Reaction of Tungsten Vinylcarbene Complexes with Enamines

Abstract

In this paper we describe the reaction of vinylcarbene complexes 4 and 7 with enamines 5 and 9 to form the η1-acyl complexes 6, 8, and 10. From a mechanistic point of view, the reaction starts with the nucleophilic addition of the β-carbon atom of the enamine to the α-carbon atom of the vinylcarbene complex, generating the zwitterionic structure 12. Instead of the expected ring closure to a metallacyclobutane derivative and concomitant metathesis, intermediate 12 undergoes nucleophilic addition of a carbonyl carbon atom to the iminium carbon atom and rearrangement to the observed η1-acyl complexes. Furthermore the reaction of the η1-vinylidene complex [(CO)(NO)(Cp)WCCH2)] (1) with the enamines 5 and 9 is described. While enamine 5 preferably reacts as a nucleophile and produces finally the alkene complex 11, the reaction of enamine 9 with 1 begins by a proton transfer step and ends with the η1-acyl complex 10. Single-crystal X-ray diffraction data of 6 and 11 are reported.

Bis(3,5-dimethylpyrazol-1-yl)acyl and Bis(3,5-dimethylpyrazol-1-yl)methide Carbonyl Tungsten Derivatives

“…The carbonyl group is bound to the tungsten in an η 1 -fashion, resulting in bis(pyrazol-1-yl)acyl acting as a novel tridentate κ 3 -[N,C,N] chelating ligand. The C(6)-C(9) bond length of 1.608 (10) Å is somewhat longer than other η 1 -acyl complexes of tungsten, 10 possibly owing to the large strain originating from the chelating Carbonyl Tungsten DeriVatiVes Organometallics, Vol. 27, No.…”

“…The fundamental molecular framework is similar to that in (p-MeC 6 H 4 ) 3 SnCH(3,5-Me 2 Pz) 2 W(CO) 4 . 6b It is worth noting that two cis-carbonyl groups are markedly distorted with the O(4)-C(4)-W(1) angle of 166.5(9)°and O(2)-C(2)-W(1) angle of 169.5 (10)°, and some angles around the Sn(1) and C(41) atoms (such as the C(18)-Sn(1)-C(41) angle of 93.3(3)°and N(4)-C(41)-Sn(1) angle of 123.9(6)°) significantly deviate from the tetrahedral geometry of the sp 3 -hybridized Sn(1) and C(41). These geometric parameters suggest a large steric repulsion in this complex, as expected.…”

“…1 H NMR: δ 1.29 (d, J ) 7.5 Hz, 6H, (CH 3 ) 2 CH), 1.91 (m, 1H, (CH 3 ) 2 CH), 1.81, 2.11 (s, s, 6H, 6H, CH 3 ), 5.65 (s, 2H, 4-position hydrogen of pyrazole ring), 6.34 (s, 1H, CHN), 7.18-7.33 (m, 10H, C 6 H 5 ). was stirred for an additional 1 h. (10) with I 2 to Yield 6. To a stirred solution of 10 (110 mg, 0.134 mmol) in CH 2 Cl 2 (15 mL) at 10 °C was dropwise added a solution of I 2 (34.0 mg, 0.134 mmol) in CH 2 Cl 2 (10 mL).…”

“…In addition, this complex can also be obtained by the reaction of CH(3,5-Me 2 Pz) 2 W(CO) 3 SnAr 3 (Ar ) C 6 H 5 (10) (5 mL). After addition was complete, the reaction mixture was stirred for an additional 2 h at room temperature.…”

Synthesis of η2‐Allene Complexes by the Reaction of a η1‐Vinylidene Tungsten Complex with Diazoalkanes

“…In recent years we have investigated the chemistry of tungsten and molybdenum η 1 -acetylide complexes 3 and the corresponding η 1 -vinylidene complexes 4. [1] A broad range of differently substituted derivatives of 3 and 4 are prepared by the reaction of the corresponding lithium acetylide 2 with the carbonyl complex 1 in THF at -30°C, which gives rise to the η 1 -acetylide 3, and by subsequent addition of electrophiles such as dilute acids, alkylating reagents like alkyltriflates, or iminium salts, which leads to the η 1 -vinylidene complexes 4 (Scheme 1).…”