CHEMISTRY OF (CARBONYL)(NITROSYL)[BIS(PHOSPHORUS DONOR)]RHENIUM COMPLEXES

The chemistry of [Re(CO)(NO)L2] fragments (L = phosphorus donor) was explored. Starting from [Re(CO)5Cl] the synthesis of [Re2Cl2(mu-Cl)2(CO)4(NO)2] (1) was accomplished via the preparation of [Et4N]2[Re2Cl2(mu-Cl)2(CO)6] and nitrosylation of this compound with [NO][BF4]. Complex 1 was converted to [ReCl2(CO)(NO)L2] complexes 2 (a L = (MeO)3P; b L = (EtO)3P; c L = (i-PrO)3P; d L = Me3P; e L = Et3P; f L = Cy3P) by heating with L in MeCN. In the case of the reaction of L = (MeO)3P, a trisubstituted compound mer-{ReCl2(NO)[P(OMe)3]3} 3 was also obtained. Replacement of the Cl ligands in 2a-e with Me groups was achieved by reacting them with MeLi in Et2O yielding cis,trans-[Re(CO)(NO)Me2L2] complexes 4a-e. Reaction of 2a-e with Li[BHEt3] led to substitution of one Cl by an H ligand with formation of [ReCl(CO)H(NO)L2] compounds 5a-e, displaying trans-H,NO geometries. The hydride-transfer agent Na[AlH2(OCH2CH2OCH3)2] transformed 2 into the cis-dihydride systems [Re(CO)H2(NO)L2] 6a-f. Reductive carbonylation of 2a-d in the presence of Na/Hg and CO gave pentacoordinate [Re(CO)2(NO)L2] complexes 7b-d, and under comparable conditions the Cl substituents of 2b-f were replaced by tolane using Mg or t-BuLi giving trigonal bipyramidal [Re(CO)(NO)L2(PhC=CPh)] compounds 8b-f. Complexes 5c, 6a, and 8d were characterized by X-ray crystal-structure analysis.