Synthesis and characterization of the monomeric imides Ar'MNAr' ' (M = Ga or In; Ar' or Ar' ' = terphenyl ligands) with two-coordinate gallium and indium

Reaction of Ar'MMAr' (M = Ga or In) with N3Ar' ' (Ar' = C6H3-2,6-Dipp2, Dipp = C6H3-2,6-Pri2, Ar' ' = C6H3-2,6(Xyl-4-But)2) afforded the first monomeric imides of heavier group 13 elements with two-coordinate metals. Planar, trans-bent structures with short M-N bond distances were observed, which are consistent with lone pair character at both M and N and a bond order less than the formally expected triple one.     

Synthesis and reactivity of dimeric Ar'TlTlAr' and trimeric (Ar"T1)3 (Ar', Ar" = bulky terphenyl group) thallium(I) derivatives: Tl(I)-Tl(I) bonding in species ligated by monodentate ligands

The synthesis and characterization of three new organothallium(I) compounds are reported. Reaction of (Ar'Li)(2) (Ar' = C(6)H(3)-2,6-(C(6)H(3)-2,6-Pr(i)(2))(2)) and Ar"Li (Ar" = C(6)H(3)-2,6-(C(6)H(3)-2,6-Me(2))(2)) with TlCl in Et(2)O afforded (Ar'Tl)(2) (1) and (Ar' 'Tl)(3) (2). The "dithallene" 1 is the heaviest group 13 dimetallene and features a planar, trans-bent structure with Ar'Tl-Tl = 119.74(14) degrees and Tl-Tl = 3.0936(8) A. Compound 2 is the first structurally characterized neutral, three-membered ring species of formula c-(MR)(3) (M = Al-Tl; R = organo group). The Tl(3) ring has Tl-Tl distances in the range ca. 3.21-3.37 A as well as pyramidal Tl geometries. The Tl-Tl bonds in 1 and 2 are outside the range (2.88-2.97 A) of Tl-Tl single bonds in R(2)TlTlR(2) compounds. The weak Tl-Tl bonding in 1 and 2 leads to their dissociation into Ar'Tl and Ar' 'Tl monomers in hexane. The Ar'Tl monomer behaves as a Lewis base and readily forms a 1:1 donor-acceptor complex with B(C(6)F(5))(3) to give Ar'TlB(C(6)F(5))(3), 3. Adduct 3 features an almost linear thallium C(ipso)-Tl-B angle of 174.358(7) degrees and a Tl-B distance of 2.311(2) A, which indicates strong association. Treatment of 1 with a variety of reagents resulted in no reactions. The lower reactivity of 1 is in accord with the reluctance of Tl(I) to undergo oxidation to Tl(III) due to the unreactive character of the 6s(2) electrons.     

Synthesis and characterization of 2,6-Dipp(2)-H(3)C(6)SnSnC(6)H(3)-2,6-Dipp(2) (Dipp = C(6)H(3)-2,6-Pr(i)(2)): a tin analogue of an alkyne

The reaction of Sn(Cl)C(6)H(3)-2,6-Dipp(2) (Dipp = C(6)H(3)-2,6-Pr(i)()(2)) with a stoichiometric amount of potassium in benzene affords 2,6-Pr(i)()(2)-H(3)C(6)SnSnC(6)H(3)-2,6-Pr(i)()(2) (1) as dark blue-green crystals. The compound 1 is a tin analogue of an alkyne. It was characterized by (1)H and (13)C NMR and UV-vis spectroscopy, cyclic voltammetry, combustion analysis and X-ray crystallography. The structural data show that 1 has a trans-bent, planar C(ipso)SnSnC(ipso) skeleton with a Sn-Sn bond distance of 2.6675(4) A and a Sn-Sn-C angle of 125.24(7) degrees. The Sn-Sn distance, which is ca. 0.15 A shorter than a conventional Sn-Sn single bond, and the trans-bent structure indicate the presence Sn-Sn multiple bond character unlike the related singly bonded ArPbPbAr species.     

