Synthesis and Structural Characterisation of [Ir4(CO)8(CH3)(mu4-eta3-Ph2PCCPh)(mu-PPh2)] and of the Carbonylation Product [Ir4(CO)8{C(O)CH3}(mu4-eta3-Ph2PCCPh)(mu-PPh2)]; First Evidence for the Formation of a CO Cluster Adduct before CO Insertion

Abstract

A desprotonação do cluster [(µ-H)Ir4(CO)10(µ-PPh2)], 1, leva à formação de [Ir4(CO)10(µ-PPh2)]que reage com Ph2PCCPh e CH3I para dar [Ir4(CO)8(CH3)(µ4-η 3-Ph2PCCPh)(µ-PPh2)], 2 (34%), além de [Ir4(CO)9(µ3-η 3-Ph2PC(H)CPh)(µ-PPh2)] e [(µ-H)Ir4(CO)9(Ph2PC≡CPh)-(µ-PPh2)]. O composto 2, caracterizado por uma análise de difração de raios-X, contem um arranjo metálico na forma de uma borboleta, com o ligante Ph2PCCPh interagindo com os quatro átomos de Ir e a metila ligada de modo terminal. A carbonilação de 2 resulta, inicialmente (20 min, 25 °C), na formação de um produto de adição ao poliedro metálico que, de acordo com estudos de espectroscopia de RMN de 31 P{ 1 H} e 13 C{ 1 H} a várias temperaturas, existe na forma de dois isomeros 4A and 4B (8:1) que diferem com relação à posição do grupo metila, e em seguida (40 °C, 7 h), à formação do produto de inserção de CO, [Ir4(CO)8{C(O)CH3}(µ4-η 3-Ph2PCCPh)(µ-PPh2)], 5. A carbonilação é reversível em ambos os estágios. A estrutura molecular de 5 é semelhante à de 2, com uma acila no lugar da metila. As reações de 2 com PPh3 e P(OMe)3 resultam nos produtos de substituição de CO, [Ir4(CO)7L(CH3)(µ4-η 3-Ph2PCCPh)(µ-PPh2)] (L = PPh3, 6 e P(OMe)3 7, respectivamente, ao invés dos produtos esperados de inserção de CO. Segundo estudos de RMN de 1 H e 31 P{ 1 H}, o composto 6 existe na forma de dois isômeros (1:1) que diferem com relação à posição da PPh3. Deprotonation of [(µ-H)Ir4(CO)10(µ-PPh2)], 1, gives [Ir4(CO)10(µ-PPh2)]that reacts with Ph2PCCPh and CH3I to afford [Ir4(CO)8(CH3)(µ4-η 3-Ph2PCCPh)(µ-PPh2)], 2 (34%), besides [Ir4(CO)9(µ3-η 3-Ph2PC(H)CPh)(µ-PPh2)] and [(µ-H)Ir4(CO)9(Ph2PC≡CPh)(µ-PPh2)]. Compound 2 was characterised by a single crystal X-ray diffraction analysis and exhibits a flat butterfly of metal atoms, with the Ph2PCCPh ligand interacting with all four Ir atoms and the methyl group bonded terminally to a wingtip Ir atom. Carbonylation of 2 yields initially (25 °C, 20 min) a CO addition product that, according to VT 31 P{ 1 H} and 13 C{ 1 H} studies, exists in solution in the form of two isomers 4A and 4B (8:1), and then (40 °C, 7 h), the CO insertion product [Ir4(CO)8{C(O)CH3}-(µ4-η 3-Ph2PCCPh)(µ-PPh2)], 5. The molecular structure of 5, established by an X-ray analysis, is similar to that of 2, except for the acyl group that remains bound to the same Ir atom. The process is reversible at both stages. Treatment of 2 with PPh3 and P(OMe)3 affords the CO substitution products [Ir4(CO)7L(CH3)(µ4-η 3-Ph2PCCPh)(µ-PPh2)] (L = PPh3, 6 and P(OMe)3, 7), instead of the expected CO inserted products. According to the 1 H and 31 P{ 1 H} NMR studies, the PPh3 derivative 6 exists in the form of two isomers (1:1) that differ with respect to the position of this ligand.

Reaction of the heterometallic cluster Os3Ru(μ-H)2(CO)13 with diphenylphosphine: phosphido-bridged tetrahedral and butterfly clusters

“…In 5, the phosphido bridge is across an open RuÁ Á ÁOs edge and hence the angle at the phosphorus atom is correspondingly large ($106°compared to $75°for 2-4); such a phosphido bridge is rather uncommon [8]. With the exception of 4, in which the hydrides were located from a low angle difference map, the hydride locations were placed by potential energy calculations using the program XHYDEX XHYDEX [9].…”

Carbon–carbon coupling on tetrahedral iridium clusters: X-ray molecular structures and multinuclear NMR studies of the two isomeric forms of [Ir4(CO)6(μ3-η2-HCCPh)(μ2-η4-C4H2Ph2)(μ-PPh2)2]

“…doi:10.1016/j.jorganchem.2004.08.010 this tetranuclear cluster under thermolytic conditions with C 2 (COOMe) 2 , to yield [Ir 4 (CO) 8 {C 2 (COOMe) 2 } 4 ] [22], and with cod (cod = cyclooctadiene), to give the alkyne containing clusters [Ir 4 (CO) 5 (cod) 2 (C 8 H 10 )] and [Ir 7 -(CO) 12 (cod)(C 8 H 11 )(C 8 H 10 )] [23,24] all in very low yields, and that of the oxidation of [Ir 6 (CO) 15 ] 2À with ferrocinium in the presence of PhCCPh to yield [Ir 6 -(CO) 14 (l 3 -g 2 -HCCPh)] and [Ir 6 (CO) 12 (l 3 -g 2 -HCCPh) 2 ] [25]. The cluster [HIr 4 (CO) 10 (l-PPh 2 )] [26] has proven itself a good entry into tetranuclear iridium organometallic chemistry [27][28][29][30][31][32][33][34][35]. Its derivative [HIr 4 -(CO) 9 (Ph 2 PC"CPh)(l-PPh 2 )] (1) undergoes a selective rearrangement under mild conditions to give [Ir 4 -(CO) 8 (l 3 -g 2 -HCCPh)(l-PPh 2 ) 2 ] (2) [34].…”