The synthesis and structural characterization of rare earth alkoxides with thiophene-based substituents are presented. Monomeric metal thienylmethoxides have been prepared by aminolysis reactions between M[N(SiMe
3
)
2
]
3
(M = Y
3+
, Nd
3+
, Er
3+
) and the structurally characterized tertiary alcohols HO-C(C
4
H
3
S)
3
(
1
) or HO-C(C
8
H
5
S
2
)
3
(
2
). The metal alkoxide derivatives of these thiophene-substituted alcohols have been isolated as air-sensitive base adducts, their molecular structures being investigated by single-crystal X-ray crystallography. The coordination spheres around the metal centres are distorted trigonal-bipyramidal for the yttrium thienylmethoxides Y[OC(C
4
H
3
S)
3
]
3
(thf)
2
(
3a
), {Y[OC(C
4
H
3
S)
3
]
3
(thf)
2
}·toluene (
3b
), Y[OC(C
4
H
3
S)
3
]
3
(py)
2
(
4a
), {Y[OC(C
4
H
3
S)
3
]
3
(py)
2
}·toluene (
4b
) and Y[OC(C
8
H
5
S
2
)
3
]
3
(thf)
2
(
5
). An almost tetrahedral geometry has been detected for Er[OC(C
8
H
5
S
2
)
3
]
3
(thf) (
9
), whereas an approximately octahedral geometry was found for {Nd[OC(C
4
H
3
S)
3
]
3
(thf)
3
}·thf (
6
), {Nd[OC(C
8
H
5
S
2
)
3
]
3
(thf)
3
}·4thf (
7
) and Er[OC(C
4
H
3
S)
3
]
3
(thf)
3
(
8
).