Classical and Nonclassical Nitrosyl Hydride Complexes of Rhenium in Various Oxidation States

The paramagnetic rhenium complex [NEt4]2[Re(Br)5(NO)] (1) has been used to prepare a series of novel mononitrosyl hydride and dihydrogen rhenium complexes:  [Re(Br)2(NO)(η2-H2)(PR3)2] (R = iPr, 2a; Cy, 2b) and [Re(H)(BH4)(NO)(PR3)2] (R = iPr, 3a; Cy, 3b). The coordinated BH3 of the derivatives 3 can be replaced by the H2 or the NO ligand, thus leading to the tetrahydride and dinitrosyl species [Re(H)4(NO)L2] (R = iPr, 4a; Cy, 4b) or [Re(H)(NO)2(PR3)2] (R = iPr, 5a; Cy, 5b). While [Re(H)4(NO)(PPh3)2] does not seem to be stable, [Re(H)(NO)2(PPh3)2] (5c) has been obtained in a fashion similar to the preparation of 3a,b from the reaction of [Re(H)(BH4)(NO)(PPh3)2] and NOBF4. Detailed investigations of the reactions of 3a,b with NOBF4 have revealed that the compounds initially formed are the isolable BF3 adducts [Re(H)(NO)(NOBF3)(PR3)2] (R = iPr, 6a; Cy, 6b). The source of BF3 is the nitrosonium salt. Dissociation of BF3 from 6a,b takes place in donor solvents such as THF, affording the BF3-free compounds 5a,b...