized from diethyl ether, the solvent-free enantiomers (1 and 2) were obtained, respectively. Molecules of both solvent-free enantiomers (1 and 2) assemble into a three-dimensional network structure through hydrogen-bonding and C–H⋯π (cyclopentadienyl rings) interactions. On the other hand, crystallization of compound 1 from benzene produced a benzene disolvate, 1·(C6H6)2. Molecules of the solvent-free and disolvated forms of compound 1 exhibit different molecular conformations and packing arrangements.

Introducing the hole-transporting carbazole moiety into an aggregation-induced emissive tetraarylethene skeleton and attaching electron-transporting dimesitylboron groups to the periphery, we obtain two novel electroluminescent materials. Their structures are fully characterized by elemental analysis, mass spectrometry, NMR spectroscopy and X-ray crystallography. Furthermore, their thermal, electrochemical, as well as photophysical properties including AIE-behavior are systematically investigated not only by experimental methods but also by DFT computation. Thereby, we show that the two compounds possess high thermal and electrochemical stability with a remarkable AIE-behavior. X-ray crystal analyses aided by DFT calculations provide insights in the origin of the luminescent properties and AIE features. Ultimately, two non-doped OLEDs (Device A and Device B) were fabricated by using PDPBCE and BDPBCE as light-emitting layer, respectively. Device A showed yellowish-green light with a turn-on voltage of 3.8 V, a maximum brightness of 59130 cd m−2 and a maximum current efficiency of 6.43 cd A−1. Device B exhibited greenish-yellow light with a turn-on voltage of 3.0 V, a maximum brightness of 67,500 cd m−2 and a maximum current efficiency of 11.2 cd A−1.

The trichlorozirconium eta (2)-hydrazonides (R=H, A; R=CH3, B) were synthesized through the finely controlled stoichiometrical reactions of anhydrous zirconium tetrachloride with the lithium salt of either 1-(furan-2-ylmethylene)-2-phenylhydrazonide or 1-(furan-2-ylethylidene)-2-phenyl hydrazonide in the solvent tetrahydrofuran (THF), respectively. These complexes were highly sensitive to air and moisture due to solely using less bulky ligand of hydrazonides. The molecular structures of the title complexes, determined by means of single crystal X-ray diffraction, were found to be the distorted pentagonal bipyramid geometry around zirconium atom, with three chlorides and the hydrazonato ligand acting as the eta (2)-coordination mode as well as two incorporated THF molecules. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), both complexes A and B exhibited catalytic activities toward ethylene polymerization, producing polyethylenes with ultra-high molecular weights.

The reactions of 2-pyridinecarboxaldehyde-phenylhydrazonatolithium C5H4Npy-CH[double bond, length as m-dash]Ni-NaLi(Ph) (abbreviated as Li) with a 1/2 equivalent of anhydrous metal (Zn, Sn, Fe and Co) chlorides or NiCl2(DME) (DME = 1, 2-dimethoxyethane) produced the corresponding mononuclear metal(ii) complexes ( and ), in which each ligand acts as a bidentate ligand and the coordination geometries around the metals are shown to be tetrahedral within the complexes , , and , respectively, and a tetragonal pyramid in the complex . The reaction of Li successively with sodium tert-butoxide and anhydrous ZrCl4 afforded the unanticipated bizirconium complex , in which each monoanionic ligand behaves as a tridentate bridge. Whereas treatment of Li with NiCl2 and then CH2Cl2 led to an interesting methylene-bridged bis(2-pyridyl-phenylhydrazone) compound in moderate yield; a comparative experiment showed that when the Li reacted with CH2Cl2, the coupling compound was also obtained but in very low yield. A plausible mechanism of compound formation was also proposed and supported by the density functional theory (DFT) calculations. All the synthesized compounds were characterized by single-crystal X-ray diffraction.

Treatment of the mixed amidinate-amido-lithium, [PhN(CH2)3NC(Ph)NSiMe3]2Li4·2Et2O, with group IV metal chlorides yields the corresponding compounds 3–5. Their structures were confirmed by X-ray diffraction analysis, showing a distorted octahedral geometry. The catalytic behaviors of compounds 3–5 were investigated in the presence of MAO as a co-catalyst. Compounds 3 and 4 showed high activities for ethylene polymerization.

