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Bicyclic guanidine 1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐a]pyrimidine (hppH) was investigated as a source of anionic or neutral ligand at antimony. Reaction of the in situ generated lithium guanidinate with SbCl3in a 1:1 or 2:1 ratio forms the expected metathesis products Sb(hpp)nCl3–n(1, n= 1; 2, n= 2). The molecular structures of 1and 2were determined by X‐ray diffraction, which shows chelating guanidinates and suggests the presence of a stereochemically active lone pair of electrons. The reaction of two equivalents of the neutral guanidine hppH with SbCl3proceeds via proton transfer between the hpp fragments, affording the ion pair [hppH2][Sb(hpp)Cl3] (3), where [Sb(hpp)Cl3]–is an unusual example of a monometallic antimonate(III) anion. The molecular structure of 3shows hydrogen bonding between two of the chlorides and the NHfunctionalities of the guanidinium cation.

Abstract. Yttrium(III) chloride was the ultimate precursor of the crystalline compounds [Y{η5‐C5H4(CH(SiMe3)2)}2(μ‐Cl)2Li(THF)2] (1), [Y{(OC(But))2CH}2{μ‐OC(But)C(H)C(But)O}]2(2), [{Mg(CH2SiMe3)(μ‐CH2SiMe3)(THF)}2] (3) and [Mg(CH2SiMe3){(N(C6H3Pri2‐2,6)C(Me))2CH}(THF)] (4). Thus, the precursors were: YCl3+ 2 Li[η5‐C5H4{CH(SiMe3)2}] for 1, [Y{N(SiMe3)2}3] + 3 [ButC(O)]2CH2for 2, and YCl3+ 3 Mg(CH2SiMe3)Cl for 3; whereas 4was obtained from 3+ 2 H[{N(C6H3Pri2‐2,6)C(Me)}2CH]. The β‐diketiminatochromium(II) compound 7was prepared from CrCl2+ 2 Li[{N(C6H4Et‐2)C(Me)}2CH] (6); the latter became available from the corresponding equally new β‐diketimine 5and LiBun. Each of the compounds 1–7was well characterised, including for 1–4and 7by single‐crystal X‐ray diffraction.

The reaction of anhydrous FeCl2with 24′,4′dimethyloxazolin2′ylthiophenolate oxphS– afforded mononuclear [FeoxphS2] A and binuclear [FeIIIoxphS2μS2] B. In B, ironIII and S2–resulted from an unexpected redox reaction involving elemental sulfur and the ironII starting material. Complexes Aand Bcocrystallise reproducibly in a 2:1 proportion. An attempt to prepare oxazolinylthiophenolatoironIII from LioxphS and anhydrous FeCl3in the presence of N,N,N′,N′tetramethylethane1,2diamine tmen gave another redox reaction with disulfide D, bis24′,4′dimethyloxazolin2′ylphenyldisulfide oxphSSphox, and trans[FeCl2tmen2] E as 1:1 cocrystallised products. Characterisation of all complexes included Mössbauer spectroscopy and singlecrystal Xray diffraction analysis. Quantum mechanical TDDFT calculations for Aand cyclic voltammetry experiments carried out with Aand Chelped to distinguish between ligand and metalbased electronic transitions and redox processes. Results add to the knowledge of the rich redox chemistry of early transition metals with soft Sdonor ligands, with possible consequences for catalytic and biochemical transformations.

The reaction of Me3SiCH2I with [PdItBu2] ItBu = 1,3ditertbutylimidazol2ylidene results, not in simple oxidative addition, but in carbon–silicon bond activation and formation of [PdMe3SiItBuμI]22 and [PdCH2ItBuI2] 3. The zwitterionic nature of the latter has been confirmed by DFT studies, and a possible mechanism for the formation of these two unexpected products is presented. Complex 2has also been synthesised independently by the direct oxidative addition of Me3SiI to [PdItBu2].© WileyVCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009

The potassium dihydrotriazinide K(LPh,tBu) (1) was obtained by a metal exchange route from [Li(LPh,tBu)(THF)3] and KOtBu (LPh,tBu= [N{C(Ph)=N}2C(tBu)Ph]). Reaction of 1with 1 or 0.5 equivalents of SmI2(thf)2yielded the monosubstituted SmIIcomplex [Sm(LPh,tBu)I(THF)4] (2) or the disubstituted [Sm(LPh,tBu)2(THF)2] (3), respectively. Attempted synthesis of a heteroleptic SmIIamido‐alkyl complex by the reaction of 2with KCH2Ph produced compound 3due to ligand redistribution. The YbIIbis(dihydrotriazinide) [Yb(LPh,tBu)2(THF)2] (4) was isolated from the 1:1 reaction of YbI2(THF)2and 1. Molecular structures of the crystalline compounds 2, 3·2C6H6and 4·PhMe were determined by X‐ray crystallography.

