A heterobimetallic journey from ambiphilic Ti phosphide to nucleophilic Ti/Ir phosphinidene

Ambiphilic phosphides (PX₂ ^-) are a scarcely studied class of chemically non-innocent ligands in which the central phosphorus atom behaves both as a nucleophile and an electrophile. Here, we show that an ambiphilic Ti phosphide engages in successive rearrangements, yielding Ti/Ir and Ti/Rh heterobimetallic complexes with intriguing properties. For instance, complex 3^Ir is a highly active hydrosilylation catalyst for carbonyl compounds with Turnover Numbers (TONs) of up to 47 500. Trimetallic Au/Ti/Ir and Fe/Ti/Ir complexes 4 and 5 were also synthesized. In addition, we report complex 7, the first structurally characterized example of a Group 4/Group 9 bridging phosphinidene, which is also highly pyramidalized and nucleophilic. The bonding situation in these complexes was studied using intrinsic bonding orbitals (IBOs) and the Quantum Theory of Atoms In Molecules (QTAIM) analysis. The correlation between the delocalization index (DI) and the penetration index (p) defines an ionicity parameter (ι) and a bonding threshold (BT), such that p = ι·DI + BT. Two atoms with p < 90% should be considered non-bonded. Within this conceptual framework, the interactions studied in this paper (Ti-Ir, Ti-Rh, Ti-P and Ir-P) correspond to more or less ionic flavors of dative bonds.