A low‐spin and mononuclear vanadium complex, (Menacnac)V(CO)(η2‐P≡C
A low‐spin and mononuclear vanadium complex, (Menacnac)V(CO)(η2‐P≡C
- PAR ID:
- 10303976
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie
- Volume:
- 133
- Issue:
- 46
- ISSN:
- 0044-8249
- Page Range / eLocation ID:
- p. 24616-24622
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract t Bu) (2 ) (Menacnac−=[ArNC(CH3)]2CH, Ar=2,6‐i Pr2C6H3), was prepared upon treatment of the vanadium neopentylidyne complex (Menacnac)V≡Ct Bu(OTf) (1 ) with Na(OCP)(diox)2.5(diox=1,4‐dioxane), while the isoelectronic ate‐complex [Na(15‐crown‐5)]{([ArNC(CH2)]CH[C(CH3)NAr])V(CO)(η2‐P≡Ct Bu)} (4 ), was obtained via the reaction of Na(OCP)(diox)2.5and ([ArNC(CH2)]CH[C(CH3)NAr])V≡Ct Bu(OEt2) (3 ) in the presence of crown‐ether. Computational studies suggest that the P‐atom transfer proceeds by [2+2]‐cycloaddition of the P≡C bond across the V≡Ct Bu moiety, followed by a reductive decarbonylation to form the V−C≡O linkage. The nature of the electronic ground state in diamagnetic complexes,2 and4 , was further investigated both theoretically and experimentally, using a combination of density functional theory (DFT) calculations, UV/Vis and NMR spectroscopies, cyclic voltammetry, X‐ray absorption spectroscopy (XAS) measurements, and comparison of salient bond metrics derived from X‐ray single‐crystal structural characterization. In combination, these data are consistent with a low‐valent vanadium ion in complexes2 and4 . This study represents the first example of a metathesis reaction between the P‐atom of [PCO]−and an alkylidyne ligand. -
Abstract Decarbonylation along with E atom transfer from Na(OCE) (E=P, As) to an isocyanide coordinated to the tetrahedral TiIIcomplex [(Tp
t Bu,Me)TiCl], yielded the [(Tpt Bu,Me)Ti(η3‐ECNAd)] species (Ad=1‐adamantyl, Tpt Bu,Me−=hydrotris(3‐tert ‐butyl‐5‐methylpyrazol‐1‐yl)borate). In the case of E=P, the cyanophosphide ligand displays nucleophilic reactivity toward Al(CH3)3; moreover, its bent geometry hints to a reduced Ad−NCP3−resonance contributor. The analogous and rarer mono‐substituted cyanoarsenide ligand, Ad−NCAs3−, shows the same unprecedented coordination mode but with shortening of the N=C bond. As opposed to TiII, VIIfails to promote P atom transfer to AdNC, yielding instead [(Tpt Bu,Me)V(OCP)(CNAd)]. Theoretical studies revealed the rare ECNAd moieties to be stabilized by π‐backbonding interactions with the former TiIIion, and their assembly to most likely involve a concerted E atom transfer between Ti‐bound OCE−to AdNC ligands when studying the reaction coordinate for E=P. -
Abstract Decarbonylation along with E atom transfer from Na(OCE) (E=P, As) to an isocyanide coordinated to the tetrahedral TiIIcomplex [(Tp
t Bu,Me)TiCl], yielded the [(Tpt Bu,Me)Ti(η3‐ECNAd)] species (Ad=1‐adamantyl, Tpt Bu,Me−=hydrotris(3‐tert ‐butyl‐5‐methylpyrazol‐1‐yl)borate). In the case of E=P, the cyanophosphide ligand displays nucleophilic reactivity toward Al(CH3)3; moreover, its bent geometry hints to a reduced Ad−NCP3−resonance contributor. The analogous and rarer mono‐substituted cyanoarsenide ligand, Ad−NCAs3−, shows the same unprecedented coordination mode but with shortening of the N=C bond. As opposed to TiII, VIIfails to promote P atom transfer to AdNC, yielding instead [(Tpt Bu,Me)V(OCP)(CNAd)]. Theoretical studies revealed the rare ECNAd moieties to be stabilized by π‐backbonding interactions with the former TiIIion, and their assembly to most likely involve a concerted E atom transfer between Ti‐bound OCE−to AdNC ligands when studying the reaction coordinate for E=P. -
Abstract 3,3′,5,5′‐Tetra‐
tert ‐butyl‐2′‐sulfanyl[1,1′‐biphenyl]‐2‐ol (H2[t Bu4OS]) was prepared in 24 % yield overall from the analogous biphenol using standard techniques. Addition of H2[t Bu4OS] to Mo(NAr)(CHCMe2Ph)(2,5‐dimethylpyrrolide)2led to formation of Mo(NAr)(CHCMe2Ph)[t Bu4OS], which was trapped with PMe3to give Mo(NAr)(CHCMe2Ph)[t Bu4OS](PMe3) (1 (PMe3)). An X‐ray crystallographic study of1 (PMe3) revealed that two structurally distinct square pyramidal molecules are present in which the alkylidene ligand occupies the apical position in each. Both1 (PMe3)Aand1 (PMe3)Bare disordered. Mo(NAd)(CHCMe2Ph)(t Bu4OS)(PMe3) (2 (PMe3); Ad=1‐adamantyl) and W(NAr)(CHCMe2Ph)(t Bu4OS)(PMe3) (3 (PMe3)) were prepared using analogous approaches.1 (PMe3) reacts with ethylene (1 atm) in benzene within 45 minutes to give an ethylene complex Mo(NAr)(t Bu4OS)(C2H4) (4 ) that is isolable and relatively stable toward loss of ethylene below 60 °C. An X‐ray study shows that the bond distances and angles for the ethylene ligand in4 are like those found for bisalkoxide ethylene complexes of the same general type. Complex1 (PMe3) in the presence of one equivalent of B(C6F5)3catalyzes the homocoupling of 1‐decene, allyltrimethylsilane, and allylboronic acid pinacol ester at ambient temperature.1 (PMe3),2 (PMe3), and3 (PMe3) all catalyze the ROMP ofrac ‐endo ,exo ‐5,6‐dicarbomethoxynorbornene (rac ‐DCMNBE) in the presence of B(C6F5)3, but the polyDCMNBE that is formed has a random structure. -
Not, available (Ed.)
Abstract Described here is a direct entry to two examples of 3d transition metal catalysts that are active for the cyclic polymerization of phenylacetylene, namely, [(BDI)M{κ2‐
C ,C ‐(Me3SiC3SiMe3)}] (2‐M ) (BDI=[ArNC(CH3)]2CH−, Ar=2,6‐i Pr2C6H3;M =Ti, V ). Catalysts are prepared in one step by the treatment of [(BDI)MCl2] (1‐M ,M =Ti ,V ) with 1,3‐dilithioallene [Li2(Me3SiC3SiMe3)]. Complexes2‐M have been spectroscopically and structurally characterized and the polymers that are catalytically formed from phenylacetylene were verified to have a cyclic topology based on a combination of size‐exclusion chromatography (SEC) and intrinsic viscosity studies. Two‐electron oxidation of2‐V with nitrous oxide (N2O) cleanly yields a [VV] alkylidene‐alkynyl oxo complex [(BDI)V(=O){κ1‐C ‐(=C(SiMe3)CC(SiMe3))}] (3 ), which lends support for how this scaffold in2‐M might be operating in the polymerization of the terminal alkyne. This work demonstrates how alkylidynes can be circumvented using 1,3‐dianionic allene as a segue into M−C multiple bonds.