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Philip P. Power

Publications and source records attributed to Philip P. Power.

11 recordsLinked to original sources
PubMed1998

Reaction of the Primary Alane (2,4,6-t-Bu(3)H(2)C(6)AlH(2))(2) with Nitriles, Isonitriles, and Primary Amines.

The reactions of the sterically encumbered primary alane (MesAlH(2))(2) (Mes = C(6)H(2)-2,4,6-t-Bu(3)) with the nitriles t-BuCN, MesCN (Mes = C(6)H(2)-2,4,6-Me(3)) or MeCN lead eventually to dimeric amido alane products in which one of the ortho t-Bu groups of the Mes ligand is metalated and the nitrile is reduced to the amide ligand N(H)CH(2)R (R = t-Bu, Mes, or Me). The compounds (R = t-Bu, 2 (cis), 3 (trans); Mes, 4 (cis), 5 (trans); Me, 6 (cis)) have been isolated and characterized spectroscopically and also by X-ray crystallography in the cases of 4 and 5. The intermediate, dimeric iminato complex [MesAl(H){&mgr;(2)-NC(H)t-Bu}](2) (1), can also be isolated under carefully controlled, mild conditions. Reaction of (MesAlH(2))(2) with the isonitrile t-BuNC affords the cyclic species {MesAlN(t-Bu)CH(2)}(2) (7) featuring a six-membered (AlNC)(2) ring which, when heated, affords the cyclometalated species (8). Recognition that the products 2-6 and 8 were derivatives of primary amides led to an investigation of synthetic approaches to these product types via the direct reaction of (MesAlH(2))(2) with some primary amines. Treatment of (MesAlH(2))(2) with H(2)NCH(2)Mes affords the dimeric amido alane [Mes(H)Al{&mgr;(2)-N(H)CH(2)Mes}](2) as a mixture of trans (9) and cis (10) isomers. Further heating of 9 and 10 affords the ortho-metalated compounds 4 and 5. The reaction of (MesAlH(2))(2) with H(2)NSiPh(3) furnishes the bis amido aluminum compound MesAl{N(H)SiPh(3)}(2) (11) and [Mes(H)Al{N(H)SiPh(3)}](2). The latter yields the dimeric imide {MesAlNSiPh(3)}(2) (12) at elevated temperature.

Journal Article↗
PubMed1998

Monomeric Alanes: Synthesis, Structure, and Thermolysis of MesAl(H)N(SiMe(3))(2) and a One-Pot Synthetic Route to Mes(2)AlH (Mes = -C(6)H(2)-2,4,6-t-Bu(3)).

The reaction of (MesAlH(2))(2) (Mes = -C(6)H(2)-2,4,6-t-Bu(3)) with HN(SiMe(3))(2) affords the monomeric amidoarylalane MesAl(H)N(SiMe(3))(2), 1. This product can also be synthesized by the reaction of [MesAlH(2)](2) with LiN(SiMe(3))(2), which, in addition, yields the byproducts LiAlH(2){N(SiMe(3))(2)}(2), 3, and MesH. Thermolysis of 1 at 175-180 degrees C affords three different the related and the imide [MesAlN(SiMe(3))](n)(), 5. In addition, the previously reported monomeric alane Mes(2)AlH was synthesized in ca. 70% yield by a one-pot reaction between LiMes (generated in situ) and AlH(3).NMe(3). All products were spectroscopically characterized, and the structure of 1 was determined by X-ray crystallography. The Al-N distance (1.819(2) Å) in 1 is relatively long. However, it has a substantial, 18.5 kcal mol(-)(1), Al-N rotation barrier which is attributed to steric congestion rather than Al-N pi bonding.

Journal Article↗
PubMed1997

Synthesis, (9)Be NMR Spectroscopy, and Structural Characterization of Sterically Encumbered Beryllium Compounds.

