Transition metal chemistry of cyclodiphosphanes containing phosphine and amide-phosphine functionalities: Formation of a stable dipalladium(II) complex containing a Pd–P σ-bond.

Abstract

Cyclodiphosphazanes containing phosphine or phosphine plus amide functionalities {((t)BuNP(OC(6)H(4)PPh(2)-o)}(2) (3), {(t)BuNP(OCH(2)CH(2)PPh(2))}(2) (4), {(t)BuHN((t)BuNP)(2)OC(6)H(4)PPh(2)-o} (5), and {(t)BuHN((t)BuNP)(2)OCH(2)CH(2)PPh(2)} (6) were synthesized by reacting cis-{(t)BuNPCl}(2) (1) and cis-[(t)BuHN((t)BuNP)(2)Cl] (2) with corresponding phosphine substituted nucleophiles. The reactions of 3 and 5 with excess of elemental sulfur or selenium produce the corresponding tetra and trichalcogenides, {((t)BuNP(E)(OC(6)H(4)P(E)Ph(2)-o)}(2) (7, E = S; 8, E = Se) and {(t)BuHN((t)BuNP)(2)OC(6)H(4)P(E)Ph(2)-o} (9, E = S; 10, E = Se), respectively, in quantitative yields. The reactions between 3 and [Rh(COD)Cl](2) or [M(COD)Cl](2) (M = Pd or Pt) afford bischelated complexes [Rh(CO)Cl{(t)BuNP(OC(6)H(4)PPh(2)-o)}](2) (11), and [MCl(2){(t)BuNP(OC(6)H(4)PPh(2)-o)}](2) (12, M = Pd; 13, M = Pt) in good yield. The 1 : 2 reaction between 3 and [PdCl(η(3)-C(3)H(5))](2) in dichloromethane resulted initially in the formation of a tripalladium complex of the type [Pd(3)Cl(4)(η(3)-C(3)H(5))(2){(t)BuNPOC(6)H(4)PPh(2)}(2)] (14a) which readily reacts with moisture to form an interesting binuclear complex, [Cl(2)Pd{μ-(PPh(2)C(6)H(4)OP(μ-(t)BuN)(2)P(O)}(μ-Cl)Pd(OC(6)H(4)PPh(2))] (14b). One of the palladium(II) atoms forms a simple six-membered chelate ring, whereas the other palladium(II) atom facilitates the moisture assisted cleavage of one of the endocyclic P-O bonds followed by the oxidation of P(III) to P(V) thus forming a Pd-P σ-bond. The broken ortho-phosphine substituted phenoxide ion forms a five-membered palladacycle with the same palladium(II) atom. Similar reaction of 5 with [PdCl(η(3)-C(3)H(5))](2) also affords a binuclear complex [{PdCl(η(3)-C(3)H(5))}(t)BuNH{(t)BuNP}(2)OC(6)H(4)PPh(2){PdCl(2)}] (15) containing a PdCl(2) moiety which forms a six-membered chelate ring via ring-phosphorus and PPh(2) moieties on one side and a PdCl(η(3)-C(3)H(5)) fragment coordinating to amide bound phosphorus atom on the other side of the ring. Treatment of 3 with four equivalents of AuCl(SMe(2)) produces a tetranuclear complex, [(AuCl)(4){(t)BuNP(OC(6)H(4)PPh(2))}(2)] (16), whereas a 1 : 3 reaction between 5 and AuCl(SMe(2)) leads to the formation of a trinuclear complex, [(t)BuNH{(t)BuNP(AuCl)}(2)OC(6)H(4)P(AuCl)Ph(2)] (17). The crystal structures of 3, 5, 9-11 and 13-17 are reported.