Heterodinuclear Cu(I)/Mo(VI) chemistry with bifunctional dibenzobarrelene ligands.

Bifunctional dibenzobarrelene ligands combining diphosphine with diol or other potentially bidentate functionalities are well-known mononucleating ligands for middle and late transition metals. These ligands generally exhibit tetradentate coordination, in which a metal is coordinated by [PC(sp)P] 3-dimensional pincer and an additional alkoxide donor. These ligands can also be envisioned as heterodinucleating ligands, which coordinate a soft, late metal ( the diphospine) and a hard, early metal ( the diolate); the heterodinucleating reactivity of these ligands has not been studied. Herein we describe our initial studies on Cu(I)/Mo(VI) chemistry of the diphosphine/diol ligand L1H2; it is compared with the dibenzobarrelene ligand combining diphosphine with diester (L2). Both ligands led to stable Cu(I) complexes in which the ligand coordinates as a bidentate diphosphine. Spectroscopic characterization (carried out in CDCl) revealed an AB system for the diastereotopic phosphine groups in P {H} NMR spectrum. The phosphorus signals appear as an AB system due to the large values of , 120-150 Hz. Cu NMR spectroscopy (conducted in concentrated CDCN solutions) revealed broad Cu signals at, or below, room temperature. The observation of a quadrupolar Cu ( = 3/2) signal was accompanied by the broadening of the P signals, which now appear as a single broad peak. The reaction of both ligands with (EtN)[MoO] failed to form well-defined products. Treatment of Cu(NCMe)(LH) with (EtN)[MoO], followed by recrystallization from DMSO/ether, revealed the structure of a trinuclear complex [MoO(μ-O){Cu(DMSO)(LH)}] in which one Mo(VI) center is linked with two Cu(I) centers oxo bridging ligands. In DMSO solution, the trinuclear complex likely forms discrete ionic species [Cu(DMSO)(LH)][MoO] or [Cu(DMSO)(LH)][EtN][MoO].