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Synthesis of Oligometallic Compounds from tripod Iron(II) Species Using Cyano Bridging Ligands − Electronic Coupling of Two Metal Termini Through Metal Dicyano and Diisocyano Entities
Author(s) -
Jacob Volker,
Huttner Gottfried,
Kaifer Elisabeth,
Kircher Peter,
Rutsch Peter
Publication year - 2001
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200111)2001:11<2783::aid-ejic2783>3.0.co;2-r
Subject(s) - comproportionation , chemistry , metal , group 2 organometallic chemistry , valence (chemistry) , crystallography , cyclic voltammetry , stereochemistry , ruthenocene , medicinal chemistry , inorganic chemistry , electrochemistry , ferrocene , molecule , organic chemistry , electrode
Organometallic monocyanometalates [M−CN] − ( 1 − ) [M = Cr(CO) 5 1a − , Cr(η 6 ‐CF 3 C 6 H 5 )(CO) 2 1b − , Mn(η 5 ‐CH 3 C 5 H 4 )(CO) 2 1c − ] produce tetrametallic ( 2 − ) and trimetallic ( 3 ) aggregates upon reaction with tripod and iron(II) salts [ tripod = CH 3 C(CH 2 PPh 2 ) 3 ]. The tetranuclear compound [ tripod Fe{NC−M} 3 ] − ( 2 − ) [M = Cr(CO) 5 ] or the trinuclear species [ tripod Fe(CO){NC−M} 2 ] ( 3 ) [M = Cr(CO) 5 3a , Cr(η 6 ‐CF 3 C 6 H 5 )(CO) 2 3b , Mn(η 5 ‐CH 3 C 5 H 4 )(CO) 2 3c ] can be selectively formed by following the appropriate reaction protocols. Organometallic dicyanometalates [NC−M′−CN] − ( 4 − ) [M′ = Mn(CO) 4 4a − , CpFe(CO) 4b − , CpCo(CN) 4c − ] react in a similar manner to give pentanuclear species [ tripod Fe{NC−M′−CN} 3 Fe tripod ] + ( 5 + ). − In compounds 2 − and 3 , two easily oxidizable organometallic groups are linked through a tripod Fe(NC) 2 unit, while in 5 + two tripod iron(II) entities are linked through a less readily oxidizable M′(CN) 2 unit. For both types of compound, at least two distinct reversible oxidations are observed by cyclic voltammetry. The potentials at which these oxidations occur are characteristic of the terminal groups in each case. The potentials of the two consecutive oxidation steps are separated by between 150 and 350 mV. The oxidation products of compounds 2 − , 3 , and 5 + can hence be classified as class III mixed‐valence species with comproportionation constants K C of between 10 2 and 10 6 . The extent of electronic coupling mediated by the M′(CN) 2 or M′(NC) 2 bridging entities is thus similar to that mediated by [RC(CN) 2 ] − bridging ligands in otherwise analogous compounds, for which K C values of around 10 4 are observed. All the aforementioned compounds have been characterized by analytical and spectroscopic techniques, including cyclic voltammetry and UV/Vis spectroscopy. In addition, X‐ray crystallographic data are reported for 2 − , 3a , 3b , 3c , and 5a + .