Table S1. Selected  bond lengths [Å], angles [deg] and torsion angles [deg] for compound 1

  P(1)-O(1)           1.502(2)      P(2)-C(1)         1.834(3)
  P(1)-O(2)           1.497(2)      N(1)-C(1)         1.512(3)
  P(1)-O(3)           1.566(2)      N(1)-C(2)         1.516(3)
  P(1)-C(1)           1.825(3)      C(2)-C(3)         1.508(4)
  P(2)-O(4)           1.478(2)      C(3)-C(4)         1.531(4)
  P(2)-O(5)           1.523(2)      C(4)-C(5)         1.499(4)
  P(2)-O(6)           1.556(2)      C(5)-C(6)         1.525(5)

  O(2)-P(1)-O(1)      116.6(1)      O(5)-P(2)-C(1)    106.0(1)
  O(2)-P(1)-O(3)      112.2(1)      O(6)-P(2)-C(1)    105.5(1)
  O(1)-P(1)-O(3)      107.7(1)      N(1)-C(1)-P(1)    108.1(2)
  O(2)-P(1)-C(1)      104.7(1)      N(1)-C(1)-P(2)    110.9(2)
  O(1)-P(1)-C(1)      107.1(1)      P(1)-C(1)-P(2)    117.3(2)
  O(3)-P(1)-C(1)      108.1(1)      C(1)-N(1)-C(2)    113.9(2)
  O(4)-P(2)-O(5)      118.2(1)      C(3)-C(2)-N(1)    111.6(2)
  O(4)-P(2)-O(6)      110.5(1)      C(2)-C(3)-C(4)    109.6(2)
  O(5)-P(2)-O(6)      109.4(1)      C(5)-C(4)-C(3)    113.3(3)
  O(4)-P(2)-C(1)      106.4(1)      C(4)-C(5)-C(6)    113.2(3)

   C(2)-N(1)-C(1)-P(1)      -156.8(2)
   C(2)-N(1)-C(1)-P(2)        73.2(3)
   O(2)-P(1)-C(1)-N(1)        31.4(2)
   O(1)-P(1)-C(1)-N(1)       155.8(2)
   O(3)-P(1)-C(1)-N(1)       -88.4(2)
   O(2)-P(1)-C(1)-P(2)       157.8(1)
   O(4)-P(2)-C(1)-N(1)        36.4(2)
   O(5)-P(2)-C(1)-N(1)       163.1(2)
   O(6)-P(2)-C(1)-N(1)       -80.9(2)
   O(6)-P(2)-C(1)-P(1)       154.1(1)
   C(1)-N(1)-C(2)-C(3)       175.6(2)
   N(1)-C(2)-C(3)-C(4)      -172.8(2)
   C(2)-C(3)-C(4)-C(5)       180.0(3)
   C(3)-C(4)-C(5)-C(6)      -178.8(3)
   H(1)-C(1)-N(1)-H(11)     -165(2)
   H(1)-C(1)-N(1)-H(12)       78(2)
   H(1)-C(1)-N(1)-C(2)       -43(2)