Bis(cyclopentadienyl)phenylphosphine as Ligand Precursor for Assembling Heteropolymetal Complexes

The dilithium salt of bis(cyclopentadienyl)phenylphosphine has been used as a multidentate ligand to generate unprecedented heteropolymetal arrays via the bimetal precursors [MI(CO)₃]₂[(η⁵-C₅H₄)P(Ph)(η⁵-C₅H₄)] (9, M = Mo; 10, M = W). The trimetal complexes MI(CO)₃[(η⁵-C₅H₄)P(Ph)(η⁵-C₅H₄)](CO)₃MPd(PPh₃)I (14, M = Mo; 15, M = W), obtained by reaction of 9 and 10 with Pd(PPh₃)₄, respectively, have been found to lose PPh₃ converting to the hexametal derivatives {MI(CO)₃[(η⁵-C₅H₄)P(Ph)(η⁵-C₅H₄)](CO)₃MPd}(μ-I₂){PdM(CO)₃[(η⁵-C₅H₄)P(Ph)(η⁵-C₅H₄)](CO)₃MI} (18, M = Mo; 19, M = W). Compound 18 also has been prepared by reaction of 9 with a PPh₃-free zerovalent palladium species such as Pd₂(dba)₃; treatment of 18 with PPh₃ regenerated the trimetal complex 14. The pentametal complex {MoI(CO)₃[(η⁵-C₅H₄)P(Ph)(η⁵-C₅H₄)](CO)₃Mo}Pd{Mo(CO)₃[(η⁵-C₅H₄)P(Ph)(η⁵-C₅H₄)](CO)₃MoI} (22), containing a linear Mo−Pd−Mo array, has been spectroscopically observed by reacting 18 with 1,2-bis(diphenylphosphino)ethane.