Antiferromagnetic complexes involving metalmetal bonds III. Synthesis, structure and magnetic properties of heterotrinuclear complexes of the type M(CO)5L (M  Cr, Mo and w) containing [(C5H5CrSCMe3)2S] as unusual antiferromagnetic ligand L

Isostructural heterotrinuclear complexes (C 5 H 5 CrSCMe 3 ) 2 S · M(CO) 5 (II–IV) were isolated from photochemical reactions between the antiferromagnetic complex (C 5 H 5 CrSCMe 3 ) 2 S (I) (with the CrCr bond 2.689 A long and with the exchange parameter −2 J = 430 cm −1 ) and metal hexacarbonyls, M(CO) 6 , where M is Cr, Mo, or W. According to the X-ray structural data on III and IV, complex I plays the role of an unusual antiferromagnetic ligand L bound to M through the sulphide bridge (M–S 2.58(2) A). Its geometry remains practically unaffected by the complex formation (the CrCr bond length in III and IV is 2.73(1) A). The exchange parameter, −2 J (410, 440 and 440 cm −1 in II to IV, respectively), also shifts only insignificantly from that of I, which probably means that indirect exchange via the sulphide bridge in I is of minor importance compared with the direct CrCr exchange. The CrCr bond length may thus be correlated with the observed overall exchange coupling.