Rhenium(VII) Oxo and Imido Complexes: Synthesis, Structures, and Applications.

Publisher Summary This chapter discusses metal–isocyanide chemistry. In the interim, reviews have appeared on specific aspects of isocyanide chemistry. The generally accepted valence bond and molecular orbital (MO) approach to the bonding of metal isocyanides has been well described in Treichel's review, and has been used to rationalize variations in infrared (IR) stretching frequencies between bonded and nonbonded isocyanides and the better π-acceptor qualities of aryl versus alkyl isocyanide groups. A number of new synthetic routes to isocyanide complexes of chromium, molybdenum, and tungsten have been investigated. A number of attempts have been made over the years to develop reproducible synthetic routes to six- and seven-coordinate isocyanide complexes of molybdenum and tungsten. A number of routes have been employed for the synthesis of metal–isocyanide complexes by generating the isocyanide ligand on the metal atom. A number of monomeric complexes have been prepared, which may be considered as substitution products of the [Co(CNR) 5 ] + and [M(CNR) 4 ] + cations. Electrochemical investigations have been reported on a range of homoleptic and mixed carbonyl–isocyanide complexes, in attempts to rationalize substituent effects on the isocyanide with the electronic structure of the metal. Insertion reactions of isonitriles into metal–alkyl or metal–aryl bonds are now well established, occurring with metal–alkyl or –aryl groups from group IVA to IB and, recently, with uranium and thorium carbon bonds.

Metal Isocyanide Complexes

A variety of tetracoordinate molecules which deviate fundamentally from tetrahedral symmetry have been surveyed anew by ab initio Becke3LYP density functional computations. These refine the earlier findings that electropositive substituents (i.e. metals) drastically reduce the planar-tetrahedral energy difference and favour planar “anti-van't Hoff” arrangements. The lowest lying energy minima of 1,1- and 1,2-dilithioethylene, and of 1,1-dilithiocyclopropane have planar tetracoordinate carbons. Planar geometries also are favoured by π acceptors. Owing to aromatic delocalization and the small CCspiroC angle, planar 2,3-diboraspiropentane (unlike diboracyclopropane itself) is a true minimum. Planar tetracoordinate carbons also are present in 3,3-dilithio-l,2-diboracyclopropane and in a C2B2H4 isomer.

Planar and inherently non-tetrahedral tetracoordinate carbon: a status report *

Highly stable structures with planar tetracoordinate central atoms, Al4O, Al4N–, Al3SiN, cis-Al2Si2C, trans-Al2Si2C and AlSi3B, are predicted computationally at the ab initio MP4SDTQ/6-311 + G*//MP2(full)/6-31G* level.

A new, general strategy for achieving planar tetracoordinate geometries for carbon and other second row periodic elements

Trianionic pincer and pincer-type ligands are the focus of this review Metal ions from across the periodic table, from main group elements, transition metals, and the rare earths, are combined with trianionic pincer ligands to produce some of the most interesting complexes to appear in the literature over the past decade This review provides a comprehensive examination of the synthesis, characterization, properties, and catalytic applications of trianionic pincer metal complexes Some of the interesting applications employing trianionic pincer and pincer-type complexes include: (1) catalyzed aerobic oxidation, (2) alkene isomerization, (3) alkene and alkyne polymerization, (4) nitrene and carbene group transfer, (5) fundamental transformations such as oxygen-atom transfer, (6) nitrogen-atom transfer, (7) O2 activation, (8) C–H bond activation, (9) disulfide reduction, and (10) ligand centered storage of redox equivalents (ie redox active ligands) Expansion of the architecture, type of donor atoms, chelate ring size, and steric and electronic properties of trianionic pincer ligands has occurred rapidly over the past ten years This review is structured according to the type of pincer donor atoms that bind to the metal ion The type of donor atoms within trianionic pincer and pincer-type ligands to be discussed include: NCN3−, OCO3−, CCC3−, redox active NNN3−, NNN3−, redox active ONO3−, ONO3−, and SNS3− Since this is the first review of trianionic pincer and pincer-type ligands, an emphasis is placed on providing the reader with in-depth discussion of synthetic methods, characterization data, and highlights of these complexes as catalysts

Trianionic pincer and pincer-type metal complexes and catalysts

Rhenium(V) oxide complexes. Crystal and molecular structures of the compounds trans-ReI2O(OR)(PPh3)2 (R = Et, Me) and of their hydrolysis derivative ReIO2(PPh3)2

Isolation, reactions and x-ray structure of tetraethylammonium dihydridotetracarbonylrhenate

A new carbonylhydridorhenium cluster

Synthesis and x-ray chracterization of the dianions trihydridodecacarbonyltrirhenate(2—)and trihydrido-μ3-oxoenneacarbonyltrirhenate(2—)

Rhenium(V) oxide complexes. Crystal and molecular structures of ReOI2(PPh3)2(OReO3) and of ReOI2(PPh3)(OPPh3)(OReO3)·0.5C6H6 obtained from the reaction of ReO2I(PPh3)2 with oxygen

Maria Freni

Papers

Rhenium(V) oxide complexes. Crystal and molecular structures of the compounds trans-ReI2O(OR)(PPh3)2 (R = Et, Me) and of their hydrolysis derivative ReIO2(PPh3)2

Isolation, reactions and x-ray structure of tetraethylammonium dihydridotetracarbonylrhenate

A new carbonylhydridorhenium cluster

Synthesis and x-ray chracterization of the dianions trihydridodecacarbonyltrirhenate(2—)and trihydrido-μ3-oxoenneacarbonyltrirhenate(2—)

Rhenium(V) oxide complexes. Crystal and molecular structures of ReOI2(PPh3)2(OReO3) and of ReOI2(PPh3)(OPPh3)(OReO3)·0.5C6H6 obtained from the reaction of ReO2I(PPh3)2 with oxygen