Thionitrosyl ligands

In contrast to the numerous complexes of NO which have been prepared and characterized, complexes of the thionitrosyl ligand (NS) are virtually unknown, as is the free ligand itself. The first such complex [Mo(NS)(S2CNMc2)3] was obtained as orange-red air-stable crystals by treating [MoN(S2CNMe2>3] with sulfur in... 

The thionitrosyl ligand features in [Os(NS)Cl3(PPh3)2l, the crystal structure of which has been determined. The phosphine ligands are mutually trans. ... 

In recent years, several dozen compounds containing the isoelectronic NS (thionitrosyl) ligand have been synthesized. Infrared data have indicated that, like NO, NS can function in linear, bent, and bridging modes. In general, NS is stronger than NO in its ability to act as a n acceptor ligand the relative abilities of NO and NS to accept n electrons depend on the electronic environment of... 

It is remarkable that not a single example of a rhodium or iridium nitrosyl with a Tp ligand has been reported. In a similar manner, analogues based on arenediazenido and thionitrosyl ligands have yet to appear for group 9 metals, despite such compounds being reported for earlier transition metal centres. 

The related molybdenum thionitrosyl complex [Mo(NS)(S2CNEt2)3] has also been prepared in low yield as a result of a dithiocarbamate fragmentation process, after reaction of [Mo(N-p-tol)2Cl2(dme)] with 2 equiv of NH4S2CNEt2 (442). The precise nature of this process remains unknown, but the thionitrosyl ligand formally results from extrusion of the backbone carbon atom. 

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