Main Group Chemistry

The reaction of ((di-iso-propyl)amino)(chloro)phosphenium cation [i-Pr₂N-P-Cl]⁺ (1) with phenyl cyclopropane afforded cis- and trans-l-diisopropylamino-2-phenyl-phosphetane-1-oxide (3a-cis and 3a-trans), and -1-thion (4), respectively. The cis-1-diisopropylamino-2-(p-substituted-phenyl)-3-methyl-phosphetane-1-oxides (3b – 3d) were obtained in excellent yields unexpectedly from the similar reactions of trans-2-methyl-1-(p-substituted-phenyl)-cyclopropane. The six new compounds have been characterized on the basis of elemental analysis, IR, ¹H, ³¹P NMR and MS. The configurations of 3a-cis, 3a-trans and 3c were elucidated by 2D NOESY. Molecular structure of 2-p-methylphenyl-3-methyl-phosphetane-1-oxide (3c) has been established by X-ray crystallography: in 3c, 1-diisopropylamino group is cis to 2-p-methylphenyl group as well as the dihedral angle between the planes C_(l)-P-C₍₃₎ and C₍₁₎-C₍₂₎-C₍₃₎ is 15.09°, which is the least in the found values. A carbocation mechanism including the attack of P⁺ on less hindered carbon on cyclopropane ring and the cation-π interaction between the positive P⁺-N of 1 and benzene ring portion of 2 is proposed. The single-crystal data: primitive orthorhombic, space group Pbca(#61), a = 20.053(2), b = 13.955(2), c = 12.526(4), V = 3505(1) ų, Z = 8, D_C = 1.09 g cm⁻³, F(000) = 1280.00, λ(Mo-Kα) = 0.71069 Å, μ(Mo-Kα) = 1.50 cm⁻¹. Refinement with 182 parameters and 1138 independent reflections with I > 3.00 σ (I) in the range 2° < θ < 25.0° gave R = 0.051 and R_W = 0.055.

The oxidation of triphenylantimony and triphenylphosphine by tert-butylhdroperoxide in the presence of catechol gives a new complex of a hexa-coordinated antimony, (C₆H₄O₂)SbPh₃(OPPh₃).⁷ In this complex triphenylphosphine oxide plays the role of the sixth ligand in a coordination sphere of an antimony atom of triphenylantimony o-phenylenedioxide. The compound was characterized by IR, ¹H NMR, ¹³C NMR, ³¹P NMR and X-ray single-crystal diffraction method. Crystal data for 7 at T = 293 K: a = 21.111(1) Å, b = 13.910(4) Å, c = 25.052(8) Å, β = 96.48(3)°, V = 7310₄(4) ų, Z = 8, D_calc = 1.380 g/cm³, μ = 0.839 mm⁻¹, space group C2/c. The geometry of the antimony atom in the synthesized complex is a distorted octahedron. Sixth coordination Sb-O(P) – 2.33 Å – is comparable with the sum of covalent radii of antimony and oxygen atoms, 2.20 Å. Five analogous complexes containing trimethyl(triethy1)antimony o-phenylenedioxide or 2.2.2-triphenyl-1.3.2-dioxas-tibolane and triphenylphosphine oxide or triphenylantimony o-phenylenedioxide and dimethylsulfoxide or pyridine oxide as a monodentate ligand were synthesized in the same manner. These compounds were also characterized by IR, ¹H ¹³C and ³¹P NMR.

Crystal structures are reported for 2,4-(O₂N)₂C₆H₃X (2: X = NMe₂; 3: X = C₆H₄NO₂-2) and Ph₃MSC₆H₄NO₂-2 (4: M = Ge; 5; M = Sn; 6: M = Pb). Compound 2 is triclinic, Pbar1, a = 7.931(5), b = 8.159(7), c = 9.090(7) Å, a = 100.35(6), β = 81.00(6), γ = 110.74(6)°, D_x = 1.500 Mg.m⁻³, Z = 2, observed reflections = 834, R = 0.066 (Rw = 0.049). Compound 3 is orthorhombic, P2₁2₁2₁, a = 11.1424(18), b = 11.8067(18), c = 20.363(3) Å, D_x = 1.593 Mg.m⁻³, Z = 8, observed reflections = 925, R = 0.061 (Rw = 0.074). Compound 4 is monoclinic, P2₁/a, a = 14.73(4), b = 10.091(5), c = 15.526(4) Å, β = 107.43(7), D_x = 1.382 Mg.m⁻³, Z = 4, observed reflections = 2034, R1 = 0.0426 (wR2 = 0.0834). Compound 5 is orthorhombic, Pbca, a = 15.489(10), b = 15.701(5), c = 17.558(7) Å, D_x = 1.569 Mg.m⁻³, Z = 8, observed reflections = 2537,R1 = 0.0327 (wR2 = 0.0700). Compound 6 is orthorhombic, Pbca, a = 15.569(5), b = 15.702(3), c = 17.651(6) Å, D_x = 1.825 Mg.m⁻³, Z = 8, observed reflections = 2536, R1 = 0.0323 (wR2 = 0.0737). There are short non-bonded S—O interactions and near linear O—S—X angles in both 2 and 3; values are 2.166(6) Å and 177.1(3)° for 2; 2.582(14) Å and 177.1(8)°, and 2.609(13) Å and 177.9(6) (in two independent molecules) for 3. The S—O interaction in 3 involves the ortho nitro group of the dinitrophenyl ring. Intramolecular S—O interactions are absent in 4 – 6; however there are weak intermolecular M—O bonding in 5 and 6, which results in molecules being linked into chains; the geometries at the metal centres in 5 and 6 are distorted trigonal bipyramidal with Sn—O and Pb—O bond lengths of 3.337(3) and 3.180(5) Å, respectively, and S_axial—M—O_axial angles of 173.19(5) and 173.96(9)°, respectively. Compound 4 is essentially tetrahedral.

