Unusual inorganic ring systems of scandium and yttrium containing group 13 Metals: coordination of monomeric Me(2)InOMe to yttrium

Novel transformations of lanthanide(III) disiloxanediolates with group 13 metal trialkyls are reported. Treatment of the scandium metallacrown complex [{(Ph2SiO)2O}2{Li(DME)}2]ScCl.THF (1) with AlMe3 resulted in an Li-Al exchange reaction and the formation of the heterotrimetallic inorganic ring system [{(Ph2SiO)2O}2{Li(THF)2}AlMe2]ScCl.THF (2). The related yttrium metallacrown [{(Ph2SiO)2O}2{Li(THF)2}2]YCl.THF (3) reacts with InMe3 under the formation of the heterobimetallic Y/In disiloxanediolate complex [{(Ph2SiO)2O}2{InMe2(OMe)}2InMe2]Y (4). In the latter, two monomeric Me2InOMe ligands are stabilized through coordination to yttrium.     

Alkali metal complexes of sterically hindered mono- and di-carbanions containing Si-O bonds

The oxygen-bridged, silicon-substituted alkane {(Me3Si)2CH(SiMe2)}2O (1) may be prepared by the reaction of {(Me3Si)2CH}Li with ClSiMe2OSiMe2Cl in refluxing THF. Similarly, the alkane {(Me3Si)(Me2MeOSi)CH(SiMe2CH2)}2 (2) is readily accessible from the reaction between {(Me3Si)(Me2MeOSi)CH}Li and ClSiMe2CH2CH2SiMe2Cl under the same conditions. Compound 1 reacts with two equivalents of MeK to give the polymeric complex [[{(Me3Si)2C(SiMe2)}2O]K2(OEt2)]infinity [5(OEt2)] after recrystallisation. Treatment of 2 with two equivalents of either MeLi or MeK gives the corresponding complexes [{(Me3Si)(Me2MeOSi)C(SiMe2CH2)}2Li][Li(DME)3] [7(DME)3] and [{(Me3Si)(Me2MeOSi)C(SiMe2CH2)}2K2]n (8), respectively, after recrystallisation. Treatment of the alkane (Me3Si)2(Me2MeOSi)CH with one equivalent of MeK gives the polymeric complex [{(Me3Si)2(Me2MeOSi)C}K]infinity (3). These compounds have been identified by 1H and 13C{1H} NMR spectroscopy and elemental analyses and compounds 5(OEt2), 7(DME)3 and 3 have been further characterised by X-ray crystallography. Compound 7(DME)3 crystallises as a solvent-separated ion pair, whereas 5(OEt2) and 3 adopt polymeric structures in the solid state.     

Double InMe2 insertion into a 12-membered Si4O6Li2 inorganic ring system coordinated to praseodymium

A novel transformation of a lanthanide(III) disiloxanediolate complex with trimethylindium is reported. Treatment of the praseodymium “inorganic metallocene” complex [{(Ph₂SiO)₂O}₂{Li(DME)}₂]PrCl(DME) (5) with InMe₃ resulted in double insertion of InMe₂ units into the 12-membered Si₄O₆Li₂ inorganic ring system attached to praseodymium and formation of [Li(THF)₄][Pr{O(SiPh₂OInMe₂OSiPh₂OSiPh₂O)₂}] (6). The novel ionic product 6 was structurally authenticated by single-crystal X-ray diffraction.     

Synthesis and structural characterisation of lithium and sodium 2,6-dibenzylphenolate complexes

The stoichiometric treatment of 2,6-dibenzylphenol (HOdbp) or 2,2"-dimethoxy-2,6-dibenzylphenol (HOdbpOMe) with n-butyllithium or sodium bis(trimethylsilyl)amide (the latter as a solution in THF) in Et2O or DME affords the dimeric alkali metal phenolates [{M(Odbp)(L)}2] (M = Li; L = Et2O (1), L = DME (2), M = Na; L = Et2O (5), L = DME (6)), [{Li(OdbpOMe)}2] (3) and [{M(OdbpOMe)(L)}2] (M = Li; L = DME (4), M = Na; L = THF (7), L = DME (8)). Complexes 3 and 7 exhibit -OdbpOMe methoxy coordination and all four sodium complexes (5-8) display pi-aryl contacts from one phenolate radial arm to each sodium centre. The attempted synthesis of {Na(odbp)}n by direct sodiation of HOdbp yields a small quantity of the 2-benzylphenolate [{Na(Ombp)(DME)}4] (9) (-Ombp = -OC6H4-2-CH2Ph), providing a rare example of benzyl C-C bond scission.     

