SYNTHESIS AND CRYSTAL-STRUCTURES OF THE NOVEL TETRAMERIC NITRIDO COMPLEXES [(CYELO-REN)(4)(S2CNET2) (6)(MEOH)(2)(PPH3)(2)][BPH4](2.).CH2CL2.2H(2)O AND [(CYCLO-REN)(4)(S2CNET2)(4)CL-4(PME2PH)(4)].2 ACETONE

Novel tetrameric rhenium(V) complexes have been prepared from [ReNCl2( PPh3)(2)] and [ReN(PMe2Ph).(S2CNEt)(2)], respectively. [ReNCl2(PPh3)(2 )] reacts with 1.5 equivalents of KS2CNEt2 in methanol to yield the un usual dark red species -ReN}(4)(S2CNEt2)(6)(MeOH)(2).(PPh3)(2)][BPh4]( 2). CH2Cl2. 2H(2)O (1). The crystal structure of the tetramer (triclin ic, space group P (1) over bar, a = 13.842(2), b = 15.213(2), c = 16.7 96(3) Angstrom, alpha = 67.88(1), beta = 70.90(1), gamma = 88.05(1)deg rees, U = 3080.2(8) Angstrom(3), Z = 1) shows four rhenium atoms in a square configuration which are bridged via linear asymmetric Re=N-Re g roups with bond lengths of about 169 and 203 pm. The molecule contains a centre of symmetry with two distinct octahedral rhenium environment s. The first rhenium environment contains two bidentate dithiocarbamat e ligands which complete the octahedral geometry and the second contai ns a bidentate dithiocarbamate ligand, coordinated methanol and has re tained a single phosphine coligand. A symmetric compound containing th e {cyclo-ReN}(4) core is obtained from the reaction of [ReN(PMe2Ph)(S2 CNEt2)(2)] with Al2Cl6 in acetone. [{cyclo-ReN}(4)(S2CNEt2)(4)Cl-4.(PM e2Ph)(4)]. 2 acetone (2) forms red crystals (monoclinic, space group C 2/c, a = 21.432(6), b = 13.700(3), c = 28.060(9) Angstrom, beta = 102. 37(1)degrees, U = 8048(4) Angstrom(3), Z = 4) with each rhenium atom c oordinated by a bidentate dithiocarbamato, a phosphine and a chloro li gand. The non-planar 8-membered {ReN}(4) ring contains asymmetric Re=N -Re bridges (mean values: 1.69 Angstrom and 2.029 Angstrom, respective ly). In contrast, reaction of [ReNCl(S2CNEt2)(PMe2Ph)(2)] with one equ ivalent of K[S2CN(Me)CH2CH2NMe3]I gave the mixed dithiocarbamato-catio n [ReN(S2CNEt2).(S2CN(Me)CH2CH2NMe3)(PMe2Ph)](+) (3) which was isolate d as a tetraphenylborate salt.