The use of the terphenyl substituent -C(6)H(3)-2,6-Mes(2) (abbreviated Ar) has permitted the synthesis of several new low-coordinate beryllium compounds. Reaction of 1 equiv of LiAr with BeCl(2)(OEt(2))(2) or BeBr(2)(OEt(2))(2) (1) gives the monomeric complexes ArBeX(OEt(2)) (X = Cl (2); Br (3) featuring three-coordinate berylliums. Treatment of 2 with 1 equiv of LiSMes (Mes = -C(6)H(2)-2,4,6-t-Bu(3)) affords the three-coordinate thiolate derivative ArBeSMes(OEt(2)) (4). The reaction of 2 with LiNHPh, LiNHSiPh(3), or LiN(SiMe(3))(2) affords the unstable dimer (ArBeNHPh)(2) (5) or the monomers ArBeNHSiPh(3)(OEt(2)) (6) and ArBeN(SiMe(3))(2) (7). The last is the first example of a two-coordinate beryllium center in the solid state. The addition of 1 equiv of 2 to NaMo(eta(5)-C(5)H(5))(CO)(3) gives the isocarbonyl complex Ar(THF)(2)Be(OC)(3)Mo(eta(5)-C(5)H(5)) (8), which features four-coordinate beryllium bound to Ar, two THF ligands, and an oxygen from one of the molybdenum-bound carbonyls. Reaction of 2 with a 1:1 mixture of LiN(SiMe(3))(2) and PhCN affords the six-membered-ring compound PhC(NSiMe(3))(2)(BeCl)(2)N(SiMe(3))(2) (9) and the four-coordinate monomer Be{(NSiMe(3))(2)CPh}(2) (10). Compounds 1-10 were characterized by X-ray crystallography, and 1 and 4 and 6-10 were also characterized by (1)H, (9)Be, and (13)C NMR spectroscopy. X-ray data at 130 K (1-9) or 185 K (10) with Mo Kalpha (lambda = 0.710 73 Å) (1, 2a, 3, 7, 8) or Cu Kalpha (lambda = 1.541 78 Å) (2b, 4-6, 9, 10). BeBr(2)(OEt(2))(2) (1), a = 11.690(5) Å, b = 10.191(3) Å, c = 12.131(5) Å, beta = 114.67(3) degrees, V = 1313.3(9) Å(3), space group P2(1)/n, Z = 4, R(1) = 0.062; ArBeCl(OEt(2)) (2a), a = 13.136(3) Å, b = 13.877(3) Å, c = 28.092(6) Å, V = 5121(2) Å(3), space group Pbca, Z = 8, R(1) = 0.058; ArBeCl(OEt(2)) (2b), a = 8.857(1) Å, b = 8.8977(9) Å, c = 18.198(7) Å, alpha = 86.437(8) degrees, beta = 82.677(8) degrees, gamma = 62.405(7) degrees, V = 1260.5(2) Å(3), space group P&onemacr;, Z = 2, R(1) = 0.048; ArBeBr(OEt(2)) (3), a = 8.873(5) Å, b = 8.847(5) Å, c = 18.251(7) Å, alpha = 86.54(4) degrees, beta = 83.17(4) degrees, gamma = 64.14(4) degrees, V = 1280(1) Å(3), space group P&onemacr;, Z = 2, R(1) = 0.071; ArBeSMes(OEt(2)).0.5C(6)H(14) (4.0.5C(6)H(14)), a = 9.732(1) Å, b = 11.190(1) Å, c = 21.841(2) Å, alpha = 75.225(7) degrees, beta = 81.137(8) degrees, gamma = 73.382(8) degrees, V = 2195.3(4) Å(3), space group P&onemacr;, Z = 2, R(1) = 0.062; (ArBeNHPh)(2).C(4)H(10)O (5.C(4)H(10)O), a = 11.894(2) Å, b = 12.212(2) Å, c = 18.709(3) Å, beta = 99.24(1) degrees, V = 2682.4(7) Å(3), space group P2(1), Z = 2, R(1) = 0.045; ArBeNHSiPh(3)(OEt(2)) (6), a = 11.959(2) Å, b = 16.655(2) Å, c = 19.718(2) Å, beta = 105.368(9) degrees, V = 3786.9(8) Å(3), space group P2(1)/c, Z = 4, R(1) = 0.047; ArBeN(SiMe(3))(2) (7), a = 12.623(3) Å, b = 15.404(4) Å, c = 15.502(3) Å, V = 3014(1) Å(3), space group Pbcn, Z = 4, R(1) = 0.046; Ar(THF)(2)Be(OC)(3)Mo(eta(5)-C(5)H(5)).2C(7)H(8) (8.2C(7)H(8)), a = 19.111(4) Å, b = 11.976(3) Å, b = 21.241(5) Å, beta = 103.47(2) degrees, V = 4728(2) Å(3), space group P2(1)/c, Z = 4, R(1) = 0.049; PhC(NSiMe(3))(2)(BeCl)(2)N(SiMe(3))(2) (9), a = 19.996(4) Å, b = 14.816(2) Å, c = 20.183(4) Å, V = 5979(2)Å(3), space group Pbca, Z = 8, R(1) = 0.043; Be{(NSiMe(3))(2)CPh}(2) (10), a = 20.022(2) Å, b = 9.7161(9) Å, c = 19.456(2) Å, beta = 11.392(8) degrees, V = 3524.1(6) Å(3), space group P2(1)/c, Z = 4, R(1) = 0.075.

