COMPLEXATION OF TIN(II) CHLORIDE BY A NOVEL MACROCYCLE CONTAINING RHODIUM AND NITROGEN BINDING-SITES - THE PREPARATION AND X-RAY CRYSTAL-STRUCTURE OF RH2SN2(CO)2CL6[MU-2,6-BIS(DIPHENYLPHOSPHINO)PYRIDINE]2

Treatment of Rh2(CO)4(.mu.-Cl)2 with 2,6-bis(diphenylphosphino)pyridine, (Ph2P)2py, in benzene forms the yellow macrocycle Rh2(CO)2Cl2[.mu.-(Ph2P)2py]2 which in turn reacts with tin(II) chloride to form Rh2Sn2(CO)2)Cl6[.mu.-(Ph2P)2py]2. Red crystals of Rh2Sn2(CO2Cl6[(Ph2P)2py]2 .cntdot. 2CH2Cl2 belong to the orthorhombic space group Pb21.alpha. (No. 29) with .alpha. = 13.959 (8) .ANG., b = 18.441 (10) .ANG., c = 25.585 (30) .ANG., Z = 4, R = 0.053 for 3476 reflections with I > 4 .sigma.(I) and 450 parameters. The molecular core consists of the bend chain, Rh-Sn-Rh-SnCl3. The central Sn resides within the cavity of the macrocycle and is coordinated to two nitrogen atoms, two rhodium atoms, and one chloride. In a highly uncharacteristic fashion one SnII-Cl bond has undergone oxidative addition to one of the rhodium ions.