The complex Cp*Rh(PMe3)H2 (Cp* = C5Me5) reacts with C6F6, C6F5H, C12F10, or C10F8 in pyridine or 1:1 pyridine/benzene to give the C−F cleavage products Cp*Rh(PMe3)(arylF)H in high yield. Kinetic studies reveal that the reaction has autocatalytic character, and fluoride ion is shown to be responsible for the catalysis. The anion [Cp*Rh(PMe3)H]- reacts rapidly with C12F10 or C10F8 to give the same C−F cleavage products as Cp*Rh(PMe3)H2. A mechanism initiated by deprotonation of Cp*Rh(PMe3)H2 followed by nucleophilic attack of the resulting anion on the polyfluoroaromatic with subsequent loss of fluoride is proposed. The fluoride ion continues the cycle by deprotonating Cp*Rh(PMe3)H2.

The complexes Pt(PEt3)3 and Pd(PEt3)3 cleave the C−C bond of biphenylene to give (PEt3)2Pt(2,2‘-biphenyl), 1, and (PEt3)2Pd(2,2‘-biphenyl), respectively. Heating (PEt3)2Pt(2,2‘-biphenyl) in the presence of biphenylene leads to C−C cleavage of a second biphenylene to give (PEt3)2Pt(2,2‘-tetraphenyl), 2, via a Pt(IV) intermediate. 2 reductively eliminates tetraphenylene at 115 °C. At 120 °C the reaction is catalytic; Pt(PEt3)3 or 1 converts biphenylene to tetraphenylene. The intermediates in the catalytic cycle have been identified, and 1 and 2 have been characterized by X-ray analysis. Under catalytic conditions 1 and 2 approach steady-state concentrations. Kinetic analysis reveals that the steady-state concentration ratio, resting state species, and overall rate of catalysis, k obs, depend on the ratio of biphenylene to PEt3. This observation is consistent with loss of PEt3 from 1, resulting in the 14-electron species (PEt3)Pt(2,2‘-biphenyl), I. At 130 °C, I coordinates to PEt3 approximately 130 times faster than it activates the C−C bond of biphenylene. The complex (depe)Pt(2,2‘-biphenyl), 7 (depe = bis(diethylphosphino)ethane), does not cleave the C−C bond of biphenylene. Compound 2 is also capable of activating the C−H bonds of benzene and biphenylene to give trans-(PEt3)2Pt(α-biphenyl)(phenyl), 5, and trans-(PEt3)2Pt(α-biphenyl)(α-biphenylenyl), 6, respectively. Compounds 5 and 6 have been characterized by X-ray analysis. Substitution of Pd for Pt results in more rapid catalysis; (PEt3)2Pd(2,2‘-biphenyl) is a very efficient catalyst (20 turnovers/h at 120 °C).

The zirconium hydride dimer [Cp2ZrH2]2 reacts with C6F6 at ambient temperature to give Cp2Zr(C6F5)F as the major product along with Cp2ZrF2, C6F5H and H2. Neither the reaction rate nor the product ratio is affected by changes in H2 pressure or the concentration of C6F6. The reaction follows zero-order kinetics. The new compound Cp2Zr(C6F5)F has been structurally characterized. [Cp2ZrH2]2 reacts with C6F5H to give Cp2Zr(p-C6F4H)F, Cp2ZrF2, C6F4H2, and H2. The zirconium hydride Cp3ZrH has been structurally characterized and also reacts with C6F6. The products of the reaction are CpH, Cp2Zr(C6F5)F, C6F5H, Cp2ZrF2, Cp4Zr, and Cp3ZrF. The reaction rate is first order in [Cp3ZrH] and [C6F6], but the product ratio is unaffected by the concentration of C6F6. Possible mechanisms of these reactions are discussed.

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The nickel alkyne complexes (dippe)Ni(PhCtCPh), 1, (dippe)Ni(MeCtCMe), 2, (dippe)-Ni(MeO 2 CCtCCO 2 Me), 3, (dippe)Ni(CH 3 OCH 2 CtCCH 2 OCH 3 ), 4, and (dippe)Ni(CF 3 CtCCF 3 ), 5, were synthesized (dippe ) bis(diisopropylphosphino)ethane) and characterized by 1 H, 31 P, and 13 C{ 1 H} NMR spectroscopy. Complexes 1, 2, and 3 were characterized by X-ray crystallography. The thermolysis of complex 1 or 2 (120 °C) in the presence of excess biphenylene and excess alkyne results in very slow catalytic formation of the corresponding 9,10-disubstituted phenanthrene. However, addition of ∼6 mol % O 2 (based on the metal complex) to the reaction mixture results in an acceleration in catalysis at lower temperatures (∼70-80 °C). The thermolysis of complexes 3 or 4 with excess biphenylene and excess alkyne leads to the alkyne cyclotrimerization product as the major organic species formed in the reaction. Fluorenone was catalytically produced by heating (dippe)Ni(CO) 2 , biphenylene, and CO. Catalytic insertion of 2,6-xylylisocyanide into the strained C-C bond of biphenylene was also achieved by heating (dippe)Ni(2,6-xylylisocyanide) 2 , excess biphenylene, and 2,6xylylisocyanide. Mechanistic schemes are proposed for these reactions.