Formation of an imidazoliumyl-substituted [(L)P] tetracation and transition metal mediated fragmentation and insertion reaction (L = NHC).

Tetracationic cyclo-tetraphosphane [(L)P] as triflate salt ([OTf]) (L = 4,5-dimethyl-1,3-diisopropyl-imidazol-2-yl) is obtained in high yield from the reduction of [LPCl] ([OTf]) with 1,4-bis(trimethylsilyl)-1,4-dihydropyrazine () and represents the first salt of the cationic cyclo-phosphane series with the general formula [L P ] . Theoretical calculations reveal the electrophilic nature of the P atoms within the P-ring due to the influence of the imidazoliumyl-substituents. Further reduction of [OTf] with affords the unexpected formation of the notricyclane P-type cation [(L)P] ([OTf]). Selective transition metal mediated [2 + 2]-fragmentation of is achieved when [OTf] is reacted with Fe(CO), Pd(PPh) and Pt(PPh) leading to the formation of the dicationic diphosphene complexes [(η-LP[double bond, length as m-dash]PL)Fe(CO)] ([OTf]) and [(η-LP[double bond, length as m-dash]PL)M(PPh)] ([OTf] for M = Pd; [OTf] for M = Pt). In contrast, the reaction of [OTf] with an excess of AuCl(tht) gives rise to the formation of the five-membered ring complex [((L)P)AuCl] ([OTf]), where the Au(i) atom reductively inserts into a P-P bond of .