Synthesis and Characterization of Cluster Complexes Containing Iminium Ion Ligands. The Crystal and Molecular Structures of Two Isomers of Os₃(CO)₇(M-CNMe₂)(H₂CNMe₂)(μ-SPh)(μ-H)

The reaction of CH₂(NMe₂)2 with the cluster complex Os₃(CO)8(M-CNMe₂)(μ-SPh)0u'H)₂(3) in refluxing heptane has yielded two isomeric products with the formula Os₃(CO)₇(μ-CNMe₂) (M-H₂CNMe₂) (≡-SPh)(m-h)(4, 37% yield, and 5, 27% yield). Both products were characterized by IR and^XH NMR spectroscopies and by single-crystal X-ray diffraction analyses. For 4: space group P2i/c, a = 9.986 (1) A, b = 24.909 (5) A, c = 10.027 (1) A; 0 = 97.81 (1)°; Z = 4. The structure of 4 was solved by direct methods (MULTAN) and was refined with 3030 reflections to the final values of the residuals R = 0.038 and R_w= 0.042. The structure consists of a triangular cluster of three metal atoms and is very similar to the parent compound 3 except that it contains an iminium H₂CNMe₂⁺ ligand bridging one edge of the cluster with the carbon and nitrogen atoms bonded to different metal atoms. The C-N distance at 1.50 (2) A is slightly longer than a C-N single bond distance. For 5: space group PI, a = 13.509 (2) A, b = 12.075 (3) A, c = 9.925 (2) A; a - 102.18 (2)°, (3 = 103.39 (1)°, y = 94.89 (2)°; Z = 2. The structure was solved by a combination of Patterson and difference Fourier methods and was refined with 3581 reflections to the final values of the residuals R = 0.049 and R_w= 0.058. The structure of 5 is similar to 4 except that thet^{12 3 4 5 6 7 8 910}-iminium ligand is coordinated to only one metal atom. in this case the C-N distance (1.42 (2) A) is slightly shorter than a C-N single bond distance. When refluxed in an octane solution, 5 was converted to 4 in 86% yield. A mechanism for the transformation is proposed and discussed.