Unique formation of a pentanuclear lanthanum(III) thiolate oxide cluster via control of hydrolysis

The reaction of [(TMS)2N]3La(mu-Cl)Li(THF)3 (1) and HSPh produced a bimetallic complex [{(TMS)2N}2La(THF)]2(mu-SPh)(mu-Cl)] (2). Compound [{(TMS)2N}2La5O(SPh)10LiCl2(THF)6] (3) was prepared by control of the hydrolysis of 2 and LiCl or 1 and HSPh with the proper amount of water. 1 was treated first with 1/6 equiv of H2O and then with equimolar HSPh; a polymeric complex [{(TMS)2N}2(mu-SPh)La(mu-SPh)Li(THF)2](infinity) (4) was isolated. 3 contains a central [(mu-SPh)4(mu3-SPh)2{La(THF)}4(mu3-O)]4+ tetrahedral fragment in which two La atoms are linked by a pair of mu-SPh- and mu3-Cl- ligands to a [{(TMS)2N}2La]+ fragment, while the other two are bridged by two mu-SPh- ligands to a [Li(THF)2]+ fragment, forming a bee-shaped structure.     

New lanthanide(III) disiloxanediolates: Syntheses and structures

Three new chloro-functionalized lanthanide(III) bis(disiloxanediolate) complexes, [{(Ph₂SiO)₂O}₂{Li(DME)}₂]Nd(DME)Cl (3), [{(Ph₂SiO)₂O}₂{Li(THF)₂}₂]HoCl·2THF (4), and [{(Ph₂SiO)₂O}₂{Li(THF)₂}₂]ErCl·2THF (5) have been prepared by the treatment of anhydrous lanthanide trichlorides, LnCl₃ (Ln = Nd, Ho, Er), with two equivalents of in situ prepared (Ph₂SiOLi)₂O (2). In a similar manner, the treatment of PrCl₃ with 2 equivalents of (Ph₂SiOLi)₂O (2) in the presence of LiN(SiMe₃)₂ afforded the silylamide-functionalized derivative [{(Ph₂SiO)₂O}₂{Li(THF)₂}₂]Pr[N(SiMe₃)₂] (6). All new compounds have been structurally characterized by X-ray diffraction analyses. Compounds 4 and 5 represent a new intermediate structural type of lanthanide bis(disiloxanediolates) between the “inorganic metallocenes” (Pr, Nd, Sm) and the “metallacrowns” (Sc, Y).     

Unprecedented examples of heterobimetallic cerium(IV) disiloxanediolates

The first disiloxanediolate complexes of cerium(IV) are reported. Starting from the readily available precursor ((t)BuO)(3)Ce(IV)(NO(3))(THF)(2) (1), we prepared the novel heterobimetallic compounds [{(Ph(2)SiO)(2)O}{K(THF)(2)}](2)Ce(O(t)Bu)(2) (2) and [{(Ph(2)SiO)(2)O}(2){(DME)-KO(t)Bu}{(Ph(2)SiO(2))K}Ce](2) (3) and structurally characterized them by X-ray diffraction.     

Porous inorganic capsules in action: modelling transmembrane cation-transport parameter-dependence based on water as vehicle

Insight into basic principles of cation transport through "molecular channels", and especially details of the related fundamental H2O vehicle function, could be obtained via7Li NMR studies of the Li+ uptake/release processes by the unique porous nanocapsule [{(MoVI)MoVI5O21(H2O)6}12{MoV2O4(SO4)}30]72- which behaves as a semi-permeable inorganic membrane open for H2O and small cations; channel traffic as well as internal cavity distribution processes show a strong dependence on "environmental" effects such as exerted by solvent properties, the amount of water present, and competing complexing ligands, and end up in a complex equilibrium situation as in biological leak channels.     

