Photoreactivity of Coordinated Phenylhydrazine. Intraligand Excitation of ReCl(CO)3(PhNH-NH2)2

Hydrazine and its derivatives play an important role as ligands in coordination chemistry [1], Hy­ drazine complexes may occur as intermediates in ni­ trogen fixation and related processes [2]. Although a variety of hydrazine complexes are known the electronic spectra and photoreactivity of such com­ pounds have not yet been studied. Owing to its pe­ culiar electronic structure and redox behavior hy­ drazine may participate in diverse electronic transi­ tions. In accord with its ability to disproportionate (3 N2H4 -* 4 NH3 + N2; AH = 336.5 kJ) [3] it is reducing and oxidizing [4]. It follows that lowenergy LMCT (ligand-to-metal charge transfer) and MLCT (metal-to-ligand charge transfer) transitions are feasible. Moreover, IL (intraligand) transitions of the coordinated hydrazine may also occur. Fi­ nally, regular LF (ligand field) transitions are, of course, affected by hydrazine ligands, too. While complexes with N2H4 as ligand are fre­ quently rather unstable coordination compounds with substituted hydrazines such as PhNH-NH2 do not decompose easily. In addition, owing to the presence of the phenyl group IL ab­ sorptions of PhNH-NH2 should appear at rel­ atively long wavelengths which facilitates the study of its spectroscopy and photochemistry. As a suitable object for the present work we de­ cided to prepare and to investigate the complex ReCl(CO)3(PhNH-NH2)2. Its preparation was not anticipated to be difficult. Other hydrazine com­ plexes of Re(I) such as Re(NCO)(CO)3(P03)N2H4