Synthesis of [alkenyl(dimethylamino)carbene]tungsten complexes using the peterson reaction: X-ray crystal structure of (EHCO)5W[C(NMe2)CH=CH(η-C5H4)Fe(η-C5H5)]

David W. Macomber, Puttannachetty Madhukar, Robin D. Rogers

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Treatment of (CO)5W[C(NMe2)CH3] (1) with n-BuLi followed by Me3SiCl produced (CO)5W[C-(NMe2)CH2SiMe3] (2) in 90% yield. (CO)5W[C(NMe2)CHSiMe3]Li, which was formed in the reaction between 2 and n-BuLi, reacted with several nonenolizable aldehydes or ketones to afford moderate yields (45-61%) of the desired (alkenylaminocarbene)tungsten complexes (CO)5W[C(NMe2)CH—CR1R2] (3a-f) (a, R1 = R2 = H; b, R1 = H, R2 = Ph; c, R1 = H, R2 = 2-furyl; d, R1 = H, R2 - trans-CH=CHPh; e, R1 = H, R2 = (η-C5H4)Fe(η-C5H5); f, R1 = R2 = Ph). For compounds 3b-e, exclusive formation of the E isomer occurred. Treatment of 2 with n-BuLi followed by either CF3S03CH3 or CH2==CHCH2Br afforded complexes 4a and 4b (70-90%), (CO)5W[C(NMe2)CH(R)SiMe3] (4a, R = CH3; 4b, R = CH2CH=CH2), respectively. Complexes 4a or 4b could not be obtained by reacting the corresponding complexes 5a or 5b, (CO)5W-[C(NMe2)CH2R] (5a, R = CH3; 5b, R = CH2CH=CH2), with n-BuLi followed by Me3SiCl. Furthermore, the lithium anions (CO)5W[C(NMe2)C(R)SiMe3]Li (R = CH3, CH2CH—CH2) from 4a or 4b did not react with aldehydes or ketones to afford the desired a-substituted (alkenylaminocarbene)tungsten complexes. One example of such a complex, (CO)5W[C(NMe2)C(CH3)=CH2] (7), could, however, be prepared in 75-80% yield by treating (CO)6W[C(OCH3)C(CH3)=CH2] (6) with HNMe2 in ether. (CO)5W[C(NMe2)CHSiMe3]Li was made to react with PhCOCl to yield the enol silyl ether derivative (CO)5W[C(NMe2)CH=C(OSiMe3)Ph] (8) (26%) along with a trace of an air-sensitive complex (C0)5W[C(NMe2)CH2C(0)Ph) (9). (2S)-(CO)6W-[C(NMe2)CH=CH(η-C5H4)Fe(η-C5H5)] (3e) was further characterized by single-crystal X-ray diffraction methods. Complex 3e crystallizes in the monoclinic space group P21/c with (at 20 °C) a = 12.022 (4) Å, b = 12.857 (8) Å, c = 13.826 (8) Å, β= 102.19 (4)°, and Dcalcd = 1.88 g cm−3 for Z = 4. Least-squares refinement based on 2604 independent observed [F0≥5σ(F0)] reflections led to a final conventional R value of 0.044.

Original languageEnglish (US)
Pages (from-to)1275-1282
Number of pages8
Issue number5
StatePublished - May 1 1989


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