Models for Bonding in the Alkali Metal-Gallium Clusters K2Ga4(C6H3-2,6-Trip2)2 and Na2Ga4Trip6 (Trip=C6H2-2,4,6-i-Pr3): Importance of Alkali Metal-Aryl Interactions

Computational data for the tetragallium clusters K₂Ga₄(C₆H₃-2,6-Trip₂)₂ and Na₂Ga₄Trip₆ (Trip=C₆H₂-2,4,6-i-Pr₃) showed that significant Ga–Ga multiple bonding exists only in the latter species. The data for the M₂Ga₄R₂ (M=Li, Na or K; R=H, Me or Ph) models of K₂Ga₄(C₆H₃-2,6-Trip₂)₂, which has a distorted octahedral K₂Ga₄ core structure incorporating an almost square Ga₄ moiety, showed that they have an occupied bonding -orbital that is delocalized over the four galliums, thereby conferring formal aromatic character by the [4n+2] Hückel rule. However, the Ga–Ga bond order is approximately one, and the hypothetical free [Ga₄H₂]^2– dianion is unstable toward electron dissociation. For the cluster Na₂Ga₄Trip₆, calculations for the model compounds Ga₄H₆ and [Ga₄H₆]^2–, which involve a central gallium trigonally substituted by three GaH₂ units, confirmed that no multiple bonding exists in the neutral species Ga₄H₆ but that, upon reduction to [Ga₄H₆]^2–, a -bond is formed which is delocalized over the Ga₄ unit. The Ga–Ga distances that were calculated for all model species listed above are longer than those experimentally observed. This was attributed to the absence of alkali metal-aryl interactions in the model species.     

Formation of [Ar*Ge(CH2C(Me)C(Me)CH2)CH2C(Me)=]2 (Ar* = C6H3-2,6-Trip2; Trip = C6H2-2,4,6-i-Pr3) via reaction of Ar*GeGeAr* with 2,3-dimethyl-1,3-butadiene: evidence for the existence of a germanium analogue of an alkyne

The reduction of Ar*GeCl (Ar* = C6H3-2,6-Trip2; Trip = C6H2-2,4,6-i-Pr3) with one equivalent of potassium leads to the formation of a germanium analogue of an alkyne Ar*GeGeAr* 1; reaction of 1 with 2,3-dimethyl-1,3-butadiene yields [Ar*Ge(CH2C(Me)C(Me)CH2)CH2C(Me)=]2 2, which was structurally characterized.     

Crystal structures and magnetic properties of a sterically encumbered dithiadiazolyl radical, 2,4,6-(F3C)3C6H2CNSSN.

The sterically protected dithiadiazolyl radical (F3C)3C6H2CNSSN. (1) crystallises in two polymorphs: 1alpha, comprised of monomeric units and 1beta, containing a mixture of both pi*-pi* dimers and S = (1/2) monomers; whilst both polymorphs exhibit similar structure-directing motifs, the variation in packing leads to different magnetic behaviour.     

Synthesis and Solid-State Structure of 2,6-Trip2C6H3Tl (Trip=2,4,6-iPr3C6H2): A Monomeric Arylthallium(I) Compound with a Singly Coordinated Thallium Atom

A “one-legged thallium” is observed in the arylthallium(I ) compound 2,6-Trip₂C₆H₃Tl (Trip=2,4,6-iPr₃C₆H₂), which was synthesized from the corresponding organolithium compound and thallium chloride. X-ray structure analysis reveals that 2,6-Trip₂C₆H₃Tl is monomeric in the solid state and contains a singly coordinated thallium atom (see space-filling model on the right).     

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.     

Characterization of Ar'Sn(micro-Br)Sn(Ar')CH2C6H4-4-Pri (Ar' = C6H3-2,6-Dipp2; Dipp = C6H3-2,6-Pri2): a stable structural analogue for a heavier group 14 element monobridged alkene isomer HM(micro-H)MH2 (M = Sn or Pb)

The title compound is the first stable structural analogue for the monobridged isomer of a heavier group 14 alkene analogue.     

