Thionitrosyl complexes

A variety of routes is available for the preparation of metal-thionitrosyl complexes. The most common of these are (a) reaction of nitride complexes with a sulfur source, e.g., elemental sulfur, propylene sulfide or sulfur halides, (b) reaction of (NSC1)3 with transition-metal complexes, and (c) reaction of [SN]" salts with transition-metal complexes. An example of each of these approaches is given in Eq. 7.1,... 

The nitrogen atom in the (almost) linear metal-thionitrosyl complexes is 5p-hybridized and the NS ligand behaves as a three-electron donor. The N-S bond distances in metal complexes vary between 1.45... 

Thionitrosyl complexes have already been briefly mentioned on p. 453 and have recently been reviewed.They were first made " by reacting azido complexes directly with... 

A few thionitrosyl complexes have been synthesized. MO calculations suggest that NS is a superior <7-donor and 7r-acceptor to NO [128], Syntheses include... 

Compared with the large number of nitrosyl complexes, only a few examples of thionitrosyl complexes have been studied. Although NS does not exist, a number of synthetic approaches to thionitrosyl complexes have been reported the reaction of nitrido complexes with S2CI2 or TMSNCS, treatment of chloro or 0x0 complexes with trithiazyl chloride or S(NTMS)2, or the use of heterocyclic nitrogen-sulfur rings. Pre-formed thionitrosyl cations in [NS][SbF6] or [NS)[AsFg] have been used to prepare the cationic complex [Re(NS)(CO)5] " in liquid S02. ... 

An Os phosphoraniminato complex has also been obtained via the reaction of an osmium(II) thionitrosyl complex with PPh3 (Equation (74)) " ... 

The first thionitrosyl complex was discovered by chance during an attempted synthesis of molybdenum nitrido complexes in the presence of a source of sulfur, tetrathiuram sulfide.168 This work of Dilworth and Chatt was reported in 1974 and ultimately led to the syntheses of a range of Mo, Re and Os thionitrosyl complexes starting with the respective nitrido complexes.143,164 Nitrosyl complexes, like carbonyls, had been known for decades, and the more recent syntheses of thio-carbonyl complexes forebode the advent of thionitrosyl complexes. However, convenient synthetic routes based on analogies with syntheses of NO complexes were generally not available because the requisite precursors did not exist or were inconvenient to handle. Sulfiliminato complexes (M=N=SR2) of transition metals are as yet unknown. The chemistry of thionitrosyl complexes was the subject of a recent review.179... 

Most of the known thionitrosyl complexes have been prepared by one of two synthetic techniques. As always, each technique has limitations, and future expansion of this field of coordination chemistry will depend upon the development of new synthetic methods. 

Solvated thiazylchloride trimer (N3S3C13) acts as a source of NSC1 and can be used to prepare thionitrosyl complexes. The use of thiazylchloride is limited because it can also function as a simple halogenating or oxidizing agent (equations 61 and 62). 

Both 95Mo and 14N NMR spectra have been measured for some thionitrosyl complexes.424,427 When compared to nitrosyl analogues, the thionitrosyl caused significant downfield shifts in both the Mo and N spectra. 

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