Lithium and aluminium complexes supported by chelating phosphaguanidinates

Diisopropylcarbodiimide, (i)PrN[double bond, length as m-dash]C[double bond, length as m-dash]N(i)Pr, inserts into the lithium-phosphorus bond of in situ prepared "Ph(2)PLi(THF)(n)" to afford the lithium salt, [Li(Ph(2)PC{N(i)Pr}(2))(THF)(n)](x)(2a); alternatively, this compound can be made by deprotonation of the neutral phosphaguanidine, Ph(2)PC{N(i)Pr}{NH(i)Pr}(1a) with (n)BuLi. Displacement of the THF solvate in 2a is readily achieved with TMEDA to afford Li(Ph(2)PC{N(i)Pr}(2))(TMEDA)(3a). X-Ray crystallographic analyses show that 2a exists as a dimer in the solid state with a folded ladder structure and an N,N' chelating phosphaguanidinate, while 3a is monomeric with N,P-coordination of the ligand to lithium. Compound 2a reacts via a transmetallation pathway with AlMe(2)Cl to afford the dimethylaluminium complex, Al(Ph(2)PC{N(i)Pr}(2))Me(2)(4a), which can also be prepared by protonation of a methyl group of AlMe(3) using 1a. The formation of a series of dialkylaluminium compounds has been investigated employing this latter pathway using both 1a and the N,N'-dicyclohexyl analogue, Ph(2)PC{NCy}{NHCy}(1b), affording Al(Ph(2)PC{NR}(2))Et(2)(5a,b), Al(Ph(2)PC{NR}(2))(i)Bu(2)(6a,b) and the diphenylaluminium compound Al(Ph(2)PC{N(i)Pr}(2))Ph(2)(7a). The oily nature of most of the dialkyl compounds and high sensitivity to oxygen and moisture lead to difficulty in manipulation and characterization; however, NMR spectroscopy indicated highly pure products (>95%) upon removal of the solvent. The molecular structures of the crystalline examples 4a and 7a are reported, showing monomeric aluminium species with symmetrically chelating phosphaguanidinate ligands. The series of aluminium compounds AlLCl(2){L=[EC{NiPr}(2)](-): A, E=Me; B, E=Me(2)N; C, E=(Me(3)Si)(2)N and D, E=Ph(2)P} were investigated using density functional theory. In the more simple cases A and B, the delocalized electron density of the metallacycle was represented by a combination of the HOMO and an orbital of lower energy (A, HOMO-5; B, HOMO-6). The HOMO-1 in B was pi-bonded across the Me(2)N-C bond suggesting delocalization of electron density into the metallacycle. In the more complex systems C and D, delocalization within the metallacycle was less extensive due to the (Me(3)Si)(2)N- and Ph(2)P-moieties. A number of occupied orbitals in D, however, display phosphorus 'lone-pair' characteristics, indicating that these species have the potential to behave as Lewis bases in the formation of poly(metallic) systems.     

Reduction of carbodiimides by samarium(II) bis(trimethylsilyl)amides-formation of oxalamidinates and amidinates through C-C coupling or C-H activation

The reaction of [Sm{N(SiMe3)2}2(THF)2] (THF=tetrahydrofuran) with carbodiimides RN=C=NR (R=Cy, C6H3-2,6-iPr2) led to the formation of dinuclear SmIII complexes via differing C-C coupling processes. For R=Cy, the product [{(Me3Si)2N}2Sm(micro-C2N4Cy4)Sm{N(SiMe3)2}2] (1) has an oxalamidinate [C2N4Cy4]2- ligand resulting from coupling at the central C atoms of two CyNCNCy moieties. In contrast, for R=C6H3-2,6-iPr2, H transfer and an unusual coupling of two iPr methine C atoms resulted in a linked formamidinate complex, [{(Me3Si)2N}2Sm{micro-(RNC(H)N(Ar-Ar)NC(H)NR)}Sm{N(SiMe3)2}2] (2) (Ar-Ar=C6H3-2-iPr-6-C(CH3)2C(CH3)2-6'-C6H3-2'-iPr). Analogous reactions of RN=C=NR (R=Cy, C6H3-2,6-iPr2) with the SmII "ate" complex [Sm{N(SiMe2)3Na] gave 1 for R=Cy, but a novel C-substituted amidinate complex, [(THF)Na{N(R)C(NR)CH2Si(Me2)N(SiMe3)}Sm{N(SiMe3)2}2] (3), for R=C6H3-2,6-iPr2, via gamma C-H activation of a N(SiMe3)2 ligand.     

