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Stabilizing Heterobimetallic Complexes Containing Unsupported Ti−M Bonds (M = Fe, Ru, Co): The Nature of Ti−M Donor−Acceptor Bonds

1996; American Chemical Society; Volume: 35; Issue: 9 Linguagem: Inglês

10.1021/ic951353f

1520-510X

Stefan Friedrich, Harald Memmler, Lutz H. Gade, Wan‐Sheung Li, Ian J. Scowen, Mary McPartlin, Catherine E. Housecroft,

Synthetic Organic Chemistry Methods

The stabilization of unsupported Ti−M (M = Fe, Ru, Co) heterodinuclear complexes has been achieved by use of amidotitanium building blocks containing tripodal amido ligands. Salt metathesis of H3CC(CH2NSiMe3)3TiX (1) and C6H5C(CH2NSiMe3)3TiX (2) as well as HC{SiMe2N(4-CH3C6H4)}3TiX (3) (X = Cl, a; Br, b) with K[M(CO)2Cp] (M = Fe, Ru) and Na[Co(CO)3(PR3)] (R = Ph, Tol) gave the corresponding stable heterobimetallic complexes of which H3CC(CH2NSiMe3)3Ti−M(CO)2Cp (M = Fe, 6; Ru, 7) and HC{SiMe2N(4-CH3C6H4)}3Ti−M(CO)2Cp (M = Fe, 12; Ru, 13) have been characterized by X-ray crystallography. 6: monoclinic, P21/n, a = 15.496(3) Å, b = 12.983(3) Å, c = 29.219(3) Å, β = 104.52(2)°, Z = 8, V = 5690.71 Å3, R = 0.070. 7: monoclinic, P21/c, a = 12.977(3) Å, b = 12.084(3) Å, c = 18.217(3) Å, β = 91.33(2)°, Z = 4, V = 2855.91 Å3, R = 0.048. 12: monoclinic, I2/c, a = 24.660(4) Å, b = 15.452(3) Å, c = 20.631(4) Å, β = 103.64(3)°, Z = 8, V = 7639.65 Å3, R = 0.079. 13: monoclinic, I2/c, a = 24.473(3) Å, b = 15.417(3) Å, c = 20.783(4) Å, β = 104.20(2)°, Z = 8, V = 7601.84 Å3, R = 0.066. 1H- and 13C-NMR studies in solution indicate free internal rotation of the molecular fragments around the Ti−M bonds. Fenske−Hall calculations performed on the idealized system HC(CH2NH)3Ti−Fe(CO)2Cp (6x) have revealed a significant degree of π-donor−acceptor interaction between the two metal fragments reinforcing the Ti−Fe σ-bond. Due to the availability of energetically low-lying π-acceptor orbitals at the Ti center this partial multiple bonding is more pronounced that in the tin analogue HC(CH2NH)3Sn−Fe(CO)2Cp (15x) in which an N−Sn σ*-orbital may act as π-acceptor orbital.