William P. Schaefer

Synthesis of organic salts with large second-order optical nonlinearities

A series of organic salts, in which the cation has been designed to have a large molecular hyperpolarizability, has been prepared. Variation of the counterion (anion) in many cases leads to materials with large powder second harmonic generation efficiencies, the highest of which is roughly 1000 times that of a urea reference.

Highly electron deficient group 3 organometallic complexes based on the 1,4,7-trimethyl-1,4,7-triazacyclononane ligand system

Abstract Reaction of the neutral ligand 1,4,7-trimethyl-1,4,7-triazacyclononane (Cn) with MCl3(THF)3 (M = Sc, Y) in acetonitrile affords the novel trihalide complexes CnMCl3. The crystal structure of CnScCl3 has been determined: (CH3)3N3(C2H4)3ScCl3; monoclinic, a = 12.477(3), b = 7.462(2), c = 15.984 A , β = 90.45(3)°; P21/c, Z = 4. Subsequent alkylation with LiCH3 in THF gives the corresponding trimethyl species CnM(CH3)3 clearly. Reactivity studies reveal that the metal carbon bonds of these highly coordinatively unsaturated 12e−, d0 complexes are remarkably unreactive toward insertion chemistry with typical unsaturated substrates such as alkenes and alkynes. 2-Butyne does, however, react with CnY(CH3)3 by CH activation to give a compound that is characterized as a major allenyl isomer, Cn(CH3)2Y(η1-C(CH3)CCH2), in equilibrium with a minor propargyl isomer, Cn(CH3)2Y(η1-CH2CC(CH3)). In general, CnSc(CH3)3 is observed to be significantly more stable, and also less reactive, than CnY(CH3)3. CnSc(CH3)3 can, however, be activated by reaction with either B(C6F5)3 or [H(CH3)2NPh]+[B(C6F5)4]− to give complexes which olefin polymerization chemistry.

Synthesis and characterization of (η5-C5Me5)2TaCl(THF), a useful synthetic precursor for the preparation of oxo, imido and methylidene derivatives of permethyltantalocene

Abstract The synthesis and characterization of Cp*2Ta(O)Cl (Cp*  (η5-C5Me5)), Cp*2Ta(NPh)Cl, Cp*2Ta (O)H, Cp*2Ta(NR)H (R  Ph, CMe3), Cp*2Ta(CH2)H, Cp*2Ta(CH2)Cl, Cp*2Ta(H2 CCH2)H, and the unusual cyclometallated product Cp*(η6-C5Me4CH2)TaH2 from Cp*2TaCI(THF) (THF  tetrahydrofuran) is described. Cp*2TaCl(THF) is prepared by the Na / Hg reduction of Cp*2TaCl2 in THF and used in situ. These synthetic routes are more convenient than those previously described and in most cases give much higher yields and purer products. All attempts to isolate Cp*2TaCl(THF) as a pure crystalline solid have led instead to less reactive [Cp*2TaCl]n, whose structure is uncertain. Although Cp*2TaCl(THF) is only moderately stable in THF at room temperature, it has been characterized in solution by 1H NMR spectroscopy. Both [Cp*2TaCl]n and Cp*2TaCl(THF) react with CO to afford Cp*2TaCl(CO). An X-ray crystal structure determination for Cp*2Ta (NPh)Cl (triclinic space group P 1 (number 2) with Z = 2; a = 8.627(2); b = 9.538(5), c = 16.890(5) A, α = 74.81(3)°, β = 87.12(2)°, γ = 63.79(3)°, with V = 1200.0(8) A3) reveals a linear TaNC group, as had been found previously for the closely related complex Cp*2Ta(NPh)H.

Structure of an Oxygen-Carrying Cobalt Complex

Bis(3-fluorosalicylaldehyde) ethylenediimine cobalt(II), a reversible oxygen-carrying compound, has been crystallized as a tetramer with two oxygen molecules bound to the four cobalt atomns, each oxygen molecule bridging between two metal atoms. These dimers are further linked by two bonds between the oxygen atom of the salicylaldehyde and the cobalt atom. The oxygen-to-oxygen distance, 1.21 angstroms in molecular oxygen, has increased to 1.308(28) angstroms (where the number in parentheses is the estimated standard deviation) in this compound, the shortest distance yet observed in sutch a bridging arrangement.

New Organic And Organometallic Salts For Second-Order Nonlinear Optics

A series of organometallic and organic salts, in which the cation has been designed to have a large molecular hyperpolarizability, has been prepared. Variation of the counterion (anion) in many cases leads to materials with large powder second harmonic generation (SHG) efficiencies, the highest of which is roughly 2000 times that of a urea reference.

