A series of cobalt(II) and iron(II) siloxide complexes, [(Me 3Si) 3SiO] 2M(L n ) {M=Co, L n =none ( 1), (THF) ( 3), (THF) 2 ( 4), (DME) ( 5), (MeCN) 2 ( 6), (PhCN) 2 ( 7), (2,2′-dipyridyl) ( 8), 4,4′-dipyridyl ( 9), (Ph 3P) 2 ( 10); M=Fe, L n =none ( 2), (2,2′-dipyridyl) ( 11) were prepared by the reaction of metal silylamides [(Me 3Si) 2N] 2M (M=Co, Fe) with tris(trimethylsilyl)silanol. The crystal structures of compounds 1 and 11 have been determined by the X-ray diffraction method. Complex 1 has a dimeric structure with two [(Me 3Si) 3SiO] 2Co units bonded via the two μ 2-O atoms. The central [Co(μ 2-O)] 2 cycle has a ‘butterfly shape’ being bent along the bridging oxygen atoms. The dihedral angle between the Co(1)O(4)Co(2) and Co(1)O(3)Co(2) planes is 143.1°. The μ 2-bridging and terminal CoO distances are 1.945(7)–1.963(7) and 1.781(8), 1.793(7) Å, respectively. The Co⋯Co distance in 1 is relatively short, 2.735(2) Å. However, the high value of magnetic moment (6.0 μ B) of compound 1 indicates the absence of a direct interaction between the Co atoms in 1. The molecule of 11 is monomeric. The Fe atom is bonded to 2,2′-dipyridyl and two terminal OSi(SiMe 3) 3 groups and has a distorted tetrahedral environment. The FeN(1), FeN(2) and FeO(1), FeO(2) distances in 11 are 2.148(1), 2.164(1) and 1.863(1), 1.900(1) Å, respectively. Addition of one equivalent of PhCCH to 7 results in the substitution of one tris(trimethylsilyl)siloxy-group with the formation of the diamagnetic dimer {(PhCN)(PhC 2)CoOSi(SiMe 3) 3} 2. Subsequent addition of PhC 2H causes its oligomerisation. Complexes 1, 3 and 10 absorb carbon monoxide at ambient temperature and pressure while the others remain unreactive. Electronic spectra show fluxional behavior of complexes 1, 3 and 4 in solution.