The t Bu-ended ansa -bis(amidine) SiMe 2 [NC(Ph)NH( t Bu)] 2 ( 1 ) was prepared by treating t BuNH 2 with one equivalent of both LiBu n and PhCN, and half equivalent of SiMe 2 Cl 2 in a one-pot reaction. 1 combined with HCl to give an ion pair complex [( t Bu)NHC(Ph)NH]SiMe 2 [NC(Ph)NH( t Bu)]Cl ( 2 ) and one N–C–N moiety was converted to a cationic amidinium ion. The complexation behaviour of 1 with group IV metal chlorides was explored. Treating 1 with TiCl 4 (thf) 2 in CH 2 Cl 2 gave the titanium complex [( t Bu)NHC(Ph)N]Ti(thf) 2 Cl 3 ( 3 ), in which the mono-amidinato ligand was supposedly derived from N–Si cleavage of 1 due to the high Lewis acidity of the titanium salt. The zirconium complex [( t Bu)NHC(Ph)NH]SiMe 2 [NC(Ph)N( t Bu)]ZrCl 4 ( 4 ) and the hafnium complex 5 were obtained by treating 1 with MCl 4 (M = Zr and Hf) in THF and these complexes were crystallized from CH 2 Cl 2 . Reaction of 1 with TiCl 4 (thf) 2 in toluene yielded {SiMe 2 [NC(Ph)NH( t Bu)] 2 Ti[NC(Ph)NH 2 ( t Bu)]Cl 3 }Cl ( 6 ), indicating the N–Si cleavage could be partially suppressed in a less polar environment. Recrystallization of 4 in toluene afforded SiMe 2 [NC(Ph)NH( t Bu)] 2 ZrCl 4 ( 7 ). Similarly, recrystallization of 5 in toluene gave 8 , which is isostructural to 7 . The reaction of 4 with AlMe 3 in THF yielded the zirconium complex [( t Bu)NHC(Ph)N]Zr(thf) 2 Cl 3 ( 9 ), which is analogous to 3 . The solid state structures of complexes 2 , 3 , 4 , 6 , 7 , 8 and 9 were investigated by single crystal X-ray structural analysis. Complexes 3 and 9 were found to be moderately active towards ethylene polymerization in the presence of methylaluminoxane (MAO).

There are two independent molecules in the asymmetric unit of the title compound, [Zr(C18H24N3Si)Cl3(C7H5N)], which are connected by an N—H...Cl hydrogen bond. The Zr atoms are seven-coordinate and possess a distorted pentagonal–bipyramidal geometry. In the crystal, molecules are connected by N—H...Cl hydrogen bonds, forming ribbons along [010].

Two ferrocene-modified pyrimidinyl acyl-thiourea derivatives, N-ferrocenoyl-N′-(2-pyrimidinyl) thiourea 1 and N-ferrocenoyl-N′-(5-pyrimidinyl) thiourea 2 were prepared from the reactions of ferrocenoyl isothiocyanate with 2-aminopyrimidine or 5-aminopyrimidine, respectively. Both of the new compounds were characterized by 1H NMR, 13C NMR, IR, elemental analyses and single-crystal X-ray diffraction. Comparing with ferrocene, compounds 1 and 2 show red-shift in the absorption peaks and increasing anodic peak potentials (Epa) values in the cyclic voltammetry studies. Furthermore, the electrochemical data of compounds 1 and 2 correspondingly exhibit one-electron quasi-reversible and reversible electrochemical redox behaviors. In the solid-state, compound 1 forms a ladder-like assembly by hydrogen-bonding, whereas, compound 2 is assembled into two-dimensional network structure through hydrogen-bonding and unusual intermolecular O⋯π interactions between O-atoms of the carbonyl units and the cyclopentadienyl rings.

