Chelate and Pincer Carbene Complexes of Rhodium and Platinum Derived from Hexaphenylcarbodiphosphorane, Ph₃PCPPh₃

Abstract

The reaction of [(cod)RhCl]2 with Ph3P=C=PPh3 (1) gave the bidentate Rh(I) carbene complex, (cod)Rh[eta2-C{P(C6H4)Ph2}{PPh3}] (2), in which one of the Ph groups in 1 underwent orthometalation to form the chelate. Displacement of cod by 2 equiv of PMe3 transformed 2, via a second orthometalation event, into the Rh(III) C,C,C pincer carbene complex, HRh(PMe3)2[eta3-C{P(C6H4)Ph2}2] (3). The reaction of [Me2Pt(SMe2)]2 with 1 led directly to the analogous C,C,C pincer carbene complex of Pt(II), (Me2S)Pt[eta3-C{P(C6H4)Ph2}2] (4). DFT calculations on a model form of 3 suggest a net single sigma-bonding interaction between Rh and an sp2-hybridized carbene center, with a HOMO that is predominantly carbene pz in character.

Cyclic Carbodiphosphoranes: Strongly Nucleophilic σ‐Donor Ligands

“…The same tendency was observed with 4, which has a very long Rh1 À C1 single bond (2.115 ) that suggests very weak p donation from the metal atom to the carbodiphosphorane ligand. Interestingly, in both complexes 2 b behaves as an "inert" monodentate ligand, although all the 10] We observed similar behavior in the reaction of hexaphenylcarbodiphosphorane with [{PdClA C H T U N G T R E N N U N G (allyl)} 2 ], which gives complex 6 in near-quantitative yield (Scheme 4). [18] The carbonyl stretching frequencies of cis-[RhCl(CO) 2 L] complexes are recognized as an excellent measure for the donor and acceptor properties of the ligand L.…”

“…Several complexes with these ligands were synthesized, [9] and recently a pincertype Rh III complex was reported with hexaphenylcarbodiphosphorane as a two-electron s ligand without any p backdonation from the metal center. [10] Despite their potential, the variety of carbodiphosphoranes is very limited, due to synthetic difficulties, particularly in the cyclization, and only one cyclic carbodiphosphorane has been isolated. [11] In fact, almost all work on the coordination behavior of these ligands has been performed with hexaA C H T U N G T R E N N U N G methyl-or hexaphenylcarbodiphosphorane.…”

Reaction of Double Ylide C(PPh3)2 with [W(CO)6] – Crystal Structures of [(CO)5­W(CCPPh3)] and [(CO)5W{η1‐O2C2(PPh3)2}] and Bonding Analyses of [TM­(CCPR3)] Compounds

“…[25] When freshly prepared [(CO) 5 6 ] react in the same manner. [27] Earlier reports describe the formation of the adduct [Ph 3 PCHP{OW(CO) 5 }Ph 2 ], [28] which is not formed in our case.…”

“…[5] Similar Rh I and Rh III complexes have also been described. [6] Further compounds of the type Mǟ1, in which M are main group [7][8][9] or transition metal Lewis acids, [10][11][12] can be found in the literature.…”

“…[23] The organic chemistry of 1 has been summarized by Bestmann. [24] In this contribution we report on the outcome of the reaction of 1 with [W(CO) 6 ] in various solvents and the theoretical analysis of the main product.…”