Titanium-Promoted Synthesis of a Carbohydrazido Ligand from Carbon Monoxide and Diphenyldiazomethane: Diazoalkane Coordination and Activation by Dicyclopentadienyltitanium(II) and -vanadium(II) Complexes

Article abstract of DOI:10.1021/ja00371a021

Vanadocene, Cp2V (Cp = η⁵-C5H5), react with diethyl diazomalonate, DEDM, and diphenyldiazomethane, DPDM, giving complexes in which the diazo unit is η²-N,N bonded to metal.Titanocene dicarbonyl, Cp2Ti(CO)2, reacts with DEDM by losing carbon monoxide and giving , in which the diazo ligand is η³-N,N,O bonded to the metal through both nitrogen atoms and one oxygen of the ester groups.The complex has been spectroscopically and structurally characterized.Some relevant metrical parameters are as follows: Ti-N(1) = 1.980(5) Angstroem; Ti-N(2) = 2.219(7) Angstroem, Ti-O(1) = 2.247(4) Angstroem; C(12)-O(1) = 1.272(7) Angstroem, N(1)-N(2) = 1.214 Angstroem.This trend in both distances suggests that the complex can be partially described as resulting from the 1,4 addition of the Cp2Ti carbene-like unit to the EtOC(=O)C(-N=N)COOEt diene-like structure.When the diazoalkane does not contain substituents having donor atoms, the Cp2Ti unit promotes the reaction of CO with two diazoalkane molecules to produce a carbohydrazido ligand.When Cp2Ti(CO)2 was reacted with Ph2CN2, a trinuclear mixed valence titanium(III)-titanium(IV) complex was isolated, <(Cp2Ti)3(Ph2CN2C(O)N2CPh2)2>, which contains two unpaired electrons per unit.Three Cp2Ti units are bridged by two *C(O)N^*-N=CPh2>^2- ligands.Each ligand chelates a Cp2Ti unit by using three N^* atoms, while oxygen is engaged in bonding to the third Cp2Ti unit.Some relevant structural parameters are as follows: Ti(2)-N(1) = 2.222(5) Angstroem; Ti(2)-N(2) = 2.210(4) Angstroem; N(1)-C(17) = 1.355(8) Angstroem; N(2)-C(17) = 1.351(8) Angstroem; N(1)-N(3) = 1,375(8) Angstroem; N(2)-N(4) = 1.394(8) Angstroem; C(17)-O(1) = 1.299(7) Angstroem; Ti(1)-O(1) = 1.930(4) Angstroem.C-N^* and C-O bond distances show complete electron delocalization over the N2CO unit bonding the two different titanium atoms.This is confirmed by the absence of any CO band above 1600 cm^-1 in the IR spectrum.Crystallographic details for : space group I4^1/a (tetragonal); a = 31.369(3) Angstroem; c = 7.760(1) Angstroem; Z = 16.The final R factor was 0.049 for 1551 observed reflections.Crystallographic details for <(Cp2Ti)3(Ph2CN2C(O)N2CPh2)2>*3C7H8: space group P2¹2¹2¹ (orthorhombic); a = 27.667(2) Angstroem; b = 13.462(1) Angstroem; c = 11.846(1) Angstroem; Z = 2.The final R factor was 0.071 for 3301 observed reflections.