The First Structurally Authenticated Rb−PR3 and Cs−PR3 Contacts. Synthesis and Crystal Structures of [Rb{(Me3Si)2CP(C6H4-2-CH2NMe2)2}]n and [Cs{(Me3Si)2CP(C6H4-2-CH2NMe2)2}(toluene)]n

Metathesis between [Li{([Me 3 Si] 2 C)P(C 6 H 4 -2-CH 2 NMe 2 ) 2 }] ( 1 ) and either RbOR or CsOR (R = 2-ethylhexyl) gives the heavier alkali metal phosphinomethanide complexes [Rb{([Me 3 Si] 2 C)P(C 6 H 4 -2-CH 2 NMe 2 ) 2 }] n ( 4 ) and [Cs{([Me 3 Si] 2 C)P(C 6 H 4 -2-CH 2 NMe 2 ) 2 }(toluene)] n ( 5 ), respectively, after recrystallization. Compounds 4 and 5 represent the first examples of complexes containing a Rb−PR 3 or Cs−PR 3 bond.