The lithium β -diketiminate ( 1c , [Li{N(2,6- i Pr 2 C 6 H 3 )C(Ph)CHC( t Bu)NH}] 2 represented as (Li L ) 2 ) reacted with 3d-metal (II) chlorides to afford the corresponding compounds ( 2 – 7 ). All metal compounds were fully characterized by elemental, spectroscopic analyses and the single-crystal X-ray diffraction. The coordination geometries around the metals are shown to be tetrahedral within the trinuclear Co 2 Li compound ( 2 ), planar in M L 2 (M = Co, 3 ), pseudo-tetrahedral conformation in the M L 2 with M as Mn ( 4 ), Fe ( 5 ) or Zn ( 6 ), and square planar in the dinickel compound ( 7 ). Indicated by the trimetallic Co 2 Li compound 2 , a six-membered ring is constructed of three metal atoms and three bridged chlorides as a twisted conformation. An inversion center is present in the centroid of the Ni 2 Cl 2 four-membered ring within compound 7 . The plausible mechanism of forming M L 2 was proposed through the chloro-bridged multinuclear compounds on the basis of isolated intermediates of trinuclear ( 2 ) and dinuclearic ( 7 ) compounds. Upon treatment with methylaluminoxane (MAO), the nickel compound 7 possessed good activity towards ethylene oligomerization, whereas the other metal compounds showed moderate activities towards ethylene polymerization.

(2,6-Diisopropyl-N-(1-phenylvinyl)benzenamido)magnesium bromide (CH2(Ph)C(2,6-iPr2C6H3)NMgBr·2THF, 1b) reacted with 1 equiv of Me2NMe2SiCl to form the N-(2-((dimethylamino)dimethylsilyl)-1-phenylvi...

The reactions between the silyl-linked bis(amidinate) ligand [SiMe 2 {NC(Ph)N(Ph)Li(thf) 2 } 2 ] and ZrCl 4 in different stoichiometric chemistry, 2:1, 1:1, and 1:2, were explored. The resulting zirconium compounds, 1 , 2, and 3 , showed different molecular structural features which were confirmed by X-ray crystallographic analysis. The metal center in 1 was located in a highly saturated coordination environment with four amidinate moieties. Compound 2 exhibited an unprecedented linked tris(amidinate) N–C–N–Si–N–C–N–Si–N–C–N skeleton formed after the intermolecular rearrangement. In compound 3 , a novel silyl-linked imino-amidinate ligand via the intramolecular rearrangement was involved. The mechanism for the formation of compounds 2 and 3 was proposed. Compound 2 was found to be a highly active catalyst for ethylene polymerization in the presence of methylalumoxane (MAO).

The synthesis and characterization of a class of group 4 metal derivatives based on the silyl-linked bis(amidinate) ligands [SiMe2{NC(Ph)N(2,6-R2Ph)Li}2] [L1 (R = H) and L2 (R = Me)] are described. The metal salts coordinated with cyclopentadienyl were used in order to increase the steric hindrance and lower the Lewis acidity of metal centers, which could prevent the N-ligands from rearranging. The tetradentate ligands L1 and L2 reacted with TiCl2(C5H5)2 to give compounds 1 and 2 in tridentate and bidentate bonding modes, respectively. Treatment of the ligand L1 with ZrCl3(C5H5) produced the half-sandwich zirconium complex 3. Reactions of the ligands with ZrCl2(C5H5)2 afforded zirconium compounds 4 and 5, demonstrating the same geometry as 1. Comparing these analogous molecular structures, it suggests that the coordination modes of the N-ligands are variable according to the properties of the metal centers as well as the bulky hindrance of the terminal groups on the seven-membered N–C–N–Si–N–C–N backbone.

A novel class of silyl-linked bis(amidinate) ligands [SiMe2{NC(Ph)N(2,6-R2Ph)Li}2] [L1 (R = H), L2 (R = Me), and L3 (R = iPr)] reacted with TiCl3(C5H5) to produce the half-sandwich titanium complexes 1, 2, and 3. The molecular structures of 1–3 were confirmed successfully by X-ray crystallography. An unprecedented intramolecular ligand transformation from the linked bis(amidinate) configuration to the linked imido-amidinate configuration took place in the cases of L1 and L2. It was found that the rearrangement process was related to the steric hindrance of the terminal substituents. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

A practical synthetic pathway to alkyl-ended ansa-bis(amidinate) ligands was developed via linking the freshly prepared aliphatic group substituted lithium amidinate and the subsequent deprotonation. The lithium complexes prepared by this method were characterized by NMR spectroscopy, elemental analysis and single-crystal X-ray diffraction analysis.

