Synthesis, Structure, and Reactivity of Stable Alkyl and Aryl Iodide Complexes of the Formula 5-C5H5)Re(NO)(PPh3)(IR)>(1+)BF4(1-)

Article abstract of DOI:10.1021/ja00195a033

Reaction of methyl complex (η⁵-C5H5)Re(NO)(PPh3)(CH3) with HBF4*Et2O (CH2Cl2, -78 deg C) and then alkyl and aryl iodides RI gives adducts <(η⁵-C5H5)Re(NO)(PPh3)(IR)>(1+)BF4(1-) (3: R = a, CH3; b, CH2CH3; c, CH2CH2CH3; d, CH2CH2CH2CH3; e, CH2Si(CH3)3; f, CH2CH2CH2Cl; g, CH2Cl; h, C6H5; i, p-C6H4OCH3; 63-87percent).The structure of 3e*(CH2Cl2)0.5 is confirmed by X-ray crystallography and compared to that of iodide complex (η⁵-C5H4CH3)Re(NO)(PPh3)(I) .The C-I bond <2.18(1) Angstroem> is not significantly longer than those in free alkyl iodides.Complexes 3a-c decompose (48-60 h, CD2Cl2, 25 deg C) to bridging halide complexes (SS,RR)-<(η⁵-C5H5)Re(NO)(PPh3)>2X(1+)BF4(1-) and react with CH3CN to give acetonitrile complex <(η⁵-C5H5)Re(NO)(PPh3)(NCCH3)>(1+)BF4(1-) (82-87percent) and RI (72-82percent).Complexes 3a-c rapidly alkylate PPh3 (<15 min, CDCl3) to give phosphonium salts Ph3PR(1+)BF4(1-) (93-86percent) and iodide complex (η⁵-C5H5)Re(NO)(PPh3)(I) (>99-92percent).The reaction of 3b and PPh3 is second order (ΔH(excit.) = 12.9 +/- 0.6 kcal/mol, ΔS(excit.) = -12.0 +/- 0.9 eu) and (3.3 +/- 1.3) x 1E5 faster (298 K) than that of ICH2CH3 and PPh3 to give Ph3PCH2CH3(1+)I(1-) (ΔH(excit.) = 16.3 +/- 0.4 kcal/mol, ΔS(excit.) = -25.9 +/- 1.5 eu).Complex 3b reacts similarly with Br(1-), but 3h yields IC6H5 and (η⁵-C5H5)Re(NO)(PPh3)(Br).Ethyl bromide and chloride complexes analogous to 3b are less stable but can be prepared in situ.