Reaction of (η 5 -C 5

Mixed amidinato amido complexes [Me3SiNC(tBu)NSiMe3]M[N(SiMe3)2] (M = Sn 2, Ge 3) were prepared by the reaction of [Me3SiNC(tBu)NSiMe3]Li (1a) with SnCl2 and GeCl2(dioxane) in ether. The N(SiMe3)2 ligand in these compounds is derived from the rearrangement of the [Me3SiNC(tBu)NSiMe3]- anion with extrusion of tBuCN. The susceptibility of [Me3SiNC(tBu)NSiMe3]- to rearrangement appears to be dependent on reaction solvent and on the coordinated metal center. Single-crystal X-ray diffraction studies of 2 and 3 are presented. Replacement of Me for tBu in the ligand allowed [Me3SiNC(Me)NSiMe3]2SnII (4) to be isolated, and an X-ray structure of this compound is reported. The isolation of 4 indicates that steric factors also play a role in the stability of [Me3SiNC(tBu)NSiMe3]-. Compounds 2 and 3 are outstanding catalysts for the cyclotrimerization of phenyl isocyanates to perhydro-1,3,5-triazine-2,4,6-triones (isocyanurates) at room temperature. In contrast, complex 4 catalytically reacts with phenyl isocyanate to produce isocyanate dimer and trimer in a 52:35 ratio.

Addition of N(SiMe3)2 anion equivalents to CyNCNCy provided entry to a series of N-substituted guanidinate complexes of Sm(III) and Yb(III) with the general formula M{CyNC[N(SiMe3)2]NCy}2(μ-Cl)2Li(S)2 (M = Sm, Yb; Cy = cyclohexyl; S = Et2O, 1/2 TMEDA). Substitution of the chloro ligands of these complexes using LiCH(SiMe3)2 or LiN(SiMe3)2 yields solvent-free, monomeric alkyl and amido compounds, respectively. Definitive evidence for the molecular structures of these products is provided through single-crystal X-ray analysis, and in particular, the results for Sm{CyNC[N(SiMe3)2]NCy}2CH(SiMe3)2 (7) and Yb{CyNC[N(SiMe3)2]NCy}2N(SiMe3)2 (8) are presented. These results provide the first reported example of an organolanthanide complex supported by a guanidinate ligand.

Two new sulfido complexes of tin have been prepared by the reaction of styrene sulfide with novel tin(II) amidinate complexes. These compounds exhibit two very different bonding modes for the sulfido ligand; in one case, SSn(CyNC(tBu)NCy)2 (3), a terminal SnS moiety was found while in the other case, [(CyNC(Me)NCy)2Sn(μ-S)]2 (4), a bridging sulfido dimer is observed. The starting complexes were prepared by the reaction of 2 equiv of the appropriate lithium amidinate with SnCl2 to yield the new species Sn(CyNC(R)NCy)2 [Cy = cyclohexyl; R = Me (1); R = tBu (2)]. This account represents the first report of (CyNC(tBu)NCy)- and the coordination chemistry of this bulky ligand. Spectroscopic and elemental analyses confirmed the formulas of all of these new species. Compounds 2, 3, and 4 were further characterized by X-ray crystallography. Compound 2 possesses a coordination geometry based on a trigonal bipyramid with one equatorial vertex occupied by the stereochemically active lone pair of electrons. Crystal data for 2:  monoclinic, P21/c, a = 18.944(5) Å, b = 10.604(2) Å, c = 19.423(2) Å, β = 95.99(1)°, Z = 4, R = 0.046, R w = 0.049. Crystal data for 3:  orthorhombic, Cmcm, a = 12.3788(23) Å, b = 14.1977(15) Å, c = 20.670(3) Å, Z = 4, R = 0.057, R w = 0.070. Crystal data for 4:  monoclinic, P2/n, a = 13.0395(2) Å, b = 13.0263(2) Å, c = 23.8856(2) Å, β = 95.719(3)°, R = 0.055, R w 0.044.