Inhaltsiibersicht. Die zweikernigen Antimon(V)-Komplexe (R' =CH,, R2 =CzHS) und 5 (R' =RZ=CH3, R3 =(CH,),C6HzCHz) C1,Sb(0)[R3(R10)POz](OR2)SbCl, 1 bis 6 rnit R' =RZ =CH,, kristallisieren triklin in der Raumgruppe P-I rnit a = 984,1, CzHS und R3=C6H5CH2, (CH3)3C6HzCH2 tauschen bei RT in b = 1026,7, c = 1079,9pm, a = 87,93, /3 = 75,70, y = 87,62' Losung langsam die R2-Gruppen aus. Daneben erfolgt rasches und Z = 2 bzw. a = 1164,6, b = 1296,9, c = 1712,9pm, Umklappen des SbOPOSb-quasi-Fiinfringes. Die Isomerenbila = 109,9, /3 = 96,3, y = 100,2' und Z = 4 mit zwei kristallodung wird NMR-spektroskopisch nachgewiesen. 1 (R' =R2 = graphisch unabhangigen Molekiilen in der asymmetrischen Ein-CH,) kristallisiert orthorhombisch in der Raumgruppe Pnma heit. rnit a = 1247,0, b = 1324,1, c = 1207,9pm und Z = 4. 2 d,h-~-Benzylalkoxophosphonato-e-~-alkoxo-f-~-oxo-bis[trichloroantimony(V)] Compounds Abstract. The binuclear antimony(V) complexes Cl,Sb(0)[R3(R10)P02](OR2)SbCl, 1-6 with R' = R2 =CH3, changes the R2 groups between the oxygen atoms of the Sbz02 ring. The SbOPOSb ringsystem makes rapid pseudorotation. The isomeres are detected by nmr spectroscopy. 1 (R' = RZ = CH,) crystallizes in the orthorhombic space group Pnma with a = 1247.0, b = 1324.1, c = 1207.9 pm and Z = 4. 2 (R1 = CH,, RZ = C2Hs) and 5 (R' = R2 = CH,, R3 = (CH,), . CzH, and R3 =C,jHsCHz, (CH,),C,H,CHz in solution Slowly ex-C&CHz) crystallizes triclinic in the space group P-1 with a = 984.1, b = 1026.7, c = 1079.9pm, a = 87.93, / 3 = 75.70, y = 87.62' and Z = 2 and a = 1164.6, b = 1296.9, c = 1712.9pm, a = 109.9, fl = 96.3, y = 100.2" and Z = 4resp., with two crystallographically independent molecules in the asymmetric unit.