Journal Article↗
PubMed1997

Comparison of pi-Bond Strengths in M-E (M = B, Al, Ga; E = O, N, S) Compounds. Ab Initio Calculation of Rotational Barriers.

Results of ab initio calculations of the electronic structure of compounds of the type R(2)MER'(x) and R(2)MEMR'(2) with R = H, Me, M = Al, Ga, and E = O, N, S are reported at the Hartree-Fock level with split-valence, polarization basis sets for all atoms except hydrogen where a split-valence basis set is used. Full optimizations for the equilibrium geometry and partial optimization at constrained rotational transition states have been performed to evaluate the barriers to rotation as a measure of the pi interactions in these compounds. We conclude that, although important for determining the final conformational equilibrium geometries, pi interactions are weak in these compounds as the rotational barriers are smaller than that for ethylene by 1 or 2 orders of magnitude.

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PubMed1996

Donor-Free Alkali Metal Thiolates: Synthesis and Structure of Dimeric, Trimeric, and Tetrameric Complexes with Sterically Encumbered Terphenyl Substituents.

The synthesis and characterization of the tetrameric lithium thiolate (LiSC(6)H(2)-2,4,6-Ph(3))(4).C(7)H(8) (1), the trimeric lithium thiolate (LiSC(6)H(3)-2,6-Mes(2))(3).C(6)H(14)()()(2) (Mes = 2,4,6-Me(3)C(6)H(2)), the thiol HSC(6)H(3)-2,6-Trip(2) (3) (Trip = 2,4,6-i-Pr(3)C(6)H(2)), and the complete alkali metal series of dimeric thiolates (MSC(6)H(3)-2,6-Trip(2))(2) (M = Li (4, 5), Na (6), K (7), Rb (8), Cs (9)) are described. The compounds were characterized by (1)H, (7)Li, and (13)C NMR and IR spectroscopy and by X-ray crystallography. The compounds 1 and 2 crystallize as four- and three-rung ladder framework structures. The compounds 4-9 crystallize as dimers with M(2)S(2) cores. In addition, the metal ions interact with the ortho aryl groups to varying degrees in all the structures. The extent of these interactions appears to be determined mainly by ionic sizes and geometric factors. The coordination geometry of the thiolato sulfurs also varies from pyramidal in 1, 2, 4, 5, and 6 and one planar and one slightly pyramidal sulfur geometry in 7 to both sulfurs being planar coordinated in 8 and 9. Crystal data at 130 K are as follows: (LiSC(6)H(2)-2,4,6-Ph(3))(4).C(7)H(8) (1), a = 15.961(2) Å, b = 16.243(3) Å, c = 17.114(3) Å, alpha = 89.375(14) degrees, beta = 85.334(14) degrees, gamma = 63.343(12) degrees, V = 3950(1) Å(3), space group P&onemacr;, Z = 2, R(1) = 0.082; (LiSC(6)H(3)-2,6-Mes(2))(3).C(6)H(14)()()(2), a = 14.554(4) Å, b = 14.010(4) Å, c = 32.832(8) Å, beta = 95.20(2) degrees, V = 6667(2) Å(3), space group P2(1)/n, Z = 4, R(1) = 0.089; HSC(6)H(3)-2,6-Trip(2) (3), a = 8.180(2) Å, b = 25.437(5) Å, c = 15.752(3) Å, V = 3278(1) Å(3), space group Pnma, Z = 4, R(1) = 0.045; (LiC(6)H(3)-2,6-Trip(2))(2) (4), a = 12.652(2) Å, b = 14.218(1) Å, c = 18.713(2) Å, alpha = 83.56(1) degrees, beta = 84.36(1) degrees, gamma = 73.82(1) degrees, V = 3205(1) Å(3), space group P&onemacr;, Z = 2, R(1) = 0.055; (LiC(6)H(3)-2,6-Trip(2))(2).C(7)H(8) (5), a = 15.383(3) Å, b = 14.381(2) Å, c = 16.524(2) Å, beta = 111.10(1), V = 3410.3(9) Å(3), space group P2(1)/n, Z = 2, R(1) = 0.086; (NaSC(6)H(3)-2,6-Trip(2))(2).0.5C(7)H(8) (6), a = 13.952(2) Å, b = 20.267(2) Å, c = 24.475(3) Å, beta = 98.673(9) degrees, V = 6842(1) Å(3), space group P2(1)/n, Z = 4, R(1) = 0.068; (KSC(6)H(3)-2,6-Trip(2))(2).C(7)H(8) (7), a = 13.683(4) Å, b = 15.071(4) Å, c = 17.824(5) Å, alpha = 82.73(2), beta = 86.09(2), gamma = 88.46(2), V = 3637(2) Å(3), space group P&onemacr;, Z = 2, R(1) = 0.072; (RbSC(6)H(3)-2,6-Trip(2))(2).C(7)H(8) (8), a = 19.710(3) Å, b = 20.892(3) Å, c = 18.755(2) Å, beta = 106.900(9) degrees, V = 7389(2) Å(3), space group P2(1)/n, Z = 4, R(1) = 0.069; (CsSC(6)H(3)-2,6-Trip(2))(2) (9), a = 13.109(3) Å, b = 15.941(3) Å, c = 17.748(4) Å, alpha = 101.65(2) degrees, beta = 100.76(2) degrees, gamma = 104.25(2) degrees, V = 3410(1) Å(3), space group P&onemacr;, Z = 2, R(1) = 0.048.

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PubMed1996

Synthesis and Characterization of Sterically Encumbered Derivatives of Aluminum Hydrides and Halides: Assessment of Steric Properties of Bulky Terphenyl Ligands.

