η3-Propargyl complexes of molybdenum, tungsten, and rhenium

Abstract

The reactions of the MenC6H6_,~M(CO)_~ (M = Cr, Mo, W; n = 3, 5, 6) and CsRsM(CO) 3 (M = Mn, Re; R = H, Me) complexes wilh propargyl alcohol in acidic media under UV irradiation were studied. Novel MenC6H6_nM(CO)2(H3-C3H3)BF4 (M = Mo, W; n = 3,5,6) and CsRsRe(CO)2(rl3-C3H3)CF3SOa complexes with the 3e-propargyl ligand were synthesized, and their properties compared with those of similar rl3-allyl derivatives. The structure and dynamic properties of the compounds obtained are discussed.Key words: 2-hydroxyallyl complexes, ri3-propargyl complexes, synthesis, temperature dependence, IR spectra, IH and )3C NMR spectra.Generation of the carbenium center at the ~x-position to the double bond coordinated with the transition metal atom results in the formation of stable cationic complexes with the rl3-allyl ligand. These transformations have previously been studied IJ in detail for complexes of Group VI--Vlli metals with olefinic ligands based on allyl alcohol or conjugated dienes in acidic media. The works on studying stabilization of carbenium ions at the (z-position to the coordinated triple bond resulted in synthesis of sufficiently stable cationic complexes of Mo, 3,4 W, 3 Re, 5-7 Zr, 8 Pd, 9,10 and Pt 9,11-14 with the three-electron rl3-propargyl ligand. This work is devoted to studying the regularities of formation of mononuclear cationic complexes of Group VI and VII metals with the 3~-rl3-propargyl ligand and their structure.We have previously found I that UV irradiation of arenechromiumtricarbonyl derivatives in the presence of propargyl alcohol and aqueous tetrafluoroboric acid or its ether'ate (Scheme 1) results in the formation of cationic complexes with the 2-hydroxyallyl ligand (la--e). Cr(CO) 3Scheme 1 + HC --CCH20H + HBF a Et20 Unlike arenechromiumtricarbonyls, a similar onestage reaction of CpM(CO) 3 (M = Mn, Re) resulted in the formation of cationic complexes in low yields and was accompanied by a considerable decomposition of the reagents. For example, according to the data of ]H NMR spectroscopy, UV irradiation of an ethereal solution of CpMn(CO) 3 and propargyl alcohol followed by treatment of the n-complex with propargyl alcohol (2) formed in situ with 48% aqueous HBF 4 (Scheme 2) affords a mixture of two rt-allyl complexes 3 and 4 approximately in a ratio of 2.5 : 1.0, which, however, does not necessarily reflect the initial ratio of reaction products, because their multiple precipitation with ether from nitromethane was required to obtained a satisfactory" ~H NMR spectrum. In the case of CpRe(CO)3, this reaction in ether is impeded by the formation of a sufficiently stable

Photolysis of dicarbonyl(cyclopentadiene)rhodium complexes with a pendent alkyne unit

“…Similar intermediates with an alkyne unit bound to a CpM(CO) n fragment are reported in the literature for M = Co, n = 1 [6,7], and M = Mn, n = 2 [8,9]. Also complexes of the type ArCr(CO) 2 (alkyne) have been reported [8,[10][11][12]. However, most of them proved to be rather unstable [13] whereas the species 17 and 18 were dark red colored airstable solids.…”

Transition-Metal Complexes Containing Alkynylsilyl Functionalized η6-Arene Ligands

“…Whereas the preceding experiments aimed at intermolecular reactions of the triple bond to form multinuclear complexes, intramolecular reactions of the alkynylsilyl group with the transition-metal complex moiety are also possible. , …”

“…Irradiation-induced ligand substitutions are quite common also for silyl and stannyl complexes with unsaturated hydrocarbons. Admittedly, oligosilane chains rearrange and shorten under these conditions. ,, Even cyclic benzenetricarbonylchromium–alkyne derivatives with alkyl ether bridges are known . Consequently, solutions of compounds 1 , 3 , 4 , and 6 were irradiated with UV light , and the progress of the reaction was monitored with IR and NMR spectroscopy.…”

“…Of course, complexes with alkynylalkyl groups (such as propargyl) are known and have found application in organic synthesis . Furthermore, there are some related alkynyl­silylalkyl­silylarene, alkynyl­alkoxyalkyl­arene, alkenylsilylarene (including silaphenanthrene), , and alkenylalkylarene complexes . Alkenylsilylarene complexes have been used to synthesize metal-containing dendrimers and polymers by hydrosilylation. , Alkynyl­alkoxyalkyl­arenes as well as alkenylalkylarenes acted as chelating ligands and corresponding chromium complexes have been prepared.…”

“…Furthermore, there are some related alkynyl­silylalkyl­silylarene, alkynyl­alkoxyalkyl­arene, alkenylsilylarene (including silaphenanthrene), , and alkenylalkylarene complexes . Alkenylsilylarene complexes have been used to synthesize metal-containing dendrimers and polymers by hydrosilylation. , Alkynyl­alkoxyalkyl­arenes as well as alkenylalkylarenes acted as chelating ligands and corresponding chromium complexes have been prepared. Finally, two highly interesting chromium–iron–silicon cluster compounds can be regarded as related (ferrasilaalkenyl)­silylarene chelate complexes of chromium …”