SYNTHESIS AND REACTIVITY OF TRANS-REF(CO)3(PPH3)2 AND TRANS-(ME3SIO)3VNRE(CO)3(PPH3)2

The d6 fluoro complex trans-ReF(CO)3(PPh3)2 (1) has been prepared in good yield by reaction of trans-ReCl(CO)3(PPh3)2 (2) with Ag(SO3CF3) followed by [N(PPh3)2]F. Addition of 2 equiv of [N(PPh3)2]Cl to 1 affords not the expected simple anion-metathesis equilibrium, but a mixture containing 2 as well as other species. The lability of 1 toward carbonyl exchange with (CO)-C-13 and toward reaction with NCS- has been examined and is far greater than that for 2. Compound 1 reacts with V(NSiMe3)(OSiMe3)3 (4) to form Me3SiF and trans-(Me3SiO)3 V = NRe(CO)3(PPh3)2 (5), whereas no reaction is observed upon addition of the chloro complex 2 to 4. Reaction of 5 with Me3SiCl cleanly substitutes chlorides for the trimethylsiloxy groups on vanadium to generate trans-Cl3V = NRe(CO)3(PPh3)2 (6), with no evidence for the expected cleavage of the nitride bridge to yield 2 and 4. Spectroscopic and solution properties of this series of compounds and comparisons of the fluoro complex (1) with its heavier halo analogues are presented.