Heating Tp′Pt(Ph)(η 2 -CH 2 dCH 2 ) (5) in benzene forms an ortho-metalated phenethyl hydrido platinum-(IV) complex, Tp′Pt(CH 2 CH 2 -o-C 6 H 4 )(H) (7). Presumably this net reaction reflects phenyl migration to ethylene to give the insertion product, Tp′PtCH 2 CH 2 Ph, as an unsaturated intermediate. Intramolecular C-H activation of an ortho phenyl proton from this intermediate would produce the metallacyle product. Low-temperature protonation of the phenyl ethylene complex 5 results in the formation of a cationic 6). Low-temperature protonation of the ortho-metalated phenethyl complex 7 followed by addition of acetonitrile leads to reductive coupling of the Pt-H and the alkyl methylene group to give a cationic Pt(II) 2-ethylphenyl complex, [κ 2 -(HTp′)-Pt(C 6 H 4 -2-CH 2 CH 3 )(NCCH 3 )][BAr′ 4 ] (9). Complex 7 has also been isolated as the sole product of gentle heating of Tp′Pt(Me) 2 (H) (2) with the Lewis acid B(C 6 F 5 ) 3 in ethylbenzene. Additional analogous Pt(IV) metallacycles, Tp′Pt(CH 2 CH(Me)-o-C 6 H 4 )(H) (11a/11b) and Tp′Pt(CH 2 CH 2 -o-C 6 H 3 Et)(H) (13), have also been synthesized by this route. Note that heating of the dihydride reagent Tp′Pt(Me)(H) 2 (3) with B(C 6 F 5 ) 3 in either ethylbenzene or 2-propylbenzene gave only Tp′Pt(Ar)(H) 2 (14 and 15) products. Attempts to isolate an η 2 -propylene phenyl complex were unsuccessful; formation of the 1,2-insertion product, Tp′Pt(CH(Me)CH 2 -o-C 6 H 4 )(H) (10), and 2,1-insertion products, 11a and 11b, resulted. An in situ attempt to isolate the cationic [κ 2 -(HTp′)Pt(C 6 H 5 )(η 2 -CH 2 dCH(CH 3 ))][BF 4 ] resulted in the isolation of the Pt(II) phenyl aqua complex [κ 2 -(HTp′)Pt(C 6 H 5 )(OH 2 )][BF 4 ] (12) instead.
Gentle heating of Tp‘PtMe2H (1) in alkane solvents in the presence of B(C6F5)3 results in C−H activation
of the alkane solvent, R−H, to give Tp‘Pt(Me)(H)(R) intermediates. Further heating leads to formation
of Tp‘Pt(η
2
-olefin)(H) complexes via methane elimination followed by β-hydride elimination, a
stoichiometric alkane to olefin conversion.
To investigate soap formation in
drying oils in historic paints,
the reaction between metal acetates (K
+
, Zn
2+
, Pb
2+
) and ethyl linoleate (EL) was studied using optical
microscopy, X-ray powder diffraction, and electron microscopy. Pb(II)
and Zn(II) react rapidly with EL to form highly structured, spherulitic,
luminescent crystallites that aggregate. Evidence from Fourier transform
infrared (FTIR) and scanning electron microscopy/energy dispersive
X-ray analysis and high-resolution synchrotron powder X-ray diffraction
indicates that these are organic–inorganic hybrid complexes
or coordination polymers. FTIR absorbance peaks at ca. 1540 cm
–1
for Pb(II) and ca. 1580 cm
–1
for
Zn(II) are consistent with the formation of carboxylate complexes.
The complexes formed offer insight into the degradation processes
observed in oil paint films, suggesting that soap formation is rapid
when metal ions are solubilized and can occur with unsaturated fatty
acids that are present in fresh oils. These complexes may account
for the atypical luminescence observed in lead-containing cured oil
paint films.
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