Isocyanate Insertion into a La–P Phosphide Bond: A Versatile Route to Phosphaureate-Bridged Heterobimetallic Lanthanide–Coinage-Metal Complexes

A new route to heterobimetallic lanthanide–coinage-metal complexes is disclosed. The selective insertion of organic substrates such as phenyl iso­(thio)­cyanate into the La–P bond of the primary phosphido complex (PN) 2 La­(PHMes) (1) (with PN– = (N-(2-(diisopropylphosphanyl)-4-methylphenyl)-2,4,6-trimethylanilide) yields the phospha­(thio)­ureate complexes (PN) 2 La­(OC­(NPh)­(PHMes)) (2) and (PN) 2 La­(SC­(NPh)­(PHMes)) (3) with retention of the PH protons. Subsequent deprotonation of the phosphaureate complex 2 with potassium hexamethyldisilazide (KHMDS, K­[N­(SiMe3)2]) leads to the polymeric complex [K­{(PN) 2 La­(OC­(NPh)­(PMes))}] n (4). Complex 4 was found to be an excellent precursor for salt metathesis reactions with copper­(I) and gold­(I) chlorides supported by an N-heterocyclic carbene (NHC, 5 and 6) or a cyclic alkyl amino carbene (CAAC, 7 and 8). This resulted in the unprecedented formation of heterobimetallic lanthanum–coinage-metal complexes, containing the first example of a μ,κ2(O,N):κ1(P)-phosphaureate bridging ligand. For an alternative route to complex 8 a direct protonolysis protocol between a new basic gold­(I) precursor, namely ( Me CAAC)­Au­(HMDS), and 2 was also investigated. The complexes have been characterized by multinuclear NMR spectroscopy, IR spectroscopy, and X-ray crystallography (except for 8).