Oxido-bridged di-, tri-, and tetra-nuclear iron complexes bearing bis(trimethylsilyl)amide and thiolate ligands

A series of di-, tri-, and tetra-nuclear iron-oxido clusters with bis(trimethylsilyl)amide and thiolate ligands were synthesized from the reactions of Fe{N(SiMe(3))(2)}(2) (1) with 1 equiv of thiol HSR (R = C(6)H(5) (Ph), 4-(t)BuC(6)H(4), 2,6-Ph(2)C(6)H(3) (Dpp), 2,4,6-(i)Pr(3)C(6)H(2) (Tip)) and subsequent treatment with O(2). The trinuclear clusters [{(Me(3)Si)(2)N}Fe](3)(μ(3)-O){μ-S(4-RC(6)H(4))}(3) (R = H (3a), (t)Bu (3b)) were obtained from the reactions of 1 with HSPh or HS(4-(t)BuC(6)H(4)) and O(2), while we isolated a tetranuclear cluster [{(Me(3)Si)(2)N}(2)Fe(2)(μ-SDpp)](2)(μ(3)-O)(2) (4) as crystals from an analogous reaction with HSDpp. Treatment of a tertrahydrofuran (THF) solution of 1 with HSTip and O(2) resulted in the formation of a dinuclear complex [{(Me(3)Si)(2)N}(TipS)(THF)Fe](2)(μ-O) (5). The molecular structures of these complexes have been determined by X-ray crystallographic analysis.     

Insertion reactions of beta-diketiminate-stabilised calcium amides with 1,3-dialkylcarbodiimides

A series of heteroleptic beta-diketiminate-stabilised calcium amides of the form [{ArNC(Me)CHC(Me)NAr}Ca{NR(1)R(2)}(THF)] (Ar = 2,6-diisopropylphenyl; R(1) = H, R(2) = Ar; R(1) = H, R(2) = CH(2)CH(2)OMe; R(1) = R(2) = Ph) react with 1,3-dialkylcarbodiimides, R(3)N[double bond, length as m-dash]C[double bond, length as m-dash]NR(3) (R(3) = Cy, (i)Pr), to yield the corresponding insertion products [{ArNC(Me)CHC(Me)NAr}Ca{(R(3)N)(2)CNR(1)R(2)}(THF)] at room temperature in hydrocarbon solutions. These latter compounds contain both beta-diketiminate and guanidinate ligands bound to calcium. Solid-state data are consistent with the guanidinate ligands adopting a number of binding modes including kappa(2) through kappa(3) coordination, with varying degrees of delocalisation of the non-bound guanidinate nitrogen lone-pair across the pi-framework of the ligand. DFT computational studies have been conducted to address these variations in coordination behaviour.     

Divalent lanthanide complexes supported by the bridged bis(amidinates) L Me3SiN(Ph)CN(CH2)3NC(Ph)NSiMe3]: synthesis, molecular structures and one-electron-transfer reactions