Treatment of [M(η4-P2C2tBu2)] with the phosphaalkyne P≡CtBu leads to the formation of the unusual zwitterionic cage compounds [M(P4C4tBu4)] (M = Ge, Sn) which have been fully characterised in solution by multinuclear NMR spectroscopy and the solid-state structure of [GeP4C4tBu4] has been elucidated by a single-crystal X-ray diffraction study. DFT calculations support the zwitterionic formulation and suggest the likely reaction pathway. Whilst [GeP4C4tBu4] exhibits considerable stability, [SnP4C4tBu4] shows gradual decomposition in solution within a matter of hours. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Treatment of the lithium amide Li[NPh(SiMe3)] with 2,4,6‐tri‐tert‐butyl‐1,3,5‐triphosphabenzene, P3C3tBu3, in a 1:2 ratio afforded equimolar amounts of the lithium salt of the five‐membered 2,4,5‐tri‐tert‐butyl‐1,3‐diphospholide anion, LiP2C3tBu3(isolated as its N,N,N′,N′‐tetramethylethylenediamine (TMEDA) adduct), and the tricyclic compound 6‐[phenyl(trimethylsilyl)amino]‐3,5,7‐tri‐tert‐butyl‐1,2,4,6‐tetraphosphatricyclo[3.2.0.02,7]hept‐3‐ene. Both compounds have been structurally characterised by single‐crystal X‐ray diffraction studies. The mechanism of this remarkable reaction has been elucidated by theoretical methods at the B3LYP/6‐311+G** level of theory. The reaction involves a hitherto unobserved aminophosphinidene, which was formed by abstraction of a phosphorus atom from triphosphabenzene. The intermediate aminophosphinidene, which is further stabilised by the solvent THF, shows, in agreement with previous theoretical predictions, enhanced stability and reacts then with a second molecule of triphosphabenzene.

Fluoral arrangement: The calcium β‐diketiminate complex 1(see scheme) not only exhibits an unexpected and unprecedented binding mode of a CF3group, from which one fluorine atom coordinates to the Ca center, but also undergoes CF bond cleavage through the formation of a heteroleptic calcium fluoride complex.

Abstract: Nonparametric curve estimation is an extremely common statistical procedure. While its primary purpose has been exploratory, some advances in inference have been made. This paper provides a critical review of inferential tests that make fundamental use of a key element of nonparametric smoothing, the bandwidth, to determine the significance of certain features. A major focus is on two important problems that have been tackled using bandwidth-based inference: testing for the multimodality of a density and testing for the monotonicity of a regression curve. Early research in bandwidth-based inference is surveyed, as well as recent theoretical advances. Possible future directions in bandwidth-based inference are discussed. [Copyright &y& Elsevier]

The sequential treatment of Lewis acids with N,N′-bidentate ligands and thereafter with ButLi has afforded a series of hydride-encapsulating alkali metal polyhedra. While the use of Me3Al in conjunction with Ph(2-C5H4N)NH gives Ph(2-C5H4N)NAlMe21 and this reacts with MeLi in thf to yield the simple ’ate complex Ph(2-C5H4N)NAlMe3Li·thf 3, the employment of an organolithium substrate capable of β-hydride elimination redirects the reaction significantly. Whereas the use of ButLi has previously yielded a main group interstitial hydride in which H− exhibits µ6-coordination, it is shown here that variability in the coordination sphere of the encapsulated hydride may be induced by manipulation of the organic ligand. Reaction of (c-C6H11)(2-C5H4N)NH with Me3Al/ButLi yields [{(c-C6H11)(2-C5H4N)N}6HLi8]+[(But2AlMe2)2Li]−6, which is best viewed as incorporating only linear di-coordination of the hydride ion. The guanidine 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH) in conjunction with Me2Zn/ButLi yields the µ8-hydride [(hpp)6HLi8]+[But3Zn]−·0.5PhMe 7. Formation of the µ8-hydride [(hpp)6HLi8]+[ButBEt3]−8 is revealed by employment of the system Et3B/ButLi. A new and potentially versatile route to interstitial hydrides of this class is revealed by synthesis of the mixed borohydride–lithium hydride species [(hpp)6HLi8]+[Et3BH]−10 and [(hpp)6HLi8]+[(Et3B)2H]−12 through the direct combination of hppLi with Et3BHLi.

