New bromo-, triflato-, and hydridotricarbonylrhenium(I) complexes with diphosphinite ligands: Structural, spectral and protonation studies of various hydrides

Bromotricarbonylrhenium(I) complexes [ReBr(CO)3L] [L = Ph2PO(CH2)3OPPh2 (L1), iPr2PO(CH2)2OPiPr2 (L2), Cy2PO(CH2)2OPCy2 (L3)] were prepared by reaction of [ReBr(CO)5] with L. X-ray crystallography showed them all to be mononuclear, with the CO ligands fac. Subsequent reaction with AgOTf gave fac-[Re(OTf)(CO)3L], as shown by IR and NMR spectra. By contrast, reaction of [ReH(CO)5] with L1–3 gave hydrido complexes, the nuclearity and stereochemistry of which depended on the identity of L, as was confirmed by X-ray crystallography of mer-[ReH(CO)3L1], fac-[ReH(CO)3L2] and [{ReH(CO)4}2(μ-L3)]. Protonation of the hydrido compounds at 183 K with HBF4 · OMe2 gave the corresponding non-classical cationic dihydrogen complexes (T1(min) ∼ 15 ms at 400 MHz), which released H2 at temperatures above critical temperatures (243–263 K) that depended on the co-ligands.