SYNTHESIS, STRUCTURE, AND SPECTROSCOPIC PROPERTIES OF GERMANIUM AND TIN-COMPOUNDS CONTAINING ARYLOXIDE LIGATION - COMPARISON OF ARYLOXIDE BONDING TO GROUP-4 AND GROUP-14 METAL CENTERS

The mononuclear, four-coordinate germanium compounds Ge(OAr)2Cl2 (la), Ge(OAr)3Cl (1b), and Ge(OAr)2(NMe2)2 (2) (OAr = 2,6-diphenylphenoxide) are obtained when GeCl4 and Ge(NMe2)4 are treated with LiOAr and HOAr, respectively. In contrast to the case for the corresponding tin compounds, facile cyclometalation of the 2,6-diphenylphenoxide ligands does not occur. Both compounds 1 and 2 are thermally stable at 120 °C for extended periods of time. Similarly, the tin compound Sn(OAr′)2(NMe2)2 (3) (OAr′ = 2,6-di-tert-butylphenoxide) is obtained from Sn(NMe2)4 and HOAr′. Thermolysis of 3 leads only to decomposition products with no evidence for cyclometalation. The three compounds 1b, 2, and 3 have been structurally characterized and shown to contain an almost regular tetrahedral environment about the Ge and Sn metal centers. Despite the steric congestion within the coordination sphere, the M-O-Ar angles all lie in the 120-125° range. A comparison of aryloxide binding to group 14 and group 4 metal centers is made, showing the dramatic structural effect of π-bonding to the d-block metals. Crystal data are as follows: for GeClO3C57H45 (1b) at 20 °C, a = 41.568 (6) Å, b = 10.759 (3) Å, c = 21.675 (3) Å, β = 110.04 (1)°, Z = 8, dcalcd = 1.288 g cm-3 in space group C2/c; for GeO2N2C40H38 (2) at 20 °C, a = 10.378 (1) Å, b = 17.094 (3) Å, c = 19.076 (2) Å, Z = 4, dcalcd = 1.278 g cm-3 in space group P212121, for SnO2N2C34H50 (3) at 20 °C: a = 8.446 (4) Å, b = 23.589 (2) Å, c = 17.300 (5) Å, β = 94.05 (2)°, Z = 4, dcalcd = 1.247 g cm-3 space group P21/n. © 1990, American Chemical Society. All rights reserved.