Neutral oxygen donors

Complexes of the lanthanides with neutral oxygen donor ligands. D. K. Koppikar, P. V. Sivapul-laiah, L. Ramakrishnan and S. Soundararajan, Struct. Bonding (Berlin), 1978, 34,135-213 (406). 

Koppikar DK, Sivapullaiah PV, Ramakrishnan L, Soundararajan S (1978) Complexes of the Lanthanides with Neutral Oxygen Donor Ligands. 34 135-213 Keren B, see Valach F (1984) 55 101-151... 

The bis-phosphonium salt 56 in presence of Pd(OAc)2 leads to the formation of the neutral bis-ylide 57 which reacts with TICIO4 to give the dinuclear cationic complex 58 (Scheme 22) [89,90]. The bis-ylide part, which has potentially two carbons and one oxygen donor atoms, acts as a C,C-chelating ligand through its two soft ylidic carbons. 

Fig. 18. Plot of change in complex stability, Alogf , that occurs for the pairs of ligands cryptand-2,2,2 and EN ( ), and 18-aneN204 and EN (O), as a function of metal ion radius (20). The diagram shows how neutral oxygen donors tend to stabilize the complexes of large relative to small metal ions in macrocyclic ligands. Data from Ref. (11).

Complexes of the Lanthanides with Neutral Oxygen Donor Ligands... 

Probably, the first series of lanthanide complexes with neutral oxygen donor ligands is that of AP with the lanthanide nitrates. In 1913, Kolb (79) reported tris-AP complexes with lighter lanthanide nitrates and tetrakis-AP complexes with heavier lanthanide nitrates. Subsequently, complexes of lanthanide nitrates with AP which have a L M of 6 1 and 3 1 have also been prepared (80-82). Bhandary et al. (83) have recently shown through an X-ray crystal and molecular structure study of Nd(AP)3(N03)3 that all the nitrates are bidentate and hence the coordination number for Nd(III) is nine in this complex. Complexes of AP with lanthanide perchlorates (81, 84), iodides (81, 85), and isothiocyanates (66, 86, 87) are known. While the perchlorates and iodides in the respective complexes remain ionic, two of the isothiocyanates are coordinated in the corresponding complexes of AP with lanthanide isothiocyanates. 

General aspects of the coordination chemistry of the lanthanides with reference to the complexes of neutral oxygen donor ligands are dealt with in this section. For con venience, this section is subdivided into three parts 1. synthetic procedures, 2. stoichiometry, and 3. coordination numbers and coordination polyhedra. 

So far almost all the complexes of the lanthanides with neutral oxygen donor ligands have been prepared from hydrated salts. Quite a few of these complexes have one to three molecules of water in their composition. The coordinated or noncoor-dinated nature of water in these complexes is not well established. 

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