Jianguo Yin

Clusters containing ynamine ligands. 4. The synthesis and characterizations of ReMn(CO)8 [?-MeC2NMe2] and ReMn(CO)7 [?-MeCC(NMe2)C(NMe2)CMe] and the development of a bonding model for the coordination of ynamines to M2(CO)8 clusters

The compound ReMn(CO)8 (μ-MeC2NMe2),2 was obtained in 11% yield by the decarbonylation of ReMn(CO)10 with Me3NO followed by reaction MeC2NMe2. Compound2 will add one equivalent of MeC2NMe2 at 25°C to yield the mixed metal complex ReMn(CO)7 [μ-C(Me) C(NMe2) C(NMe2) C(Me)],3 in 7% yield. Compounds2 and3 were characterized by IR,1H NMR, and single crystal x-ray diffraction analyses. Compound2 exists as two isomers. Each isomer contains an asymmetric bridging ynamine ligand. The principal isomer has the amine-substituted carbon atom coordinated to the manganese atom. The minor isomer has the amine-substituted carbon atom coordinated to the rhenium atom. In compound3 the two ynamines have been coupled in a head-to-head fashion to produce a ferrole-like structure in which the coupled ligands are π-bonded to the manganese atom. Extended Hückel molecular orbital calculations were performed on the parent complex Re2(CO)8 (μ-MeC2NMe2),1 to try to understand the reasons for the preferred asymmetric coordination of the ynamine ligand in1 and2. It was found that the asymmetric coordination permits a strong stabilizing interaction between the one of the π* orbitals of the ligand and the metallic orbital that is principally responsible for the formation of the metal-metal bond. Crystal Data: for2: space group=P21/c,a=9.740(1)Å,b=11.293(2)Å,c=15.483(3)Å, β=97.46(1)°,Z=4, 1876 reflections,R=0.026; for3: space group=Pca21,a=17.541(2)Å,b=8.441(1)Å,c=14.033(3)Å,Z=4, 1335 reflections,R=0.022.