Preparation of Multinuclear Complexes by a Ring-Opening Reaction of a Highly Strained Cyclic Ferrocene Unit and Their Reactivity

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In this project, PhP-bridged [1] ferrocenophane (1) was utilized as a ligand having functionality for construction of multinuclear framework, because a single-atom-bridged [1] ferrocenophane readily undergoes a ring-opening reaction owing to its highly strained ring structure.When 1 or its sulfuriezed derivative is irradiated by UV-V is light in THF or CH_3CN, ring-opening polymerization takes place to give a polyferrocene derivative and trimers and dimers both of which have macrocyclic structures. A reaction mechanism was investigated for this ring-opening reaction, and was proposed as follows. 1), irradiation of 1 gives a ring-slipped product (2) in which one of the two Cp rings changes its coordination mode from n^5 to n^1. 2), the n^1-Cp of 2 attacks an iron center of another 2. 3), a ferrocene unit is reproduced and the n^1-Cp originally on the iron center of the letter 2 is expelled from the iron center. 4), a polyferrocene framework is propagated by repetition of the steps 1-3.A reaction of Pt(PMe_3)_4 with 1 coordinating to CpMn(CO)_2 and W(CO)_5 fragments gives heterodinuclear complexes (actually they are triangular complexes if an iron center of a ferrocene unit is included), in which a Pt(Pme_3)_2 fragment is inserted into a P-Cp bond of 1 to form P-Pt and N^1-C_5H_4-Pt bounds with a u-PPhFc bridge (u-PPhFc=u-PPh(C_5H_4FeC_5H_4)). X-ray analyses showed that the products are Cp(CO)_2Mn(u-PPhFc)Pt(Pme_3)_2 and(CO)_%W(uPPhFc)Pt(Pme_3)_2, respectively. Upon a similar reaction employing Pt(PPh_3)_4 in place of Pt(Pme_3)_4, CpMn(CO)\2(1) gives Cp(CO)Mn(u-CO)(u-PPhFc)Pt(PPh_3), whereas W(CO)_5(1) gives (CO)_4W(u-PPh_2)(u-PPh(C_5H_4FeC_5H_4H_4Ph))Pt(PPh_3), in which cleavage of a P-Ph bond of PPh_3 and migration of the Ph group to a ferrocene moiety take place.