MONONUCLEAR AND BINUCLEAR MOLYBDENUM(V) COMPLEXES OF THE LIGAND DIMETHYL-N,N'-BIS(2-MERCAPTOPHENYL)ETHYLENEDIAMINE - GEOMETRIC ISOMERS

The syntheses of mononuclear complexes cis-Mo(V)OXL (X = Cl, Br, OMe, OEt, OPh, SPh, NCS, OSiMe(3)) and two binuclear complexes Mo(2)(V)O(3) L(2) of the title ligand LH(2) are reported. Two forms of MoOCIL, with cis oxo and chloro ligands, were crystallized, one in space group P2( 1)/n, with a 10.440(2) Angstrom, b = 14.260(2) Angstrom, 12.041(2) Ang strom, beta = 102.76(2)degrees, V = 1748(1) Angstrom(3), and Z = 4, an d the other in P2(1)/n, with a = 13.564(4) Angstrom, b = 7.172(2) Angs trom, c = 18.242(6) Angstrom, beta = 95.19(1)degrees, V = 1767(2) Angs trom(3), and Z = 4. MoO(OSiMe(3))L crystallizes in space group P2(1)/c , with a = 15.923(3) Angstrom, b = 11.141(2) Angstrom, c = 14.186(2) A ngstrom, beta = 112.64(2)degrees, V = 2323(1) Angstrom(3), and Z = 4, while MoO(NCS)L crystallizes in Pna2(1), with a = 22.471(2) Angstrom, b = 12.136(2) Angstrom, c = 7.138(1) Angstrom, V = 1947(1) Angstrom(3) , and Z = 4. The four structures reveal two possible conformations for ligand L: one with trans S atoms (cis,trans-MoOCIL and -MoO(OSiMe(3)) L) and one with cis S atoms (cis,cis-MoOCIL and -MoO(NCS)L). The cis, cis isomers are converted to the cis,trans forms under reflux in MeCN at 80 degrees C. Only the cis,trans forms could be isolated for bulkie r ligands X (OPh, SPh, OSiMe(3)). A short H3C ... X interaction is pre sent in the cis,cis forms: C ... Cl = 3.07 Angstrom and C ... N = 2.93 Angstrom, for X = Cl and NCS, respectively. Infrared and electronic s pectral data provide unambiguous identification of the stereochemistry of ligand L in mononuclear complexes MoOXL. Effective removal of liga nd X = OR from cis,cis-MoO(OR)L (R = Me, Et) led to two binuclear comp lexes (Mo(V)OL)(2)(mu-O) of C-i and C-1 point symmetries. C-i-(MoOL)(2 )(mu-O). thf crystallizes in space group P2(1)/c, with a = 8.5650(5) A ngstrom, b = 15.1862(9) Angstrom, c = 16.8038(9) Angstrom, beta = 100. 183(1)Alpha, V = 2157.1(8) Angstrom(3), and Z = 2, while C-1-(MoOL)(2) (mu-O). CH2Cl2 crystallizes in space group P2(1)/c, with a = 12.5250(5 ) Angstrom, b = 24.673(1) Angstrom, c = 12.7253(6) Angstrom, beta = 10 8.070(4)degrees, V = 3738.6(3) Angstrom(3), and Z = 4. C-i-(MoOL)(2)(m u-O). thf features two cis,trans-Mo(V)OXL centers with X = mu-O, while C-1-(MoOL)(2)(mu-O). CH2Cl2 contains a cis,trapls and a cis,cis cente r. In the latter, the Mo-O-Mo link is asymmetric, allowing relief of s teric crowding on the cis,cis side of the molecule.