Asymmetrical Platinum and Rhodium Dinuclear Complex Strongly Bound to Filled d Complexes by Unbridged Pt−Metal Bonds: Toward Heterometallic‐Extended Metal Atom Chains

Abstract

Heterometallic extended metal atom chains (EMACs) aligned with three types of metal were rationally synthesized by forming unbridged metal−metal bonds based on the interactions between highest occupied and lowest unoccupied molecular orbitals at the d z2 ${{_{{\rm z}{^{2}}}}}$ orbital. These chains form pentanuclear structures aligned as Rh−Pt−M−Pt−Rh with relatively large formation constants of 5.0×1013 M−2 for M=Pt and 6.3×1011 M−2 for M=Pd, while retaining their backbones in solution. In the case of M=Cu, the original Cu(+2) atoms were reduced to Cu(+1) during the synthetic process. Cu(+1) has an unprecedented trigonal bipyramidal coordination geometry. The reported synthesis based on asymmetrical dinuclear complexes provides a guideline for the synthesis of hetero‐EMACs to allow several analogs through judicious combinations realized by tuning the number of metal nuclei and metal species.

Structure and redox behaviour of a paramagnetic Rh–Pt–Cu–Pt–Rh heterometallic-extended metal-atom chain

“…Crystal 2 contains MeCN molecules from the mother solvent but no countercations and anions from the starting materials. The unbridged Pt–Cu distances (3.14655(12) Å) in 2 are similar to those found in 3 (3.1632(11) and 3.0472(9) Å), 39 but are longer than the bridged Pt–Cu distances in cis -[Pt 2 Cu(piam) 4 (NH 3 ) 4 ](PF 6 ) 2 (2.6870(6) Å) 45 and trans -[Pt 2 Cu(piam) 4 (NH 3 ) 4 ](ClO 4 ) 2 (2.6495(5) and 2.6575(5) Å). 46 The Rh–Pt distances (2.7328(2) Å) in 2 are slightly longer than those in 1 (2.7289(8) Å) and 3 (2.7197(5) and 2.7092(5) Å).…”

“…44 Rapid evaporation of the orange solution yields orange single crystals of 3 . 39 As shown in proposed experimental scheme (Scheme S1†), this reaction involves various species. The paramagnetism in the solution was quantitatively evaluated using electron paramagnetic resonance (EPR) measurements (Fig.…”

“…HOMO–LUMO interactions between the d z 2 orbitals of the constituents are useful in the synthesizing diamagnetic, 37,38 solution-stable Rh–Pt–M–Pt–Rh EMACs. 39 Although the d x 2 − y 2 orbital is the SOMO in d 9 [Cu II Cl 4 ] 2− , a mixture of 1 with [CuCl 4 ] 2− produces a trigonal bipyramidal [Cu I Cl 3 ] 2− unit within the diamagnetic pentanuclear [PtRhCl 2 (piam) 2 (NH 3 ) 2 (PPh 3 )] 2 [CuCl 3 ] ( 3 ), aligned as Rh–Pt–Cu–Pt–Rh. 39 This structure is an unprecedented example of a trigonal bipyramidal Cu( i ) complex, although several Cu( i ) species have trigonal planar geometries.…”

“…39 Although the d x 2 − y 2 orbital is the SOMO in d 9 [Cu II Cl 4 ] 2− , a mixture of 1 with [CuCl 4 ] 2− produces a trigonal bipyramidal [Cu I Cl 3 ] 2− unit within the diamagnetic pentanuclear [PtRhCl 2 (piam) 2 (NH 3 ) 2 (PPh 3 )] 2 [CuCl 3 ] ( 3 ), aligned as Rh–Pt–Cu–Pt–Rh. 39 This structure is an unprecedented example of a trigonal bipyramidal Cu( i ) complex, although several Cu( i ) species have trigonal planar geometries. 40–43 In this study, we isolated paramagnetic [PtRhCl 2 (piam) 2 (NH 3 ) 2 (PPh 3 )] 2 [CuCl 4 ]·2MeCN ( 2 ) as a Rh–Pt–Cu–Pt–Rh chain by mixing [CuCl 4 ] 2− with 1 (Fig.…”

“…46 The Rh–Pt distances (2.7328(2) Å) in 2 are slightly longer than those in 1 (2.7289(8) Å) and 3 (2.7197(5) and 2.7092(5) Å). 39…”