Ortho Phosphorylation of PPh₃To Give a Diphosphine and Formation of a “Butterfly” Structure on a Tetrairidium Framework

Abstract

A brief thermolysis of the bis-phosphine-substituted tetrairidium cluster Ir4(CO)10(PPh3)2 (1) in chlorobenzene (CB) converts it rapidly to the diphosphine cluster Ir4(CO)7(μ-CO)3{κ2-Ph2P(o-C6H4)PPh2} (2) in 53% yield, providing evidence for ortho phosphorylation at the tetrairidium cluster framework. Treatment of 2 with excess C60 affords the “butterfly” Ir4−C60 complex Ir4(CO)6(μ-CO){μ3-κ2-Ph2P(o-C6H4)P(η1-o-C6H4)}(μ3-η2:η2:η2-C6 0) (3) in 71% yield. Interestingly, compound 3 can be prepared directly from the thermolysis of 1 with excess C60 in moderate yield (52%). Compounds 2 and 3 have been characterized by microanalysis, spectroscopy, and single-crystal X-ray diffraction studies. A molecular structure determination reveals that complex 2 adopts a regular tetrahedral geometry with three edge-bridging CO groups around the basal triangle and a diphosphine κ2-Ph2P(o-C6H4)PPh2 ligand chelating one of the basal iridium atoms. In contrast, complex 3 possesses a “butterfly” geometry in which the C60 ligand is coordinated to the lower wing of the “butterfly” by an arene type μ3-η2 :η2 :η2-C60 bonding mode. One unique feature of 3 is the presence of both ortho phosphorylated and ortho-metalated phenyl rings forming five-membered [Ir−P−C−C−P] and [Ir−Ir−P−C−C] metallocycles joined in a spiro union at the iridium−iridium-bridged phosphorus atom. A crossover experiment confirms that the conversion of 1 to 2 is intramolecular. Plausible reaction pathways for the formation of 2 and 3 are proposed.

Ligand degradation and phosphorus scavenging in the reaction between 1,2-bis(diphenylphosphino)benzene (dppbz) and Ru6(μ6-C)(CO)17: Synthesis and X-ray structure of the edge-bridged square-pyramidal cluster HRu6(μ5-C)(μ3-P)(CO)14(dppbz)

“…A check of the Cambridge Structural Database for dppbz-substituted clusters reveals Ir 4 (CO) 10 (dppbz) as the only entry. Here the chelating dppbz ligand was formed from an ortho phosphorylation of the PPh 3 ligands in Ir 4 (CO) 10 -(PPh 3 ) 2 [16]. The Ru(3)-C(32)-O(2) and Ru(2)-C(34)-O(4) carbonyls are weakly semibridging based on bond angles of 166.3(7)°and 162.9(7)°, respectively, and bent slightly towards the Ru(1) center.…”

Stabilization of coordinatively unsaturated Ir4clusters with bulky ligands: a comparative study of chemical and mechanical effects

“…32,33 Related surface reconstruction phenomena have been extensively characterized in functional systems dealing with catalysis on surfaces and selective adsorption.…”

Organo‐Transition‐Metal Cluster Complexes

“…Thermolysis of Ir 4 (m-CO) 3 (CO) 7 (PPh 3 ) 2 in chlorobenzene affords the orthophosphorylated tetrahedral cluster 41; this reacts with C 60 to give the butterfly complex 42, where the orthometallated phosphine spans three of the metal centres. 61 A study into the reactivity of Ir 4 (CO) 4 with GeHPh 3 has afforded the series of clusters 43-47 containing GePh 3 , GePh 2 and GePh in a variety of coordination modes, including ortho-metallated and m 4 -face-capping. 62 8.4 Clusters containing mixed group 9 metal atoms Reaction of the tetrahedral complex Co 2 Rh 2 (CO) 12 with two equivalents of dimethyl acetylenedicarboxylate (dmad) results in cluster fragmentation and metal redistribution to give 48 and 49; the expected simple substitution product Co 2 -Rh 2 (m 4 -dmad)(CO) 10 is not observed.…”