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The synthesis of the following crystalline complexes is described: [Li(L)(thf)2] (2), [Li(L)(tmeda)] (3), [MCl2(L)] [M = Al (4), Ga (5)], [In(Cl)(L)(µ-Cl)2Li(OEt2)2] (6), [In(Cl)(L){N(H)C6H3Pri2-2,6}] (7), [In(L){N(H)C6H3Pri2-2,6}2] (8), [{In(Cl)(L)(µ-OH)}2] (10), [L(Cl)In–In(Cl)(L)] (11) (the thf-solvate 11a, the solvate-free 11band the hexane-solvate 11c), [{In(Cl)L}2(µ-S)] (12) and [InCl2(L)(tmeda)] (13) ([L]−= [{N(C6H3Pri2-2,6)C(H)}2CPh]−). From H(L) (1), viaLi(L) in Et2O, and thf, tmeda, AlCl3, GaCl3or InCl3there was obtained 2, 3, 4, 5or 6, respectively in excellent yield. Compound 6was the precursor for each of 7–11, 13and [{InCl3(tmeda)2{µ-(OSnMe2)2}}] (14) by treatment with one (7) or two (8) equivalents of K[N(H)(C6H3Pri2-2,6)], successively Li[N(SiMe3)(C6H3Pri2-2,6)] and moist air (10), Na in thf (11a), tmeda (13), or successively tmeda and Me3SnSnMe3(14). Crystals of 11b(with an equivalent of In) and 11cwere obtained from InCl or thermolysis of [In(Cl)(L){N(SiMe3)(C6H3Pri2-2,6)}] (9) {prepared in situfrom 6and Li[N(SiMe3)(C6H3Pri2-2,6)] in Et2O}, respectively. Compound 12was obtained from a thf solution of 11aand sulfur. X-Ray data for crystalline 1–6, 8, 11a, 11b, 11c, 12and 14are presented. The M(L) moiety in each (not the L-free 14) has the monoanionic L ligated to the metal in the N,N′-chelating mode. The MN1C1C2C3N2 six-membered M(L) ring is π-delocalised and has the half-chair (2, 3and 11) or boat (4–8, 10and 13) conformation.

A number of metal complexes containing one of the following ligands: the 1-azaallyl [N(R)C(Ph)C(H)R]−(L−), the 1,3-diazaallyl(≡ LL′−) and the isomeric β-diketiminate [{N(R)C(Ph)]}2CH]−(≡ LL−) have been prepared (R = SiMe3). These are the crystalline compounds H(LL) (2), Na(LL) (3), [Na(LL)(thf)2] (4), Na(L) (6), [Na(µ-LL′)]8(7), [K(µ-L)(η6-C6H6)]2(8), [K(µ-LL′)(thf)]2(9), [K(thf)2(µ-LL)]∞(10) and [Ni(LL′)2] (11). A new synthesis of Na[C(H)R2] (1) involved Hg[C(H)R2]2and Na/Hg as reagents. The β-diketimine 2was obtained from Li(LL) and cyclopentadiene. Under different conditions compounds 3, 6and 7were isolated from 1and benzonitrile, and compounds 8, 9and 10from K[C(H)R2] and PhCN. Complex 11was derived from [Li(LL′)]2and [NiBr2(dme)]. The solution obtained from 1+ 2 PhCN in Et2O at ambient temperature was a mixture (5) of 3(predominantly) and 7. The 1-azaallyl complex 8has the ligand bound to the metal as the enamide, and this is also probably (NMR) the case for 6. The molecular structures of the crystalline complexes 7, 8and 11are presented; that of 10was published earlier. Compound 7, a cyclooctamer, is particularly interesting, in that each LL′−ligand is bridging viaone of its N atoms to two neighbouring sodium ions and is not only N,N′- but also (η2-CC)-chelating to one of them.

