No abstract

Platinum bisphosphine complexes bearing dichalcogen-derivatised naphthalene, acenaphthene or phenanthrene ligands have been prepared by either oxidative addition to zero-valent platinum species or from [PtCl(2)(PPhR(2))] (R=Ph or Me) and the disodium or dilithium salts of the parent disulfur, diselenide or mixed S/Se species. The parent naphthalene, acenaphthene and phenanthrene chalcogen compounds were treated with either [Pt(PPh(3))(4)] or [Pt(C(2)H(4))(PMe(3))(2)] (prepared in situ from [PtCl(2)(PMe(3))(2)], ethene and sodium naphthalide or super hydride [LiBEt(3)H]) to give the appropriate platinum(II) species. The dilithium salts of 1,8-E(2)-naphthalene (E=S or Se) prepared in situ by reduction of the E-E bond with [LiBEt(3)H] were treated with [PtCl(2)(PPh(3))(2)] to give [Pt(1,8-E(2)-nap)(PPh(3))(2)]. The tetraoxides [Pt(1,8-(S(O)(2))(2)-nap)(PR(3))(2)] (PR(3)=PPh(3) or PMe(2)Ph) were prepared in a similar metathetical manner from the appropriate [PtCl(2)(PR(3))] complexes and the disodium salt of naphthalene 1,8-disulfinic acid (1,8-(S(O)ONa)(2)-nap). The X-ray structures of selected examples reveal bidentate coordination with the naphthalene-E(2) unit hinged (111-137 degrees) with respect to the coordination plane. The naphthalene ring suffers significant distortion from planarity.

The molecular structures of naphtho[1,8-cd][1,2]dithiole, naphtho[1,8-cd][1,2]diselenole, naphtho[1,8-cd][1,2]ditellurole, naphtho[1,8-cd][1,2]dithiole I-oxide, naphtho[1,8-cd][1,2]dithiole 1,1-dioxide, and naphtho[1,8-cd][1,2]dithiole 1,1,2-trioxideand naphtho[1,8-cd][1,2]dithiole 1,1,2,2-tetroxide are compared. The E-E distance varies, broadly reflecting the degree of distortion imposed by the rigid naphthalene backbone as well as the degree of oxidation at sulfur. The naphthalene backbone imposes shortening of E-E bond lengths when E = S and Se compared to Ph-E-E-Ph systems but is itself subject to distortion as a consequence of the steric bulk of the E atoms

In recent years, there has been a rapid development in the field of II±VI semiconductors for use in photovoltaic devices due to their intermediate energy bandgaps. [1] ZnSe and ZnS are promising materials for blue/blue±green laser diode devices [2±4] which could lead to high-density optical storage systems, as well as fast switching devices. [5±7] Cadmium chalcogenides have applications in solid state solar cells [8,9] and photoconductors, in field effect transistors, sensors, and transducers. [10] Considerable efforts have been made to develop singlesource precursors for the deposition of semiconductor compounds. There are many reports in the literature of attempts to develop effective single-source precursors for the deposition of such materials by metal±organic (MO)CVD. [1,11±15] Over the years, we have been particularly interested in the deposition of thin films of chalcogenide from diseleno-or dithio-carbamato complexes of cadmium and zinc. [16] Introduction of asymmetrical bulky substituents to the selenium ligand was particularly successful, and metal selenide (CdSe, ZnSe) films were deposited. Gas chromatography (GC) and mass spectrometry (MS) experiments, using pyrolysis, have shown that the use of methyl(n-hexyl) derivative instead of symmetric alkyl hinders the formation of diethyldiselenide and therefore inhibits the deposition of selenium during growth. [16] Another class of metal±organic compounds for metal selenide films, based on bis(diphenylphosphino)amines, e.g., [Ph 2 (Se)NHP(Se)Ph 2 ], which can coordinate with numerous metals, has now been developed. [17] Schmidpeter and Groeger first synthesized imidodiphosphinates [NH(SPPh 2 ) 2 ], [18] then later the seleno analogue was prepared by oxidation of Ph 2 PNHPPh 2 with potassium selenocyanate, followed by acidic work up, [19] or by direct reaction with selenium under reflux in toluene. [20] Thin films of CdSe and ZnSe have been grown by low pressure (LP)-MOCVD using M[(SePPh 2 ) 2 N] 2 (M = Zn or Cd), air stable single-source precursors. The precursors were prepared as described in an earlier paper. [21] In the single crystal structure of Cd[(SePPh 2 ) 2 N] 2 , the metal center is coordinated to the selenium atoms by two bidentate ligands, forming six-membered chelate rings, and the ligands display a symmetric coordination to the cadmium(II). [21] Thermogravimetric analysis (TGA) of cadmium and zinc showed that the precursors are reasonably volatile and begin to evaporate at 375 C.Metal selenide films were deposited at various growth temperatures (475, 500, and 525 C) maintaining the precursor temperature at 375 C. Little or no growth was observed at 475 C, but as growth temperature was increased, deposition of films occurred. Zinc selenide films produced at 525 C were dark orange in color, transparent, and welladherent to the glass surface (scotch tape test), however, they could be removed with a scalpel, CdSe films grown at 525 C were black in color and fairly adherent to the surface, whilst at 500 C, non-uniform gray films were deposited, ...

The molecular and crystal structure of the title compound, 5‐oxo‐1,3,2,4‐dithiadiazole or Roesky’s ketone (1), is studied experimentally by re‐determining the crystal structure and theoretically by calculations at the density functional level of theory using an extended basis set. A comprehensive set of properties, consisting of orbital topologies, atomic charges, atomic and molecular dipoles, aromaticity parameters and Fukui functions of the title compound and a number of its constitutional isomers was calculated in order to formulate a description of its structure, its aromaticity and reactivity. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)