Copper(II) and Nickel(II) Octabromo-tetrakis(pentafluorophenyl)Porphyrin Complexes

The copper and nickel complexes of 2,3,7,8,12,13,17, 18-octabromo-5,10,15,20-tetrakis(pentaftuorophenyl) porphyrin ({4,5,9,10,14,15,19,20-octabromo-2,7,12,17-tetrakis(pentaftuorophenyl)-21,22,23,24-tetraazapentacyclo[l6.2.1.1^(3,6).l^(8,11).l^(13,16)]tetracosa-l,3-(22),4,6,8(23),9,11,13(24),14,16,18(21),19-dodecaene }copper(II) 0.5-dichloromethane solvate and {4,5,9,10,14,15,19,20-octabromo-2,7,12,17-tetrakis(pentaftuorophenyl)-21,22,23,24-tetraazapentacyclo( 16.2.1.1^(3,6).l^(8,11).l^(13,16)]tetracosa-l,3(22),4,6,8(23),9,ll,13(24),14,16,18(21),19-dodecaene} nickel(II)0.5-dichloromethane solvate) form isostructural crystals. There is significant distortion from planarity of the porphyrin ring caused by the octabromo substituents interacting with the meso-pentafluorophenyl groups and with each other, with departures of the Br atoms from the plane defined by the four N atoms of up to 2.36 A. This tetrahedral distortion of the molecule does not result in any significant changes in bond distances from those in non-halogenated tetraphenylporphyrin complexes.

Synthesis and characterization ofM2(CCR)4(PMe3)4 dimetallapolyynes

The reaction betweenM2Cl4(PMe3)4 (M = Mo, W) and four equivalents of LiCCR (R = Me,i-Pr,t-Bu, SiMe3, Ph) in dimethoxyethane solution yields alkynyl-substituted, quadruply bonded complexes of the type M2(CCR )4(PMe3)4 in 10–90% yield. The electronic-absorption and1H-,1313C-, and31P-NMR spectroscopic data for these dimetallapolyyne complexes indicate that they are uncontaminated by chloride-containing impurities, and that they possess theD2d geometry expected of compounds of the M2X4L4 type. A single-crystal X-ray diffraction study of Mo2(CCPri)4(PMe3)4 confirms this latter conclusion, and also reveals that the Mo2 core of the complex is three-way disordered within the ordered quasi-cubic array of ligating atoms.

A highly solvated zinc(II) tetrakis(pentafluorophenyl)-β-octabromoporphyrin

The title compound, {4,5,9,10,14,15,19,20-octabromo-2,7,12,17-tetrakis(pentafluorophenyl)-21,22,23,- 24-tetraazapentacyclo[16.2.1.1^(3,6).1^(8,11).1^(13,16)]tetracosa-1,3(21),4,6,8(22),9,11,13(23),14,16,18(24),19-dodecaene }zinc(II) (carbon tetrachloride, o-dichlorobenzene, acetone, methanol, water solvate) has a large tetrahedral distortion, with the Br atoms as much as 1.83 A from the plane of the N atoms. The distortion affects primarily bond angles and bond torsion angles; bond distances in the molecule are normal. Several different solvents are incorporated into the crystal, providing a close (2.16 A) O atom as an axial neighbor to Zn and a more distant (3.16 A) Cl atom, in the opposite axial site.

A Silicon-Bridged Bis(substituted Cp) Yttrium Complex

rac-Bis(tetrahydrofuran)lithium [bis(2-trimethylsilyl-4-tert-butyl-η^5-cyclopentadienyl)dimethylsilane] dichloroyttrate, [Li(C_4H_80)_2][Y(C_(26)H_(48)-Si_3)Cl_2], M_r= 755.87, triclinic, Pl, ɑ = 13.110 (8), b = 17.163 (15), c = 20.623 (14) A, ɑ= 104.02 (7), β = 99.38 (5), y = 100.24 (6)o, V = 4326 (6) A^3, z = 4, D_x = 1.16 g cm^(-3), λ(Mo Kɑ)= 0.71073 A, μ = 15.86 cm^(-1), F(000) = 1608, room temperature, R = 0.056 for 6136 reflections with F_o^2 > 3σ(F_o^2). There are two virtually identical molecules in the asymmetric unit. In each, the Y atom is tetrahedrally coordinated to a substituted Si-bridged bis(cyclopentadienyl) ligand and to two Cl ions in the cleft. The Li atom is 2.35 A from each Cl ion, and two molecules of tetrahydrofuran are connected to the Li, completing its tetrahedral coordination.

A μ-Oxo-bis[iron(III) porphyrin] Complex

Partial nitration of iron(III) 2,3,7,8,12,13,17,18-octaethylporphyrin chloride [Fe III (OEP)Cl] gives the μ-oxo-bis(5,15-dinitro) compound μ-oxo-bis[2,3,7,8,12,-13,17,18-octaethyl-5,15-dinitroporphyrinato)iron(III)], [Fe 2 (C 36 H 42 N 6 O 4 ) 2 O], which is similar to other μ-oxo-iron(III) porphyrin complexes but with less ruffling of the porphyrin structure. The porphyrin planes are not parallel [the angle between plane normals is 169 (2)°] and the Fe-O-Fe angle is 167.9(3)°. As expected, the Fe atoms are significantly displaced from the porphyrin planes towards the bridging O atom : 0.46 A for Fe1 and 0.49 A for Fe2. The two porphyrin residues are eclipsed with respect to their C atoms, but the nitro groups are staggered by 90° from one residue to the other.