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Synthesis and Characterisation of ν 3 ‐Octahedral [Ni 36 Pd 8 (CO) 48 ] 6− and [Ni 35 Pt 9 (CO) 48 ] 6− Clusters Displaying Unexpected Surface Segregation of Pt Atoms and Molecular and/or Crystal Substitutional Ni/Pd and Ni/Pt Disorder
Author(s) -
Femoni Cristina,
Iapalucci Maria Carmela,
Longoni Giuliano,
Svensson Per H.,
Zanello Piero,
Fabrizi de Biani Fabrizia
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200305210
Subject(s) - bimetallic strip , octahedron , crystallography , nickel , crystal structure , chemistry , cluster (spacecraft) , inorganic chemistry , catalysis , organic chemistry , computer science , programming language , biochemistry
The synthesis and structure, as well as the chemical and electrochemical characterisation of two new ν 3 ‐octahedral bimetallic clusters with the general [Ni 44− x M x (CO) 48 ] 6− (M = Pd, x = 8; M = Pt, x = 9) formula is reported. The [Ni 35 Pt 9 (CO) 48 ] 6− cluster was obtained in reasonable yields (56 % based on Pt) by reaction of [Ni 6 (CO) 12 ] 2− with 1.1 equivalents of Pt II complexes, in ethyl acetate or THF as the solvent. The [Ni 36 Pd 8 (CO) 48 ] 6− cluster was obtained from the related reaction with Pd II salts in THF, and was isolated only in low yields (5–10 % based on Pd), mainly because of insufficient differential solubility of its salts. The unit cell of the [NBu 4 ] 6 [Ni 35 Pt 9 (CO) 48 ] salt contains a substitutionally Ni–Pt disordered [Ni 24 (Ni 14− x Pt x )Pt 6 (CO) 48 ] 6− ( x = 3) hexaanion. A combination of crystal and molecular disorder is necessary to explain the disordering observed for the Ni/Pt sites. The unit cell of the corresponding [Ni 36 Pd 8 (CO) 48 ] 6− salt contains two independent [Ni 30 (Ni 8− x Pd x )Pd 6 (CO) 48 ] 6− ( x = 2) hexaanions. The two display similar substitutional Ni–Pd disorder, which probably arises only from crystal disorder. The structure of [Ni 36 Pd 8 (CO) 48 ] 6− establishes the first similarity between the chemistry of Ni‐Pd and Ni‐Pt carbonyl clusters. A comparison of the chemical and electrochemical properties of [Ni 35 Pt 9 (CO) 48 ] 6− with those of the related [Ni 38 Pt 6 (CO) 48 ] 6− cluster shows that surface colouring of the latter with Pt atoms decreases redox as well as protonation propensity of the cluster. In contrast, substitution of all internal Pt and two surface Ni with Pd atoms preserves the protonation behaviour and is only detrimental with respect to its redox aptitude. A qualitative rationalisation of the different surface‐site selectivity of Pt and Pd, based on distinctive interplays of MM and MCO bond energies, is suggested.