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3a,6a-Diaza-1,4-diphosphapentalene (DDP) reacts with halocarbons to give addition products to one or both phosphorus atoms depending on the substrate. Chlorotriphenylmethane affords a 1,4-addition product, which slowly decomposes in solution to form the Ph3C radical and the chloro-DDP coupling product with a P–P bond. Benzyl chloride is added to one phosphorus atom to form hypervalent (trivalent, four-coordinate) phosphorus with a N···P distance (nonvalent interaction) of 2.191(2) A. A workup of the latter with GeCl2 results in a complex salt containing the GeCl3– anion and cation with covalent N–P bonding.

The lithium salt of 3,5-dimethyl-1-phenyl-1H-pyrazole (PyrC6H4Li) reacts with (Et2N)2PCl to give the precursor [PyrC6H4P(NEt2)2] (2), which, after reaction with PCl3, affords PyrC6H4PCl2 (3) in 79 % yield. The phosphorus atom in 3 has four-coordinate disphenoidal geometry with an axial arrangement of Cl atoms. The length of the hypervalent N–P bond in this compound [1.775(1) A] is comparable to that of common single bonds. The structure of 3 is better described by canonical formulae containing charges on the N, P, and Cl atoms. The 1H NMR spectrum of 3 in CDCl3 shows five pairs of nonequivalent Me groups, which correspond to the positional isomers that exist in the equilibrium mixture. Compound 3 easily exchanges chlorine with methyl iodide to form the diiodo derivative 4 (PyrC6H4PI2) with nonequivalent P–I bonds. The reduction of 3 with aluminium foil or [GeCl2(diox)] gave cationic diphosphines [(PyrC6H4P)2(μ-Cl)][AlCl4] (8) and [(PyrC6H4P)2(μ-Cl)][GeCl3] (9), respectively, with a chloride bridge between the phosphorus atoms. Compounds 4, 8 and 9 show a disphenoidal arrangement around the hypervalent phosphorus atoms. The dichloro and diiodo derivatives 3 and 4 are destroyed on heating in pyridine to give diphosphines [(PyrC6H4PCl)2] (10) and [(PyrC6H4P)2(μ-I)]+[I] (12), respectively, containing hypervalent (trivalent four-coordinate) phosphorus. The crystal structure of 10 shows multiple C···C, C···Cl, H···H, and C···H short contacts between the adjacent molecules. Compound 3 exchanges chlorine for oxygen atoms on heating in dimethylformamide to give the dioxide PyrC6H4PO2 (13) with an N–PV distance [1.808(1) A] even longer than that in 3.

New tris-o-benzosemiquinonato complexes of Al, Ga, and In based on the sterically hindered o-benzoquinone 5,8-di-tert-butyl-2,3-dihydro-1,4-ethanoquinoxaline-6,7-dione (NN-3,6-Q) were synthesized. The structures of the hexacoordinate metal compounds were investigated by X-ray diffraction. The magnetic properties of the complexes obtained were found to be strongly dependent on their molecular geometry. The octahedral Al and Ga derivatives demonstrate ferromagnetic exchange between the magnetic centers, whereas the trigonal-prismatic In complex shows an antiferromagnetic coupling.

A series of lanthanide monoborohydrido complexes {C6H4-1,2-[NC(R)NR′]2}Ln(BH4)(L)n (Ln = Y, Nd, Sm; R = tBu, Ph; R′ = 2,6-Me2C6H3, SiMe3; L = dme = dimethoxyethane, n = 1; L = thf, n = 2), in which lanthanides are coordinated by bulky ansa-bis(amidinato) ligand systems with a conformationally rigid o-phenylene linker ({C6H4-1,2-[NC(R)NR′]2}2–), were synthesized by the salt metathesis reactions of equimolar amounts of Ln(BH4)3(thf)3 and {C6H4-1,2-[NC(R)NR′]2}X2(thf)n (X = Li, Na) in thf. X-ray diffraction studies revealed that the complexes are monomeric. Depending on the denticity of the donor ligand (L = dme or thf), the terminal borohydrido ligand coordinated to the metal ion can be located in either an equatorial (L = thf) or an apical (L = dme) position. All complexes are efficient catalysts for the ring-opening polymerization of rac-lactide, which allows to convert up to 1000 equiv. of monomer into a polymer at room temperature within 10–150 min and affords atactic polylactides with high molecular weights and moderate molecular-weight distributions (1.28–2.16). Yttrium–borohydrido complexes coordinated by the {C6H4-1,2-[NC(tBu)N(2,6-Me2C6H3)]2}2– ligand system showed enhanced catalytic activity compared to that of the analogue complexes containing the {C6H4-1,2-[NC(Ph)NSiMe3]2}2– ligand. The obtained borohydrido complexes catalyze the hydrophosphonylation of benzaldehyde at room temperature with good reaction rates.

