Insights into the Metathesis Reaction Involving M−M, C−C, and M−C Triple Bonds from Computations Employing Density Functional Theory on Model Compounds M₂(OH)₆ and M₂(SH)₆, Where M = Mo and W

Abstract

Calculations employing density functional theory (Gaussian 98, B3LYP, LANL2DZ, 6-31G) have been undertaken to interrogate the factors influencing the metathesis reaction involving M-M, C-C, and M-C triple bonds for the model compounds M(2)(EH)(6), M(2)(EH)(6)(mu-C(2)H(2)), and [(HE)(3)M(tbd1;CH)](2), where M = Mo, W and E = O, S. Whereas in all cases the ethyne adducts are predicted to be enthalpically favored in the reactions between M(2)(EH)(6) compounds and ethyne, only when M = W and E = O is the alkylidyne product [(HO)(3)W(tbd1;CH)](2) predicted to be more stable than the alkyne adduct. For the reaction M(2)(EH)(6)(mu-C(2)H(2)) --> [(HE)(3)M(tbd1;CH)](2), the deltaG degrees values (kcal mol(-)(1)) are -6 (M = W, E = O), +5 (M = Mo, E = O), +18 (M = W, E = S), and +21 (M = Mo, E = S) and the free energies of activation are calculated to be deltaG() = +19 kcal mol(-)(1) (M = W, E = O) and +34 kcal mol(-)(1) (M = Mo, E = O), where the transition state involves an asymmetric bridged structure M(2)(OH)(4)(mu-OH)(2)(CH)(mu-CH) in which the C-C bond has broken; C.C = 1.89 and 1.98 A for W and Mo, respectively. These results are discussed in terms of the experimental observations of the reactions involving ethyne and the symmetrically substituted alkynes (RCCR, where R = Me, Et) with M(2)(O(t)()Bu)(6) and M(2)(O(t)()Bu)(2)(S(t)()Bu)(4) compounds, where M = Mo, W.

Amide-Directed Formation of Five-Coordinate Osmium Alkylidenes from Alkynes

“…The donor atoms forming the base are approximately in one plane, whereas the osmium atom is shifted 0.3447(5) Å above this plane toward the apical position. In agreement with other osmium vinylidene compounds, ,, the vinylidene is bound to the metal in a linear fashion with an Os–C(1)–C(2) angle of 180° (crystallographically imposed) and Os–C(1) and C(1)–C(2) bond lengths of 1.798(4) and 1.314(6) Å, respectively. In the 13 C­{ 1 H} NMR spectrum in benzene- d 6 , at room temperature, the carbon atoms of the unsaturated chain display a triplet ( 2 J C–P = 12.1 Hz) at 271.1 (C α ) ppm and a singlet at 111.0 (C β ) ppm.…”

“…In this contest, the reactions summarized in Scheme and eq are certainly notable because they prove that the five-coordinate osmium alkenylidene complexes 2 and 4 are intermediate species in the osmium-mediated rupture of the carbon–carbon triple bond of N -phenylhexen-5-ynamide and N -(phenyl-4-yn-1-yl)­benzamide, respectively, under mild conditions. Previously achieved homogeneous metal-mediated cleavages of the alkyne triple bond have been performed under drastic conditions by means of metathesis reactions, which imply M–M, C–C, and M–C triple bonds . A number of metal-mediated cleavages that involved water and propargyl rearrangement have been also reported, in addition to strategies involving the transformation of the alkyne into other functionalities…”

Prediction of fluorophilicity of organic and transition metal compounds using molecular surface areas

“…In this case, some experimental data is Table 1, this was used throughout as the MM method, while three different basis sets with the widely used B3LYP functional were tested for the central QM region. Table 3 contains comparison of selected geometrical and surface area properties, from which it is evident that Lanl2DZ provides adequate agreement with experimental geometries, in agreement with myriad studies of transition metal complexes [25]. It is also apparent that the larger SDD ECP/basis set, or the polarized, all electron 3-21G* basis set, provide little improvement over Lanl2DZ.…”

20 Organometallic chemistry of bi- and poly-nuclear complexes

“…20 The interest in metathesis catalysts has led to a number of reports featuring unsaturated hydrocarbon ligands bonded to high-oxidation state W 2 moieties. [21][22][23][24][25][26] The third order NLO properties of a variety of species such as [Mo 2 (OPr…”