Die Struktur von [Li(tmeda)2][Zn(2,4,6-i-Pr3C6H2)3]

X-Ray Structure of [Li(tmeda)₂][Zn(2,4,6- i Pr₃C₆H₂)₃] A side reaction of zinc halide containing VCl₂(tmeda)₂ and Li(2,4,6-iPr₃C₆H₂) formed [Li(tmeda)₂][Zn(2,4,6-iPr₃C₆H₂)₃] · 0,5[(tmeda)Li(μ-Cl)]₂. The crystal structure (orthorhombic, Pbca, a = 26,226(2), b = 19,739(2), c = 27,223(5) Å, Z = 8, R = 0,062, wR² = 0,154) contains trigonal planar zinc anions with Zn–C distances of 2,039(7) Å (average) and a propeller like arrangement of the aryl rings.     

Neutrale Thiolate und ein Iodidthiolat von Antimon(III). Die Kristallstrukturen von Sb(SC6H5)3, Sb(SC6H2Me3-2,4,6)3 und SbI(SC6H2Me3-2,4,6)2

Neutral Thiolates and a Iodothiolate of Antimony(III). Crystal Structures of Sb(SC₆H₅)₃, Sb(SC₆H₂Me₃-2,4,6)₃, and SbI(SC₆H₂Me₃-2,4,6)₂ The crystal structures of Sb(SC₆H₅)₃ ( 1 ), Sb(SC₆ · H₂Me₃-2,4,6)₃ ( 2 ), and the novel compound SbI(SC₆H₂Me₃-2,4,6)₂ ( 3 ) have been determined by X-ray crystallography. In addition to the expected trigonal pyramidal coordination of antimony intermolecular interactions are observed for 1 (Sb … O: 363.3 pm) and 3 (Sb … S: 2 × 369.4 pm) but not for 2 . The reasons for these differences are discussed.     

Hypervalent organobismuth(iii) carbonate, chalcogenides and halides with the pendant arm ligands 2-(Me2NCH2)C6H4 and 2,6-(Me2NCH2)2C6H3

R2BiOH (1) [R = 2-(Me2NCH2)C6H4] and (R2Bi)2O (2) are formed by hydrolysis of R2BiCl with KOH. Single crystals of were obtained by air oxidation of (R2Bi)2. The reaction of R2BiCl and Na2CO3 leads to (R2Bi)2CO3 (3). 3 is also formed by the absorption of CO2 from the air in solutions of 1 or 2 in diethyl ether or toluene. (R2Bi)2S (4) is obtained from R2BiCl and Na2S or from (R2Bi)2 and S8. Exchange reactions between R2BiCl and KBr or NaI give R2BiX [X = Br (5), I (6)]. The reaction of RBiCl2 (7) with Na2S and [W(CO)5(THF)] gives cyclo-(RBiS)2[W(CO)5]2 (8). cyclo-(R'BiS)2 (9) [R' = 2,6-(Me2NCH2)2C6H3] is formed by reaction of R'BiCl2 and Na2S. The structures of were determined by single-crystal X-ray diffraction.     

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.     

Synthesis of [(HIPTNCH2CH2)3N]Cr Compounds (HIPT = 3,5-(2,4,6-i-Pr3C6H2)2C6H3) and an evaluation of chromium for the reduction of dinitrogen to ammonia

Red-black [HIPTN3N]Cr (1) ([HIPTN3N]3- = [(HIPTNCH2CH2)3N]3- where HIPT = 3,5-(2,4,6-i-Pr3C6H2)2C6H3 = HexaIsoPropylTerphenyl) can be prepared from CrCl3, while green-black [HIPTN3N]Cr(THF) (2) can be prepared from CrCl3(THF)3. Reduction of {1|2} (which means either 1 or 2) with potassium graphite in ether at room temperature yields [HIPTN3N]CrK (3) as a yellow-orange powder. There is no evidence that dinitrogen is incorporated into 1, 2, or 3. Compounds that can be prepared readily from {1|2} include red [HIPTN3N]CrCO (4), blood-red [HIPTN3N]CrNO (6), and purple [HIPTN3N]CrCl (7, upon oxidation of {1|2} with AgCl). The dichroic (purple/green) Cr(VI) nitride, [HIPTN3N]CrN (8) was prepared from Bu4NN3 and 7. X-ray studies have been carried out on 4, 6, and 7, and on two co-crystallized compounds, 7 and [HIPTN3N]CrN3 (65:35) and [HIPTN3N]CrN3 and 8 (50:50). Exposure of a degassed solution of {1|2} to an atmosphere of ammonia does not yield "Cr(NH3)" as a stable and well-behaved species analogous to Mo(NH3). An attempt to reduce dinitrogen under conditions described for the catalytic reduction of dinitrogen by [HIPTN3N]Mo compounds with 8 yielded a substoichiometric amount (0.8 equiv) of ammonia, which suggests that some ammonia is formed from the nitride but none is formed from dinitrogen.     

