Transformation of a Phosphorus-Bound Cp* Moiety in the Coordination Sphere of Manganese Carbonyl Complexes

Abstract

The reaction of Cp*PCl 2 with K[Mn(CO) 5 ] yields two novel anionic products, [Mn 2 (CO) 8 (μ-PC 11 H 14 O)] − (1 − ) and [Mn 2 (CO) 8 (μ-PHCp*)] − (2 − ), instead of the expected phosphinidene complexes with a delocalized Mn−P−Mn bond system. By treating these anionic complexes with [Ph 3 PAuCl], they are converted into corresponding neutral derivatives [Mn 2 (CO) 8 (μ-PC 11 H 14 O)(μ-AuPPh 3 )] (3) and [Mn 2 (CO) 8 (μ-PHCp*)(μ-AuPPh 3 )] (4). NMR investigations and X-ray structural analyses for 1 − , 3, and 4 show that the compounds 1 − and 3 as well as 2 − and 4 reveal similar molecular structures in which the neutral complexes 3 and 4 contain AuPPh 3 units bridging Mn−Mn bonds. In comparison to 1 and 3, complexes 2 and 4 possess one additional H atom bound at the P atom. The structures of 1 and 3 include a novel bicyclic unit consisting of a C 5 ring of the former Cp* moiety conjugated to a CCC(O)P four-membered ring. The latter is built by a CO group of a former Mn carbonyl fragment connecting a P and a C atom of the cycle. One of the methyl groups of the Cp* ligand became a CH 2 unit, resulting in two isomers containing an exocyclic CH 2 moiety in the positions three or five of the C 5 ring. Both isomers were found in the reaction mixture, with one as the major isomer. The proposed reaction pathway is based on XRD, NMR, and MS data and includes the reduction of a transient [Cp*P(Mn(CO) 5 ) 2 ] complex by [Mn(CO) 5 ] − , a proton transfer from the neutral to the reduced complex, and a successive reduction of the protonated species. The neutral bicyclic compound 3, containing a 2phosphacyclobutanone ring, is light sensitive and decomposes to tetramethylfulvene, possibly by a radical decarbonylation mechanism via a transient phosphacyclobutane derivative, [C 5 (CH 3 ) 4 (CH 2 )P(Mn(CO) 4 ) 2 AuPPh 3 ] (5), detected by NMR spectroscopy.

Phosphinidene-bridged binuclear complexes

“…Compound 56 displays relatively short PN bonds of ca. 1.59 Å, a figure indicative of significant  interaction with the P atom, which accounts for its relatively low These reactions seem to involve the abstraction of the chlorine atom by 17-electron metal fragments generated upon M-M homolysis of the parent carbonyls, and in most cases yielded the corresponding PNR 2 -bridged binuclear complexes 57-59, except for [Ru 3 (CO) 12 ], which led instead to trimetallic or higher nuclearity compounds containing μ 3 -or μ 4 -PNR 2 ligands. All the new binuclear phosphinidene complexes were fully characterised by multinuclear NMR (range of δ P = 654-578 ppm) and X-ray diffraction, which revealed a trigonal planar environment at phosphorus compatible with delocalisation of a π bonding electron pair over the central M 2 P core.…”

“…Ang and coworkers studied the reactions of (F 3 CP) 4 and (F 3 CP) 5 towards several osmium and ruthenium clusters, obtaining a wide variety of polynuclear complexes containing phosphinidene or phosphanyl ligands derived from these reagents [68]. The only product containing a μ 2 -phosphinidene ligand was the ruthenium cluster [Ru 4 (μ-H) 2 (μ-PCF 3 )(μ 3 -PCF 3 ) 2 (CO) 12 ], a compound obtained in very low yield (8%) in the reaction of both cyclophosphanes with [Ru 4 (μ-H) 2 (CO) 12 ]. The main point of interest in this compound was the pyramidal coordination of the μ 2 -phosphinidene ligand in the crystal, which gives rise to a 31 P signal (δ P = 223 ppm) which falls between those expected for μ 3 -PCF 3 and μ 4 -PCF 3 phosphinidene ligands.…”

Reactivity Study of Pyridyl‐Substituted 1‐Metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes of Group 4 Metallocenes

“…This resulted in the thiadiazole 16 a,i nt he elimination of the Cp* ligand and in af ormal Ti species[ Cp*Ti] with only one Cp* ligand (Scheme 12). The eliminated Cp* ligand was identified as decamethylfulvalene (Cp* 2 ), [31] tetramethylfulvene [32] and pentamethylcyclopentadiene (Cp*H), [33] by comparison of the typical NMR signals to those published in the literature (below all three species are mentioned as [Cp*] for ab etter readability). In order to complete this conversion the mixture was warmed to 60 8Cf or 38 h. Afterwards, we identified [Cp*],t he formal [Cp*Ti] species, the thiadiazole 16 a and, unfortunately,s till 15 a.T hus, Cp* 2 TiCl 2 (13)s eems to be necessary for the conversion of 15 a to 16 a.T ot est this assumption,w ed issolved pure 15 a and warmed it to 85 8C.…”