11106-18-6Relevant articles and documents
Molecular spectroscopy of uranium(IV) bis(ketimido) complexes. Rare observation of resonance-enhanced Raman scattering from organoactinide complexes and evidence for broken-symmetry excited states
Da Re, Ryan E.,Jantunen, Kimberly C.,Golden, Jeffrey T.,Kiplinger, Jaqueline L.,Morris, David E.
, p. 682 - 689 (2005)
Electronic absorption and resonance-enhanced Raman spectra for ketimido (azavinylidene) complexes of tetravalent uranium, (C5Me 5)2U[-N=C(Ph)(R)]2 (R = Ph, Me, and CH 2Ph), have been recorded. The absorption spectra exhibit four broad bands between 13 000 and 24 000 cm-1. The highest-energy band is assigned to the ketimido-localized p⊥(N)→π*(N=C) transition based on comparison to the spectra of (C5H 5)2Zr[-N=CPh2]2 and (C 5Me5)2Th[-N=CPh2]2. Upon excitation into any of these four absorption bands, the (C5Me 5)2U[-N=C(Ph)(R)]2 complexes exhibit resonance enhancement for several Raman bands attributable to vibrations of the ketimido ligands. Raman bands for both the symmetric and nominally asymmetric N=C stretching bands are resonantly enhanced upon excitation into the p ⊥(N)→π*-(N=C) absorption bands, indicating that the excited state is localized on a single ketimido ligand. Raman excitation profiles for (C5Me5)2U[-N=CPh2] 2 confirm that at least one of the lower-energy electronic absorption bands (Emax ～ 16300 cm-1) is a charge-transfer transition between the U(IV) center and the ketimido ligand(s). The observations of both charge-transfer transitions and resonance enhancement of Raman vibrational bands are exceedingly rare for tetravalent actinide complexes and reflect the strong bonding interactions between the uranium 5f/6d orbitals and those on the ketimido ligands.
Reactions of 1,4- and 2,3-diazadienes with titanocene and zirconocene complexes of bis(trimethylsilyl)-acetylene: Acetylene coupling or substitution including subsequent C-H activation, C-C coupling, and N-N cleavage to heterobimetallic complexes
Zippel, Thorsten,Arndt, Perdita,Ohff, Andreas,Spannenberg, Anke,Kempe, Rhett,Rosenthal, Uwe
, p. 4429 - 4437 (2008/10/08)
The reaction of 1,4-diazadienes RN=CHCH=NR with the titanocene and zirconocene complexes of bis(trimethylsilyl)acetylene Cp2M(L)(η2-Me3SiC2SiMe 3) (M = Ti, without L (1); M = Zr, L = THF (2), pyridine (3)) is a general and new method to obtain 1-metalla-2,5-diazacyclopent-3-ene complexes Cp2M(η2-1:4-RNCH=CHNR) (M = Zr, R = 2,6-iPr2C6H3 (4a), 4-Me-C6H4 (4b), Cy (4c); M = Ti, R = 2,6-iPr2C6H3 (5a), 4-Me-C6H4 (5b), Cy (5c)). In the analogous reaction with differently substituted azines RR′C=NN=CRR′ the products depend strongly on the metals used, Zr and Ti, as well as on the substituents R and R′. With R = R′ -Me and M = Ti, a substitution of the alkyne by the azine and a subsequent CH activation to the 1-titana-2,3-diazacyclopent-3-ene species 6 was observed. Using R = Ph and R′ = H the acetylene was also substituted and, by a reductive coupling of two azine molecules, the paramagnetic binuclear Ti(III) complex (Cp2Ti)2[μ-(η 4-2:3,6:7-PhHC=NNCHPhCHPhNN= CHPh) (7) was formed. With M = Zr and R = Ph and R′ = H no substitution of the acetylene was observed, but one of the C=N double bonds of the azine inserts into the Zr-C bond of the zirconacyclopropene moiety of the starting acetylene complex to yield the 1-zircona-2-azacyclopent-4-ene species 8, which is additionally stabilized by N-coordination of the second imino group as a substituent in α position to the metal. Using R = R′ = Ph, the central N-N single bond of the azine is cleaved by both of the metals and the bis(imido) complexes Cp2M(-N=CPh2)2 (M = Zr (9), Ti (10)) were isolated. The central C-C bond of 7 is cleaved in a subsequent reaction with CpCo(C2H4)2 and, after an activation of the N-N bond of the azine, the heterobimetallic complex (Cp2Ti)(μ-N=CHPh)2(CpCo) (11) was formed. In the reaction of benzaldehyde azine with CpCo(C2H4)2 the isoelectronic homobimetallic bis-(alkylideneamido) complex (CpCo)(μ-N=CHPh)2(CpCo) (12) was prepared. In reactions of 9 and 10 with CpCo(C2H4)2 heterobimetallic complexes of this type analogous to complex 11 were not obtained. All new complexes have been characterized by spectroscopic methods, and additionally, 4a, 7, 8, 10, 11, and 12 were characterized by single-crystal X-ray structure analysis.
