Reactions of the cationic fragments [RuCp(PPh2NHR) 2]+ and [RuTp(PPh2NHR)2]+ (R = Ph, re-Pr) with Alkynes: Formation of four-membered azaphosphacarbenes

Article abstract of DOI:10.1021/om050247a

The synthesis of RuCp(PPh₂NHR)₂Cl (1a,b; R = Ph, n-Pr) and RuTp(PPh₂NHR)₂Cl (2a,b) is reported. Chloride abstraction from 1a with AgCF₃SO₃ affords RuCp(PPh ₂NHPh)₂(η¹-OSO₂CF₃) (3), whereas when AgSbF₆ is used instead [RuCp(κ²(P, P)-PPh₂NHC₆H₄PPh₂)(NH ₂-Ph)]⁺ (4) is formed. In the course of this reaction the P-N bond of one PPh₂NHPh ligand is cleaved while a new P-C bond is formed, with concomitant formation of an aniline ligand. In the presence of Ag⁺ (CF₃SO₃^- or SbF₆ ^-) complexes 1 and 2 react with terminal alkynes HC≡CR′ (R′ = Ph,p-C₆H₄Me, n-Bu) and propargylic alcohols to give novel azaphosphacarbene complexes of the types [RuCp(κ ²(C,P)=C(CH₂R′)N(R)PPh₂) (κ¹(P)-PPh₂NHR)]⁺ (5a-c, 6a-c), [RuTp(κ²(C,P)=C(CH₂R′)N(R)PPh ₂)(κ¹(P)-PPh₂NHR)]⁺ (14a,b, 15a-c), [RuCp(κ²(C,P)= C(CH=CPh₂)N(Pr ⁿ)PPh₂)(κ¹(P)-PPh₂NHPr ⁿ)]+ (12), and [RuTp(κ²(C,P)=C(CH=CPh ₂)N(Prⁿ)-PPh₂)(κ¹(P)-PPh ₂NHPrⁿ)]⁺ (17). These reactions proceed via vinylidene and allenylidene intermediates, respectively, which could be isolated in some cases: viz. [CpRu(PPh₂NHPh)₂-(=C=C=CPh ₂)]⁺ (11) and [RuTp(PPh₂NHR) ₂(=C=C=CPh₂)]⁺ (16a,b). Furthermore, complexes 1a,b react with 3-butyn-1-ol to yield the oxacyclopentylidene complexes [CpRu(PPh₂-NHR)₂(=C₄H₆O)] ⁺ (7a,b). In sharp contrast to 6a-c (R = n-Bu), 5a-c (R = Ph) turned out to be quite sensitive toward traces of water, leading eventually to the formation of the aminocarbene complexes [RuCp(=C(CH₂R)NHPh)(PPh ₂NHPh)(κ¹(P)-PPh₂OH)]⁺ (8a,b) featuring a κ¹(P)-coordinated PPh₂OH ligand. This ligand could be easily deprotonated to yield the neutral complex RuCp(=C(CH ₂Ph)NHR)(PPh₂NHPh)(κ¹(P)-OPPh ₂) (10a,b). The formation of these complexes is reversible. Finally, representative structures have been determined by X-ray crystallography.