An Acyclic Dimer of Cyclodiphosphazane {^<i>t</i>BuHN(^<i>t</i>BuNP)₂OCH₂}₂ Containing Alkoxo and Amido Functionalities: Synthesis, Derivatization, Bi- (Pd^II, Rh^I), and Tetranuclear (Pd^II, Au^I, Rh^IAu^I) Transition Metal Complexes

Acyclic bis(cyclodiphosphazane) [tBuHN(tBuNP)2OCH2]2 (2) containing alkoxo and amido functionalities was synthesized by reacting cis-[tBuHN(tBuNP)2Cl] (1) with ethylene glycol and upon further treatment with 4 equiv of elemental sulfur or selenium affords the corresponding tetrachalcogenides [tBuHN(tBuNPE)2OCH2]2 (3, E = S; 4, E = Se) in quantitative yield. The reaction of 2 with 2 equiv of elemental sulfur results in the oxidation of only the amido-phosphorus atoms to form the di(sulfide) derivative [tBuHN(S)P(μ-tBuN)POCH2]2 (5). The reaction of 2 with 2 equiv of [PdCl(η3-C3H5)]2 afforded the tetrametallic complex [{Pd(η3-allyl)Cl}4{tBuHN(tBuNP)2OCH2}2] (7) containing four independent [PdCl2(η3-C3H5)] moieties each coordinated to a phosphorus atom. In contrast, the reaction between [Pd(PEt3)Cl2]2 and 2 leads to the addition of two metal atoms with the formation of [{Pd(PEt3)Cl}2{tBuHN(tBuNP)2OCH2}2] (8), in which alternating phosphorus atoms of the bis(cyclodiphosphazane) are coordinated to palladium. Interestingly, the palladium(II) atom coordinated to the phosphorus atom bearing the t-butylamino substituent adopts a trans geometry, whereas that coordinated to the phosphorus atom connected to the −OCH2CH2O− linker prefers a cis conformation. The reaction between 2 and [Rh(COD)Cl]2 produces exclusively the bimetallic complex [{Rh(COD)Cl}2{tBuHN(tBuNP)2OCH2}2] (6) irrespective of the stoichiometry of the reactants and the reaction conditions. In complex 6, only the alkoxo-phosphorus atoms are coordinated. However, complex 6 upon treatment with AuCl(SMe2) in a 1:2 ratio gives the heterometallic tetrasubstituted complex [{Rh(COD)Cl}2(AuCl)2{tBuHN(tBuNP)2OCH2}2] (10). The reaction between 4 equiv of AuCl(SMe2) and 2 resulted in the formation of a tetrametallic gold complex [(AuCl)4{tBuHN(tBuNP)2OCH2}2] (9). The crystal structures of 2−4 and 7−10 are reported.