Taking TiF4 complexes to extremes - the first examples with phosphine co-ligands

The first soft donor adducts of TiF4, [TiF4(diphosphine)] (diphosphine = o-C6H4(PMe2)(2), R2P(CH2)(2)PR2, R = Me or Et) have been prepared from [TiF4(MeCN)(2)] and the diphosphines in rigorously anhydrous CH2Cl2, as extremely moisture sensitive yellow solids, and characterised by multinuclear NMR (H-1, P-31, F-19), IR and UV/vis spectroscopy. The crystal structure of [TiF4{Et2P(CH2)(2)PEt2}] has been determined and shows a distorted six-coordinate geometry with disparate Ti-F-transF and Ti-F-transP distances and long Ti-P bonds. Weaker soft donor ligands including Ph3P, Ph2P(CH2)(2)PPh2, o-C6H4(PPh2)(2), Ph2As(CH2)(2)AsPh2, o-C6H4(AsMe2)(2) and (PrS)-Pr-i(CH2)(2)(SPr)-Pr-i do not form stable complexes with TiF4, although surprisingly, fluorotitanate(IV) salts of the previously unknown doubly protonated ligand cations [LH2][Ti4F18] (L = o-C6H4(PPh2)(2), o-C6H4(AsMe2)(2) and (PrS)-Pr-i(CH2)(2)(SPr)-Pr-i) are formed in some cases as minor by-products. The structure of [o-C6H4(PPh2H)(2)][Ti4F18] shows the first authenticated example of a diprotonated o-phenylene-diphosphine. The synthesis and full spectroscopic characterisation are reported for a range of TiF4 adducts with hard Nor O-donor ligands for comparison purposes, along with crystal structures of [TiF4(thf)(2)], [TiF4(Ph3EO)(2)]center dot 2CH(2)Cl(2) (E = P or As), and [TiF4(bipy)].