Rhenium complexes isocyanides

Irradiation of [Re(CNC6Fl3-2,6-Me2)6] with UV light in CH2CI2 in the presence of halide ions yields complexes of the type [Re(CNCgH3-2,6-Me2)5X] (X = Cl, Br, or I). The quantum yield of this reaction is high and results in chemical yields between 30% and 40%. Products of the same composition have been obtained directly from the cleavage of the metal-metal bond in quadruply bonded rhenium complexes of various compositions in the presence of isocyanides. ... 

Addition of electrophiles to electron-rich isocyanide complexes is a proven synthetic method for the synthesis of aminocarbyne complexes (5,6). Reaction of the trimethylsilyl isocyanide rhenium complex 34 with HBF4 was reported by Pombeiro and co-workers (68). It leads to loss of the trimethylsilyl group and formation of the parent aminocarbyne ligand CNHj [Eq. (28)]. The CNHj ligand is easily interconverted to the CNH... 

NOCgHj, Benzoyl isocyanide, chromium complex, 26 32,34,35 N0C,3H,3, Formanide, N-(l-(l-naphthal-enyl)ethyll-, rhenium complex, 29 217 NOPCjsHjj, Benzamide. 2-(diphenylphos-phino)-N-phenyl-, 27 324 NOPCjjHjj, Benzamide, Af-[2-(diphenyl-phosphino)phenyl]-, 27 323 NO2CH3, Methane, nitro-, antimony complex, 29 113 cobalt complex, 29 114 NOjCjHj, 4-Pyridinecarboxylic acid, rhodium complex, 27 292 NO2P2C3JH33, Phosphorus(l-t-), p-nitrido-bis(triphenyl-, acetate, 27 296 NO2SC3H7, L-Cysteine, molybdenum complex, 29 255,258... 

ONCgHj, Benzoyl isocyanide, chromium complex, 26 32, 34, 35 ONC13H13, Formanide, iV-(l-(l-naphthal-enyl)ethyl]-, rhenium complex, 29 217 ONNiPC22H4o, Nickel(II), [1-butan-... 

Rhenium isocyanide complex chemistry has not been nearly so extensively studied as that of other elements and so further efforts are obviously necessary. 

Compared to 32 (see Sect. 3.2), these compounds have the advantage that they react quantitatively under ambient conditions, in water as well as in polar organic solvents. The behaviour towards the ligands depicted in Scheme 7 proved to be identical for rhenium and technetium. The compounds listed in Scheme 7 have been fully characterized. The heterogenous reaction in THF in the presence of isocyanides yielded quantitatively the neutral complex [TcC1(CN-R)2(CO)3]... 

In a three-component reaction, a cationic platinum isocyanide complex [(Ph3P)2Pt(CNR)Cl][BF4] is reacted with a /3-bromoamine and butyl lithium to give an imidazoldin-2-ylidene complex.This transformation can be a two-component reaction if the isocyanide ligand contains already the necessary amine functionality. This was shown for chromium, molybdenum, tungsten, and rhenium carbonyls. 

The chemistry of rhenium(I) is dominated by organometallic compounds which are not covered by this review. Thus, cyclopentadienyl and related compounds, where the organometallic part of the molecule dominate the properties will generally not be considered. Nevertheless, compounds with carbonyl or isocyanide co-ligands will be treated when they can be regarded as constituents of a typical coordination compound or the compounds are of fundamental interest in a radiopharmaceutical context such as the hexakis(isocyanide)rhenium(I) cations. For the same reason a separate section has been included which gives a brief summary of recent attempts to develop synthetic routes to tiicarbonylrhenium(I) complexes for nuclear medical applications. 

Rhenium(0) compounds are rare and frequently lie in the realm of the organometallic chemistry. A simple example is decacarbonyldirhenium(0) in which two staggered, square-pyramidal Re(CO)5 fragments are held together by a single rhenium-rhenium bond. Substitution of carbonyl ligands is possible by tertiary phosphines and arsines, silanes and isocyanides, and binuclear Re-Re, Mn-Re, and Co-Re complexes have been studied. " Successive replacement of CO ligands can readily be observed by vibrational spectroscopy. This has been demonstrated... 

These expressions have been applied to the series isocyanide and carbonyl complexes of rhenium(I) tr ns-[ReL2(dppe)2]" (L = CNR, CO) [19, 20] and of nitrile and carbonyl compounds of iron(II) tmns-[FeL2(depe)2]2+ (L = NCR, CO) [35], and the Es and /J values of the corresponding trons- ReL(dppe)2 " and trans- FeL(depe)2 " " centers, which are given in Table 9, have been discussed earlier. 

Since the organometallic chemistry of rhenium is surveyed in the companion series Comprehensive Organometallic Chemistry,6 every effort has been made to minimize overlap with these topics, although an occasional reference is made in the present review to certain alkyl, aryl, carbonyl and isocyanide complexes that may be covered more fully in the excellent review by Boag and Kaesz.6... 

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