A structural, spectroscopic and theoretical study of the triphenylphosphine chalcogenide complexes of tungsten carbonyl, [W(XPPh3)(CO)5], X=O, S, Se

Controlled CO labilization of tungsten carbonyl precursors for the low-temperature synthesis of tungsten diselenide nanocrystals

We report a low-temperature colloidal synthesis of WSe2 nanocrystals from tungsten hexacarbonyl and diphenyl diselenide in trioctylphosphine oxide (TOPO). We identify TOPO-substituted intermediates, W(CO)5TOPO and cis-W(CO)4(TOPO)2 by infrared spectroscopy. To confirm these assignments, we synthesize aryl analogues of phosphine-oxide-substituted intermediates, W(CO)5TPPO (synthesized previously, TPPO = triphenylphosphine oxide) and cis-W(CO)4(TPPO)2 and fac-W(CO)3(TPPO)3 (new structures reported herein). Ligation of the tungsten carbonyl by either the alkyl or aryl phosphine oxides results in facile labilization of the remaining CO, enabling low-temperature decomposition to nucleate WSe2 nanocrystals. The reactivity in phosphine oxides is contrasted with syntheses containing phosphine ligands, where substitution results in decreased CO labilization and higher temperatures are required to induce nanocrystal nucleation.

Synthetic, structural, NMR and catalytic studies of phosphinic amide-phosphoryl chalcogenides (chalcogen = O, S, Se) as mixed-donor bidentate ligands in zinc chemistry

Synthesis and catalytic activity of the title compounds are reported.

Relaxed but highly compact diansa metallacyclophanes

A series of monoansa [μ-1,1'-PR-3,3'-Co(1,2-C(2)B(9)H(10))(2)](-) and diansa [8,8'-μ-(1'',2''-benzene)-μ-1,1'-PR-3,3'-Co(1,2-C(2)B(9)H(9))(2)](-) (R = Ph, (t)Bu) cobaltabisdicarbollidephanes have been synthesized, characterized and studied by NMR, MALDI-TOF-MS, UV-visible spectroscopy, cyclic voltammetry, and DFT calculations. Single crystal X-ray diffraction revealed a highly relaxed structure characterized by the title angle α of 3.8° ([7](-)), this being the smallest angle α for a metallacyclophane. In such compounds, the metal-to-phosphorus distance is less than the sum of their van der Waals radii. The availability of a phosphorus lone pair causes an electron delocalization through the metal, as shown by the abnormal (31)P NMR chemical shift. Remarkably, the combination of a phosphine donor and a phenyl acceptor moieties causes a synergistic effect that is observed through the different techniques used in this study. The importance of having an available lone pair is demonstrated by the oxidation of phosphorus with hydrogen peroxide, sulfur, and elemental black selenium to produce the corresponding P(V) compounds. When the electron lone pair is used to form the bond with the corresponding chalcogen atom, the communication between the donor and acceptor moieties on the diansa metallacyclophane is shut down.