A series of racemic N-aryl-substituted trans-1,2-diaminocyclohexyl (t-1,2-DACH)-linked bis(amidines) were synthesised and their solution behaviour, and solid-state structures were investigated. The amidine functionalities within these compounds were extremely sterically hindered, with ortho-aryl substitution found to hinder N–Ar bond rotation. The results of these studies were used to rationalise the lack of reactivity of these compounds with [Y{N(SiMe3)2}3]. Dilithiation of the t-1,2-DACH linked bis(amidines) did, however, proceed easily and the solution behaviour and solid-state structures of the resulting THF-solvated lithium amidinates were investigated. All the compounds showed similar structures in the solid-state, while NMR experiments indicated that the solid-state structures were likely to be maintained in solution. Attempted metathesis reactions with YCl3did not, however, yield the desired yttrium chloride complexes.

Reduction of Cl2Si[(NR)2C6H4-1,2] (R = CH2But) with potassium is known to lead to the stable silylene Si[(NR)2C6H4-1,2] (1). However, silylene 1is now shown to react further with an alkali metal (Na or K) to yield the (1)22−, c-(1)3−, c-(1)32−or c-(1)42−derivatives. Reduction of Cl2Si[(NR)2C6H4-1,2] (R = CH2CH3or CH2CHMe2) with potassium does not lead to an isolable silylene, but such a silylene is proposed to be an intermediate and, as for 1, reacts further to afford the potassium salts of c-[Si{(NR)2C6H4-1,2}]4− and c-[Si{(NR)2C6H4-1,2}]42−. The pathways leading to the anionic cyclotri- and cyclotetrasilanes are discussed and supported experimentally; including by X-ray structures of relevant intermediates.

M(η6-arene)2species (M = Cr, arene = 1,3,5-Me3C6H3; M = Mo, arene = 1,3,5-Me3C6H3, 1,3,5-iPr3C6H3), have been prepared by a modified Fischer–Hafner synthesis or by metal vapour techniques. The reaction of Cr(η6-1,3,5-Me3C6H3)2with the fulvene derivatives pentacarbomethoxycyclopentadiene (pcmcpH), 1-benzoyl-6-hydroxy-6-phenylfulvene (dbcpH), or 1-benzoyl-3-nitro-6-hydroxy-6-phenylfulvene (dbncpH) proceeds with evolution of dihydrogen and formation of the ionic derivatives [Cr(η6-1,3,5-Me3C6H3)2][E], where E = pcmcp, dbcp, or dbncp. Mo(η6-arene)2derivatives (arene = toluene, 1,3,5-Me3C6H3, 1,3,5-iPr3C6H3) are oxidized to [Mo(η6-arene)2]+by pcmcpH. The crystal and molecular structures of [M(η6-1,3,5-R3C6H3)2][pcmcp] (M = Cr, R = Me; M = Mo, R = Me, iPr) have been solved by X-ray single crystal diffraction.

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)(CH2But)}2C6H4-1,2] (abbreviated as H2L): [Y(L)(μ-Cl)2Li(OEt2)2]2(1), [Li(OEt2)2Li(μ2-Cl)4(μ3-Cl)2{Zr(L)}2]2(2), [Zr(L)2(μ-Cl){Li(OEt2)2}(μ2-Cl)2Zr(L)] (3), [Ce{(μ-L)M}3(OEt2)1/2] (3M = Li1.82Na1.18) (4), [Ce{(μ-L)Na}3(OEt2)] (5) and [Ce{(μ-L)Na}3] (6). Compounds 1–3were obtained from Li2(L) and YCl3(the colourless 1) or ZrCl4(the red 2and 3), while the red 4and 5were isolated from CeCl3and M2(L) (3M = Li1.82Na1.18) (4) or Na2(L) (5). Attempted oxidation of 5with Br2in hexane yielded the black 6. The ligand Lis N,N′-chelating to each of the d- or f-block metals in 1–6; and in 4–6Lis also acting as a bridge between Ce and the alkali metal, to which Lis thus also chelating.

Reactions between sodium amides Na[N(SiMe3)R1] [R1= SiMe3(1), SiMe2Ph (2) or But(3)] and cyanoalkanes RCN (R = Ad or But) were investigated. In each case the nitrile adduct [Na{µ-N(SiMe3)2}(NCR)]2[R = Ad (1a) or But(1b)], trans-[Na{µ-N(SiMe3)(SiMe2Ph)}(NCR)]2[R = Ad (2a) or But(2b)], [(Na{µ-N(SiMe3)But})3(NCAd)3] (3a) or [(Na{µ-N(SiMe3)But})3(NCBut)n] [n= 3 (3b) or 2 (3c)] was isolated. The reaction of complexes 3aor 3bwith benzene afforded the ketimido complex [Na{µ-NC(Ad)(Ph)}]6·2C6H6(4a) or [Na{µ-NC(But)(Ph)}]6(4b); the former was also prepared in more conventional fashion from NaPh and AdCN. The synthesis and structure of an analogue of complex 1a, [Li{µ-N(SiMe3)2}(NCAd)]2(5a), is also presented. The compounds 1a, 1b, 2a, 2b, 3, 3b, 4a, 4band 5awere characterised by X-ray diffraction.

