94294-83-4Relevant articles and documents
Insertion of CO2-like molecules into zirconium-carbon bonds: Reactivity of dialkylbis(cyclopentadienyl)zirconium(IV) with diphenylketene, aryl isocyanates, and p -tolylcarbodiimide
Gambarotta,Strologo,Floriani,Chiesi-Villa,Guastini
, p. 654 - 660 (2008/10/08)
Diphenylketene, aryl isocyanates, and p-tolylcarbodiimide insert into Zr-C bonds of (cp)2ZrR2 (cp = η5-C5H5; R = Me (I), PhCH2 (II), Ph (III)). The insertion of the >C=O unit of diphenylketene into the Zr-R bond gives {(cp)2Zr(R)[O-C(R)=CPh2]} complexes (II), which, because of the presence of a vacant coordination site on the metal, add a further molecule of diphenylketene to form {(cp)2Zr[O-C(R)=CPh2]2}. The structures of both kinds of complexes were confirmed by an X-ray analysis on {(cp)2Zr(Me)[O-C(Me)=CPh2]} (IV) and {(cp)2Zr[O-C(Me)=CPh2]2} (V). The vinyl-oxo ligand has normal structure characteristics, and the C=C bond does not interact with the metal. Reaction of isocyanates (ArNCO) with complexes (I-III) led to the formation of an imido ligand bonding the metal in a bidentate fashion, {(cp)2Zr(R)[O..-C(R)..-NAr]}. The X-ray analysis on {(cp)2Zr(Me)[O..-C(Me)..-NPh]} (VIII) is reported. The insertion of a second molecule of ArNCO is prevented by the absence of a free coordination site on the metal in complexes VI-VIII. Analogous results have been obtained by reacting complexes I-III with p-tolylcarbodiimide, as shown by the isolation of {(cp)2Zr(R)[p-MeC6H4N..-C(R).. -NC6H4Me-p]} (XI). Insertion of the CO2-like molecule into the Zr-R bond occurs according to the following sequence: Me > Ph >> PhCH2. Moreover, the occurrence of the reaction does strongly depend on the nature of the heterocumulene in the order Ph2C=C=O > PhN=C=O > p-MeC6H4N=C=CNC6H4Me-p >> CO2. This order suggests that an important factor determining the insertion of the CO2-like molecule can be polarization of the cumulene structure, thus making carbon dioxide the most difficult to insert. Crystallographic details for {(cp)2Zr(Me)[O-C(Me)=CPh2]}: space group Pca21 (orthorhombic); a = 25.814 (6), b = 8.646 (2), c = 9.851 (6) A?; V = 2198.6 (9) A?3; Z = 4; Dcalcd = 1.35 g cm-3. The final R factor was 0.033 for 1792 observed reflections. Crystallographic details for {(cp)2Zr[O-C(Me)=CPh2]2}: space group P1 (triclinic); a = 15.817 (2), b = 18.705 (3), c = 12.965 (2) A?; α = 104.81 (2), β = 98.16 (2), γ = 113.98 (2)°; V = 3254.3 (8) A?3; Z = 4; Dcalcd = 1.31 g cm-3. The final R factor was 0.051 for 4693 observed reflections. Crystallographic details for {(cp)2Zr(Me)[O..-C(Me)..-NPh]}: space group P21/n* (monoclinic); a = 11.582 (2), b = 12.039 (2), c = 12.243 (2) A?; β = 95.73 (2)°; V = 1698.6 (5) A?3; Z = 4; Dcalcd = 1.45 g cm-3. The final R factor was 0.041 for 2238 observed reflections.
