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Issue 19, 2006
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Syntheses and structural analyses of variable-stoichiometric Au–Pt–Ni carbonyl/phosphine clusters, Pt3(Pt1−xNix)(AuPPh3)22-CO)4(CO)(PPh3)3 and Pt2(Pt2−yNiy)(AuPPh3)22-CO)4(CO)2(PPh3)2, with ligation-induced site-specific Pt/Ni substitutional disorder within butterfly-based Pt3(Pt1−xNix)Au2 and Pt2(Pt2−yNiy)Au2 core-geometries

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Abstract

In ongoing attempts of directed synthesis of high-nuclearity Au–Pt carbonyl/phosphine clusters with [Ni6(CO)12]2− used as reducing agent and CO source, we have isolated and characterized two new closely related variable-stoichiometric trimetallic clusters, Pt3(Pt1−xNix)(AuPPh3)22-CO)4(CO)(PPh3)3 (1) and Pt2(Pt2−yNiy)(AuPPh3)22-CO)4(CO)2(PPh3)2 (2). Their M4Au2 cores may be envisioned as substitutional disordered butterfly-based M4Au2 frameworks (M = Pt/Ni) formed by connections of the two basal MB atoms with both (Au–Au)-linked Au(PPh3) moieties. Based upon low-temperature CCD X-ray diffraction studies of eight crystals obtained from different samples, ligation-induced site-specific Pt/Ni substitutional disorder (involving formal insertion of Ni in place of Pt) in a given crystal was found to occur only at the one OC-attached basal MB site in 1 or at both OC-attached basal MB sites in 2 corresponding to a crystal composite of the Pt3(Pt1−xNix)Au2 core in 1 or of the Pt2(Pt2−yNiy)Au2 core in 2; the Ph3P-attached MB site (MB = Pt) in 1 and two wingtip Mw sites (Mw = Pt) in 1 and 2 were not substitutionally disordered. The resulting variable stoichiometry of the M4Au2 core in 1 may be viewed as a crystal composite of two superimposed individual stereoisomers, Pt4(AuPPh3)22-CO)4(CO)(PPh3)3 (1a) and Pt3Ni(AuPPh3)22-CO)4(CO)(PPh3)3 (1b), in the averaged unit cell of a given crystal. Likewise, 2 represents the crystal-averaged composite of three individual stereoisomers, Pt4(AuPPh3)22-CO)4(CO)2(PPh3)2 (2a), Pt3Ni(AuPPh3)22-CO)4(CO)2(PPh3)2 (2b), and Pt2Ni2(AuPPh3)22-CO)4(CO)2(PPh3)2 (2c). Formal Ni substitution for Pt at only the basal MB site(s) in the four crystal composites each of 1 and 2 was found to vary widely from 17% to 79% Ni in 1 and from 21% to 95% Ni in 2. Nevertheless, reasonably close Pt/Ni occupancy factors were found within each of the four pairs of composite crystals selected from samples obtained from duplicate syntheses. Both 1 and 2 may be formally derived from the electronically equivalent classic butterfly Pt42-CO)5(PPh3)4 cluster by replacement of its bridging µ2-CO ligand spanning the basal MB–MB edge with two one-electron donating (Au–Au)-linked AuPPh3 moieties along with the substitution of a terminal CO in place of one or both MB-attached PPh3 ligands in 1 and 2, respectively; site-specific Pt/Ni substitutional disorder occurs only at the CO-attached MB sites. The variable-stoichiometric 1 and 2 are also electronically equivalent and geometrically related to the crystal-ordered butterfly-based Pt42-CO)4(PR3)43-HgX)2 clusters (R3 = Ph3, MePh2; X = CF3, Br, I).

Graphical abstract: Syntheses and structural analyses of variable-stoichiometric Au–Pt–Ni carbonyl/phosphine clusters, Pt3(Pt1−xNix)(AuPPh3)2(µ2-CO)4(CO)(PPh3)3 and Pt2(Pt2−yNiy)(AuPPh3)2(µ2-CO)4(CO)2(PPh3)2, with ligation-induced site-specific Pt/Ni substitutional disorder within butterfly-based Pt3(Pt1−xNix)Au2 and Pt2(Pt2−yNiy)Au2 core-geometries

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Supplementary files

Article information


Submitted
04 Oct 2005
Accepted
26 Jan 2006
First published
14 Feb 2006

Dalton Trans., 2006, 2291-2300
Article type
Paper

Syntheses and structural analyses of variable-stoichiometric Au–Pt–Ni carbonyl/phosphine clusters, Pt3(Pt1−xNix)(AuPPh3)22-CO)4(CO)(PPh3)3 and Pt2(Pt2−yNiy)(AuPPh3)22-CO)4(CO)2(PPh3)2, with ligation-induced site-specific Pt/Ni substitutional disorder within butterfly-based Pt3(Pt1−xNix)Au2 and Pt2(Pt2−yNiy)Au2 core-geometries

N. de Silva, R. V. Nichiporuk and L. F. Dahl, Dalton Trans., 2006, 2291
DOI: 10.1039/B514105M

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