Quasi-isomeric gallium amides and imides GaNR2 and RGaNR (R = organic group): reactions of the digallene, Ar'GaGaAr' (Ar' = C6H3-2,6-(C6H3-2,6-Pri2)2) with unsaturated nitrogen compounds

Reactions of the "digallene" Ar'GaGaAr'(1) (Ar' = C(6)H(3)-2,6-(C(6)H(3)-2,6-Pr(i)(2))(2)), which dissociates to green :GaAr' monomers in solution, with unsaturated N-N-bonded molecules are described. Treatment of solutions of :GaAr' with the bulky azide N(3)Ar(#) (Ar(#) = C(6)H(3)-2,6-(C(6)H(2)-2,6-Me(2)-4-Bu(t))(2)), afforded the red imide Ar'GaNAr(#) (2). Addition of the azobenzenes, ArylNNAryl (Aryl = C(6)H(4)-4-Me (p-tolyl), mesityl, and C(6)H(3)-2,6-Et(2)) yielded the 1,2-Ga(2)N(2) ring compound Ar'GaN(p-tolyl)N(p-tolyl)GaA' (3) or the products MesN=NC(6)H(2)-2,4-Me(2)-6-Ga(Me)Ar' (4) and 2,6-Et(2)C(6)H(3)N=NC(6)H(3)-2-Et-6-Ga(Et)Ar' (5). Reaction of GaAr' with N(2)CPh(2) yielded the 1,3-Ga(2)N(2) ring compound Ar'Ga(mu:eta(1)-N(2)CPh(2))(2)GaAr' (6), which is quasi-isomeric to 3. Calculations on simple model isomers showed that the Ga(I) amide GaNR(2) (R = Me) is much more stable than the isomeric Ga(III) imide RGaNR. This led to the synthesis of the first stable monomeric Ga(I) amide, GaN(SiMe(3))Ar' ' (8) (Ar' ' = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-Me(3))(2) from the reaction of LiN(SiMe(3))Ar' ' (7) and "GaI". Compound 8 is also the first one-coordinate gallium species to be characterized in the solid state. The reaction of 8 with N(3)Ar' ' afforded the amido-imide derivative Ar' 'NGaN(SiMe(3))Ar' ' (9), a gallium nitrogen analogue of an allyl anion. All compounds were spectroscopically and structurally characterized. In addition, DFT calculations were performed on model compounds of the amide, imide, and cyclic 1,2- and 1,3-species to better understand their bonding. The pairs of compounds 2 and 8 as well as 3 and 6 are rare examples of quasi-isomeric heavier main group element compounds.     

Synthesis and Characterization of Ge(II), Sn(II), and Pb(II) Monoamides with -NH2 Ligands

The synthesis and characterization of the first divalent germanium, tin, and lead monoamide derivatives of the parent amide group -NH(2) are presented. They have the general formula (ArMNH(2))(2) (M = Ge, Ar = Ar'(C(6)H(3)-2,6-Pr(i)(2)) or Ar* (C(6)H(3)-2,6(C(6)H(2)-2,4,6-Pr(i)(3))); M = Sn, Ar = Ar*; M = Pb, Ar = Ar*). For germanium and tin, they were obtained by reacting the corresponding terphenyl halides of the group 14 elements with liquid ammonia in diethyl ether. The lead amide derivative (Ar*PbNH(2))(2) was synthesized by reaction of LiNH(2) with Ar*PbBr in diethyl ether. The compounds were characterized by IR and multinuclear NMR spectroscopies and by X-ray crystallography in the case of the (Ar'GeNH(2))(2) or (Ar*SnNH(2))(2) derivatives. They possess dimeric structures with two -NH(2) groups bridging the germanium and tin centers. For lead, the reaction with ammonia led to isolation of a stable ammine complex of formula Ar*PbBr(NH(3)) which was characterized by IR and NMR spectroscopies and by X-ray crystallography. It is the first structural characterization of a divalent lead ammine complex.     

