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The W(IV) bis(dithiocarbamate) complexes W(S)(PhC=CPh)(S2Cm)2 (R = CH3, C2H5) lose one sulfur atom when treated with an equivalent of triethylphosphine at -78 O C . The products W(S)(PhC= CPh)(SCN€Q(S2CN&) contain a thiocarboxamido ligand in place of one dithiocarbamate. The molecular structure of the ethyl derivative was determined by a single-crystal X-ray diffraction study (monoclinic, B1/a; a = 16.927 (6) A, b = 9.951 (3) A, c = 17.669 (6) A, j3 = 118.49 (3)O, and 2 = 4; R = 0.078 and R, = 0.064 for 1962 reflections with I > 341)). The carbenoid carbon of the thiocarboxamido ligand lies cis to the alkyne ligand in the plane defined by the metal-alkyne triangle. The orientation of the s2-SCNEt, fragment allows the unique p orbital of the three-coordinate carbon to overlap with the lone filled d.rr orbital of the roughly octahedral d2 tungsten(1V) ion. A dynamic process equilibrates the two dithiocarbamate alkyl substituents on the NMR time scale with an activation barrier of 15.9 kcal/mol. We suggest that this process is promoted by dechelation of the q2-thiocarboxamido sulfur to generate a fluxional five-coordinate intermediate.

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Kontinuierliche und Blitzliehtphotolyse in aprotischen Lösungsmitteln zeigen eine photochemische Disproportionierung der Titelverbindung unter Bildung des Fe(II)‐ und eines Fe(IV)‐Ferryl‐tetraphenylporphin‐Kom‐ I28 plexes, eines starken Oxidationsmittels.