SYNTHESIS OF LOW-COORDINATE CHALCOGENOLATO COMPLEXES OF ZINC WITH O, N, S, AND P DONOR LIGANDS - MOLECULAR AND CRYSTAL-STRUCTURES OF ZN(S-T-BU3C6H2-2,4,6)2(L) (L=NC5H3ME2-2,6,PMEPH2), ZN(SE-T-BU3C6H2-2,4,6)2(OSC4H8), AND ZN(S-T-BU3C6H2-2,4,6)2(N-METHYLIMIDAZOLE)2

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-coo rdinate monomeric complexes, Zn(EAr'')2(L) (L = 2,6-lutidine, tetrahyd rothiophene, PMe3, PMePh2). From the reaction of [Zn(SeAr'')2]2 (1b) w ith excess tetrahydrothiophene the S-oxide complex Zn(SeAr'')2(OSC4H8) (12b) was also isolated and identified by X-ray diffraction. The soli d-state structures of these three-coordinate complexes are characteriz ed 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 i ncreasing E-Zn-E angles, in agreement with changes in the hybridizatio n of zinc from approximately sp2 in 12b to sp in 2a. A semiquantitativ e theoretical interpretation of these observations is proposed. With e xcess N-methylimidazole (imid) tetracoordinate complexes were obtained , Zn(EAr'')2(imid)2 (4a,b) WhiCh readily lost one donor ligand on recr ystallization from toluene to give Zn(EAr'')2(imid) (5a,b). The struct ures 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 = 20.3 52(9), c = 11.835(l) angstrom; beta = 95.03(2)-degrees; V = 4432.86 an gstrom3; R = 0.0458, R(w) = 0.0492; 2572 reflections with F(o) > 3sigm a(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 ref lections 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 = 0.05 5, 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) > 2 sigma(F(o)).