Ring-opening polymerisation of rac-lactide mediated by cationic zinc complexes featuring P-stereogenic bisphosphinimine ligands

The diastereomerically pure P-stereogenic bis(phosphinimine) ligands 4,6-(ArN[double bond, length as m-dash]PMePh)(2)dbf [Ar = 4-isopropylphenyl (Pipp): rac-4, meso-4; Ar = 2,6-diisopropylphenyl (Dipp): rac-4a; dbf = dibenzofuran] were synthesised and complexed to zinc using a protonation-alkane elimination strategy. The cationic alkylzinc complexes thus obtained, RZn[4,6-(ArN[double bond, length as m-dash]PMePh)(2)dbf][B(Ar')(4)] [Ar = Pipp, Ar' = C(6)H(3)(CF(3))(2): rac-6 (R = Et), meso-6 (R = Et), rac-7 (R = Me) meso-7 (R = Me); Ar = Dipp: rac-6a (R = Et, Ar' = C(6)H(3)(CF(3))(2)), rac-6b (R = Et, Ar' = C(6)F(5))] were investigated for their competency as initiators for the ring-opening polymerisation of rac-lactide. The formation of polylactide was achieved under relatively mild conditions (40 °C, 2-4 h) and the microstructures of the resulting polymers exhibited a slight heterotactic bias [polymer tacticity (P(r)) = 0.51-0.63].     

Solid-state 119Sn NMR and Mössbauer spectroscopy of "distannynes": evidence for large structural differences in the crystalline phase

The "distannynes" Ar'SnSnAr' (Ar' = C6H3-2,6(C6H3-2,6-Pr(i)2)2) and ArSnSnAr (Ar = C6H3-2,6(C6H2-2,4,6-Pr(i)3)2) were examined by solid-state (119)Sn NMR and M?ssbauer spectroscopy. The two compounds display substantially different spectroscopic parameters, while differing only in the absence (Ar'SnSnAr') or presence (ArSnSnAr) of a para-Pr(i) group in the flanking aryl rings of their terphenyl substituents. The spectroscopic differences can be interpreted in terms of a more trans-bent geometry and a longer Sn-Sn bond for ArSnSnAr in comparison to the wider Sn-Sn-C angle (125.24(7) degrees ) and shorter Sn-Sn bond length (2.6675(4)A) determined from the crystal structure of Ar'SnSnAr'. The differences are consistent with previously published calculations by Nagase and Takagi for ArSnSnAr.     

Isomeric forms of divalent heavier group 14 element hydrides: characterization of Ar'(H)GeGe(H)Ar' and Ar'(H)(2)GeGeAr'.PMe(3) (Ar' = C(6)H(3)-2,6-Dipp(2); Dipp = C(6)H(3)-2,6-Pr(i)(2))

The reduction of Ar'GeCl (Ar' = C6H3-2,6-Dipp2; Dipp = C6H3-2,6-Pri2) with LiBH(Bus)3 affords the first heavier group 14 element dimetallene hydride Ar'(H)GeGe(H)Ar' which, upon further reaction with PMe3, yields the base-stabilized isomeric form Ar'(H)2GeGeAr'.PMe3.     

The [2 + 4] Diels-Alder cycloadditon product of a probable dialuminene,Ar'AlAlAr' (Ar' = C(6)H(3)- 2,6-dipp(2); dipp = C(6)H(3)-2,6-Pr(i)(2)), with toluene

Reduction of Ar'AlI2 (Ar' = Ar'= C6H3-2,6-Dipp2; Dipp = C6H3-2,6-Pri2) with KC8 in diethyl ether most probably affords the first "dialuminene", Ar'AlAlAr'; it was characterized by its reaction with toluene which yielded a [2 + 4] cycloaddition product incorporating the Ar'AlAlAr' unit.     

