Pentacarbonyl(2-ferrocenylpyridine)metal(0) complexes of Group 6 elements. Synthesis and characterization

2-Ferrocenylpyridine (2-Fcpy) was prepared according to the literature procedure. 1,1-Dipyridylferrocene was also obtained as a minor product and characterized by ¹H- and ¹³C-n.m.r. spectroscopy. Prolonged irradiation of Cr(CO)₆ in the presence of 2-Fcpy in n-hexane gave Cr(CO)₅(2-Fcpy) which could not be isolated due to its instability even at low temperature, but was detected in solution by i.r. spectroscopy. The preparation of Mo(CO)₆(2-Fcpy) from direct photolysis of Mo(CO)₅ with 2-Fcpy could not be achieved. However, the reaction of Mo(CO)₅ (THF) with 2-Fcpy gave Mo(CO)₅ (2-Fcpy) which was isolated and characterized by i.r., ¹H- and ¹³C-n.m.r. spectroscopic techniques. W(CO)₅ (2-Fcpy) was prepared by irradiation of W(CO)₆ in the presence of 2-Fcpy in n-hexane. The complex was isolated and characterized by i.r., ¹H-, ¹³C-n.m.r. spectroscopic techniques. W(CO)₅ (2-Fcpy) thus appears to be more stable than the Mo and Cr analogues. The main reason for the general instability of the M(CO)₅ (2-Fcpy) complexes is assigned to the weak -accepting ability of 2-ferrocenylpyridine.