The asymmetric unit of the title compound, C15H16N2·C4H8O, contains two amidine molecules (AandB) with slightly different conformations and two tetrahydrofuran (THF) solvent molecules. In the amidine molecules, the dimethylphenyl ring and the NH2group lie to the same side of the N=C bond and the dihedral angles between the aromatic rings are 54.25 (7) (moleculeA) and 58.88 (6) ° (moleculeB). In the crystal, N—H...N hydrogen bonds link the amidine molecules into [100]C(4) chains of alternatingAandBmolecules. Both amidine molecules form an N—H...O hydrogen bond to an adjacent THF solvent molecule.

Two four-membered bissilylene-linked bisamidines of type (V) are prepared from lithium complexes (I) obtained from primary amines in four steps.

Lithium N-[(N,N-dimethylamino)dimethylsilyl]-2-pyridylamidate (2) was prepared from the reaction of new compound N-[(N,N-dimethylamino)dimethylsilyl]-2-pyridylamine (1) and LiBu(n). Treatment of the lithium salt (2) with an equal equivalent of MgBr(2)(THF)(2), FeCl(2) and CoCl(2) afforded the corresponding dinuclear complexes , , and , in which metal atoms possess similar trigonal bipyramidal geometries and each ligand functions as a bimetallic bridging binding aminopyridinato moiety with N-donation from the dimethylamino group. While the stoichiometric reaction of with ZrCl(4) gave the mononuclear zirconium complex (6); the seven coordinated zirconium atom adopts a distorted pentagonal bipyramid geometry and the ligand acts as monoanionic η(2)-aminopyridinato moiety with the pendant arm coordinated via N(CH(3))(2). The reaction of with one equivalent of TiCl(4)(THF)(2) produced the interesting dinuclear titanium complex (7) owing to the elimination of a (N,N-dimethylamino)dimethylsilyl group from the original ligand, and the two titanium centers present different coordination geometries. The molecular structures of the crystalline metal complexes have been confirmed by X-ray single crystal diffraction analysis. Upon activation with methylaluminoxane (MAO), both complexes and exhibited moderate catalytic activities toward ethylene polymerization and produced high molecular weight polyethylenes with broad molecular weight distributions.

The two title crystalline compounds,viz.meso-bis{η5-1-[1-(dimethylamino)ethenyl]-3-(trimethylsilyl)cyclopentadienyl}iron(II), [Fe(C12H20NSi)2], (II), andmeso-bis{η5-1-[1-(dimethylamino)ethenyl]-3-(trimethylsilyl)cyclopentadienyl}cobalt(II), [Co(C12H20NSi)2], (III), were obtained by the reaction of lithium 1-[1-(dimethylamino)ethenyl]-3-(trimethylsilyl)cyclopentadienide with FeCl2and CoCl2, respectively. For (II), the trimethylsilyl- and dimethylaminoethenyl-substituted cyclopentadienyl (Cp) rings present a nearly eclipsed conformation, and the two pairs of trimethylsilyl and dimethylaminoethenyl substituents on the Cp rings are arranged in an interlocked fashion. In the case of (III), the same substituted Cp rings are perfectly staggered leading to a crystallographically centrosymmetric molecular structure, and the two trimethylsilyl and two dimethylaminoethenyl substituents are oriented in opposite directions, respectively, with the trimethylsilyl group of one Cp ring and the dimethylaminoethenyl group of the other Cp ring arranged more closely than in (II).

The mononuclear silyl-linked bis(amidinate) titanium compound 2 was prepared by salt metathesis of 1 and TiCl(4)(thf)(2). Alkylation of 2 with methyllithium gave analogue 3. Both 2 and 3 exhibited a configuration similar to ansa-metallocene and showed good activity towards ethylene polymerization after activation with MAO.

A novel silyl-linked amidinate-amidine monoanionic ligand 3 was synthesized by double additions of PhCN starting from silyl-linked bis(amino) monoanion 2, which underwent an intramolecular Li/H metathesis and double silyl shift. The related Zr(IV) complex 4 was prepared and confirmed by X-ray diffraction revealing a structural rearrangement from its precursor. The mechanisms for the reaction processes have been proposed. Each of compounds 2, 3 and 4 was characterized by NMR spectroscopy, elemental analysis and X-ray diffraction. Complex 4 exhibited moderate activity for ethylene polymerization in the presence of methylalumoxane (MAO).

