The transformation of heteroatom substituted alkynes into substituted vinylidene ligands accompanied by carbonyl insertion

Abstract

The reactions of Mn,(CO),NCMe (1) with the alkynes M e C S X (X = OEt, NMe,) have ylelded the substituted bridging vinylidene complexes Mn,(CO),[p-C=C(Me)C=O(X)] (2a, X = E t ; 2b, X = NMe, ) in 39% and 10% yields, respectively, by a rearrangement of the alkyne accompanied by a CO insertion. Compound 2b also adds 1 equiv of MeC--VNMe, to form the complex Mn,(CO), Summary: Organoianthanide complexes of the type Cp' ,LnR (Cp' = $-Me, C, ; Ln = La, Nd, Sm, Y, Lu; R = H, CH(SiMe3),), Me,Si Cp",LnR (Cp" = q5-Me,C,; Ln = Nd; R = CH(SIMe3),), Cp' ,Sm, and Cp' ,Sm(THF), catatyze the rapid dehydrogenative oligomerization of PhSi H,.Kinetic and mechanistic arguments exclude the importance of metakentered redox processes in the catalytic cycle and support instead "four-center'' "heterolytic" bond-scission/bond-forming sequences.

Synthesis and molecular structure of [Re2(μ:η6-C24H18N4)(CO)6] containing the rtct-tetrakis(2-pyridyl)cyclobutandiyl ligand, derived from the reaction of [Re2(CO)8(MeCN)2] and 1,2-bis(2-pyridyl)ethene

“…Complex [Re 2 (l:g 3 -C 12 H 10 N 2 )(CO) 8 ] (1) The m(CO) absorption spectrum of 1 indicates that only terminal carbonyl groups are present and its band pattern resembles that for [Re 2 (CO) 8 (l-MeC 2 NMe 2 )] [12]. The 1 H NMR spectrum exhibits two doublets (d = 6.18 and 4.16 ppm) assigned to the ethylenic protons, and eight different signals in the aromatic region are associated to two different pyridine systems, which implies a loss of the free ligand symmetry.…”

New bridging ligands from methylation reactions of μ-vinyliminium diiron complexes

“…The selective N-methylation of the bridging vinylalkylidene ligand in 2a is an interesting result because electrophilic attack to uncoordinated enamines [R 2 N-C a @C b ] usually involves C b [13] rather than the nitrogen atom [14]. Comparisons with the reactivity of metal-coordinated enamines [15], including binuclear complexes [16], would be more appropriate, but unfortunately this matter is still largely uncovered. The observed selectivity could simply depend upon the nature of the substituents in the bridging ligand (i.e.…”

Low-valent Organorhenium Compounds

“…30 9 ], 4 5 electron-rich ynamines give an r| 3 -ynamine complex (II). 51 Further reaction of (11) with ynamine at 68 °C gives dinuclear metallacyclopentadiene products (12), resulting from head-to-head, head-to-tail, and tail-to-tail coupling of two ynamines (Scheme 2). Reduction of (11) with H 2 (10 atm, 70 Reaction of [Re 2 (CO) 9 (NCMe)] with electrophilic alkynes results in alkyne insertion into the rhenium-rhenium bond to give dimetallated alkene complexes (14) (Equation (3)).…”

“…165 Wenzel and Bergman have thoroughly investigated the C-H activation chemistry o f [Re(PMe 3 ) 3 (Cp)] (51) (Scheme 10). 138 The highly air sensitive (51) was prepared fro m [Re(Cl) 3 (PMe 3 ) 3 ] and Na/Hg, CpH, K 2 CO 3 , and purified in 38% yield by filtration through alumina(III) at -100 °C. Photolysis o f (51) in cyclopropane (5-10 °C) or hexane (-30 °C) gives the isolable hydridoalkyl complexes (52) and (53) respectively.…”

“…138 The highly air sensitive (51) was prepared fro m [Re(Cl) 3 (PMe 3 ) 3 ] and Na/Hg, CpH, K 2 CO 3 , and purified in 38% yield by filtration through alumina(III) at -100 °C. Photolysis o f (51) in cyclopropane (5-10 °C) or hexane (-30 °C) gives the isolable hydridoalkyl complexes (52) and (53) respectively. No products o f insertion into a secondary C-H bond were observed with hexane substrate.…”