The reactivity of gallium-(I), -(II) and -(III) heterocycles towards Group 15 substrates: attempts to prepare gallium-terminal pnictinidene complexes

The reactivity of a series of Ga(I), Ga(II) and Ga(III) heterocyclic compounds towards a number of Group 15 substrates has been investigated with a view to prepare examples of gallium-terminal pnictinidene complexes. Although no examples of such complexes were isolated, a number of novel complexes have been prepared. The reactions of the gallium(I) N-heterocyclic carbene analogue, [K(tmeda)][:Ga{[N(Ar)C(H)](2)}] (Ar = 2,6-diisopropylphenyl) with cyclo-(PPh)(5) and PhN[double bond, length as m-dash]NPh led to the unusual anionic spirocyclic complexes, [{kappa(2)P,P'-(PhP)(4)}Ga{[N(Ar)C(H)](2)}](-) and [{kappa(2)N,C-PhNN(H)(C(6)H(4))}Ga{[N(Ar)C(H)](2)}](-), via formal reductions of the Group 15 substrate. The reaction of the digallane(4), [Ga{[N(Ar)C(H)](2)}](2), with (Me(3)Si)N(3) afforded the paramagnetic, dimeric imido-gallane complex, [{[N(Ar)C(H) ](2)}Ga{mu-N(SiMe(3))}](2), via a Ga-Ga bond insertion process. In addition, the new gallium(III) phosphide, [GaI{P(H)Mes*}{[N(Ar)C(H)](2) }], Mes* = C(6)H(2)Bu(t)(3)-2,4,6; was prepared and treated with diazabicycloundecane (DBU) to give [Ga(DBU){P(H)Mes*}{[N(Ar)C(H)](2)}], presumably via a gallium-terminal phosphinidene intermediate, [Ga{[double bond, length as m-dash]PMes*}{[N(Ar)C(H)](2) }]. The possible mechanisms of all reactions are discussed, all new complexes have been crystallographically characterised and all paramagnetic complexes have been studied by ENDOR and/or EPR spectroscopy.     

Reversible and irreversible higher-order cycloaddition reactions of polyolefins with a multiple-bonded heavier group 13 alkene analogue: contrasting the behavior of systems with π-π, π-π*, and π-n+ frontier molecular orbital symmetry

The heavier group 13 element alkene analogue, digallene Ar(iPr(4))GaGaAr(iPr(4)) (1) [Ar(iPr(4)) = C(6)H(3)-2,6-(C(6)H(3)-2,6-(i)Pr(2))(2)], has been shown to react readily in [n + 2] (n = 6, 4, 2 + 2) cycloaddition reactions with norbornadiene and quadricyclane, 1,3,5,7-cyclooctatetraene, 1,3-cyclopentadiene, and 1,3,5-cycloheptatriene to afford the heavier element deltacyclane species Ar(iPr(4))Ga(C(7)H(8))GaAr(iPr(4)) (2), pseudoinverse sandwiches Ar(iPr(4))Ga(C(8)H(8))GaAr(iPr(4)) (3, 3(iso)), and polycyclic compounds Ar(iPr(4))Ga(C(5)H(6))GaAr(iPr(4)) (4) and Ar(iPr(4))Ga(C(7)H(8))GaAr(iPr(4)) (5, 5(iso)), respectively, under ambient conditions. These reactions are facile and may be contrasted with other all-carbon versions, which require transition-metal catalysis or forcing conditions (temperature, pressure), or with the reactions of the corresponding heavier group 14 species Ar(iPr(4))EEAr(iPr(4)) (E = Ge, Sn), which give very different product structures. We discuss several mechanistic possibilities, including radical- and non-radical-mediated cyclization pathways. These mechanisms are consistent with the improved energetic accessibility of the LUMO of the heavier group 13 element multiple bond in comparison with that of a simple alkene or alkyne. We show that the calculated frontier molecular orbitals (FMOs) of Ar(iPr(4))GaGaAr(iPr(4)) are of π-π symmetry, allowing this molecule to engage in a wider range of reactions than permitted by the usual π-π* FMOs of C-C π bonds or the π-n(+) FMOs of heavier group 14 alkyne analogues.     