The synthesis and characterization of several sterically encumbered monoterphenyl derivatives of aluminum halides and aluminum hydrides are described. These compounds are [2,6-Mes(2)C(6)H(3)AlH(3)LiOEt(2)](n)() (1), (Mes = 2,4,6-Me(3)C(6)H(2)-), 2,6-Mes(2)C(6)H(3)AlH(2)OEt(2) (2), [2,6-Mes(2)C(6)H(3)AlH(2)](2) (3), 2,6-Mes(2)C(6)H(3)AlCl(2)OEt(2) (4), [2,6-Mes(2)C(6)H(3)AlCl(3)LiOEt(2)](n)() (5), [2,6-Mes(2)C(6)H(3)AlCl(2)](2) (6), TriphAlBr(2)OEt(2) (7), (Triph = 2,4,6-Ph(3)C(6)H(2)-), [2,6-Trip(2)C(6)H(3)AlH(3)LiOEt(2)](2) (8) (Trip = 2,4,6-i-Pr(3)C(6)H(2)-), 2,6-Trip(2)C(6)H(3)AlH(2)OEt(2) (9), [2,6-Trip(2)C(6)H(3)AlH(2)](2) (10), 2,6-Trip(2)C(6)H(3)AlCl(2)OEt(2) (11), and the partially hydrolyzed derivative [2,6-Trip(2)C(6)H(3)Al(Cl)(0.68)(H)(0.32)(&mgr;-OH)](2).2C(6)H(6) (12). The structures of 2, 3a, 4, 6, 7, 9a, 10a, 10b, 11, and 12 were determined by X-ray crystallography. The structures of 3a, 9a, 10a, and 10b, are related to 3, 9, and 10, respectively, by partial occupation of chloride or hydride by hydroxide. The compounds were also characterized by (1)H, (13)C, (7)Li, and (27)Al NMR and IR spectroscopy. The major conclusions from the experimental data are that a single ortho terphenyl substituent of the kind reported here are not as effective as the ligand Mes (Mes = 2,4,6-t-Bu(3)C(6)H(2)-) in preventing further coordination and/or aggregation involving the aluminum centers. In effect, one terphenyl ligand is not as successful as a Mes substituent in masking the metal through agostic and/or steric effects.

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PubMed1996

Imide Transfer Properties and Reactions of the Magnesium Imide ((THF)MgNPh)(6): A Versatile Synthetic Reagent.

