Below is a neat looking borax anion.
While exploring the molecule in a computer simulation (Gaussian 16, level of theory: HF/3-21G), I found that the oxygen atoms in the 8-membered outer ring had sp2 hybrid orbitals. My curiosity led me to question the presented data. Using Natural Bond Orbital analysis, I found out that:
BD(1)B1(O2) 1s(20.94%)p3.78(79.06%) BD(1)O2(B1) 2s(10.48%)p8.54(89.52%) BD(1)O2(B3) 2s(23.60%)p3.24(76.40%) BD1(1)B3(O2) 3s(36.38%)p1.75(63.62%) LP(1)O2 s(17.50%)p4.71(82.50%) LP(2)O2 s(48.39%)p1.07(51.61%)
Here BD denotes a 2-centered bond with atom(i)atom(j) and LP(i) denotes the lone pair and the s,p characters follow. My question is as follows:
Given the chaotic data, how does one analyse or interpret the harmony and claim that the oxygen is indeed ~sp2 hybridised?
What is the correct hybridisation of the oxygen atoms not connected to a hydrogen?