Synthesis and characterization of three-coordinate and related beta-diketiminate derivatives of manganese,iron, and cobalt

Treatment of M[N(SiMe(3))(2)](2) (M = Mn, Fe, Co) with various bulky beta-diketimines afforded a variety of new three-coordinate complexes which were characterized by UV-vis, (1)H NMR and IR spectroscopy, magnetic measurements, and X-ray crystallography. Reaction of the beta-diketimine H(Dipp)NC(Me)CHC(Me)N(Dipp) (Dipp(2)N(wedge)NH; Dipp = C(6)H(3)-2,6-Pr(i)(2)) with M[N(SiMe(3))(2)](2) (M = Mn or Co) gave Dipp(2)N(wedge)NMN(SiMe(3))(2) (M = Mn, 1; Co, 3) while the reaction of Fe[N(SiMe(3))(2)](2) with Ar(2)N(wedge)NH (Ar = Dipp, C(6)F(5), Mes, C(6)H(3)-2,6-Me(2), or C(6)H(3)-2,6-Cl(2)) afforded the series of iron complexes Ar(2)N(wedge)NFe[N(SiMe(3))(2)] (Ar = Dipp, 2a; C(6)F(5), 2b; Mes, 2c; C(6)H(3)-2,6-Me(2), 2d; C(6)H(3)-2,6-Cl(2), 2e). This represents a new synthetic route to beta-diketiminate complexes of these metals. The four-coordinate bis-beta-diketiminate complex Fe[N(wedge)N(C(6)F(5))(2)](2), 4, was also isolated as a byproduct from the synthesis of 2b. Direct reaction of the Dipp(2)N(wedge)NLi with CoCl(2) gave the "ate" salt Dipp(2)N(wedge)NCoCl(2)Li(THF)(2), 5, in which the lithium chloride has formed a complex with Dipp(2)N(wedge)NCoCl through chloride bridging. The Fe(III) species Dipp(2)N(wedge)NFeCl(2), 6, was obtained cleanly from the reaction of FeCl(3) with Dipp(2)N(wedge)NLi. Magnetic measurements showed that all the complexes have a high spin configuration. The different substituents in the series of iron complexes 2a-e allowed assignment of their paramagnetically shifted (1)H NMR spectra. The X-ray crystal structures 1-2d and 3 showed that they have a distorted three-coordinate planar configuration at the metals whereas complexes 4-6 have highly distorted four-coordinate geometries.     

Terphenyl ligand stabilized lead(II) derivatives: steric effects and lead-lead bonding in diplumbenes

The reaction of PbBr(2) with the lithium reagents LiC(6)H(3)-2,6-(C(6)H(3)-2,6-Pr(i)(2))(2) (LiArPr(i)(2)) and Et(2)O.LiC(6)H(3)-2,6-(2,6-Pr(i)-4-Bu(t)C(6)H(2))(2) (Et(2)O.LiArPr(i)(2)Bu(t)) furnished the bromide bridged organolead(II) halides [Pb(mu-Br)ArPr(i)(2)](2) (1) and[Pb(mu-Br)ArPr(i)(2)Bu(t)](2) (2) as orange crystals. Treatment of 1 with a stoichiometric amount of methylmagnesium bromide resulted in the "diplumbene" Pr(i)(2)Ar(Me)PbPb(Me)ArPr(i)(2) (3). The addition of 1 equiv of 4-tert-butylphenylmagnesium bromide to 1 afforded the feebly associated, Pb-Pb bonded species [Pb(C(6)H(4)-4-Bu(t))ArPr(i)(2)](2) (4), whereas the corresponding reaction of tert-butylmagnesium chloride and 1 afforded the monomer Pb(Bu(t))ArPr(i)(2) (5). The reaction of the more crowded aryl lead(II) bromide [Pb(mu-Br)ArPr(i)(3)](2) (Ar = C(6)H(3)-2,6(C(6)H(2)-2,4,6-Pr(i)(3))(2)) with 4-isopropyl-benzylmagnesium bromide or LiSi(SiMe(3))(3) yielded the monomers 6, [Pb(CH(2)C(6)H(4)-4-Pr(i))ArPr(i)(3)], or 7, [Pb(Si(SiMe(3))(3))ArPr(i)(3)]. All compounds were characterized with use of X-ray crystallography, (1)H, (13)C, and (207)Pb NMR (3-7), and UV-vis spectroscopy. The dimeric Pb-Pb bonded (Pb-Pb = 3.1601(6) A) structure of 3 may be contrasted with the previously reported monomeric structure of Pb(Me)ArPr(i)(3), which differs from 3 only in that it has para Pr(i) substituents on the flanking aryl rings. The presence of these groups is sufficient to prevent the weak Pb-Pb bonding seen in 3. The dimer 4 displays a Pb-Pb distance of 3.947(1) A, which indicates a very weak lead-lead interaction, and it is possible that this close approach could be caused by packing effects. The monomeric structures of 6 and 7 are attributable to steric effects and, in particular, to the large size of ArPr(i)(3).     