Reaction of [(ⁱBu)₂AlH]₂ with l-ephedrine yields [(ⁱBu)₂A1{μ-OC(H)(Ph)CH(Me)N(H)Me}]₂ (1). Reaction of Al(^tBu)₃ with (2S,3R)-(+)-4-(dimethylamino)-l,2-diphenyl-3-methyl-2-butanol (Chirald^®) yields (^tBu)₂Al[OC(CH₂Ph)(Ph)CH(Me)CH₂NMe₂] (2). The molecular structures of compounds 1 and 2 have been determined by X-ray crystallography. Compound 2 is monomeric with a six membered chelate heterocyclic ring. In contrast, compound 1 exists as a bridged dimer. The formation of monomeric chelate species for compound 2, rather than the alkoxide bridged dimer as is found for 1 is found to be due to the steric bulk of the aluminum alkyl and substitution at the ligand’s α-carbon. Crystal data: (1) orthorhombic, P2₁2₁2₁, a=10.987(2), b=18.795(4), c =19.270(4) Å, V=3979(1) ų, Z=4, R=0.1056, R_w=0.2454. (2) tetragonal, 14, a=22.236(3), c=10.784(1) Å, V=5332.0(5) ų, Z=8, R=0.0485, R_w=0.0537.

Hydroalumination of H₂C==CHCH₂SMe with [(^tBu)₂Al(μ-H)]₃ yields the monomeric thioether compound (^tBu)₂Al(CH₂CH₂CH₂SMe). The molecular structure of (^tBu)₂ Al(CH₂CH₂CH₂SMe) consists of discreet monomers in which the thioether-alkyl ligand acts as a chelate ligand with an Al-S interaction [2.511(2) Å] that is significantly shorter than observed for other intra-molecular coordination compounds, 2.78–2.95 Å. The coordination about aluminum is highly distorted from tetrahedral and is therefore best described as capped trigonal planar or trigonal bipyramidal with a vacant coordination site. Crystal data: monoclinic, P2₁/n (No. 14), a = 6.6357(5), b = 13.630(1), c = 16.959(1) Å, β = 95.416(6)°. V = 1527.0(2) ų, Z = 4, R = 0.0412, R_w = 0.0503.

The possibility for the existence of the tellurium-containing chalcogen ring molecules has been explored by use of ab initio molecular orbital techniques. The full geometry optimization has been carried out for all isomers in the series Te_xS_8–x(x=l,2) and Te_xSe_yS_8–(x+y) (x=l;y=1,2) at HF/3-21G^* level of theory. Each molecule is a crown-shaped eight-membered ring like S₈. All calculated bond parameters indicate single bonds and agree with experimental parameters where available. The relative stabilities of the different isomers have been calculated by taking the effects of electron correlation into account involving the second-order Møller-Plessett perturbation theory. The most stable species are TeS₇, 1,2,-Te₂S₆, 1,2-TeSeS₆, and 1,2,8-TeSe₂S₅. The calculations are consistent with the observation that 1,2-Te₂S₆ and 1,2-TeSeS₆, are initially formed when [Ti(MeC₅H₄)₂(Te₂)₂-Ti(MeC₅H₄)₂] or [Ti(MeC₅H₄)₂(Te_xE_2-x)₂Ti(MeC₅H₄)₂] (E=S,Se) are treated with chalcogen chlorides. When (Me₃Si)₂Te is treated with ClSeS₅SeCl, 1,2,8-TeSe₂S₅ is formed. All these products decompose on standing with the formation of TeS₇ and some insoluble material.