The reactions of the lithium silylarylamides [1,2-C6H4(NSiMe3)2Li2]2 and [1,3-C6H4(NSiMe3)2Li2] with two equivalents of PhCN [tetrahydrofuran (thf), room temp.] is an efficient synthetic approach to the ansa-bis(amidinate) ligand systems [1,2-C6H4{NC(Ph)NSiMe3}2Li2(thf)]2 and [1,3-C6H4{NC(Ph)NSiMe3}2Li2(thf)2]2, which were isolated in 54 and 60 % yields, respectively. However, lithium silylarylamide [2,6-C5H3N(NSiMe3)2Li2] containing a pyridine fragment does not undergo PhCN insertion even at elevated temperatures (thf, toluene), and the reaction affords the silylarylamido complex [2,6-C5H3N{NSiMe3}2Li2]3·(C6H5CN)4, which contains a coordinated benzonitrile molecule. The different reactivity of the compounds correlates with the changes in the molecular orbital energies estimated by DFT calculations. The salt metathesis reaction of anhydrous YCl3 with lithium amidinate [1,2-C6H4{NC(Ph)NSiMe3}2Li2(thf)]2 in 2:1 molar ratio (thf, 20 °C) afforded a neutral bis(amidinate) chloro yttrium complex [1,2-C6H4{NC(Ph)NSiMe3}2]YCl(thf)2 in 80 % yield. With NdCl3, the analogous reaction resulted in a trinuclear neodymium chloro ate complex with a rather unusual μ-bridging lateral coordination of the amidinate fragment [1,2-C6H4{NC(Ph)NSiMe3}2Nd(thf)(μ-Cl)(1,2-C6H4{NC(Ph)NSiMe3}2Nd{μ-Cl}2)][Li(thf)2].

Two new amidines that contain a pendant Lewis base in the side arm, 2-MeOC6H4NC(tBu)NH(2,6-R2C6H3) (R = Me, iPr), were synthesized and successfully employed as tridentate ligands for the preparation of the dialkyl rare earth complexes [2-MeOC6H4NC(tBu)N(2,6-R2C6H3)]Ln(CH2SiMe3)2(L)n {Ln = Y, Lu; R = Me, iPr; L = thf (n = 2), dme (n = 1)}. These ligands provided enhanced stability for the complexes. The X-ray structure determinations revealed that intramolecular coordination of the 2-MeOC6H4 group is realized if a thf molecule is coordinated to the metal center (Ln = Y, Lu), which results in the coordination number of six. The treatment of complex [2-MeOC6H4NC(tBu)N(2,6-Me2C6H3)]Lu(CH2SiMe3)2(thf) with dme afforded a six-coordinate dme adduct in which the methoxy group of the amidinate ligand has drifted out from the metal coordination sphere. The reaction of [2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(CH2SiMe3)2(thf) with 2,6-diisopropylaniline in hexane at 70 degrees C, regardless of the ratio of the reagent, afforded the six-coordinate diamido compound [2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(NHC6H3-2,6-iPr2)2(thf), for which intramolecular coordination of the oxygen atom of the side chain was detected by an X-ray study. Complex [2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(CH2SiMe3)2(thf) was evaluated as a precatalyst for isoprene polymerization. The ternary system [2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(CH2SiMe3)2(thf)/[Ph3C][B(C6F5)4]/AliBu3provided isoprene polymerization with moderate activity but without control of the regioselectivity (3,4-regularity was slightly predominant at 52?%). Nevertheless, high 1,4-trans-selectivity was found (96%) for the 1,4-polyisoprenes. The obtained polyisoprene has a Mn of 13.0 x 10(4) and moderate polydispersity (2.12).

