SYNTHESIS AND CHARACTERIZATION OF FORMALDEHYDE-BRIDGED BIMETALLIC COMPLEXES FROM ETA(2)-COMPLEXES OF MOLYBDENUM, VANADIUM, AND IRON

Reactions of Cp(2)Mo(CH2O) (1) and Cp(2)V(CH2O) (5) with Lewis acids s uch as cis-Re(CO)(4)-(L)(F-BF3) [L = PPh(3) or P(OPh)(3)] (2a,b) or Zn Br2 lead to formaldehyde-bridged complexes 3a, 3b, 4, 6a, and 6b; reac tion of Fe(CO)(2)[P(OCH3)(3)](2)(CH2O) (7) with ZnBr2 yields 8. All ar e the mu(2)-eta(3) type. Two of the products have been characterized b y X-ray crystallography. Crystal data for [Cp(2)Mo(CH2O)]2ZnBr2 (4): C 22H24O2Br2Mo2Zn, space group P $($) over bar$$ 1, a = 14.440(12) Angst rom, b = 15.049(9) Angstrom, c = 12.691(13) Angstrom, alpha = 104.36(6 )degrees, beta = 91.11(8)degrees, gamma = 62.21(5)degrees, V = 2348(3) Angstrom(3), and Z = 4. The structure was refined to R = 5.2% and R(w ) = 5.8%. Crystal data for {Fe(CO)(2)[P(OCH3)(3)](2)(CH2O)ZnBr2}(2) (8 ): C18H40Br4Fe(2)O(18)P(4)Zn(2), space group P ($) over bar 1, a = 10. 262(4) Angstrom, b = 11.826(9) Angstrom, c = 10.154(8) Angstrom, alpha = 95.79(6)degrees, beta = 118.56(5)degrees, gamma = 75.96(5)degrees, V = 1049(1) Angstrom(3), and Z = 1. The refinement converged with R = 4.1% and R(w) = 4.5%. Reaction of Et(4)NBr with any of the formaldehyd e-bridged complexes readily displaces the Lewis acid and liberates the original formaldehyde complex. In contrast, trifluoroacetic anhydride reacts with 1, 5, and 7 with cleavage of the metallaoxirane ring to g ive (trifluoroacetoxy)methyl trifluoroacetate derivatives 9-11, respec tively.