Preparation of trihydridostannyl complexes of rhenium stabilised by isocyanide ligands

Mixed-ligand complexes [ReBr(CO)2(CNR)nL3−n] (1–4) [R = 4-CH3OC6H4, 4-CH3C6H4, C(CH3)3; L = P(OEt)3, PPh(OEt)2; n = 1, 2] were prepared by allowing carbonyl compounds [ReBr(CO)4L] and [ReBr(CO)3L2] to react with an excess of isocyanide. Treatment of these bromocomplexes [ReBr(CO)2(CNR)nL3−n] with SnCl2 · 2H2O yielded the trichlorostannyl derivatives [Re(SnCl3)(CO)2(CNR)nL3−n] (5–8). Trihydridestannyl complexes [Re(SnH3)(CO)2(CNR)nL3−n] (9–12) were prepared by allowing trichlorostannyl compounds 5–8 to react with NaBH4 in ethanol. The trimethylstannyl derivative [Re(SnMe3)(CO)2(CNC6H4-4-CH3){PPh(OEt)2}2] (13b) was also prepared by treating [Re(SnCl3)(CO)2(CNC6H4-4-CH3){PPh(OEt)2}2] with an excess of MgBrMe in diethylether. Reaction of the tin trihydride complexes [Re(SnH3)(CO)2(CNR)nL3−n] (9–12) with CO2 (1 atm) led to dinuclear OH-bridging bis(formate) derivatives [Re{Sn(OC(H)O)2(μ-OH)}(CO)2(CNR)nL3−n]2 (14, 15). The complexes were characterised spectroscopically (IR, 1H, 31P, 13C, 119Sn NMR) and by X-ray crystal structure determination of [Re(SnH3)(CO)2{CNC(CH3)3}{PPh(OEt)2}2] (10b).