Isothiocyanato complexes linkage isomerism

An interesting study with BATO compounds concerns the linkage isomerization of coordinated [NCS] in [Tc(NCS)(cdoh)2(cdo)(BMe)] (440). Both a red, N-bond isothiocyanato complex [Tc(NCS)(cdoh)2(cdo)(BMe)] and the brown, S-bond thiocyanato complex [Tc(SCN)(dmg)3(BR)] (441) were isolated from the direct synthesis from [Tc04] . The N-bound (440) was found to be thermodynamically more stable than the S-bound isomer (441) and the conversion was monitored elegantly by spectroscopic methods. The X-ray crystal structure of (440) was determined. The NCS and SCN -substituted analogues exhibited r c N stretch at 2,114-2,124 cm and at 2,055-2,079 cm , respectively. " (Scheme 59). 

Linkage isomerization to the N-bonded isothiocyanato-complex /w j-[Co(acac)2-(NCS)py] was observed to have a half-life of ca. 4 h in chloroform solution. In the solid state linkage isomerization at 341 K has a half-life of ca. 12 h, and this is followed by geometric isomerization with a half-life of ca. 2 days. The latter process is suspected to be catalysed by cobalt(ii). 

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