3H-Phosphaallenes are accessible
on a new and facile route and
show a fascinating chemical behavior. The thermally induced rearrangement
of Mes*PCC(H)R′ (R′ = tBu, Ad) afforded by C–H activation, isobutene elimination,
and C–C and P–H bond formation bicyclic 1-benzo-dihydrophosphetes
(2) with PC3 heterocycles. DFT calculations
suggest a mechanism with intramolecular nucleophilic aromatic substitution
and replacement of an alkyl group by the nucleophilic α-C atom
of the phosphaallene. These bicycles formed W(CO)5 complexes
(3) or afforded 1,2-dihydrophosphetes with P-bound alkenyl
groups by catalyst-free hydrophosphination of alkynes (4 and 5). The resulting bulky phosphines formed complexes
with IrCp*Cl2, RuCl2, AuCl, or CuO3SCF3. The Ru atom is coordinated by the P atom and a phenyl
group. Irradiation of TripPCC(H)tBu led by the insertion of the central C atom of the PCC
group into the α-C–H bond of an iPr substituent and by C–C
and P–C bond formation to a new isomer of phosphaallenes, 10, which features a strained PC2 heterocycle.
It formed adducts with M(CO)5 (M = Cr, Mo, W) and AuCl
and reacted with SO2Cl2 by cleavage of one of
the phosphirane P–C bonds to yield PC4 or PC5 heterocycles. Hydrolysis yielded a PC5 compound
with a P(O)Cl group.
A family of Pt(II) complexes bearing
monoanionic C^N^N ligands
as luminophoric units as well as a set of monodentate ligands derived
from allenylidene and carbene species were synthesized and characterized
in terms of structure and photophysical properties. In addition, we
present the extraordinary molecular structure of a phosphorescent
complex carrying an allenylidene ligand. Depending on the co-ligand,
an effect can be observed in the photoluminescence lifetimes and quantum
yields as well as in the radiative and radiation less deactivation
rate constants. Their correlation with the substitution pattern was
analyzed by comparing the photoluminescence in fluid solution at room
temperature and in frozen glassy matrices at 77 K. Moreover, in order
to gain a deeper understanding of the electronic states responsible
for the optical properties, density functional theory calculations
were performed. Finally, the cytotoxicity of the complexes was evaluated in vitro, showing that the cationic complexes exhibit strong
effects at low micromolar concentrations. The calculated half-maximum
effective concentrations (EC50 values) were 4 times lower
in comparison to the established antitumor agent oxaliplatin. In contrast,
the neutral species are less toxic, rendering them as potential bioimaging
agents.
Hydroalumination of the dialkynylgermane Ph2Ge(C≡CtBu)2 (1) and the digermanes Phn(tBuC≡C)3–nGe–Ge(C≡CtBu)3–nPhn (2a: n = 2; 2b: n = 1) with two equivalents of H–AltBu2 or H–AlEt2 yielded the mixed Al/Ge compounds Ph2Ge[C(AltBu2)=CH‐tBu]2 (3), [Ph2GeC(AltBu2)=CH‐tBu]2 (4a), and [Ph2GeC(AlEt2)=CH‐tBu]2 (4b). Reactions of 2b with both aluminum hydrides afforded inseparable mixtures of products. 3 reacted with heterocumulenes by retrohydroalumination. Phenyl isocyanate gave insertion of the C=N group into the resulting Ge–C(≡C–tBu) bond (5), whereas the NCS and NCN groups of phenyl isothiocyanate and a carbodiimide inserted into Al–Cvinyl bonds (6 and 7) with unaffected terminal Ge–C≡C–tBu moieties. The generation of 5 represents the first example of the insertion of a heterocumulene into a Ge–C bond, which may be favored by the activation of the isocyanate group by the Lewis acidic Al atom and the increased polarity of the N=C=O fragment as determined by NBO calculations. The reactions of the digermanes 4 with heterocumulenes were unselective and afforded inseparable mixtures. Treatment of 4a with the azide (4‐tBu)C6H4CH2–N3 led interestingly to reductive coupling of two azide molecules, and the hexazene complex (tBuC6H4CH2N3–N3C6H4tBu)(AltBu2)2 (8) was isolated in moderate yield. Six nitrogen atoms form a dianionic chain, which coordinated two AltBu2 fragments by formation of two joint AlN4 heterocycles.
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