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.     

Synthesis and characterization of HC[C(Me)N(C(6)H(3)-2,6-i-Pr(2))](2)MX(2) (M = Al, X = Cl, I; M = Ga, In, X = Me, Cl, I): sterically encumbered beta-diketiminate group 13 metal derivatives

A series of group 13 metal complexes featuring the beta-diketiminate ligand [[(C(6)H(3)-2,6-i-Pr(2))NC(Me)](2)CH](-) (i.e., [Dipp(2)nacnac](-), Dipp = C(6)H(3)-2,6-i-Pr(2)) have been prepared and spectroscopically and structurally characterized. The chloride derivatives Dipp(2)nacnacMCl(2) (M = Al (3), Ga (5), In (8)) were isolated in good yield by the reaction of 1 equiv of Dipp(2)nacnacLi.Et(2)O (2) and the respective metal halides. The iodide derivatives Dipp(2)nacnacMI(2) (M = Al (4), Ga (6), In (9)), which are useful for reduction to afford M(I) species, were made by a variety of routes. Thus, 4 was obtained by treatment of the previously reported Dipp(2)nacnacAlMe(2) with I(2), whereas the gallium analogue 6 was obtained as a product of the reaction of "GaI" with Dipp(2)nacnacLi.Et(2)O, and 9 was obtained by direct reaction of InI(3) and the lithium salt. The methyl derivatives Dipp(2)nacnacMMe(2) (M = Ga (7), In (10)), which are analogous to the previously reported Dipp(2)nacnacAlMe(2), were synthesized by the reaction of GaMe(3) with Dipp(2)nacnacH (1) or by reaction of the indium chloride derivative 8 with 2 equiv of MeMgBr in diethyl ether. The compounds 3-10 exist as colorless, air- and moisture-sensitive crystalline solids. Their X-ray crystal structures feature nearly planar C(3)N(2) arrays in the Dipp(2)nacnac ligand backbone with short C-C and C-N distances that are consistent with a delocalized structure. However, there are large dihedral angles between the C(3)N(2) plane and the N(2)M metal coordination plane which have been attributed mainly to steric effects. The relatively short M-N distances are consistent with the coordination numbers of the metals and the normal/dative character of the nitrogen ligands. The compounds were also characterized by (1)H and (13)C NMR spectroscopy. (1)H NMR data for 7 revealed equivalent methyl groups whereas the spectrum of 10 displayed two In-Me signals which indicated that ring wagging was slow on the (1)H NMR time scale.     