The synthetic pathway to a new bis(amidine) ligand with a conformationally rigid naphthalene linker, 1,8-C10H6[NHC-(tBu)=N(2,6-Me-2-C6H3)][N=C(tBu)NH(2,6-Me-2-C6H3)] (3) was elaborated. Deprotonation of this bis(amidine) ligand with two equivalents of nBuLi and subsequent reaction with anhydrous LnCl(3) (Ln = Y, Nd, Sm) allowed the synthesis of the chlorido complexes [1,8-C10H6{NC(tBu)N-2,6-Me2C6H3}(2)]YCl(dme) (4), [1,8-C10H6{NC(tBu)N-2,6-Me(2)C6H(3)}(2)]Nd(dme)(mu-Cl)(2)Li(dme) (5), and [1,8-C10H6{NC(tBu)-N-2,6-Me-2-C6H3}(2)]Sm(thf)(mu-Cl)(2)Li(thf)(2) (6), which are coordinated by the linked dianionic bis(amidinate) ligand. The structures of complexes 4-6 were established by X-ray diffraction studies, which reveal that the new ligand framework can coordinate to the lanthanide atoms in different fashions depending on the central atom ion size. Alkylation of complex 6 with equimolar amounts of LiCH2SiMe3 afforded the unexpected amido-amidinate complex [{1,8-C10H6(NC(tBu)-N-2,6-Me-2-C6H3)(2)}{1,8-C10H6(NC(tBu)N-2,6-Me-2-C6H3)-(NH)}Sm][Li(dme)(3)] (7), which obviously results from the cleavage of one amidinate group during decomposition of the transient alkyl species and ligand redistribution.

Reaction of (dpp-BIAN)Mg(THF)3 (1) {dpp-BIAN = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene} with one molar equivalent of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) proceeds with oxidation of the dpp-BIAN dianion in 1 to the radical-anion and affords the (dpp-BIAN)Mg(TEMPO)(thf) (2) complex. The reaction of dpp-BIAN with an excess amount of magnesium and 0.5 molar equivalents of I2 in Et2O gives (dpp-BIAN)MgI(Et2O)n, which then reacts in situ with (Me3Si)2NK to produce (dpp-BIAN)Mg[N(SiMe3)2](Et2O) (3). Solvent-free magnesium amide (dpp-BIAN)Mg[N(SiMe3)2] (4) was synthesized by treating equimolar amounts of MgI2, dpp-BIAN, and sodium in toluene at reflux followed by treatment with (Me3Si)2NK. Deprotonation of diphenylacetonitrile with [(dpp-BIAN)Mg(μ-Me)]2 (5) produces keteniminate complex (dpp-BIAN)Mg(N=C=CPh2)(Et2O) (6). Complexes 2–4 and 6 were characterized by ESR and IR spectroscopy; their molecular structures were determined by single-crystal X-ray analysis. Compounds 1–3 catalyze the ring-opening polymerization of L- and rac-lactides to give high molecular weight isotactic and stereoblock polylactides correspondingly.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