Imide transfer properties of ((THF)MgNPh)(6) (1) and the synthesis of the related species {(THF)MgN(1-naphthyl)}(6).2.25THF (2), via the reaction of dibutylmagnesium with H(2)N(1-naphthyl), in a THF/heptane mixture are described. Treatment of 1 with Ph(2)CO, 4-Me(2)NC(6)H(4)NO, t-BuNBr(2) (3), PCl(3), or MesPCl(2) (Mes = 2,4,6-Me(3)C(6)H(2)-) leads to the isolation of Ph(2)CNPh (4), 4-Me(2)NC(6)H(4)NNPh (5), t-BuNNPh (6), (PhNPCl)(2) (7), or (MesPNPh)(2) (8) in moderate yield. Reaction between 1 and GeCl(2).dioxane, SnCl(2), or PbCl(2) affords the M(4)N(4) (M = Ge, Sn, Pb) cubane imide derivative (GeNPh)(4) (9), [(SnNPh)(4).{MgCl(2)(THF)(4)}](infinity) (10), (SnNPh)(4).0.5PhMe (11), or (PbNPh)(4).0.5PhMe (12). Interaction of 1 with Ph(3)PO, (Me(2)N)(3)PO, or Ph(2)SO furnishes the complex (Ph(3)POMgNPh)(6) (13), {(Me(2)N)(3)POMgNPh}(6).2PhMe (14), or (Ph(2)SOMgNPh)(6) (15). The addition of 3 equiv of MgBr(2) to 1 gives 1.5 equiv of ((THF)Mg)(6)(NPh)(4)Br(4) (16) in quantitative yield, whereas treatment of 16 with 4 equiv of 1,4-dioxane is an alternative synthetic route to 1. Compounds 2, 3, 9, 10, and 14 were characterized by X-ray crystallography. The reactions demonstrate that 1 is a versatile and useful reagent for the synthesis of a variety of main group imides. Crystal data at 130 K with Mo Kalpha (lambda = 0.710 73 Å) radiation for 3 or Cu Kalpha (lambda = 1.541 78 Å) radiation for 2, 9, 10, and 14: 2, C(93)H(108)Mg(6)N(6)O(7.25), a = 28.101(7) Å, b = 35.851(7) Å, c = 36.816(7) Å, Z = 2, space group Fddd, R = 0.068 for 3500 (I > 2sigma(I)) data; 3, C(4)H(9)Br(2)N, a = 6.682(2) Å, b = 10.834(3) Å, c = 11.080(3) Å, alpha = 66.25(2) degrees, beta = 89.88(2) degrees, gamma = 82.53(2) degrees, Z = 4, space group P&onemacr;, R = 0.038 for 2043 (I > 2sigma(I)) data; 9, C(24)H(20)Ge(4)N(4), a = 10.749(2) Å, b = 12.358(3) Å, c = 35.818(7) Å, Z = 8, space group Pbca, R = 0.040 for 2981 (I > 2sigma(I)) data; 10, C(40)H(52)Cl(2)MgN(4)O(4)Sn(4), a = 12.770(3) Å, b = 13.554(3) Å, c = 25.839(5) Å, Z = 4, space group P2(1)2(1)2(1), R = 0.040 for (I > 2sigma(I)) data; 14, C(86)H(154)Mg(6)N(4)O(6)P(6), a = 22.478(4) Å, b = 16.339(3) Å, c = 29.387(6) Å, Z = 4, space group Pbcn, R = 0.081 for 4696 (I >2sigma(I)) data.