The following crystalline, or microcrystalline (4), metal diamides have been prepared under mild conditions from the N,N′-disubstituted 1,2-diaminobenzene [N(R)H2C6H4-1,2] (H2L: R = CH2But; H2L′: R = SiMe2NPri2): [Li(thf)(µ-L)(µ-I)Ca(thf)] (1), [Li(thf)4][Zn(µ-L)3(µ3-Cl)] (2), [Li(thf)4][Zn(L)2] (3), [Li(OEt2)(µ-L)Zn2(µ-L)] (4), [Li(OEt2)(µ-L)Zn(µ-L)Zn(LH)] (5) and [Li(thf)(µ-L′)Li(thf)2] (6). Compounds 1–5were obtained from [Li2(L)] and CaI2(1) or ZnCl2(2–5) while 6was derived from H2(L′) and LiBun. Compound 5was isolated as a very minor by-product from the synthesis of 4, and is assumed to have been formed therefrom by adventitious hydrolysis. The green salt 3was paramagnetic with the negative charge uniformly delocalised on the two ligands. The other compounds were colourless and diamagnetic. The X-ray structures of each, except 4, are reported and discussed.

The series of group 10 homo- and hetero-dimetallic sulfur-bridged complexes [Ni(ema)(μ-S,S′)M(diphos)], [M = nickel, palladium or platinum; diphos = 1,3-bis(diphenylphosphanyl)propane or 1,2-bis(diphenylphosphanyl)ethane], have been synthesised. Their properties and the crystal structures of five of the series are described. The dinickel complexes are good structural analogues of the dinickel subunit of the nickel-containing enzyme acetyl-CoA synthase. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Mononuclear palladium‐hydroxo complexes of the type [Pd(N–N)(C6F5)(OH)][(N–N) = 2,2′‐bipyridine (bipy), 4,4′‐dimethyl‐2,2′‐bipyridine (Me2bipy), 1,10‐phenantroline (phen) or N,N,N′,N′‐tetramethylethylenediamine (tmeda) react with phenols ArOH in tetrahydrofuran giving the corresponding aryloxo complexes [Pd(N–N)(C6F5)(OAr)]. Elemental analyses and spectroscopic (IR, 1H and 19F) methods have been used to characterize the new complexes. The X‐ray crystal structure of [Pd(tmeda)(C6F5)(OC6H4NO2‐p)] has been determined. In the crystal packing the planes defined by two C6H4rings show a parallel orientation. There are also intermolecular C–H···F and C‐H···O hydrogen bonds.

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The synthesis of a series of group 4 metal complexes supported by the boroxide anion, [OB(mes)2]^-, is described and their application in α-olefin polymerization discussed. The compounds M{OB(mes)2}2Cl2(THF)2 [1, M = Ti; 2, M = Zr; 3, M = Hf] have been synthesized from MCl4(THF)n [M = Ti, n = 0; M = Zr/Hf, n = 2] and 2 equiv of lithiated dimesitylborinic acid. Accidental hydrolysis during the preparation of the zirconium analogue afforded the dimeric hydroxyl species [Zr{OB(mes)2}3(μ-OH)]2 (4), which was characterized crystallographically. The four-coordinate titanium bis(amide) complex, Ti{OB(mes)2}2(NEt2)2 (5), was prepared by protonolysis of the titanium-tetra(amide) using the parent borinic acid. X-ray structural analyses of 1 and 3 showed distorted, octahedral geometry at the metal with cis-boroxide and trans-chloride ligands. A series of mixed-ligand cyclopentadienyl/boroxide chlorides of the group 4 metals are also described. TiCp‘{OB(mes)2}Cl2 (Cp‘ = η-C5Me4H, 6) and MCp2{OB(mes)2}Cl [7, M = Ti; 8, M = Zr] are formed upon replacement of a chloride with a boroxide ligand using the appropriate TiCp‘Cl3 and MCp2Cl2 starting materials. X-ray diffraction studies showed compounds 6 and 7 exist as monomers in the solid state, with distorted tetrahedral geometry around the metal. Selected complexes were tested for ethylene polymerization activity, using MAO as activator. Polymerization behavior was observed similar to that of ZrCp2Cl2 tested under the same conditions, which, supplemented by complementary reactivity studies and polymer analysis, suggests possible transfer of the boroxide ligand to aluminum during polymerization. To circumvent the problems associated with activation using MAO, a family of group 4 alkyl compounds have been synthesized. The titanium and hafnium compounds M{OB(mes)2}n(CH2Ph)4-n [9, M = Ti, n = 2; 10, M = Ti, n = 3; 11, M = Hf, n = 3; 12, M = Hf, n = 4] were synthesized by protonolysis of the tetra(benzyl) compounds. NMR studies of the reaction between 9 and B(C6F5)3 demonstrated that a well-defined cationic titanium compound was generated in solution; however, strong interaction with the anion prevented the system from being active for polymerization.

