The synthesis and structural characterization of six 1,1,3,3-tetramethylguanidine ( H-TMG ) solvated lanthanide aryloxide complexes are reported. Ln[N{Si(CH 3 ) 3 } 2 ] 3 (Ln = Nd , La ) was reacted with two equivalents of both H-TMG and HOAr { HOAr = HOC 6 H 2 (CMe 3 ) 2 -2,6 ( H-DBP ) or HOC 6 H 2 (CMe 3 ) 2 -2,6-CH 3 -4 ( H-4MeDBP )} and one equivelent of ethanol ( HOEt ) to yield the corresponding [ Nd(H-TMG) 2 (4MeDBP) 2 (OEt) ] (1) and [La(H-TMG) 2 (DBP) 2 (OEt)] (2). Compounds 1 and 2 were further reacted with 4-pentyn-1-ol {HO(CH 2 ) 3 C CH} to isolate [Nd(H-TMG) 2 (4MeDBP) 2 {O(CH 2 ) 3 C CH}] (3) and [La(H-TMG) 2 (DBP) 2 {O(CH 2 ) 3 C CH}] (4), respectively. Three equivalents of HOAr and one equivalent of H-TMG were additionally reacted with Ln[N{Si(CH 3 ) 3 } 2 ] 3 to generate [ Nd(4MeDBP) 3 (H-TMG) ] (5) and [La(DBP) 3 (H-TMG)] (6). In order to examine the formation of 1–6, the interaction of H-TMG and HOAr was further examined in solution and the hydrogen bonded complexes ( H-TMG : HOAr ), 7 and 8, were isolated. Upon successful isolation of 1–6, the utility of 1, 2, 4 and 5 as pre- catalysts for the intramolecular hydroalkoxylation of 4-pentyn-1-ol was investigated. The bulk powders for all complexes were found to be in agreement with the crystal structures based on elemental analyses, FT-IR spectroscopy , and 1 H and 13 C NMR investigations.