Synthetic and Structural Studies of Cyclodistib(V)azanes

High-yielding syntheses of complexes based around the cyclodistibazane (Sb2N2) core are described from the reaction of organoantimony(V) chlorides with varying stoichiometric amounts of lithiated primary amines, LiN(H)R. Thus, mixing Ph3SbCl2 with 2 equiv of LiN(H)R (R = CH2Ph) produces Ph3Sb((mu)-NR)2SbPh3 (1). Mixed amido/imido complexes of formula {R(H)N}Ph2Sb((mu)-NR)2SbPh2{N(H)R} (2) (R = CH2Ph, 2-OMe-5-tBu-C6H3, and Cy) are made from the corresponding 3:1 molar ratio combination of LiN(H)R with Ph2SbCl3. A similar reaction employing only 2 equiv of LiN(H)R (R = CH2Ph) with 1 equiv of Ph2SbCl3 yields ClPh2Sb((mu)-NR)2SbPh2Cl (3). Compounds 2a-c and 3 possess reactive functionality which may make them useful synthetic reagents in the preparation of more complex main group imido architectures. All of the complexes have been characterized by 1H NMR spectroscopy, elemental analysis (CHN), and X-ray crystallography. An investigation of all known crystallographically characterized Sb-N fragments from the Cambridge Structural Database highlights a series of parameters that appear to influence the observed Sb-N bond lengths.