Synthesis and crystal structures of the complexes [RhPt(µ-H)(µ-CO)(PEt3)2(PPh3)(η5-C2B9H11)] and [RhPt{σ-C(C6H4Me-4)C(C6H4Me-4)H}(CO)(PEt3)(PPh3)(η5-C2B9H11)]

Abstract

The reaction between [NEt₄][Rh(CO)(PPh₃)(η⁵-C₂B₉H₁₁)] and [PtCl(H)(PEt₃)₂] in acetone, in the presence of TIBF₄, affords the dimetal compound [RhPt(µ-H)(µ-CO)(PEt₃)₂(PPh₃)(η⁵-C₂B₉H₁₁)]. The structure of this complex has been established by an X-ray diffraction study. The Rh–Pt bond [2.734(2)Å] is bridged by a hydrido ligand [Rh–H 1.7(2), Pt–H 1.8(2)Å] and by a carbonyl group [Rh–CO 1.99(1), Pt–CO 1.99(1)Å; Rh–C–O 133(1), Pt–C–O 141(1)°]. The platinum atom carries the two PEt₃ ligands [Pt–P 2.275(4) and 2.335(4)Å], while the rhodium atom is co-ordinated by the PPh₃ molecule [Rh–P 2.257(4)Å] and the five atoms [graphic omitted] in the pentagonal face of the nido-C₂B₉H₁₁ cage. Treatment of this dimetal compound with the alkynes RCCR (R = Ph or C₆H₄Me-4) in tetrahydrofuran at room temperature affords the complexes [RhPt{σ-C(R)C(R)H}(CO)(PEt₃)(PPh₃)(η⁵-C₂B₉H₁₁)]. An X-ray diffraction study on the species with R = C₆H₄Me-4 revealed the following structural features. The Rh–Pt bond [2.762(1)Å] is bridged by the C₂B₉H₁₁ cage such that the latter is η⁵ co-ordinated to the rhodium atom while forming an exopolyhedral bond to the platinum via a three-centre B–H ⇀ Pt linkage. The boron atom involved lies in the pentagonal face of the cage ligating the rhodium, and is in the β site with respect to the two carbon atoms. The rhodium atom is co-ordinated by a PPh₃[Rh–P 2.294(2)Å] and a CO [Rh–CO 1.845(8)Å] group. The platinum atom carries the PEt₃ ligand [Pt–P 2.221(2)Å] and a σ bonded cis-C(C₆H₄Me-4)C(C₆H₄Me-4)H vinyl group [Pt–C 2.036(7)Å]. N.m.r. data (¹H,¹³C-{¹H},³¹P-{¹H}, and ¹¹B-{¹H}) for the compounds are reported and discussed.