Metathesis reactions of YbI(2) with Li(2)L (L = Me(3)SiN(Ph)CN(CH(2))(3)NC(Ph)NSiMe(3)) in THF at a molar ratio of 1:1 and 1:2 both afforded the Yb(II) iodide complex [{YbI(DME)(2)}(2)(μ(2)-L)] (1), which was structurally characterized to be a dinuclear Yb(II) complex with a bridged L ligand. Treatment of EuI(2) with Li(2)L did not afford the analogous [{EuI(DME)(2)}(2)(μ(2)-L)], or another isolable Eu(II) complex, but the hexanuclear heterobimetallic cluster [{Li(DME)(3)}(+)](2)[{(EuI)(2)(μ(2)-I)(2)(μ(3)-L)(2)(Li)(4)}(μ(6)-O)](2-) (2) was isolated as a byproduct in a trace yield. The rational synthesis of cluster 2 could be realized by the reaction of EuI(2) with Li(2)L and H(2)O in a molar ratio of 1:1.5:0.5. The reduction reaction of LLnCl(THF)(2) (Ln = Yb and Eu) with Na/K alloy in THF gave the corresponding Ln(II) complexes [Yb(3)(μ(2)-L)(3)] (3) and [Eu(μ(2)-L)(THF)](2) (4) in good yields. An X-ray crystal structure analysis revealed that each L in complex 3 might adopt a chelating ligand bonding to one Yb atom and each Yb atom coordinates to an additional amidinate group of the other L and acts as a bridging link to assemble a macrocyclic structure. Complex 4 is a dimer in which the two monomers [Eu(μ(2)-L)(THF)] are connected by two μ(2)-amidinate groups from the two L ligands. Complex 3 reacted with CyN═C═NCy and diazabutadienes [2,6-(i)Pr(2)C(6)H(3)N═CRCR═NC(6)H(3)(i)Pr(2)-2,6] (R═H, CH(3)) (DAD) as a one-electron reducing agent to afford the corresponding Yb(III) derivatives: the complex with an oxalamidinate ligand [LYb{(NCy)(2)CC(NCy)(2)}YbL] (5) and the complexes containing a diazabutadiene radical anion [LYb((i)Pr(2)C(6)H(3)NCRCRNC(6)H(3)(i)Pr(2))] (R = H (6), R = CH(3) (7)). Complexes 5-7 were confirmed by an X-ray structure determination.     

Extremely bulky amido-group 14 element chloride complexes: potential synthons for low oxidation state main group chemistry

The preparation of a series of extremely bulky secondary amines, Ar*N(H)SiR(3) (Ar* = C(6)H(2){C(H)Ph(2)}(2)Me-2,6,4; R(3) = Me(3), MePh(2) or Ph(3)) is described. Their deprotonation with either LiBu(n), NaH or KH yields alkali metal amide complexes, several monomeric examples of which, [Li(L){N(SiMe(3))(Ar*)}] (L = OEt(2) or THF), [Na(THF)(3){N(SiMe(3))(Ar*)}] and [K(OEt(2)){N(SiPh(3))(Ar*)], have been crystallographically characterised. Reactions of the lithium amides with germanium, tin or lead dichloride have yielded the first structurally characterised two-coordinate, monomeric amido germanium(II) and tin(II) chloride complexes, [{(SiR(3))(Ar*)N}ECl] (E = Ge or Sn; R = Me or Ph), and a chloride bridged amido-lead(II) dimer, [{[(SiMe(3))(Ar*)N]Pb(μ-Cl)}(2)]. DFT calculations on [{(SiMe(3))(Ar*)N}GeCl] show its HOMO to exhibit Ge lone pair character and its LUMO to encompass its Ge based p-orbital. A series of bulky amido silicon(IV) chloride complexes have also been prepared and several examples, [{(SiR(3))(Ar*)N}SiCl(3)] (R(3) = Me(3), MePh(2)) and [{(SiMe(3))(Ar*)N}SiHCl(2)], were crystallographically characterised. The sterically hindered group 14 complexes reported in this study hold significant potential as precursors for kinetically stabilised low oxidation state and/or low coordination number group 14 complexes.     

