Synthesis, coordination chemistry and reactivity of cyano-functionalised N-pyrrolyl phosphines

Abstract

The cyano-functionalised N-pyrrolyl phosphines PPh 2(NC 4H 3CN-2) ( L 1 ) and P(NC 4H 4) 2(NC 4H 3CN-2) ( L 2 ) have been prepared from the reaction of PClR 2 (R=Ph, NC 4H 4) with lithium 2-cyanopyrrolide, itself generated in situ from 2-cyanopyrrole and BuLi. The reaction of L 1 or L 2 with [MCl 2(cod)] gives [MCl 2(L-κ 1 P) 2] ( 1, M=Pt, L= L 1 ; 2, M=Pd, L= L 1 ; 3, M=Pt, L= L 2 ; 4, M=Pd, L= L 2 ) and both cis- 1 and trans- 4 have been structurally characterised. The crystal structure of cis- 1 reveals the presence of an unusually wide PPtP angle [107.22(5)°], which has its origin in an intramolecular interaction between the two 2-cyanopyrrole rings. The reaction of L 1 with [M(dmba)(μ-Cl)] 2 (Hdmba= N, N-dimethylbenzylamine) results in formation of [MCl(dmba)( L 1 -κ 1 P)] ( 5, M=Pt; 6, M=Pd). Compounds 5 and 6 react with TlPF 6 to give oligomeric P, N-coordinated compounds of empirical formula [M(dmba)( L 1 )][PF 6]. The dimeric compound [Pt(dmba)(μ- L 1 -κ 1 P,κ 1 N)] 2(PF 6) 2 ( 7), has been isolated and structurally characterised, and coordination of the cyano groups leads to formation of a 12-membered ring. Compound 6 reacts with PhCH 2CH(NH 2)CH 2OH in the presence of TlPF 6 to yield [Pd(dmba)(PPh 2NC 4H 3{CNCH(CH 2Ph)CH 2O-2})]PF 6 ( 8) in which the cyano group has been transformed into an oxazoline group. The molybdenum complex [MoCl(CO) 3(η 5-C 5H 5)] reacts with L 1 to give [MoCl(CO) 2( L 1 -κ 1 P)(η 5-C 5H 5)] ( 9) which has been structurally characterised. In contrast to the reaction of 5 or 6, compound 9 does not react with TlPF 6 or AgBF 4 to give tractable oligomeric products. Reaction of the rhodium complex [Rh(acac)(CO) 2] with L 1 occurs to give [Rh(acac)(CO)( L 1 -κ 1 P)] ( 10). The infrared spectrum of 10 indicates the electronic properties of L 1 are very similar to those for PPh 2(NC 4H 4).