Treatment of the biphenyl derivative [S=C{(NCH2But)2C6H3‐3,4}]2or [Cl2Si{(NCH2But)2C6H3‐3,4}]2with C8K afforded the new bis(carbene) 1or the first bis(silylene) 2, respectively. The X‐ray structure of 2is presented.

The main C1 isomer of C70F38 is shown by single-crystal X-ray analysis to contain four planar aromatic hexagons and four isolated C&dbd;C bonds, has two fluorines on the equator, and is related to C2 C70F38 by means of three 1,3-fluorine shifts. The C1 and C2 isomers thus parallel the T and C3/C1 isomers of C60F36 in containing three and four aromatic rings, respectively, and in the fluorine shift relationship.

The “selective” protonolysis of the β-diketiminato calcium derivative [Ca{(NDippCMe)2CH}{N(SiMe3)2}(THF)] (Dipp = C6H3ⁱPr2-2,6) with a selection of terminal alkynes has produced a series of dimeric acetylides [Ca{(NDippCMe)2CH}{μ-C&tbd1;CR}]2, which have been characterized in solution and in the solid state. The asymmetry of the Ca−C−Ca‘ bridges is subtly dependent upon the extent of “side-on” (π-type) interaction between the acetylide unit and the Ca‘ centers.

The following crystalline oligonuclear metal alkyls have been synthesised under mild conditions and structurally characterised: THFLiμ-Aμ-Clμ3-OMeZn23, Liμ-A2Tl24and 4′, Li4μ-A3μ3-OMe 5, μ-ALi2μ-A2μ3-OMeCeA6 and CeAμ2-OMeμ2-OSOCF3O211A CHSiMe3SiMeOMe2. Compounds 2–6were obtained from Liμ-A∞1 and ZnCl23, TlCl (4and 4′ and 5) and CeCl36, and 11was isolated from KA prepared from 1 KOBut and ceriumiii triflate CeOTf3. The principal novel features are i and ii as follows. As for i, the diversity of ligand-to-metal bonding is noteworthy, the ligand being aC,O-bridging in 3as in the known compounds 1and in Li2Mg5μ3-OMe6μ2-OMe2μ2-A42; bC,O,O′-bridging and O,O′-chelating in 4and 4′; cC,O,O′-bridging in 5; dC,O,O′-bridging and C,O-chelating in 6; and eC,O-chelating in 11. Regarding ii, it is interesting that the ligand A−is surprisingly ready to undergo fragmentation by Si–OMe cleavage and thereby present bridging methoxy ligands μ2-OMe2to a pair of Ce3ions in 11, or μ3-OMe acting as a cap for triangular arrays of three hard metal ions Mg3in 2, LiZn2in 3, Li3in 5, and Li2Ce in 6.

The thermally stable silylene SiNCH2But2C6H4-1,2 1undergoes oxidative addition reactions with the lithium amides LiNRR′ R SiMe3, R′ But; R SiMe3, R′ C6H3Me2-2,6; R R′ Me or R R′ Pri to afford the new lithium amides LiTHF2NRSiSiMe3NCH2But2C6H4-1,2 R But2 or R C6H3Me2-2,6 3a or the new trisaminofunctionalised silyllithiums LiTHFxSiNCH2But2C6H4-1,2NRR′ R SiMe3, R′ C6H3Me2-2,6, x 2 3; R R′ Me, x 3 4 or R R′ Pri, x 3 5. Compounds 4and 5are stable at ambient temperature but compound 3is thermally labile and converts into 3aupon heating. The pathway for the formation of 2and 3is discussed and the X-ray structures of 2–5are presented.

