Cycloaddition Reactions of the Phosphinidene-Bridged Complex [Mo₂Cp(μ-κ¹:κ¹,η⁵-PC₅H₄)(CO)₂(η⁶-HMes*)] with Diazoalkanes and Other Heterocumulenes

Abstract

The title phosphinidene complex reacted at room temperature with CS 2 and SCNPh to give the phosphanyl derivatives [Mo 2 Cp{- 2

P–N and N–Mo Bond Formation Processes in the Reactions of a Pyramidal Phosphinidene-Bridged Dimolybdenum Complex with Diazoalkanes and Organic Azides

“…60° with respect to the Mo 2 PN plane, thus completing a distorted-trigonal-pyramidal (TP) environment around the P atom, as found in the aforementioned derivatives of 1 . This local geometry around phosphorus has been also found in different derivatives of the trigonal phosphinidene complex [Mo 2 Cp­{μ-κ 1 :κ 1 ,η 5 -PC 5 H 4 }­(η 6 -HMes*)­(CO) 2 ] with carbene, chalcogens, alkynes, and metal carbonyl fragments added at the Mo–P multiple bond of this substrate, although in these cases steric effects seem to play a significant role as well. We further note that the P atom in compounds 2b and 3 bridges the Mo atoms in a symmetrical way (Mo–P lengths of ca.…”

“…As noted in the Introduction, reactions of the trigonal precursor of 1 with diazoalkanes proceeded in all cases along with denitrogenation, to give the corresponding phosphaalkene derivatives (Scheme ). In those instances, the reactions seem to be initiated by diazoalkane coordination at the Mo­(CO) 2 center, whereby the diazoalkane molecule behaves as a base, this eventually resulting in the formation of a P–C bond . In the case of compound 1 , as was also the case of diiron complexes [Fe 2 Cp 2 (μ-PR)­(μ-CO)­(CO) 2 ] previously investigated by us (Scheme ), the electron-precise and nucleophilic properties of its phosphinidene ligand force the reaction to be initiated the other way, that is, with the nucleophilic attack of the P atom at the terminal N atom of the diazoalkane molecule, the latter now acting as the electrophile partner in the acid–base reaction, while precluding any P–C bond formation process and therefore any subsequent denitrogenation.…”

“…6 On the other hand, we found that spontaneous denitrogenation also dominated reactions of the trigonal phosphinidene complex of type B [Mo 2 Cp(μ-κ 1 :κ 1 ,η 5 -PC 5 H 4 )(CO) 2 (η 6 -HMes*)] (Cp = η 5 -C 5 H 5 ; Mes* = 2,4,6-C 6 H 2 t Bu 3 ) with different diazoalkanes, which yielded in all cases the corresponding κ 1 :η 2 phosphaalkene-bridged derivatives, although an unprecedented and reversible H shift resulting in the formation of a MoNNCP metallacycle was detected for diazomethane on the way to the final phosphaethene product (Scheme 3). 7 We note that the electron contribution of the phosphaalkene ligand to the dimetal site in the dimolybdenum complexes is distributed differently from that in the dicobalt complex mentioned above (Scheme 1), as a result of the different electronic requirements of the metal centers in each case.…”

Chemistry of CS2- and SCNPh-adducts of the pyramidal phosphinidene-bridged complex [Mo2Cp(μ–κ1:κ1,η5-PC5H4)(CO)2(η6-HMes*)(PMe3)]

“…Therefore, it is not surprising that 2b can be protonated easily at this site. Actually, 2b reacts readily with the weak acid (NH 4 )PF 6 was even formed at a small extent when a dichloromethane solution of 2b was stirred in the presence of Na(BAr´4), due to reaction with trace amounts of water in the solvent, as noted above. In contrast, the CS 2 adduct 2a, lacking a highly charged site at the bridging ligand, failed to react with (NH 4 )PF 6 under similar conditions.…”

Unprecedented Reaction Mode of Phosphorus in Phosphinidene Rare-Earth Complexes: A Joint Experimental–Theoretical Study

“…Despite tremendous advances in insertions of CS 2 into various metal–ligand bonds and CS 2 as a source of thiocarbonyl, examples of fragmentation/recombination reactions of CS 2 are rare . Unlike transition-metal and other rare-earth metal-bridged phosphinidene complexes, ,,, the treatment of complexes 1 with 2 equiv of CS 2 in toluene at room temperature affords the unusual tandem desulfurization/coupling/cyclization products 9a and 9b in excellent yields (Scheme ). This one-pot sequence of transformations leading to the formations of two C–P bonds and one C–C bond, provides a straightforward method for the construction of 1-methyl-1 H -phosphindole-2,3-dithiol rings.…”