The reaction of deep-blue SmI2(THF)2 with two equiv. of 1a or 1b in THF at room temperature afforded, upon removal of all volatiles in vacuo, 2a and 2b as paramagnetic purple solids in 85% and 65% yield, respectively (Figure ). The molecular structures of 2a and 2b were confirmed using single crystal X-ray diffraction (SC-XRD) analysis. The results obtained for 2a are shown in Figure . This result clearly demonstrates that two molecules of 1a coordinate to the Sm(II) center in an anti--O fashion (torsion angle of C1-N1-P-O1 = +157.4(7)°, C1*-N1*-P1*-O1* = -157.4(7)°), and that the carbene carbon atoms remain intact. This selective complexation can be expected to proceed via a higher affinity between the hard Lewis-basic Nphosphinoyl oxygen atom and the hard Lewis-acidic Sm(II) center. This result also indicates the induction of N-P axial chirality following the complexation process (vide infra). The elongation of the P-O1(O1*) bond to 1.493(6) Å compared to 1.482(1) Å in free 1a occurs through the formation of the Sm-O1(O1*) bond. The samarium center lies on a crystallographic inversion center and adopts a distorted octahedral geometry that consists of two axial iodides (I1, I1*) and four equatorial oxygen atoms (O1 and O1* from 1a, O2 and O2* from THF). The Sm-O1(O1*) lengths of 2.443(6) Å are obviously shorter than the Sm-O2(O2*) bonds which measure 2.521 (7) Å, suggesting that a stronger interaction occurs in the former. These results are almost identical with those observed in the diiodosamarium(II) complex SmI2(TMU)2(THF)2 (TMU = tetramethylurea; Sm-O(TMU) = 2.446(7) Å; Sm-O(THF) = 2.528(9) Å), which has one of the shortest Sm-O interactions to be crystallographically confirmed. However, significantly longer Sm-O distances have been confirmed in well-identified hexacoordinate Sm(II) complexes such as SmI2(HMPA)4 (HMPA = hexamethylphosphoric triamide; Sm-O = 2.500(6) Å). Given that interatomic distances of shorter than ca. 2.3 Å should be observed between Sm(III) and O atoms, the samarium atom in 2a should thus exist in a neutral divalent state rather than as Sm(III). Although SmI2(THF)2 has been used as a single-electron-transfer (SET) reagent in modern organic synthesis, an intramolecular electron transfer from the Sm(II) center to the 1a ligand is unlikely to occur in 2a. The Sm atom and the two I atoms are linearly arranged (I1-Sm-I1* = 180.0°) with bond lengths of 3.2587(7) Å. These are obviously shorter than those in SmI2(TMU)2(THF)2 (Sm-I = 3.312(1) Å) and in SmI2(HMPA)4 (Sm-I = 3.390(2) Å). This suggests that, like urea and unlike THF and HMPA, 1a is an oxygen-based ligand that strongly coordinates to Sm(II).