The dimeric complexes [Zn(EAr")2]2 (la, E = S; lb, E = Se) (Ar" = 2,4,6-t-Bu3C6H2) reacted with N. S. or P donor ligands to give three-coordinate monomeric complexes, Zn(EAr")2(L) (L = 2,6-lutidine, tetrahydrothiophene, PMe3, PMePh2). From the reaction of [Zn(SeAr")2]2 (1b) with excess tetrahydrothiophene the S-oxide complex Zn(SeAr")2(OSC4H8) (12b) was also isolated and identified by X-ray diffraction. The solid-state structures of these three-coordinate complexes are characterized by a surprisingly wide variation of the E-Zn-E angles, ranging from 129.0(2)-degrees (L = OSC4H8) to 156.26(4)-degrees (L = 2,6-lutidine). The Zn-E bond distances are bond angle dependent and decrease with increasing E-Zn-E angles, in agreement with changes in the hybridization of zinc from approximately sp2 in 12b to sp in 2a. A semiquantitative theoretical interpretation of these observations is proposed. With excess N-methylimidazole (imid) tetracoordinate complexes were obtained, Zn(EAr")2(imid)2 (4a,b) WhiCh readily lost one donor ligand on recrystallization from toluene to give Zn(EAr")2(imid) (5a,b). The structures of these three- and four-coordinate complexes illustrate that the metal-ligand bond lengths even in zinc chalcogenolato complexes with a high degree of steric hindrance are determined by electronic rather than steric factors. Crystal data are as follows. Zn(SAr")2(NC5H3Me2-2,6) (2a) : monoclinic space group C2/c; Z = 4; a = 18.475(2), b = 20.352(9), c = 11.835(l) angstrom; beta = 95.03(2)-degrees; V = 4432.86 angstrom3; R = 0.0458, R(w) = 0.0492; 2572 reflections with F(o) > 3sigma(F(o)). Zn(SAr")2(imid)2 (4a) : monoclinic space group P2(1)/c, Z = 4; a = 17.438(5), b = 15.894(5), c = 17.964(5) angstrom; beta = 109.58(2)-degrees; V = 469 1.o angstrom3; R = 0.0665, R(w) = 0.0933; 2768 reflections with F(o) > 6sigma(F(o)). Zn(SAr")2(PMePh2) (8a) : monoclinic space group P2(1)/c; Z = 4; a = 16.971(2), b = 15.887(l), c = 19.509(5) angstrom, beta = 117.87(1)-degrees; V = 4649.88 angstrom3; R = 0.055, R(w) = 0.059; 6788 reflections with F(o) > 2sigma(F(o)). Zn(SeAr")2(OSC4H8) (12b) : monoclinic space group C2/c; Z = 4; a = 17.706(6), b = 9.141(2), c = 27.338(8) angstrom; beta = 104.64(3)-degrees; V = 4281.21 angstrom3; R = 0.068, R(w) = 0.073; 2047 reflections with F(o) > 2sigma(F(o)).