In the title cobalt(II) compound, [Co(C(12)H(21)N(2)Si)Cl(C(6)H(16)N(2))], the ethane-1,2-diamine donor mol-ecule coordin-ates the metal atom in an N,N'-chelating mode, with Co-N distances of 2.136 (2) and 2.140 (3) Å. An anilide ligand connects to the Co(II) atom with a σ-bond, the Co-N(anilide) distance being 1.931 (2) Å. The four-coordinate Co(II) atom demonstrates a slightly distorted tetra-hedral geometry.

Deprotonation of the aminofulvene 1 with LiCH(SiMe3)2 provides 2, which reacts with MCl4 (M=Zr or Hf) by intramolecular NMe2H elimination and coupling of the fulvene moieties to form complex 3 or 4. This reaction is a useful synthetic pathway to allyl-bridged ansa-metallocenes, especially those with a conjugated 14 π electron system. R′=dimethylamino.

In the crystal structure of the title salt, NH(4) (+).[(C(6)H(5))P(O)(2)(OH)](-) or NH(4) (+)·C(6)H(6)O(3)P(-), the N and O atoms inter-act via hydrogen bonds to generate a layer motif. The phenyl rings are stacked above and below this layer, sandwiching the hydrogen-bonded layer.

A novel type of linked bis(amidinate) ligands (D) were developed successfully. Their lithium derivatives 1-4 were synthesized by treating the silyl-bridged diamines I-IV with two equivalents of LiBu(n) and PhCN in sequence, which underwent a silyl-bridge migration process. In addition, the linked bis(amidinate) configuration proved to be the thermodynamically stable form rather than the mono(amidinate) type by contrasting reaction of I with one equivalent of LiBu(n) and PhCN in sequence.

Reaction of dilithium derivatives of N , N’ -(dimethylsilanediyl)diamines, Me 2 Si[N(Li)R] 2 with benzonitrile followed by treatment with Me 2 SiCl 2 afforded 1,3-bis[1-( N -R-imino)-1-phenylmethyl]-1,3,2,4-diazadisiletidines, the neutral four-membered bissilylene-linked bisamidines, whose structure was established by X-ray diffraction.

Deprotonation of the aminofulvene 1 with LiCH(SiMe

In the title mol­ecule, C9H13N, all bond lengths and angles show normal values. In the crystal structure, weak C—H⋯π inter­actions link the mol­ecules into centrosymmetric dimers. The crystal packing is further stabilized by van der Waals forces.

The title compound, [Li(C16H17N2)(C4H8O)2]n, is an unsymmetrical benzamidinate exhibiting a one-dimensional chain made up of lithium-linked N—C—N units. Two tetra­hydro­furan mol­ecules complete the distorted LiO2N2 tetra­hedral coordination.

The symmetric title molecule, [Hf(C26H40N4Si)Cl4], lies about a twofold rotation axis. The HfIVand Si atoms lie on the rotation axis with all other atoms being in general positions. The HfIVatom is six-coordinated by two N atoms from theN2,N2′-(dimethylsilanediyl)bis(N-tert-butyl-3-methylbenzimidamidate) ligand and four Cl−ions in a slightly distorted octahedral geometry. The two amidinate moieties are connected through the central Si atom with Si—N bond length of 1.762 (3) Å, generating the characteristic N—C—N—Si—N—C—N skeleton of a silyl-linkedansa-bis(amidine) species.

The ZrIV atom in the title half-sandwich organometallic zirconium(IV) compound, [Zr(C5H5)(C32H35N4Si)Cl2]·CH2Cl2, is N,N′,N′′-chelated by the silyl-linked imino-amidinato monoanion in the first example of such an organozirconium derivative. The three N-donor atoms along with a Cl atom form a square, above and below which are the cyclo­penta­dieny ring and the second Cl atom. The coordination geometry is octa­hedral.

Bis(silyl-substituted) methyllithium has been found to catalyze a conversion of α-hydrogen-free nitriles directly to yield 2,4,6-trisubsituted s-triazines. The generally high yields and relatively mild reaction conditionsof this procedure suggest an alternative to other aromatic nitrile cyclotrimerization reactions. Silicotropic rearrangements from C to N or N to N and an unusual elimination of LiCR 2 R' (R=SiMe 3 , R'=SiMe 2 NMe 2 ) were observed.