The molecular mechanism of precursor evolution in the synthesis of colloidal group II−VI semiconductor nanocrystals was studied using 1H, 13C, and 31P NMR spectroscopy and mass spectrometry. Tri-n-butylphosphine chalcogenides (TBPE; E = S, Se, Te) react with an oleic acid complex of cadmium or zinc (M−OA; M = Zn, Cd) in a noncoordinating solvent (octadecene (ODE), n-nonane-d20, or n-decane-d22), affording ME nanocrystals, tri-n-butylphosphine oxide (TBPO), and oleic acid anhydride ((OA)2O). Likewise, the reaction between trialkylphosphine selenide and cadmium n-octadecylphosphonic acid complex (Cd−ODPA) in tri-n-octylphosphine oxide (TOPO) produces CdSe nanocrystals, trialkylphosphine oxide, and anhydrides of n-octadecylphosphonic acid. The disappearance of tri-n-octylphosphine selenide in the presence of Cd−OA and Cd−ODPA can be fit to a single-exponential decay (kobs = (1.30 ± 0.08) × 10-3 s-1, Cd−ODPA, 260 °C, and kobs = (1.51 ± 0.04) × 10-3 s-1, Cd−OA, 117 °C). The reaction approaches completion at 70...

Mechanistic study of precursor evolution in colloidal group II-VI semiconductor nanocrystal synthesis.

The reaction of ZnEt2 with HO(O)P(OtBu)2 gives the insoluble polymer {Zn[O2P(OtBu)2]2}n (1). In the presence of slight amounts of water, this reaction produces good yields of the oxo-centered tetranuclear cluster Zn4(μ4-O)[O2P(OtBu)2]6 (2), which has been characterized by X-ray crystallography. Compound 2 is thermally labile and eliminates isobutene and water over the temperature range 130−220 °C. The ceramic yield at 900 °C corresponds to the theoretical yield for a Zn4P6O19 material, and the observed products at this temperature are α-Zn2P2O7 and β-Zn(PO3)2 (by XRD). When heated in ethanol at 85 °C for 30 h, 2 converts to polymer 1 and ZnO. This transformation is facilitated by acids, which allow the conversion to occur at room temperature. Polymer 1, characterized by X-ray crystallography, adopts a zigzag structure with zinc atoms linked alternately by one and then three bridging phosphate groups. This structure is therefore different from that adopted by the other two organozincophosphate {Zn[O2P(OR)2...

Zinc di(tert-butyl)phosphate complexes as precursors to zinc phosphates. Manipulation of zincophosphate structures

Inorganic (carbon-free) chelate rings

Reactions of HO(O)P(OtBu)2 with Al2Me6 and [Al(OiPr)3]4 gave the new molecular aluminum phosphate complexes [Me2AlO2P(OtBu)2]2 (1) and [Al(OiPr)2O2P(OtBu)2]4 (2), respectively. In the solid state, 1 exists as a centrosymmetric dimer consisting of two four-coordinate Al centers bridged by two phosphate groups. In the solid state 2 exists as a centrosymmetric tetramer in which the unique half of the tetramer consists of two aluminum atoms bridged by two di(tert-butyl)phosphate groups. The central part of the molecule contains a planar Al2O2 four-membered ring containing two symmetry-related Al(1) atoms bridged by two −OiPr ligands. Solution-phase thermolyses of 1 and 2 in organic solvents led to the formation of transparent and opaque xerogels, respectively, after air-drying. The xerogel derived from 1 in 2-propanol had a surface area of 442 m2 g-1 after calcination to 600 °C in air. Thin, transparent films of aluminum phosphate were prepared by chemical vapor deposition (CVD) using both 1 and 2 as molecula...

Di(tert-butyl)phosphate Complexes of Aluminum: Precursors to Aluminum Phosphate Xerogels and Thin Films

In this review we have assessed the current state of knowledge of the chemistry and properties of ditiophosphate complexes. Although the pioneering work of JOrgensen 132) served to call attention to R-dtp compounds, many additional studies remain to be done. Compounds of many elements in the periodic table have not been characterized and a limited amount of structural data is available. The effect of substituent variation has been shown to affect structures but not to significantly vary electronic properties of complexes with similar structures. It is hoped that this work will assist investigations into the chemistry of dithiophosphate complexes. Although it has not been emphasized, there is an appreciable similarity between dithiophosphinate 9.425,426) and dithiophosphate complexes although significant differences in the properties of the compounds frequently occur.

C.M. Mikulski

Papers

Neutral organophosphorus chalcogenide-metal salt interactions: Addition and decomposition products