Journal Article↗
PubMed1996

New Routes to Synthetically Useful, Sterically Encumbered Arylaluminum Halides and Hydride Halides.

The synthesis and structural characterization of the compounds MesAlCl(2)(THF) (1), MesAlCl(2) (2), MesAl(H)Cl(THF) (3a), MesAl(H)Cl (4a), and (MesAlH(2))(2) (5) (Mes = 2,4,6-t-Bu(3)C(6)H(2)(-)) are described as well as those for two compounds 3b and 4b that are analogs of 3a and 4a but have H:Cl ratios that are less than 1:1. All compounds were characterized by (1)H, (13)C NMR, and IR spectroscopy, and 1, 2, 3a, and 4b were additionally characterized by X-ray crystallography. Compound 1 is best synthesized by the reaction of [(THF)(2)LiH(3)AlMes](2) (6) with 6 equiv of Me(3)SiCl. A more conventional route involving the addition of (THF)(2)LiMes to 2 equiv of AlCl(3) in toluene usually affords a mixture of 1 and AlCl(3).THF. Recrystallization of 1 from n-hexane results in a species that has less than 1 equiv of THF per MesAlCl(2). The THF free complex 2 may be obtained in quantitative yield by heating 1 for 20 min at 90 degrees C under reduced pressure. Compound 3a may be obtained by treating a 1:1 mixture of MesLi(THF)(2) and LiAlH(4) with 2 equiv of Me(3)SiCl or by the addition of slightly less than 4 equiv of Me(3)SiCl to 6. The THF can be removed from 3a by sublimation to give 4a. The related compounds 3b and 4b, which display an aluminum-bound H:Cl ratio that is deficient in H, can be obtained by reactions with slightly more than 2 equiv of Me(3)SiCl. Crystal data at 130 K with Cu Kalpha (lambda = 1.541 78 Å) radiation: 1, C(22)H(37)AlCl(2)O, a = 11.889(3) Å, b = 9.992(3) Å, c = 19.704(5) Å, orthorhombic, space group Pca2(1), Z = 4, R = 0.068 for 1556 (I > 2sigma(I)) data; 2, C(18)H(29)AlCl(2), a = 12.147(5) Å, b = 18.042(6) Å, c = 17.771(7) Å, beta = 95.77(3) degrees, monoclinic, space group P2(1)/n,Z = 8, R = 0.032 for 4610 (I > 2sigma(I)) data; 3a, C(22)H(38)AlClO, a = 16.887(7) Å, b = 16.333(6) Å, c = 8.739(3) Å, beta = 101.41(3) degrees, monoclinic, space group P2(1)/c, Z = 4, R = 0.073 for 2752 (I > 2sigma(I)) data; 4b, C(18)H(29.64)AlCl(1.36), a = 12.077(3) Å, b = 17.920(3) Å, c = 17.634(5) Å; beta = 95.21(2) Å, monoclinic, space group P2(1)/n,Z = 8, R = 0.070 for 4261 (I > 2sigma(I)) data.

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