Coordination polymers derived from magnesium and barium complexes of redox-active ligands

The reactions of monomeric complexes [(dpp-bian)M(THF)_n](M = Mg, n = 3; M = Ba, n = 5; dpp-bian = 1,2-bis[(2,6-di-isopropylphenyl)imino]acenaphthene) with 4,4'-bipyridine (4,4'-bipy) in THF proceed with electron transfer from dpp- bian2– to 4,4'-bipy0 to afford 1D coordination polymers [(dpp-bian)M(4,4'-bipy)(THF)_n]_m (M = Mg, n = 1; M = Ba, n = 2) that contain simultaneously radical anion ligands dpp-bian– and 4,4'-bipy . Addition of DME to coordination polymer [(dpp-bian)Mg(4,4'-bipy)(THF)_n]_m results in fragmentation of polymeric chains to give dinuclear magnesium species [{(dpp-bian)Mg(DME)}₂(4,4'-bipy)]. Barium analogue [{(dpp-bian)Ba(DME)₂}₂(4,4'-bipy)] has been prepared by reacting of complex [(dpp-bian)Ba(DME)2.5] with 4,4'-bipy in DME.     

Reactions inside a porous nanocapsule/artificial cell: encapsulates' structuring directed by internal surface deprotonations

In the cavities of unprecedentedly functionalised, spherical, porous capsules of the type {Pentagon}12{Linker}30 identical with [{(Mo)Mo5O21(H2O)6}12{Mo2O4(ligand)}30]n- reactions with the ligands -i.e. at the internal shell surfaces - can be performed, in the present case deliberate aquation/hydration and deprotonation reactions at the linker fragments {(Mo2O4)C2O4H}+ similar to that reported in the literature for [(NH3)5CoC2O4H]2+ in solution.     

Insertion of the Ga(I) bis-imidinate Ga(DDP) into the metal halogen bonds of Rh(I) complexes. How electrophilic are coordinated Ga(DDP) fragments?

The reactivity of Ga(DDP) (DDP = 2-((2,6-diisopropylphenyl)amino-4-((2,6-diisopropylphenyl)imino)-2-pentene) towards the rhodium-chloride bonds of [RhCl(PPh3)3] and [RhCl(COE)2]2 (COE = cyclooctene) is investigated. Reaction of the first complex leads to [(Ph3P)2Rh{Ga(DDP)}(mu-Cl)] (1), exhibiting a chloride bridging the gallium and the rhodium atoms, whereas the second complex leads to a full insertion of the Ga(DDP) ligand into the Rh-Cl bond giving [(COE)(benzene)Rh{(DDP)GaCl}] (2) on coordination of the solvent C6H6. Compounds 1 und 2 readily react with the halide abstracting reagent Tl[BArF] (BArF = B[3,5-(CF3)2C6H3]4), yet the products could not be isolated and characterized because of their lability. The Au(I) complex [{(DDP)Ga}Au{Ga(DDP)}Cl] reacts with Na[BArF] giving the linear, symmetric cationic complex [{(DDP)Ga.THF}2Au][BArF] (3.2THF), exhibiting two THF molecules coordinated to the Ga(DDP) moieties.     

Construction of polymeric and oligomeric lanthanide(III) thiolates from preformed complexes [(TMS)2N]3Ln(mu-Cl)Li(THF)3 (Ln = Pr, Nd, Sm; (TMS)2N = Bis(trimethylsilyl)amide)

The complex [{(TMS)2N}4(mu4-Cl)Sm4(mu-SPh)4(mu3-Cl)Li(THF)] has been formed by protonolysis of [(Me3Si)2N]3Sm(mu-Cl)Li(THF)3 with 1 equiv of HSPh, which contains a square array of Sm(III) ions connected by a central mu4-Cl ligand. The edges of the square Sm4 array are bridged by four mu3-Cl and four mu-SPh ligands. The four Sm atoms and Li atom are connected by four mu3-Cl ligands.     

