FORMATION OF METAL-CLUSTERS OR NITROGEN-BRIDGED ADDUCTS BY REACTION OF A BIS(AMINO)STANNYLENE WITH HALIDES OF 2-VALENT TRANSITION-METALS

When the cyclic bis(amino)stannylene Me(2)Si(NtBu)(2)Sn is allowed to react with metal halides MX(2) (M = Cr, Fe, Co, Zn; X = Cl, Br [Zn]) a dducts of the general formula [Me(2)Si(NtBu)(2)Sn . MX(2)](n) are obta ined. The compounds are generally dimeric (n 2) except the ZnBr2 adduc t, which is monomeric in benzene. The crystal structures of [Me(2)Si(N tBu)(2)Sn . CoCl2](2) (triclinic, space group <(P)over bar 1>; a = 8.6 20(9) Angstrom, b = 9.160(9) Angstrom, c = 12.280(9) Angstrom, alpha = 101.2(1)degrees, beta = 97.6(1)degrees, gamma = 105.9(1)degrees, Z = 1) and of [Me(2)Si(NtBu)(2)Sn . ZnCl2](2) (monoclinic, space group P2( 1)/c; a = 8.156(9) Angstrom, b = 16.835(12) Angstrom, c = 13.206(9) An gstrom, beta = 94.27(6)degrees, Z = 2) were determined by X-ray diffra ction techniques. The two compounds form similar polycyclic, centrosym metrical assemblies of metal atoms bridged by chlorine or nitrogen ato ms. While in the case of the cobalt compound Co is pentacoordinated by three chlorine and two nitrogen atoms, in the zinc derivative Zn is a lmost tetrahedrally coordinated by three chlorine atoms and one nitrog en atom. The iron derivative [Me(2)Si(NtBu)(2)Sn . FeCl2](2) seems to be isostructural with the cobalt compound as can be deduced from the c rystal data (triclinic, a = 8.622(7) Angstrom, b = 9.158(8) Angstrom, c = 12.353(8) Angstrom, alpha = 101.8(1)degrees, beta = 96.9(1)degrees , gamma = 105.9(1)degrees, Z = 1). If NiBr2, PdCl2, or PtCl2 is combin ed with the stannylene, the reaction product is totally different: 4 e quiv of the stannylene are coordinating per metal halide, forming the molecular compound [Me(2)Si(NtBu)(2)Sn](4)MX(2), which crystallizes wi th half a mole of benzene per molecular formula. The crystal structure s of [Me(2)Si(NtBu)(2)Sn](4) . NiBr2.1/2C6H6 (tetragonal, space group I4(1)/a, a = b = 43.86(4) Angstrom, c = 14.32(2) Angstrom, Z = 16) and [Me(2)Si(NtBu)(2)Sn](4) . PdCl2.1/2C6H6 (tetragonal, space group I4(1 )/a, a = b = 43.99(4) Angstrom, Angstrom, c = 14.318(14) Angstrom, Z = 16) reveal the two compounds to be isostructural. The molecules have an inner Sn(4)M pentametallic core (mean distances: Sn-Ni 2.463 Angstr om, Sn-Pd 2.544 Angstrom) with the transition metal in the center of a slightly distorted square formed by the four tin atoms, the distortio n from planarity resulting in a weak paramagnetism of 0.2 mu(B) for th e nickel compound. The halogen atoms form bridges between two of the t in atoms and have no bonding interaction with the transition metal. Th e nickel compound has also been prepared by direct interaction of Br-2 or NR(4)Br(3) with [Me(2)Si(NtBu)(2)Sn]Ni-4 as a minor product, the m ain products being Me(2)Si(NtBu)(2)Sn(NtBu)(2)SiMe(2), Me(2)Si(NtBu)(2 )SnBr3, NiBr2 and SnBr2. Other metal clusters have been obtained by th e reaction of Me(2)Si(NtBu)(2)Sn with tetrakis(triphenyphosphine)palla dium or by the reaction of Me(2)Si(NtBu)(2)Ge with RhCl(PPh(3))(3). In the first case Ph(3)PPd[Sn(NtBu)(2)SiMe(2)](3)PdPPh(3) (rhombohedral, space group R3c, a = b = 21. 397(12) Angstrom, c = 57.01(5) Angstrom, alpha = beta = 90 degrees, gamma = 120 degrees, Z = 12) is formed and is characterized by X-ray techniques to be composed of a central PdSn 3Pd trigonal bipyramid with the tin atoms occupying the equatorial pos itions (Pd-Sn = 2.702(5) Angstrom). In the second reaction all the tri phenylphosphine ligands are replaced from rhodium and Rh[Ge(NtBu)(2)Si Me(2)]Cl-4 is formed (monoclinic, space group P2(1)/n, a = 12.164(2) A ngstrom, b = 23.625(5) Angstrom, c = 24.128(5) Angstrom, beta = 102.74 (3)degrees, Z = 4). The central core of this molecule is made up of a rhodium atom which is almost square planarly coordinated by the german ium atoms, two of which are bridged by chlorine (mean GeRh = 2.355 Ang strom).