Redox Properties of the Dinitrogen-Cyanamide Complexes trans-[Mo(N2) (NCNR2)(Ph2PCH2CH2PPh2)2]

Abstract

The electrochemical behaviour, as studied by cyclic voltammetry and controlled potential electrolysis, of the dinitrogen-organocyanamide complexes tram-[Mo(N 2)(NCNR 2)(dppe) 2 ] (1, R = Me; 2, R = Et; dppe = Ph 2 PCH 2 CH 2 PPh 2) is reported, and the electrochemical P L ligand parameter for the cyanamides is estimated showing that they behave as effective net electron-donors with a remarkable stabilizing influence on the coordination of dinitrogen.

Electron-donor/acceptor properties of carbynes, carbenes, vinylidenes, allenylidenes and alkynyls as measured by electrochemical ligand parameters

“…A dependence on the binding metal center has been also recognized for isocyanides [27,31,32,42] and related unsaturated ligands such as cyanide [46], nitriles [34], cyanamides [33,[51][52][53] and possibly vinylidenes, as discussed above, and has been interpreted mainly on the basis of p-effects.…”

“…Other indirect methods for the estimate of E s , b and/or P L have been used for certain types of 18-electron complexes, such as [M s LL 0 ] [31][32][33] and [M s L n ] [5,13] Values of the P L and E L parameters for selected ligands are shown in Table 2 [14,18,21,27,[29][30][31][32][33][34]36,[41][42][43][44][45][46][47][48][49][50][51][52][53][54], whereas E s , b and S M , I M parameters are listed in Tables 3 [5,14,27,30,[32][33][34][35]42,[44][45][46][47]49,55,56] and 4 [18,19,…”

“…Although the ligand parameters P L and E L were initially considered to be independent of the binding metal center, it has later been recognized, in some situations, the influence of the latter, namely for isocyanides [27,31,32,42] and cyanide [46] (Table 2), nitriles [34] and cyanamides [33,[51][52][53]. Hence, at an electron-rich site such as trans-{ReCl(dppe) 2 } (E s = 0.68 V) with a high p-electron releasing character, the isocyanides are quite effective p-acceptors [57], present a bent geometry at N [58] (form a with a carbene character) and have P L values ca.…”