Synthesis and redox properties of the cycloheptatrienylmolybdenum complexes [MoX(N–N)(η-C7H7)]z+, (N–N=2,2′-bipyridine or 1,4-But2-1,3-diazabutadiene; z=0, X=Br or Me; z=1, X=NCMe, CNBut or CO)

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

“…Most of them have been obtained in this work from the quoted oxidation potential of their complexes commonly with the {M(CO) 5 } (M = Cr, Mo, W) metal center [5,30,[35][36][37][77][78][79][80][81], but, in the case of the cyclic oxocarbene CCH 2 CH 2 CH 2 O, the available complex has the halfsandwich cycloheptatrienyl {Mo(g 7 -C 7 H 7 )(dppe)} + center [55,56]. P L has been calculated by using either its definition expression (Eq.…”

“…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,…”

“…The Pickett model, initially proposed only to 18-electron six-coordinate octahedral-type complexes, has been extended to open-shell 17-electron [34] and square planar 16-electron [35] complexes, and further extensions to even lower numbers of valence electrons can be anticipated, when the redox potentials of suitable series of complexes will become available. The possibility of being extended to 18-electron half-sandwich g 7 -cycloheptatrienyl complexes has also been shown [55].…”

“…Half-sandwich b {Mo(g 7 -C 7 H 7 )(dppe)} + 1.16 c 1.04 [55], TW c {Mo(g 7 -C 7 H 7 )( t Bu-dab)} + 1.14 0.68 [ dependent on their electronic and structural features [5,6,20,21] such as infra-red data [28,35,53,[59][60][61][62][63], the TolmanÕs electronic parameter (TEP) [64] for phosphines and a computed electronic parameter (CEP) [26] based (as TEP) on the infrared A 1 m(CO) frequency in [NiL(CO) 3 ] (also dependent on the electronic effect of L), the HammettÕs and related constants [23,24,26,42,60,65], the photoelectron binding energies or gas-phase vertical ionization potentials [66], the energy of a metal-to-ligand charge transfer [21] and chemical reactivity [14,43,62,63,67,68]. Ligand coordination criteria have also been proposed [14,15,42,48] on the basis of the electrochemical parameters.…”

“…b Cycloheptatrienyl complexes; t Bu-dab=1,4-t Bu 2 -1,3-diazabutadiene; bipy = 2,2 0 -bipyridine. c E S as the intercept from the plot of E (values taken from[56]) vs. P L (more data points than those in[55]). d Square planar.…”