Complexes of an anionic gallium(I) N-heterocyclic carbene analogue with group 14 element(II) fragments: synthetic, structural and theoretical studies

The reactions of the anionic gallium(I) N-heterocyclic carbene (NHC) analogue, [K(tmeda)][:Ga{[N(Ar)C(H)]2}], Ar = C6H3Pri2-2,6, with the heavier group 14 alkene analogues, R2E=ER2, E = Ge or Sn, R = -CH(SiMe3)2, have been carried out. In 2:1 stoichiometries, these lead to the ionic [K(tmeda)][R2EGa{[N(Ar)C(H)]2}] complexes which exhibit long E-Ga bonds. The nature of these bonds has been probed by DFT calculations, and the complexes have been compared to neutral NHC adducts of group 14 dialkyls. The 4:1 reaction of [K(tmeda)][:Ga{[N(Ar)C(H)]2}] with R2Sn=SnR2 leads to the digallyl stannate complex, [K(tmeda)][RSn[Ga{[N(Ar)C(H)]2}]2], presumably via elimination of KR. In contrast, the reaction of the gallium heterocycle with PbR2 affords the digallane4, [Ga{[N(Ar)C(H)]2}]2, via an oxidative coupling reaction. For sake of comparison, the reactions of [K(tmeda)][:Ga{[N(Ar)C(H)]2}] with Ar'2E=EAr'2, E = Ge, Sn or Pb, Ar' = C6H2Pri3-2,4,6, were carried out and led to either no reaction (E = Ge), the formation of [K(tmeda)][Ar'2SnGa{[N(Ar)C(H)]2}] (E = Sn), or the gallium(III) heterocycle, [Ar'Ga{[N(Ar)C(H)]2}] (E = Pb). Salt elimination reactions between [K(tmeda)][:Ga{[N(Ar)C(H)]2}] and the guanidinato group 14 complexes [(Giso)ECl], E = Ge or Sn, Giso = [Pri2NC{N(Ar)}2]-, gave the neutral [(Giso)EGa{[N(Ar)C(H)]2}] complexes. All complexes have been characterized by NMR spectroscopy and X-ray crystallographic studies.     

Substituent effects in formally quintuple-bonded ArCrCrAr compounds (Ar = terphenyl) and related species

The effects of different terphenyl ligand substituents on the quintuple Cr-Cr bonding in arylchromium(I) dimers stabilized by bulky terphenyl ligands (Ar) were investigated. A series of complexes, ArCrCrAr (1-4; Ar = C6H2-2,6-(C6H3-2,6-iPr2)2-4-X, where X = H, SiMe3, OMe, and F), was synthesized and structurally characterized. Their X-ray crystal structures display similar trans-bent C(ipso)CrCrC(ipso) cores with short Cr-Cr distances that range from 1.8077(7) to 1.8351(4) A. There also weaker Cr-C interactions [2.294(1)-2.322(2) A] involving an C(ipso) of one of the flanking aryl rings. The data show that the changes induced in the Cr-Cr bond length by the different substituents X in the para positions of the central aryl ring of the terphenyl ligand are probably a result of packing rather than electronic effects. This is in agreement with density functional theory (DFT) calculations, which predict that the model compounds (4-XC6H4)CrCr(C6H4-4-X) (X = H, SiMe3, OMe, and F) have similar geometries in the gas phase. Magnetic measurements in the temperature range of 2-300 K revealed temperature-independent paramagnetism in 1-4. UV-visible and NMR spectroscopic data indicated that the metal-metal-bonded solid-state structures of 1-4 are retained in solution. Reduction of (4-F3CAr')CrCl (4-F3CAr' = C6H2-2,6-(C6H3-2,6-iPr2)2-4-CF3) with KC8 gave non-Cr-Cr-bonded fluorine-bridged dimer {(4-F3CAr')Cr(mu-F)(THF)}2 (5) as a result of activation of the CF3 moiety. The monomeric, two-coordinate complexes [(3,5-iPr2Ar*)Cr(L)] (6, L = THF; 7, L = PMe3; 3,5-iPr2Ar* = C6H1-2,6-(C6H-2,4,6-iPr3)2-3,5-iPr2) were obtained with use of the larger 3,5-Pri2-Ar* ligand, which prevents Cr-Cr bond formation. Their structures contain almost linearly coordinated CrI atoms, with high-spin 3d5 configurations. The addition of toluene to a mixture of (3,5-iPr2Ar*)CrCl and KC8 gave the unusual dinuclear benzyl complex [(3,5-iPr2Ar*)Cr(eta3:eta6-CH2Ph)Cr(Ar*-1-H-3,5-iPr2)] (8), in which a C-H bond from a toluene methyl group was activated. The electronic structures of 5-8 have been analyzed with the aid of DFT calculations.     

