Hydrido-Silyl-Komplexe. V. Strukturelle Änderungen in Hydrido-Silyl-Komplexen infolge Si?H-Wechselwirkung; Strukturvergleich zwischen (π-CH3C5H4)(CO)2Mn(H)SiR3- und analogen (π-C5H5)(CO)2FeSiR3-Komplexen

Hydrido Silyl Complexes. V. Structural Changes in Hydrido Silyl Complexes Due to Si? H Interaction; Comparison between the Structures of (π-CH₃C₅H₄)(CO)₂Mn(H)SiR₃ and Analogous (π-C₅H₅)(CO)₂FeSiR₃ Complexes The structures of the complexes Cp(CO)₂FeSiFPh₂ ( 2a ) and Cp(CO)₂FeSiCl₃ ( 2b ), containing ?normal”? metal-silicon bonds, are compared with the known structures of the complexes MeCp(CO)₂Mn(H)SiFPh₂ ( 1a ) and MeCp(CO)₂Mn(H)SiCl₃ ( 1b ), containing Mn? H? Si three-center bonds. 2a crystallizes in space group P2₁/c, a = 805.8(3), b = 1417.5(6), c = 1498.2(4) pm, β = 90.99(3)°, 2b in space group P2₁/n, a = 817(1), b = 1244(1), c = 1142(1)pm, β = 99.9(1)°. In 2a gauche conformation in respect to the Fe? Si bond is found; in 2b the silylligand is rotated 12° around the Fe? Si axis out of a staggered conformation. Possible reasons for the unsymmetrical conformations are discussed. Lengthening of the Fe? Si distance from 221.6(1)pm in 2b to 227.8(1) pm in 2a corresponds to the expected increase in the bond radius of silicon due to exchange of the substituents at silicon. Additional lengthening of the Mn? Si distance by about 3.5 pm in 1a compared with 1b is attributed to the increased delocalization of the Mn? H? Si bond in 1a .