Photochemistry of binuclear ferraazetines: carbon monoxide vs alkyne insertion

Abstract

An investigation of the low-temperature matrix isolation photochemistry of ferraazetines, Fe2(g-CRCHNBul 2)(CO)6 (la, R = H; lb, R = CH=CHPh) in rigid matrices is reported. Near-UV irradiation of la and lb in CO-saturated methylcyclohexane (MCH) at 298 K yields ferrapyrrolinones 2a and 2b, Fe2|g-CRCHNBulC(0)|(C0)6, and in the presence of ZerZ-butylacetylene, la and lb form ferrapyridines 3a and 3b, 2(µ-€ € = :)(€0)6.The photoinduced insertion of CO and ZerZ-butylacetylene occur at different positions in the ferraazetine metallacycle. CO insertion occurs between the Fe-N bond of the metallacycle whereas Zerz-butylacetylene insertion occurs between the Fe-C bond. At 15 or 8 K in MCH, 1:1 ZerZ-butyl acetylene/MCH, or CO matrices, the primary photoprocess for la and lb involves Fe-N bond cleavage to yield coordinatively unsaturated compounds 4a and 4b, respectively. Irradiation of 4a in a MCH matrix gives bridging CO compound 5, ß2(µ-0 0 1)(µ-0 )(0 )5, which is formed by a CO ligand swinging from the adjacent Fe center to occupy the vacant coordination site created by the Fe-N cleavage. In a 1:1 zerz-butylacetylene/ MCH matrix, irradiation of 4a at 98 K gives a Zez-r-butylacetylene adduct 6, ß2(µ-0 0 )(0 )6( 1€=0 ). When warmed to 298 K, 6 inerts the ZerZ-butylacetylene ligand to form 3a. Irradiation of 4a in a 13CO matrix at 8 K gives CO insertion product 2a with l3CO incorporation at a terminal position with no evidence of incorporation at the carbonyl of the acyl ligand. When 4b is irradiated in MCH at 15 K, compound 7, Fe2^-C(CH=NBu')CHCHPh)(CO)6, is formed. 7 derives from a ligand exchange of the C=NBu' group of the ferraazetine ring in 4b for its pendant styryl group, CH=CHPh. When irradiated at 98 K or 298 K in MCH, lb forms 7 with no detectable intermediates and the photoconversion is much faster at these temperatures than at 15 K. At 298 K 7 quantitatively re-forms lb after 2 h in the dark.

Isolation and Reactivity of an Iron Azametallacyclobutene Complex

“…Subsequent reductive elimination provides the β-alkynyl enamine product. This reactivity differs from what has been observed for titanium, wherein exposure of the azatitanacyclobutene to terminal alkynes leads to metal–carbon migratory insertion to form azatitanacyclohexadiene complexes (Scheme a). ,− …”

Insertion of Acetylene and Nitriles into a Ru−C Bond of a Dicationic Triruthenium Complex Having a μ3-η3-C3 Ring: Formation of Six-Membered Ruthenacycles on a Triruthenium Core

“…A series of bimetallic complexes having a μ-η 3 -2-azametallacyclohexadienyl ligand, M 2 (CO) 6 (μ-η 3 -NRCH−CHCRCR−)(M = Fe and Ru) have been synthesized by Geoffroy’s group and Elsevier’s group. , The release of pyrrole from the diiron center of Fe 2 (CO) 6 (μ-η 3 -NR′CH−CHCRCR−) has been observed upon thermolysis or oxidation using AgBF 4 . In contrast to the diiron complex, 18 was inert to thermolysis; this is probably due to the trimetallic skeleton of 18 , namely, the C 4 N ligand was tightly bound to the three ruthenium atoms.…”