Syntheses of Group 14 bis(tert-butylamido)cyclodiphosph(III)azane dichlorides, and the solid-state structures of the silicon and tin derivatives

To test the synthetic utility of bis(tert-butylamido)cyclodiphosph(III)azanes as ligands we extended the coordination chemistry of these diamides from Group 4 to Group 14. The syntheses of compounds of the formula cis-[tBuNP(μ-tBuN)2PNtBu]ECl2, E = Si (1), Ge (2), Sn (3) and the solid-state structures of 1 and 3 are reported. Silicon tetrachloride reacted with dilithiobis(tert-butylamido)cyclodiphosph(III)azane to cleanly produce cis-[tBuNP(μ-tBuN)2PNtBu]SiCl2, but for the germanium and tin analogues the interaction of GeCl4 or SnCl4 with the diazastannylene cis-[tBuNP(μ-tBuN)2PNtBu]Sn proved to be a better method. Single-crystal X-ray studies on both 1 and 3 revealed that they had Cs-symmetric structures, the central element being coordinated by two amide nitrogens and two chlorides, in addition to being weakly coordinated by one of the cyclodiphosph(III)azane ring nitrogens. Using structural comparisons between crystallographically-independent 1a and 1b, between 1 and 3, and between 3 and its isomorphous zirconium analogue, the nature of this donor bond is discussed.