An unusual product formation is observed for the insertion reaction of the thermally stable silylene SiNCH2But2C6H4-1,2 abbrev. as SiNN into the carbon–halogen bond of alkyl or aryl halides RHal Hal Cl, Br. In general, depending on the halogen, the reaction either results in a disilane of type NNSiHal-RSiNN for Hal Cl or a mixture of disilane and the monosilane NNSiRHal for Hal Br. The results are put into context to previously suggested mechanisms. The disilane NNSiHal-RSiNN Hal Cl or Br is thermally labile and mild thermolysis yields the corresponding monosilane NNSiRHal and silylene 1. Additionally, strong evidence is presented for a radical pathway for the reaction of 1and RHal.

Diisopropylcarbodiimide, iPrNCNiPr, inserts into the lithium–phosphorus bond of in situprepared “Ph2PLiTHFn” to afford the lithium salt, LiPh2PCNiPr2THFnx2a; alternatively, this compound can be made by deprotonation of the neutral phosphaguanidine, Ph2PCNiPrNHiPr 1a with nBuLi. Displacement of the THF solvate in 2ais readily achieved with TMEDA to afford LiPh2PCNiPr2TMEDA 3a. X-Ray crystallographic analyses show that 2aexists as a dimer in the solid state with a folded ladder structure and an N,N′ chelating phosphaguanidinate, while 3ais monomeric with N,P-coordination of the ligand to lithium. Compound 2areacts viaa transmetallation pathway with AlMe2Cl to afford the dimethylaluminium complex, AlPh2PCNiPr2Me24a, which can also be prepared by protonation of a methyl group of AlMe3using 1a. The formation of a series of dialkylaluminium compounds has been investigated employing this latter pathway using both 1aand the N,N′-dicyclohexyl analogue, Ph2PCNCyNHCy 1b, affording AlPh2PCNR2Et25a, b, AlPh2PCNR2iBu26a,b and the diphenylaluminium compound AlPh2PCNiPr2Ph27a. 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 4aand 7aare reported, showing monomeric aluminium species with symmetrically chelating phosphaguanidinate ligands. The series of aluminium compounds AlLCl2L ECNiPr2−: A, E Me; B, E Me2N; C, E Me3Si2N and D, E Ph2P were investigated using density functional theory. In the more simple cases Aand 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 Bwas π-bonded across the Me2N–C bond suggesting delocalization of electron density into the metallacycle. In the more complex systems Cand D, delocalization within the metallacycle was less extensive due to the Me3Si2N- and Ph2P-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 polymetallic systems.

No Abstract

Dimesityl borinic acid, (mes)2BOH [mes = 2,4,6-Me3C6H2], has been employed as a source of boroxide ligand in lithium, zinc, and magnesium chemistry; for structural comparisons, the alkoxide ligand [OCH(mes)2]^- has also been used. The lithium compounds [Li{OB(mes)2}(L)n]2 [1a, L = Et2O, n = 1; 1b, L = Py, n = 1; 1c, L = MeCN, n = 2] have been structurally characterized, showing a common bimetallic core with bridging boroxide ligands that differ in the relative rotation of the “BC2” unit about the Li2O2 metallacycle. The zinc compounds [Zn{OR}Me]2 [2, R = B(mes)2; 3, R = CH(mes)2] have been synthesized from the reaction of ZnMe2 with the corresponding ROH species. As for the Li salts, 2 and 3 display a dimeric solid-state structure with μ-OR ligands. Reaction of the in situ generated lithium boroxide 1a with MgBr2·Et2O afforded an unprecedented tetrametallic compound, [Mg{OB(mes)2}Br·LiBr(OEt2)2]2 (4), in which the lithium bromide side product is retained in a tricyclic structure containing a “Li(μ-Br)2Mg{μ-OB(mes)2}Mg(μ-Br)2Li” core. The magnesium alkyl compounds [Mg{OB(mes)2}R(THF)]2 [5, R = Me; 6, R = Bu] were obtained from the reaction of the Li salt with the Grignard reagent, MgMeBr, and protonolysis of MgBu2 with (mes)2BOH, respectively. X-ray crystallography showed formation of a dimer in each case, where in 6 only the n-butyl group was observed in the solid state. Attempts at combining the boroxide ligand with the widely used β-diketiminate ligand, [HC{C(Me)NAr}2]^- (BDI), at a zinc center are discussed, and a brief study into the potential of selected zinc complexes to initiate the ring-opening polymerization of ε-caprolactone and rac-lactide is described.

