Systematic Heterodinuclear Complexes with MM′(μ-meppp) Centers That Tune the Properties of a Nesting Hydride (M = Ni, Pd, Pt; M′ = Rh, Ir; H2meppp = meso-1,3-Bis[(mercaptoethyl)phenylphosphino]propane)

Mononuclear complexes with a P2S2 ligand, [M­(meppp)] (M = Ni (1a), Pd (1b), Pt (1c); H2meppp = meso-1,3-bis­[(mercaptoethyl)­phenylphosphino]­propane), were treated with [M′Cp*Cl2]2 or [M′Cp*­(NO3)2] (Cp* = η5-pentamethylcyclopentadienyl) to afford a series of bisthiolate-bridged MIIM′III heterodinuclear complexes, [M­(μ-meppp)­M′Cp*X]­X′ (M = Ni, Pd, Pt; M′ = Rh, Ir; X = Cl, NO3; X′ = Cl, PF6, NO3). The nitrate complexes [M­(μ-meppp)-M′Cp*­(NO3)]­NO3 (M′ = Rh ([4a–c]­NO3), Ir ([5a–c]­NO3); M = Ni (a), Pd (b), Pt (c)) further reacted with sodium formate in water or methanol to be transformed into bisthiolate- and hydride-bridged complexes, [M­(μ-meppp)­(μ-H)­M′Cp*]­NO3 (M′ = Rh ([6a–c]­NO3), Ir ([8a–c]­NO3); M = Ni (a), Pd (b), Pt (c)). Complexes [6a]­NO3 (M = Ni, M′ = Rh) and [8a]­NO3 (M = Ni, M′ = Ir) were characterized by X-ray analyses to reveal that a hydride is stabilized in a semibridging mode on the heterometal centers. In the PdIIRhIII ([6b]­NO3) and PtIIRhIII ([6c]­NO3) complexes, the hydrides were extremely unstable and were likely to undergo an unusual metal-to-Cp* ring hydrogen transfer, resulting in η4-C5Me5H MIIRhI complexes, [M­(μ-meppp)­Rh­(η4-C5Me5H)]­NO3 (M = Pd ([7b]­NO3), Pt ([7c]­NO3)). The property of the hydride was drastically switched by varying the anchoring metal ions of the M′ site (Rh, Ir); that of [6a]­NO3 (M′ = Rh) is not protic and decomposes in water below pH 4, while those of [8a–c]­NO3 (M′ = Ir) are protic, subject to H+/D+ exchange reactions, and stable below pH 4. [6a]­NO3 reacted with phenylacetylene to give [Ni­(μ-meppp)­RhCp*­(CCPh)]­NO3 ([10a]­NO3), which is in contrast with the inertness of the NiIIIrIII hydride complex [8a]­NO3. The reaction is assumed to involve an alkenyl complex, [Ni­(μ-meppp)­RhCp*­(CHCHPh)]­NO3 (9a), formed through an insertion of phenylacetylene into the metal–hydride bond. Analogous MIIRhIII alkynyl complexes, [M­(μ-meppp)­RhCp*­(CCPh)]­NO3 (M = Pd ([10b]­NO3), Pt ([10c]­NO3)), were synthesized by treating [4b,c]­NO3 with phenylacetylene in basic media, and the structural differences among [10a–c]­NO3 were discussed. These results interestingly demonstrated that the structures, properties, and reactivities of the nesting hydride on the {MM′(μ-meppp)} cores were tuned by varying metal ions of the M and M′ sites.