Reduction of digermenes with alkali metals: salts of formula M2[[Ge(H)Ar']2] (m = Li, Na, Or K, Ar' = terphenyl) with three different structures

The reduction of the digermene Ar'(H)GeGe(H)Ar' (Ar' = C6H3-2,6(C6H3-2,6-Pri2)2) with Li, Na, or K afforded [Li(THF)3Et2O][LiAr'(H)GeGe(H)Ar'] (1), Na2Ar'Ge(mu-H)2GeAr' (2), or K2{Ar'(H)GeGe(H)Ar'} (3), which have three different structures. 1 features a planar C(ipso)H)GeGe(H)C(ipso) dianion core with an associated Li+ cation. In contrast, 2 features a unique bridged hydride structure in which two Na+ ions also bridge the germaniums. In 3, the C(ipso)(H)GeGe(H)C(ipso) array has a nonplanar trans bent core with associated K+ ions. There is single Ge-Ge bonding in 1 and 3, but the Ge-Ge bonding in 2 may involve biradical character.     

Synthesis and characterisation of yttrium complexes supported by the beta-diketiminate ligand {ArNC(CH3)CHC(CH3)NAr}- (Ar = 2,6-Pr(i)2C6H3)

Reaction of YI(3)(THF)(3.5) with one equivalent of the potassium beta-diketiminate (BDI) complex [HC{C(CH(3))NAr}(2)K] (Ar = 2,6-Pr(i)(2)C(6)H(3)) affords the monomeric, mono-substituted yttrium BDI complex [HC{C(CH(3))NAr}(2)YI(2)(THF)] in good yield. Reaction of with DME affords [HC{C(CH(3))NAr}(2)YI(2)(DME)] in quantitative yield, which is monomeric also. Reaction of the primary terphenyl phosphane Ar*PH(2) (Ar* = 2,6-(2,4,6-Pr(i)(3)C(6)H(2))(2)C(6)H(3)) with potassium hydride, and recrystallisation from hexane, affords the potassium primary terphenyl phosphanide complex [{Ar*P(H)K(THF)}(2)] in high yield. Compound is dimeric in the solid state, constructed around a centrosymmetric K(2)P(2) four-membered ring, the coordination sphere of potassium is supplemented with an eta(6) K[dot dot dot]C(aryl) interaction. The reaction of with one molar equivalent of in THF affords the THF ring-opened compound [HC{C(CH(3))NAr}(2)Y{O(CH(2))(4)P(H)Ar*}(I)(THF)]. Compound is formed as a mixture of endo(OR) and exo(OR) isomers (: = approximately 2 : 1) which may be separated by fractional crystallisation from hexane-toluene to give pure . Attempted alkylation of with two equivalents of KCH(2)Si(CH(3))(3) affords the potassium yttriate complex [Y{micro-eta(5):eta(1)-ArNC(CH(3))[double bond, length as m-dash]CHC([double bond, length as m-dash]CH(2))NAr}(2)K(DME)(2)] in moderate yield; contains two dianionic dianilide ligands, which are derived from C-H activation of a backbone methyl group, each bonded eta(5) to yttrium in the solid state. The reaction of with one equivalent of KC(8) affords [{HC(C[CH(3)]NAr)(2)YI(micro-OCH(3))}(2)], derived from C-O bond activation of DME, as the only isolable product in very low yield. Compounds , , , , , and have been characterised by single crystal X-ray diffraction, NMR spectroscopy and CHN microanalyses.