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Linear, soluble copolymers containing titanium are of interest for use in targets for inertial-confinement fusion (ICF) experiments because the titanium is a useful spectroscopic probe for studying the nuclear fusion process. We have studied the reactions of dichloro- titanocene and diphenyltitanocene with carboxylic acids to determine if these can be used to prepare such polymers. Model reactions of dichlorotitanocene with p-toluic acid show that both mono- and di-carboxylates are formed. We have prepared a soluble titanium-containing copolymer via the reaction of poly(styrene-co-methacrylic acid) with an excess of dichlorotitanocene but attempts to remove the excess molecular titanocene from the copolymer result in crosslinking of the copolymer. Model reactions of benzoic and pivalic acids with diphenyltitanocene demonstrate that monosubstituted carboxylato(phenyl)titanocenes are formed but that these products are stable only at low temperatures and decompose readily at ambient temperature. Proton NMR studies of the reaction of diphenyltitanocene and benzoic acid at −20 °C indicate that this reaction is second order, suggesting that the reaction does not proceed through a benzyne intermediate. © 1997 by John Wiley & Sons, Ltd.

Photochemistry offers a technique to synthesize unique catalysts, control catalytic reactions, and perturb and better understand conventional catalytic cycles. Recent studies in the author's laboratory concerning photoinduced catalysis using mono-, di-, and trinuclear organometallic catalyst precursors are summarized. Specific systems considered here are (M(CO)nL5-n) (M = Fe, Ru; L = PPh; n = 5,4,3), (M3(CO)12) (M = Fe, Ru, Os), (Ru3(CO)g(PPh3)3), and (Co2(CO)6L2) (L = P(n-Bu)3, P(OPh)3) used to effect catalytic chemistry of 1-pentene including isomerization, hydrogenation, and hydrosilation. (Author)

The photocatalyzed isomerization of 1-pentene to trans- and cis-2-pentene by Ru(CO)4PPh3 and Ru3(CO)9(PPh3)3 is reported along with data for Ru3(CO)12, Fe3(CO)12, and Fe(CO)5. The primary photoprocess in Ru(CO)4PPh3 is dissociative loss of CO giving a coordinatively unsaturated species having the same empirical formula Ru3(CO)9(PPh3)3; the trinuclear species undergoes Ru-Ru bond rupture and ultimate declusterification subsequent to photo-excitation giving a quantitative yield of Ru(CO)4PPh3 under CO or Ru(CO)3(PPh3)2 in the presence of PPh3. The crucial result is that the cluster yields a different catalytically active species compared to Ru(CO)4PPh3, since the initial ratio of trans- and cis-2-pentene is different for the two photocatalysts. The photocatalysis and primary photoprocesses suggest that the isomerization from the Ru3(CO)9(PPh3)3 results from an active form of the cluster. By way of contrast, Fe(CO)5 and Fe3(CO)12 yields the same initial ratio of photocatalytic products, implicating a common, mononuclear catalytic species. Since the clusters are good visible absorbers compared to the mononuclear species, photoactivation of cluster catalysis can be effected with low energy visible light.

A styrene-1% divinylbenzene resin whose phenyl rings have been derivatized with --PPh2 groups serves as an 'anchor' for Fe(CO)(n)(n = 3,4) groups; the anchor is the Fe-P bond. The photocatalytic activity of suspensions of the polymer-anchored Fe(CO)(n) has been compared to homogeneous solutions of Fe(CO)(n)(PPh3)(5-n)(n = 5,4,3). 1-Pentene isomerization and reaction with HSiEt3 can be effected with each system. Observed quantum yields for 1-pentene isomerization exceed unity for each catalyst precursor and the initial trans- to cis-2-pentene ratio depends on the catalyst precursor implicating the retention of the triarylphospine groups in the actual catalytically active species. Irradiation of Fe(CO)n(PPh3)(5-n)(n = 4) results in loss of CO, not PPh3, suggesting a photoinert anchor to the Fe(CO)n groups in the polymer systems. These experiments establish the viability of photogenerating catalysts anchored to polymer supports without destruction of the the anchor bond in the photogeneration procedure. (Author)