Synthesis, structure, and reactivity of iridium(III) complexes containing a 4,6-dimethyl-1,3-benzenediphenylimine pincer ligand.

A nonheterocyclic bis(imino)aryl ligand with blocking methyl substituents, 4,6-dimethyl-1,3-benzenediphenylimine (NCHN), has been synthesized. Metalation via oxidative addition proceeds under mild conditions with the Ir(I) reagent [Ir(CH(2)═CH(2))(2)(Cl)](2) to produce the Ir(III) product (NCN)Ir(CH(2)CH(3))(Cl). Neutral nucleophiles such as water or triphenylphosphine add readily to the vacant sixth coordination site. Protonation of the ethyl group results in loss of ethane and formation of a dicationic chloride-bridged (NCN)Ir dimer. Alternatively, the chloride ligand can be abstracted from (NCN)Ir(CH(2)CH(3))(Cl) to provide access to various neutral and cationic species, including (NCN)Ir(CH(2)CH(3))(OAc) (OAc = acetate), [(NCN)Ir(CH(2)CH(3))(bpy)][BF(4)] (bpy = 4,4'-bipyridine), [(NCN)Ir(CH(2)CH(3))(NCCH(3))(2)][BF(4)], and [(NCN)Ir(CH(2)CH(3))(OH(2))(2)][BF(4)], which is water soluble.

Crystal structures of 5,5'-bis(-hydroxy-methyl)-3,3'-biisoxazole and 4,4',5,5'-tetrakis-(hydroxy-methyl)-3,3'-biisoxazole.

The mol-ecular structure of 5,5'-bis(-hydroxy-methyl)-3,3'-biisoxazole, C8H8N2O4 (1), is composed of two trans planar isoxazole rings [r.m.s deviation = 0.006 (1) Å], each connected with a methyl hydroxyl group. Similarly, the structure of 4,4',5,5'-tetrakis-(hydroxy-methyl)-3,3'-biisoxazole, C10H12N2O6 (2), is composed of two planar isoxazole rings [r.m.s. deviation = 0.002 (1) Å], but with four hydroxymethyl groups as substituents. Both mol-ecules sit on a center of inversion, thus Z' = 0.5. The crystal structures are stabilized by networks of O-H⋯N [for (1)] and O-H⋯O hydrogen-bonding inter-actions [for (2)], giving rise to corrugated supra-molecular planes. The isoxazole rings are packed in a slip-stacked fashion, with centroid-to-centroid distances of 4.0652 (1) Šfor (1) (along the b-axis direction) and of 4.5379 (Å) for (2) (along the a-axis direction).

Crystal structure of 3,3'-biisoxazole-5,5'-bis(methyl-ene) dinitrate (BIDN).

The mol-ecular structure of the title energetic compound, C8H6N4O8, is composed of two planar isoxazole rings and two near planar alkyl-nitrate groups (r.m.s deviation = 0.006 Å). In the crystal, the mol-ecule sits on an inversion center, thus Z' = 0.5. The dihedral angle between the isoxazole ring and the nitrate group is 69.58 (8)°. van der Waals contacts dominate the inter-molecular inter-actions. Inversion-related rings are in close slip-stacked proximity, with an inter-planar separation of 3.101 (3) Š[centroid-centroid distance = 3.701 (3) Å]. The measured and calculated densities are in good agreement (1.585 versus 1.610 Mg m-3).

Synthesis of bis-Isoxazole-bis-Methylene Dinitrate: A Potential Nitrate Plasticizer and Melt-Castable Energetic Material.

The efficient and scalable synthesis of 3,3'-bis-isoxazole-5,5'-bis-methylene dinitrate and its energetic properties are described. The material has favorable sensitivity properties; energetic properties point toward its potential as both a melt-castable secondary explosive and as a propellant plasticizer.

Synthesis and oxidation of d6 tungsten pincer complexes: a complete series of tungsten(II) hydridocarbonyl and halocarbonyl pincer complexes.

Reaction of the neutral P(H)NP ligand [HN(SiMe(2)CH(2)PPh(2))(2)] with tungsten hexacarbonyl resulted in coordination of P(H)NP through both phosphorus donor atoms to form the tungsten complex [W(P(HN)P)(CO)(4)] (1). Reaction of P(H)NP with tris(acetonitrile)tricarbonyl tungsten gave both facial and meridional tridentate isomers [W(P(H)NP)(CO)(3)] (2-fac and 3-mer). These three d(6) tungsten complexes could be interconverted under appropriate conditions. The thermodynamically favored isomer 3 was protonated to form seven-coordinate [W(P(H)NP)(CO)(3)H][BF(4)] (4). A related series of cationic tungsten(II) halide complexes was synthesized, [W(P(H)NP)(CO)(3)X](+) (6, X = I; 7, X = Br; 8, X = Cl; 9, X = F), by various routes. All of the tungsten(II) complexes underwent deprotonation at the amine site of the P(H)NP ligand when triethylamine was added, resulting in neutral seven-coordinate complexes. Variable temperature (1)H, (31)P{(1)H}, and (13)C{(1)H} NMR spectroscopy showed fluxional behavior for all the seven-coordinate complexes reported here. Analysis of IR and NMR spectroscopic data showed trends through the series of coordinated halides. Crystal structures of tetracarbonyl 1, meridional tricarbonyl 3, and cationic hydride 4 were determined to confirm the coordination mode of the P(H)NP ligand.