The reactions of (dpp-bian)Mg(thf)3 (1) {dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene} with 0.5 molar equivalents of RS–SR (R = Bz, sBu, C(S)NMe2) occur with a cleavage of the S–S bond to afford monosulfide complexes (dpp-bian)Mg(SBz)(dme) (2), (dpp-bian)Mg[S(sBu)](dme) (3), and (dpp-bian)Mg[SC(S)NMe2](thf) (4). Compounds 2, 3, and 4 are paramagnetic due to the presence of dpp-bian radical-anions that are formed in the course of one-electron transfer from the dpp-bian dianion in 1 to the sulfur-containing substrate. Reduction of BzS–SBz with gallane (dpp-bian)Ga–Ga(dpp-bian) (5) gives a mononuclear GaIII complex with the dpp-bian radical-anion, (dpp-bian)Ga(SBz)2 (6). The reaction of 5 with RS–SR (R = C(S)NMe2) proceeds with a cleavage of the S–S and Ga–Ga bonds and affords (dpp-bian)Ga[SC(S)NMe2] (7), in which the dpp-bian ligand retains its dianionic state. Complexes 2, 3, 4, and 6 have been characterized by ESR and IR spectroscopy, and complex 7 has been studied by 1H MNR spectroscopy. The molecular structures of 2–4, 6, and 7 have been determined by X-ray crystallography. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Lewis base free hydrido complexes of yttrium and lutetium supported by bulky cyclohexyl- substituted guanidinato ligands, [Ln(mu-H){(Me3Si)(2)NC(NCy)(2)}(2)](2) (Ln = Y, Lu), were synthesized and characterized. Single-crystal X-ray diffraction studies revealed dimeric structures. H-1 NMR spectroscopy shows that complex [Y(mu-H){(Me3Si)(2)NC(NCy)(2)}(2)](2) retains its dimeric structure in C6D6 solution. Scrambling of the hydrido complexes [Ln(mu-H){(Me3Si)(2)NC(NCy)(2)}(2)](2) (Ln = Y, Lu) in C6D6 resulted in an equilibrium mixture containing the heterodimetallic species [{(Me3Si)(2)NC(NCy)(2)}(2)Y(mu-H)(2)-Lu{(Me3Si)(2)NC(NCy)(2)}(2)], indicating the dissociation of dimers and the presence of monomeric species in solution. Both compounds initiate the polymerization of ethylene: the activity of the cyclohexyl- substituted yttrium complex, [Y(mu-H){(Me3Si)(2)NC(NCy)(2)}(2)](2), is much lower than that of the isopropyl-substituted analogue, [Y(mu-H){(Me3Si)(2)NC(NiPr)(2)}(2))(2), while in the case of lutetium the activities of [Ln(mu-H){(Me3Si)(2)NC(NR)(2)}(2)](2) (R = iPr, Cy) are similar. Complexes [Ln(mu-H){(Me3Si)(2)NC(NR)(2)}(2)](2) (Ln = Y, Lu; R = iPr, Cy) were shown to catalyze efficiently the hydrosilylation of 1-nonene with PhSiH3 (at a 1:1 substrates mol ratio) to give the terminal silane PhSiH2(n-C9H19) exclusively. If the hydrosilylation reaction is carried out in the presence of a twofold molar excess of 1-nonene, double addition takes place and leads to the formation of tertiary silane PhSiH(n-C9H19)2, which was obtained in 96% yield. The hydrido complexes [Ln(mu-H){(Me3Si)(2)NC(NiPr)(2)}(2)](2) (Ln = Y, Lu) efficiently initiate the ring-opening polymerization of epsilon-caprolactone to give polymers with molar mass up to 80000. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).

