THE FIRST COMPLETE CRYSTAL-STRUCTURE OF A STANNATRANE - TRIMERIC METHYL(2,2',2''-NITRILOTRIETHOXY)STANNANE HEXAHYDRATE (REPRINTED FROM INORG CHEM, VOL 22, PG 3692, 1983)

An X-ray analysis of the 1-methylstannatrane hexahydrate [MeSn(OCH2CH2 )(3)N](3) . 6H(2)O (4) revealed a trimeric formulation. It crystallize s in the monoclinic space group C2/c (Z = 4) with a = 9.206 (3) Angstr om, b = 13.774 (5) Angstrom, c = 26.581 (4) Angstrom, and beta = 93.33 (2)degrees. The structure refined to R = 0.074 and R(w) = 0.086. The trimeric unit is disordered about a twofold axis, which passes through the central Sn atom. The geometry around this central atom closely ap proximates a pentagonal bipyramid. The two crystallographically equiva lent end tin atoms have distorted-octahedral geometries. Strong associ ation of the three monomeric methylstannatrane units formally leading to the trimer is suggested by the short Sn-O bond lengths involved. Th ese have values of 2.11 (1) and 2.21 (1) Angstrom, as compared to corr esponding values within the monomers of 2.17 (1) and 2.23 (1) Angstrom , respectively. The solid-state structure agrees with solution NMR dat a suggesting its retention in solution. The trimeric unit is indicated in solution as is the presence of three nonequivalent tin centers. Th e structure of 4 is compared with other seven-coordinated tin compound s. The six water molecules of 4 appear hydrogen bonded to each other, forming hexagonal rings that contain inversion centers. Additional hyd rogen bonding binds the rings to adjacent molecules of 4.