Synthesis and structural characterization of beta-diketiminate-lanthanide amides and their catalytic activity for the polymerization of methyl methacrylate and epsilon-caprolactone

The synthesis and catalytic activity of lanthanide monoamido complexes supported by a beta-diketiminate ligand are described. Donor solvents, such as DME, can cleave the chloro bridges of the dinuclear beta-diketiminate ytterbium dichloride {[(DIPPh)2nacnac]YbCl(mu-Cl)3Yb[(DIPPh)2nacnac](THF)} (1) [(DIPPh)2nacnac = N,N-diisopropylphenyl-2,4-pentanediimine anion] to produce the monomeric complex [(DIPPh)2nacnac]YbCl2(DME) (2) in high isolated yield. Complex 2 is a useful precursor for the synthesis of beta-diketiminate-ytterbium monoamido derivatives. Reaction of complex 2 with 1 equiv of LiNPri2 in THF at room temperature, after crystallization in THF/toluene mixed solvent, gave the anionic beta-diketiminate-ytterbium amido complex [(DIPPh)2nacnac]Yb(NPri2)(mu-Cl)2Li(THF)2 (3), while similar reaction of complex 2 with LiNPh2 produced the neutral complex [(DIPPh)2nacnac]Yb(NPh2)Cl(THF) (4). Recrystallization of complex 3 from toluene solution at elevated temperature led to the neutral beta-diketiminate-lanthanide amido complex [{(DIPPh)2nacnac}Yb(NPri2)(mu-Cl)]2 (5). The reaction medium has a significant effect on the outcome of the reaction. Complex 2 reacted with 1 equiv of LiNPri2 and LiNC5H10 in toluene to produce directly the neutral beta-diketiminate-lanthanide amido complexes 5 and [{(DIPPh)2nacnac}Yb(NC5H10)(THF)(mu-Cl)]2 (6), respectively. These complexes were well characterized, and their crystal structures were determined. Complexes 4-6 exhibited good catalytic activity for the polymerization of methyl methacrylate and epsilon-caprolactone.     

Terphenyl substituted derivatives of manganese(II): distorted geometries and resistance to elimination

Reaction of {Li(THF)Ar'MnI(2)}(2) (Ar' = C(6)H(3)-2,6-(C(6)H(2)-2,6-(i)Pr(3))(2)) with LiAr', LiC≡CR (R = (t)Bu or Ph), or (C(6)H(2)-2,4,6-(i)Pr(3))MgBr(THF)(2) afforded the diaryl MnAr'(2) (1), the alkynyl salts Ar'Mn(C≡C(t)Bu)(4){Li(THF)}(3) (2) and Ar'Mn(C≡CPh)(3)Li(3)(THF)(Et(2)O)(2)(μ(3)-I) (3), and the manganate salt {Li(THF)}Ar'Mn(μ-I)(C(6)H(2)-2,4,6-(i)Pr(3)) (4), respectively. Complex 4 reacted with one equivalent of (C(6)H(2)-2,4,6-(i)Pr(3))MgBr(THF)(2) to afford the homoleptic dimer {Mn(C(6)H(2)-2,4,6-(i)Pr(3))(μ-C(6)H(2)-2,4,6-(i)Pr(3))}(2) (5), which resulted from the displacement of the bulkier Ar' ligand in preference to the halogen. The reaction of the more crowded {Li(THF)Ar*MnI(2)}(2) (Ar* = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-(i)Pr(3))(2)) with Li(t)Bu gave complex Ar*Mn(t)Bu (6). Complex 1 is a rare monomeric homoleptic two-coordinate diaryl Mn(II) complex; while 6 displays no tendency to eliminate β-hydrogens from the (t)Bu group because of the stabilization supplied by Ar*. Compounds 2 and 3 have cubane frameworks, which are constructed from a manganese, three carbons from three acetylide ligands, three lithiums, each coordinated by a donor, plus either a carbon from a further acetylide ligand (2) or an iodide (3). The Mn(II) atom in 4 has an unusual distorted T-shaped geometry while the dimeric 5 features trigonal planar manganese coordination. The chloride substituted complex Li(2)(THF)(3){Ar'MnCl(2)}(2) (7), which has a structure very similar to that of {Li(THF)Ar'MnI(2)}(2), was also prepared for use as a possible starting material. However, its generally lower solubility rendered it less useful than the iodo salt. Complexes 1-7 were characterized by X-ray crystallography and UV-vis spectroscopy. Magnetic studies of 2-4 and 6 showed that they have 3d(5) high-spin configurations.