Synthesis and Structures of (μ-Bis(carbene))dimetal Complexes of Chromium and Tungsten

David W. Macomber, Mu Huang Hung, Puttannachetty Madhukar, Mong Liang, Robin D. Rogers

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Abstract

Treatment of the α-lithio carbene anions (CO)5M1[C(X1R)C(R1)C(R2)]Li (1) (M1 = Cr, W; X1R = OCH3, OCH2Ph, OCH2CH2Ph, N(CH3)2; R1, R2 = H, CH3, n-C3H7, Si(CH3)3) with the α,β-unsaturated carbene complexes (CO)5M2[C(X2R)C(R4)=CHR3] (2) (M2 = Cr, W; X2R = OCH3, OCH2Ph, N(CH3)2; R3, R4 = H, CH3, Si(CH3)3, (−CH2-)3, (−CH2−)4, (−CH2−)6) produced the intermediate α-lithio (μ-bis(carbene))dimetal anions {(CO)5M1[C(X1R)C(R1)(R2)CH(R3)C(R4)C(X2R)]M2(CO)5}Li (3), which were subsequently quenched with various electrophilic reagents E-X (E-X = CH3OS02CF3, CH2=CHCH2Br, PhCH=CHCH2Br, PhCH2Br, (CH3)3SiCl, HCl) to afford the (μ-bis(carbene))dimetal complexes (CO)5M1[C(X1R)C-(R1)(R2)CH(R3)C(R4)(R5)C(X2R)]M2(CO)5 (4a-z) (R1 = H, CH3, CH2CH=CH2, CH2CH=CHPh, CH2Ph) in 46–78% yields. Along with the desired (μ-bis(carbene))dimetal complexes (4) were produced small amounts of the vinyl ether derivatives (CO)5M1[C(X1R)C(R1)(R2)CH(R3)C(R4)=CH(OCH3)] (5). Complexes 4c-f,h,j-l,r-t,w,x, which each have two asymmetric carbon centers, were produced as one major diasteromer. Complexes 4j (M1 = M2 = W; X1R = X2R = OCH3; R1 = R2 = H; R3, R4 = (−CH2−)3; R5 = CH2CH=CH2), 4s (M1 = Cr, M2 = W, X1R = X2R = OCH3, R1 = R3 = R5 = H, R2 = R4 = CH3), and 4x (M1 = M2 = W; X1R = N(CH3)2; X2R = OCH3; R1 = R2 = H; R3, R4 = (−CH2−)3; R5 = CH2CH=CH2) were also characterized by single-crystal X-ray diffraction methods. Complex 4s crystallizes in the centric Pbcα space group with cell constants a = 14.083 (7) Å, 6 = 18.032 (3) Å, c = 19.380 (5) Å, and Dcalcd = 1.81 g cm−3 for Z = 8. Least-squares refinement based on 2471 independent observed [Fo ≥ 5σ(Fo)] reflections led to a final conventional R value of 0.044. Complexes 4j and 4x, which differ only in the heteroatom substituent X1R, crystallize in the centric Pbcα space group with cell constants a = 11.931 (6) Å, b = 14.404 (8) Å, c = 31.496 (9) Å, and Dcalcd = 2.10 g cm−3 for Z = 8 and monoclinic P21/c space group with cell constants α = 13.931 (3) Å, b = 12.729 (2) Å, c = 16.032 (2) Å, β = 93.47 (2)°, and Dcalcd = 2.03 g cm−3 for Z = 4, respectively. Both were refined via least squares, 4j to a conventional R value of 0.064 based on 2868 independent observed [Fo ≥ 5σ(Fo)] reflections and 4x to 0.028 (based on 4037 reflections).

Original languageEnglish (US)
Pages (from-to)737-746
Number of pages10
JournalOrganometallics
Volume10
Issue number3
DOIs
StatePublished - Mar 27 1991

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