Synthesis of [(HIPTNCH2CH2)3N]V compounds (HIPT = 3,5-(2,4,6-i-Pr3C6H2)2C6H3) and an evaluation of vanadium for the reduction of dinitrogen to ammonia

Green [HIPTN3N]V(THF) ([HIPTN3N]3- = [(HIPTNCH2CH2)3N]3-, where HIPT = 3,5-(2,4,6-i-Pr3C6H2)2C6H3) can be prepared in a 70-80% yield via the addition of H3[HIPTN3N] to VCl3(THF)3 in THF, followed by the addition of LiN(SiMe3)2. From [HIPTN3N]V(THF), the following have been prepared: {[HIPTN3N]VN2}K, [HIPTN3N]V(NH3), [HIPTN3N]V=NH, [HIPTN3N]V=NSiMe3, [HIPTN3N]V=O, [HIPTN3N]V=S, and [HIPTN3N]V(CO). No ammonia is formed from dinitrogen using {[HIPTN3N]VN2}K, [HIPTN3N]V=NH, or [HIPTN3N]V(NH3) as the initial species under conditions that were successful in the analogous [HIPTN3N]Mo system. X-ray structural studies are reported for [HIPTN3N]V(THF) and [HIPTN3N]V(NH3).     

Convergent syntheses of [Sn7{C6H3-2,6-(C6H3-2,6-iPr2)2}21: a cluster with a rare pentagonal bipyramidal motif

Two complementary synthetic routes to a pentagonal bipyramidal Sn7 cluster, Sn7Aryl2 (Aryl = terphenyl ligand), are reported.     

Structural studies on bulky phosphines: X-ray crystal structures of [2,4,6-(t-Bu)3C6H2P(SiMe3)2] and

The crystal and molecular structures of two bulky phosphines containing the 2,4,6-(t-Bu)₃C₆H₂ group are reported. Compound1, [2,4,6-(t-Bu)₃C₆H₂P(SiMe₃)₂], crystallizes in the monoclinic space group P2₁/c; a = 9.450(8), b = 17.154(6), c = 17.790(5)Å, β = 101.19(5)°. Compound2,

, also crystallizes in the monoclinic space group P2₁/c: a = 18.224(5), b = 9.394(2), c = 12.321(2)Å, β = 107.28(2)°. Structural features resulting as a consequence of the bulky 2,4,6-(tBu)₃C₆H₂ group, in particular the geometry at phosphorus, are discussed.     

X-ray structure and dynamic behaviour in solution of N-methylthio-N'-2,6-dimethylphenyl).2,6-dimethyl-1,4-quinonediimine formed by the alcoholysis of [Me2 Al{2,6-Me2C6H3NS(Me)NC6H3Me2-2,6}]2

Reaction of [Me₂Al{RNS(Me)NR}]₂ (R = 2,6-Me₂C₆H₃) with t-BuOH affords N-methylthio-N-(2,6-dimethylphenyl)-2,6-dimethyl-1,4-quinonediimine in 67% yield. The X-ray structure of this compound shows that two conformational isomers are present in the solid. Temperature dependent ¹³C and ¹H NMR measurements show that in solution these conformers exchange at a rate which is fast on the NMR time scale at + 60°C and slow at ?₆₀°C. From the coalescence point of two of the ¹³C resonances, the free energy of activation is estimated to be 13.7 + 1.0 $\text{kcal}\text{mol}$ at 10°C. Possible processes for the exchange are discussed, and also a reaction scheme for the formation of the title compound is discussed.