Primary lacrimal gland plexiform neurofibroma: a case report and review of the literature.

Neurofibromatosis type 1 (NF1) affects cell growth in neural tissues, resulting in neurofibromas of the internal organs, peripheral nerves and/or autonomic nerves. We describe a highly unusual case of plexiform neurofibroma presenting with lacrimal gland enlargement in an 18 year old male, which led to a diagnosis of NF1.

Regioselective insertion of 2-vinylpyridine in niobium and tantalum aryloxide complexes: an alternate route to pyridylalkyl metallacycles.

A series of niobium and tantalum aryloxide complexes containing pyridylethyl ligation have been synthesized via 2-vinylpyridine insertion to metal hydride complexes.

Novel, stereoselective tricyclization of a dienyne by titanium aryloxide centers.

Titanium centers supported by aryloxide ligation mediate the tricyclization of a dienyne via intramolecular insertion of an olefin into the titanium-vinyl bond of a titanacyclopent-2-ene.

Facile resolution of constrained geometry indenyl-phenoxide ligation.

The 2-(inden-3-yl)phenoxide ligand can be resolved at both tetrahedral and octahedral Group 4 metal centers using chiral binaphthoxide ligands.

Structural Distortions in Six-Coordinate Adducts of Niobium(V) and Tantalum(V).

The mixed chloro-aryloxide compounds [M(OC(6)H(3)Pr(i)(2)-2,6)(2)Cl(3)](2) (M = Nb (1a), Ta (1b); both structurally characterized) and [M(OC(6)H(3)Pr(i)(2)-2,6)(3)Cl(2)] (M = Nb (2a), Ta (2b)) react with pyridine (py) and PMe(2)Ph to produce a series of adducts cis-mer-[MCl(3)(OC(6)H(3)Pr(i)(2)-2,6)(2)(L)] (M, L: Nb, py (3a); Ta, py (3b); Nb, PMe(2)Ph (4a); Ta, PMe(2)Ph (4b)) and trans-mer-[MCl(2)(OC(6)H(3)Pr(i)(2)-2,6)(3)(L)] (M, L: Nb, py (5); Nb, PMe(2)Ph (6a); Ta, PMe(2)Ph (6b)). The assigned geometric arrangement of ligands is based upon (1)H NMR studies and single-crystal X-ray diffraction analyses of 3a, 3b, 4, 6a, and 6b. The salt complex [HPMe(2)Ph](+)[mer-NbCl(3)(OC(6)H(3)Pr(i)(2)-2,6)(3)](-) (7) has also been isolated and structurally characterized. The structural parameters for the neutral adducts are compared with those of previously reported hydrido aryloxides of tantalum. A small but consistent distortion away from octahedral geometry involving the bending of mutually trans anionic ligands toward the neutral donor group is observed. Theoretical analysis at several levels of theory (RHF, MP2, and DFT) on model compounds [Ta(OH)(2)(H)(2)(PH(3))(X)] (X = Cl, OH, H) show a distortion involving bending of the trans-hydride groups toward the PH(3) ligand for X = Cl and OH. This distortion can be accounted for in terms of an improvement in both X p to metal d pi-bonding and Ta-H sigma-bonding. The contribution of sigma-bonding effects is clearly shown in the case of X = H, where again a bend of the two hydride ligands toward the Ta-P bond is calculated. A smaller distortion of the Cl ligands in trans-mer-[Ta(OH)(3)(Cl)(2)(PH(3))] is also predicted.

The nature of aryloxide and arylsulfide ligand bonding in dimethyltitanium complexes containing cyclopentadienyl ligation.

A series of dimethyltitanium compounds [CpTi(EAr)Me2](E = O, S) ligated by one cyclopentadienyl (Cp) and one aryloxide (OAr) or arylsulfide (SAr) have been structurally characterized in order to gain a better understanding of aryloxide and arylsulfide bonding in these systems. Experimental structures were compared to those predicted by density functional theory (DFT). Bonding in the arylsulfide systems was found to be significantly different from bonding in the aryloxide systems. The aryloxide ligands exhibited wide Ti-O-Ar angles > or = 150 degrees) with the Ar group oriented proximal to the Cp group. DFT computations revealed two conformers for the arylsulfide systems. Arylsulfides with the Ar group proximal to the Cp group had a predicted Ti-S-Ar angle of approximately 120 degrees while those with the Ar group distal to the Cp group had a measured and predicted Ti-S-Ar angle of approximately 100 degrees. Molecular and natural bond orbital (NBO) analyses were employed to explain the nature of ligand bonding in these systems.

Synthesis of group 1 metal 2,6-diphenylphenoxide complexes [M(OC6H3Ph2-2,6)] (M = Li, Na, K, Rb, Cs) and structures of the solvent-free complexes [Rb(OC6H3Ph2-2,6)]x and [Cs(OC6H3Ph2-2,6)x: one-dimensional extended arrays of metal aryloxides.

Reaction of 2,6-diphenylphenol (HOC(6)H(3)Ph(2)-2,6) with (n)BuLi, NaH, KH, or Rb or Cs metal in benzene gives the solvent-free complexes [M(OAr)]x in excellent yield. The complex [Rb(OC(6)H(3)Ph(2)-2,6)](x)() exhibits a ladderlike structure in the solid state with triply bridging oxygen atoms and Rb-O distances of 2.743(3), 2.930(2), and 2.973(2) A. The Rb cations interact with the pi-electron cloud of the arene moieties, giving rise to a high Rb coordination number. The cesium-containing congener forms a layered, columnlike structure consisting of [Cs(2)(mu(2)-OAr)(2)] units, with nearly identical Cs-O distances of 2.945(2) and 2.947(2) A. The individual layers are held together solely by Cs-arene pi-interactions.