Redox Properties and Ligand Effects for the Hydrido-Technetium-Dinitrogen, -Carbonyl and -Isocyanide Complexes trans-[TcH(L)(Ph2PCH2CH2PPh2)2] (L = N2, CO or CNR)

Characterization of Coordination Compounds by Electrochemical Parameters

“…Although such a behaviour poses difficulties to the application of this model, the recognition of the failure of Equation (2) in particular cases enables us to propose corrections to the P L values for such cases. This has been recognized for isocyanides, [24,25,34,35] nitriles, [27] cyanamides [26,[47][48][49] and cyanide. [30] A high electron richness of the metal centre and a strong electron release from the trans ligand promote the net π-electron acceptance (or hamper the net electron donation) of the ligand under study, resulting in a positive correction (up to 0.34 V) for its usual P L value.…”

“…0.26 V) or linear (weaker π-acceptors), respectively. For trans-{TcH(dppe) 2 }, with a higher electron richness (E s = 0.34 V), an even greater correction (+0.34 V) [35] is required.…”

“…-0.7 to -0.9 [16] O 2----1.8 [73] [a] Ordered generally from higher to lower Isocyanides show P L values that are spread over a wide range, from +0.2 to -0.4 V ( Table 1): benzoyl isocyanide [30] Ͼ bent isocyanides [24,25,34,35] Ͼ ferricinium isocyanides [38,39] Ͼ phosphonium isocyanides [41] Ն linear isocyanides. [24,25,34,43] Metallo-cyanide adducts and other cyano adducts are quite sensitive to the Lewis acid but are always stronger net electron acceptors than cyanide: CNBF 3 - - [40] Ͼ CN -.…”

“…1.2 [36] Benzoyl isocyanide (CϵNCOPh) 0.20 [30] 0.16 [30] PF 3 0.14 [32] --Aminocarbyne (=CNH 2 + ) 0.09 [31] ca. 1.1 [36] CO 0 [10] 0.99 [13] η 1 -Phosphaalkyne (η 1 -PϵCtBu) -0.04 [33] --N 2 -0.07 [10] --Isocyanides (bent) (CϵNR) [b] -0.07 to -0.18 [24,25,34,35] --Hydrazinium (NH 2 NH 3 + ) --0.80 [57] Ethylene (CH 2 =CH 2 ) --0.76 [13] N-Pyrrolylphosphanes --0.69 to 0.53 [28] PPh n (NC 4 H 4 ) 3-n (n = 0-3) Vinylidenes (=C=CHR) 0 to -0.6 [29,36] 0.7 to 0.2 [36] P(OPh) 3 -0.18 [10] 0.58 [13] η 2 -Allene (η 2 -CH 2 =C=CHPh) -0.21 [31] 0.56 [36] Metallo-dinitriles (NϵC-X-CϵN-ML n-1 ) -0.18 to -0.40 [37] 0.58 to 0.39 [36] Ferricinium isocyanides -0.22 to -0.28 [38,39] 0.55 to 0.50 [36] Nitriles (NϵCR) -0.23 to -0.58 [10,27] 0.49 to 0.33 [13] CϵN-BF 3 --0.24 [30] 0.20 [30] Metallo-cyanides (CϵN-ML n-1 -) -0.25 to -0.61 [30,40] 0.50 to 0.21 [36] Phosphonium isocyanides -0.28 to -0.36 [41] 0.50 to 0.43 [41] Allenylidenes (=C=C=CR 2 ) 0 t o -0.8 [36,42] 0.8 to 0 [36] Me 2 SO (S-coordinated) -0.19 <...>…”

“…(13) E s and β values are known [10,[24][25][26][27][28]34,35,41,43,56,[58][59][60][61] for the following {M s } centres, ordered, within each group, according to decreasing E s values: (a) 16-electron squarepyramidal ones: {FeL(depe) 2 } 2+ (L = CO, NCR), [26] {W(ϵCR)(CO) 2 (dppe)} + , [43] {M(CO) 5 } (M = Cr, Mo, W), [41] {ReL(dppe) 2 } + (L = CO, N 2 , CNR), [5,24,25] {FeX(LL) 2 } + (X = Br, H; LL = depe, dppe), [27,10] {Mo(NO)(dppe) 2 } + , [10] {Mn(CO)(dppm) 2 } + , [58] {ReX(dppe) 2 } (X = CN, NCS, Cl, NCO, N 3 ), [34,59,60] cis{ReCl(dppe) 2 }, [27] {TcH(dppe) 2 }, [35] {MoL(dppe) 2 } (L = CO, N 2 , NCPh), [10] {Mo(N 3 )(dppe) 2 } -; [10] (b) 16-electron half-sandwich ones: {Mo(η 7 -C 7 H 7 )(LL)} + (LL = dppe, tBu 2 -diazabutadiene, bipyridine); [56,61] (c) 15-electron ones: {FeBr(depe) 2 } 2+ , [27] cis-{ReCl(dppe) 2 } + ; [27] (d) 14-electron T-shaped one: {Rh(acac)(CO)}. [28] The electron richness is unfavoured (increase of E s ) by the presence, within {M s }, of ligands (e.g.…”