A series of new lanthanide borohydride complexes supported by bulky guanidinate ligands [(Me3Si)2NC(N-Cy)2]2Ln(μ-BH4)2Li(THF)2 [Ln = Nd (1), Sm (2), Yb (3)] was synthesized by the reaction of related tris(borohydride)s Ln(BH4)3(THF)2 with a twofold molar excess of [(Me3Si)2NC(N-Cy)2]Li in toluene at 65 °C. The complexes were isolated after recrystallization from hexane in 66, 64, and 68 % yield, respectively. X-ray diffraction studies revealed that compounds 1–3 are heterodimetallic complexes that have two borohydride ligands μ-bridging the lanthanide and lithium atoms. Those compounds, especially neodymium complex 1, act as monoinitiators for the ring-opening polymerization of racemic lactide, providing atactic polymers with a good degree of control, that is, controlled molecular weights and relatively narrow polydispersities (1.09 < Mw/Mn < 1.77), provided moderate substrate-to-initiator ratios are used. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The reactions of anhydrous LnCl3 (Ln = Y, Nd, Sm, Lu) with two equiv. of sodium N,N′-dicyclohexyl-N′′-bis(trimethylsilyl)guanidinate Na[(Me3Si)2NC(NCy)2], obtained from Na[N(SiMe3)2] and the 1,3-dicyclohexyl-substituted carbodiimide CyN=C=NCy in THF, yield the monochloro bis(guanidinate) tetrahydrofuranate complexes [(Me3Si)2NC(NCy)2]2LnCl(THF) [Ln = Y (1), Nd (2), Sm (3) and Lu (4)]. The analogous reactions of YCl3 and LuCl3 with the lithium guanidinate [Li(Et2O)][(Me3Si)2NC(NCy)2] afford the bis(guanidinate) “ate” complexes [(Me3Si)2NC(NCy)2]2Ln(μ-Cl)2Li(THF)2 [Ln = Y (5) and Lu (6)]. Treatment of 5 with dimethoxyethane results in the formation of [(Me3Si)2NC(NCy)2]2Y(μ-Cl)2Li(DME) (7). The carbyl complexes [(Me3Si)2NC(NCy)2]2Y-tBu] (8), [(Me3Si)2NC(NCy)2]2Y(μ-Me)2Li(TMEDA) (10) and [(Me3Si)2NC(NCy)2]2YPh(THF) (13) were obtained by interaction of complex 1 with RLi (R = tBu, Me or Ph). The molecular structures of 1, 6, 7, 8 and the side product [Li(TMEDA)][(Me3Si)2NC(NCy)2] have been determined by single-crystal X-ray analyses. Agostic interactions between the yttrium atom and the tert-butyl group in complex 8 in the solid state as well as in solution have been substantiated by 13C NMR spectroscopy and X-ray analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Heating NdI2 (1) or DyI2 (2) with vanadocene (3) in benzene at 85 °C led to the formation of bis(benzene)vanadium in 10 and 24 % yields, respectively. The lanthanide products were isolated in the form of CpLnI2(THF)3 after crystallization from THF. The interaction of 2 with 3 in isopropylbenzene at 90 °C yielded a mixture of (arene)2V complexes from which a small amount of bis(isopropylbenzene)vanadium was isolated. The same reaction did not occur in mesitylene. From the reaction of 2 with 3 in molten naphthalene at 100 °C, the heterobimetallic cluster {[CpDy(μ-I)2]7Cp2V(μ-I)}(4) was isolated in low yield. The reaction of Cp2Cr with 1 or 2 in benzene at ambient temperature afforded the dimer [CpCr(μ-I)]2 (5) and a dysprosium complex, Cp2DyI (6) (in the reaction with 2). When the reaction with 2 was carried out at 80 °C, along with compound 6, the -ate complex {[Cp2DyI2]–[Cp2Cr]+}(7) was crystallized from the reaction solution. Nickelocene was reduced by 2 in benzene at 80 °C to nickel metal. The dysprosium product was isolated as solvent-free complex 6. Ferrocene and cobaltocene did not react with 1 and 2 in benzene. The molecular structures of compounds 4, 5, and 7 were characterized by X-ray diffraction analysis.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

The reaction of anhydrous LuCl3 with a twofold molar excess of lithium guanidinate [Li{(Me3Si)2NC(NiPr)2}], obtained in situ from the amide [LiN(SiMe3)2(Et2O)] and 1,3-diisopropylcarbodiimide in THF, yields the bis(guanidinate) “ate” complex [Lu{(Me3Si)2NC(NiPr)2}2(μ-Cl)2Li(THF)2] (1). The alkyllutetium derivative [Lu{(Me3Si)2NC(NiPr)2}2(CH2SiMe3)] (2) was synthesized by a metathesis reaction of 1 with LiCH2SiMe3 in toluene. The treatment of 2 with an equimolar amount of PhSiH3 in hexane at room temperature results in the first known dimeric lanthanide hydride in a bis(guanidinate) coordination environment, [Lu{(Me3Si)2NC(NiPr)2}2(μ-H)]2 (3). The crystal structures of complexes 1 and 3 have been determined by X-ray crystallography. The hydrido complex 3 was found to catalyze polymerization of ethylene, propylene and styrene. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The reduction of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (2,6-iPr2C6H3-BIAN) with metallic magnesium or calcium in THF affords the monomeric complexes (2,6-iPr2C6H3-BIAN)Mg(THF)3 (1) and (2,6-iPr2C6H3-BIAN)Ca(THF)4·(THF)1/2 (2). The crystallisation of 1 and 2 from benzene causes the removal of one of the coordinated THF molecules, yielding (2,6-iPr2C6H3-BIAN)Mg(THF)2·(C6H6)1/2 (3a) and (2,6-iPr2C6H3-BIAN)Ca(THF)3 (4). Repeated recrystallisation of 1 from benzene gives (2,6-iPr2C6H3-BIAN)Mg(THF)2·(C6H6)2 (3b). Although the crystals of 3a and 3b differ in colour and in their crystallographic parameters, their molecular dimensions are very similar. Recrystallisation of 1 from pyridine produces (2,6-iPr2C6H3-BIAN)Mg(py)3·(py)2 (5). Complexes 1−5 have been characterised by elemental analysis, UV, IR and 1H NMR spectroscopy, as well as by single-crystal X-ray diffraction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)