The steric effect of adjacent methyl and methoxyl groups and the electronic effect of parasubstituents on the rotation of the plane of an aromatic nitro group relative to the plane of the aromatic ring has been investigated by X-ray crystallography. An electron-donating substituent in the paraposition decreases the rotation whilst an electron-withdrawing substituent increases the rotation of the plane of the nitro group relative to the aromatic ring.

Treatment of {HNR}2C10H6‐1, 8 [R = SiMe3(1), CH2But(2)] with Sn[N(SiMe3)2]2afforded the cyclic stannylene Sn[{NR}2C10H6‐1, 8] [R = SiMe3(3), CH2But(4)]. From 3and SnCl2in THF and crystallisation from toluene, the product was the crystalline tetracyclic compound $Sn(Cl)[\{\overline{N(SiMe_{3})\}_{2}C_{10}H_{6}-1, 8]Sn}Cl$(5) as the (toluene)0.5‐solvate. Reaction of 4with the silylene Si[(NCH2But)2C6H4‐1, 2] (6) [abbreviated as Si(NN)] in benzene and crystallisation in presence of Et2O furnished the crystalline tricyclic complex Sn[{Si(NCH2But)2C6H4‐1′, 2′}2‐{(NCH2But)2C10H6‐1, 8}] (7) as the Et2O‐solvate. Complex 5slowly dissociated into its factors 3and SnCl2in toluene, but rapidly in THF. Solutions of 7in C6D6, C7D8or THF‐d8, studied by multinuclear, variable temperature NMR spectroscopy, revealed the presence of an equilibrium between 8(an isomer of 7, in which the skeletal atoms of the eight‐membered ring were $\overline{SnNCCCNSiSi}$, rather than the $\overline{SnSiNCCCNSi}$of 7) and 4+ 2 Si(NN), with 8dominant in PhMe but not in THF; additionally 8was shown to be fluxional and solutions of 8in C6D6or C7D8decomposed to give the silane Si(NN)[(NCH2But)2C10H6‐1, 8], 6and Sn metal. The X‐ray structures of 3, 5and 7are presented.

The FeCl3‐catalysed arylation of C60F18gives tri‐substituted compounds C60F15Ar3, where Ar=phenyl, 4‐tolyl, 4‐methoxyphenyl, 4‐phenoxyphenyl, 4‐chlorophenyl, 3,4‐dichlorophenyl, 2‐biphylenyl and 2‐fluorenyl, together with some bis‐ and mono‐substituted product. Bis‐substitution was achieved with biphenylene and fluoranthene, and mono‐substitution with biphenylene (2‐position), pyrene (1‐position), and naphthalene (1‐ and 2‐positions); the tris‐phenyl and tris‐biphenylene derivatives are fluorescent. The 2‐naphthyl substituent freely rotates at 328 K, whereas rotation of the 1‐naphthyl substituent is prevented by interaction of the peri‐hydrogen atom with fluorine. The 1‐naphthyl derivative eliminates a molecule of HF during EI mass spectrometry, whilst the 2‐naphthyl derivative eliminates HF and all fluorenes to give a naphthaleno[60]fullerene. The reaction rate is relatively unaffected by electron supply in the aryl rings, but no product was obtained with benzotrifluoride which defines the lower reactivity limit. The low discrimination between aromatics makes it possible to isolate derivatives having different aryl groups attached to the cage. Reactions occur mainly when the reagent solutions (or solutions in 1,2‐dichlorobenzene) are evaporated to dryness. In most FeCl3‐catalysed reactions, unreacted C60F18was recovered, more if the less effective SnCl4was used as a catalyst; use of AlCl3resulted in polyarylation and degradation of the C60F18. The structure of C60F17(1‐biphenylyl) was confirmed by single‐crystal X‐ray analysis. Reaction of C60F18with perylene/FeCl3/o‐dichlorobenzene gave red fluorescent “tagliatelli”‐like threads (up to 1 cm long) of self‐assembled π‐stacked tetrachloroperylene arising from chlorination by FeCl3.