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

Cyclodiphosphazanes containing phosphine or phosphine plus amide functionalities {((BuNP)-Bu-t(OC6H4PPh2-o)}(2) (3), {(BuNP)-Bu-t(OCH2CH2PPh2)}(2) (4), {(BuHN)-Bu-t((BuNP)-Bu-t)(2)OC6H4PPh2-o} (5), and {(BuHN)-Bu-t((BuNP)-Bu-t)(2)OCH2CH2PPh2} (6) were synthesized by reacting cis-{(BuNPCl)-Bu-t}(2) (1) and cis-[(BuHN)-Bu-t((BuNP)-Bu-t)(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, {((BuNP)-Bu-t(E)(OC6H4P(E) Ph-2-o)}(2) (7, E = S; 8, E = Se) and {(BuHN)-Bu-t((BuNP)-Bu-t)(2)OC6H4P(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{(BuNP)-Bu-t(OC6H4PPh2-o)}](2) (11), and [MCl2{(BuNP)-Bu-t(OC6H4PPh2-o)}](2) (12, M = Pd; 13, M = Pt) in good yield. The 1 : 2 reaction between 3 and [PdCl(eta(3)-C3H5)](2) in dichloromethane resulted initially in the formation of a tripalladium complex of the type [Pd3Cl4(eta(3)-C3H5)(2){(BuNPOC6H4PPh2)-Bu-t}(2)] (14a) which readily reacts with moisture to form an interesting binuclear complex, [Cl2Pd{mu-(PPh2C6H4OP(mu-(BuN)-Bu-t)(2)P(O)}(mu-Cl)Pd(OC6H4PPh2)] (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 sigma-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(eta(3)-C3H5)](2) also affords a binuclear complex [{PdCl(eta(3)-C3H5)}(BuNH)-Bu-t{(BuNP)-Bu-t}(2)OC6H4PPh2{PdCl2}] (15) containing a PdCl2 moiety which forms a six-membered chelate ring via ring-phosphorus and PPh2 moieties on one side and a PdCl(eta(3)-C3H5) fragment coordinating to amide bound phosphorus atom on the other side of the ring. Treatment of 3 with four equivalents of AuCl(SMe2) produces a tetranuclear complex, [(AuCl)(4){(BuNP)-Bu-t(OC6H4PPh2)}(2)] (16), whereas a 1 : 3 reaction between 5 and AuCl(SMe2) leads to the formation of a trinuclear complex, [(BuNH)-Bu-t{(BuNP)-Bu-t(AuCl)}(2)OC6H4P(AuCl)Ph-2] (17). The crystal structures of 3, 5, 9-11 and 13-17 are reported.