Nb3Os2 crystallizes in the orthorhombic Cmm2 space group. There are seven inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 15-coordinate geometry to one Nb(1), one Nb(6), two equivalent Nb(3), two equivalent Nb(5), two equivalent Nb(7), one Os(5), two equivalent Os(2), and four equivalent Os(4) atoms. In the second Nb site, Nb(2) is bonded in a 11-coordinate geometry to one Nb(2), two equivalent Nb(4), two equivalent Os(1), two equivalent Os(5), and four equivalent Os(3) atoms. In the third Nb site, Nb(3) is bonded in a 7-coordinate geometry to one Nb(1), one Nb(3), one Os(5), two equivalent Os(3), and two equivalent Os(4) atoms. In the fourth Nb site, Nb(4) is bonded in a 4-coordinate geometry to one Nb(2), two equivalent Os(3), and two equivalent Os(4) atoms. In the fifth Nb site, Nb(5) is bonded in a 7-coordinate geometry to two equivalent Nb(1), two equivalent Nb(7), one Os(2), two equivalent Os(3), and two equivalent Os(4) atoms. In the sixth Nb site, Nb(6) is bonded in a 7-coordinate geometry to one Nb(1), one Os(1), two equivalent Os(3), two equivalent Os(4), and two equivalent Os(5) atoms. In the seventh Nb site, Nb(7) is bonded in a 7-coordinate geometry to two equivalent Nb(1), two equivalent Nb(5), one Os(2), two equivalent Os(3), and two equivalent Os(4) atoms. There are five inequivalent Os sites. In the first Os site, Os(1) is bonded to two equivalent Nb(6), four equivalent Nb(2), two equivalent Os(5), and four equivalent Os(3) atoms to form distorted OsNb6Os6 cuboctahedra that share corners with eight equivalent Os(3)Nb9Os3 cuboctahedra, corners with eight equivalent Os(4)Nb9Os3 cuboctahedra, edges with two equivalent Os(1)Nb6Os6 cuboctahedra, and faces with four equivalent Os(3)Nb9Os3 cuboctahedra. In the second Os site, Os(2) is bonded to two equivalent Nb(5), two equivalent Nb(7), four equivalent Nb(1), and four equivalent Os(4) atoms to form OsNb8Os4 cuboctahedra that share corners with eight equivalent Os(3)Nb9Os3 cuboctahedra, corners with eight equivalent Os(4)Nb9Os3 cuboctahedra, edges with two equivalent Os(2)Nb8Os4 cuboctahedra, and faces with four equivalent Os(4)Nb9Os3 cuboctahedra. In the third Os site, Os(3) is bonded to one Nb(5), one Nb(6), one Nb(7), two equivalent Nb(2), two equivalent Nb(3), two equivalent Nb(4), one Os(1), one Os(3), and one Os(5) atom to form distorted OsNb9Os3 cuboctahedra that share corners with two equivalent Os(1)Nb6Os6 cuboctahedra, corners with two equivalent Os(2)Nb8Os4 cuboctahedra, corners with three equivalent Os(3)Nb9Os3 cuboctahedra, corners with four equivalent Os(4)Nb9Os3 cuboctahedra, edges with three equivalent Os(3)Nb9Os3 cuboctahedra,  a faceface with one Os(1)Nb6Os6 cuboctahedra, faces with two equivalent Os(3)Nb9Os3 cuboctahedra, and faces with four equivalent Os(4)Nb9Os3 cuboctahedra. In the fourth Os site, Os(4) is bonded to one Nb(5), one Nb(6), one Nb(7), two equivalent Nb(1), two equivalent Nb(3), two equivalent Nb(4), one Os(2), one Os(4), and one Os(5) atom to form distorted OsNb9Os3 cuboctahedra that share corners with two equivalent Os(1)Nb6Os6 cuboctahedra, corners with two equivalent Os(2)Nb8Os4 cuboctahedra, corners with three equivalent Os(4)Nb9Os3 cuboctahedra, corners with four equivalent Os(3)Nb9Os3 cuboctahedra, edges with three equivalent Os(4)Nb9Os3 cuboctahedra,  a faceface with one Os(2)Nb8Os4 cuboctahedra, faces with two equivalent Os(4)Nb9Os3 cuboctahedra, and faces with four equivalent Os(3)Nb9Os3 cuboctahedra. In the fifth Os site, Os(5) is bonded in a distorted linear geometry to one Nb(1), two equivalent Nb(2), two equivalent Nb(3), two equivalent Nb(6), one Os(1), two equivalent Os(3), and two equivalent Os(4) atoms.
Nb3Os2 crystallizes in the orthorhombic Cmm2 space group. There are seven inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 15-coordinate geometry to one Nb(1), one Nb(6), two equivalent Nb(3), two equivalent Nb(5), two equivalent Nb(7), one Os(5), two equivalent Os(2), and four equivalent Os(4) atoms. The Nb(1)-Nb(1) bond length is 2.93 Å. The Nb(1)-Nb(6) bond length is 3.26 Å. Both Nb(1)-Nb(3) bond lengths are 2.73 Å. Both Nb(1)-Nb(5) bond lengths are 3.19 Å. Both Nb(1)-Nb(7) bond lengths are 3.21 Å. The Nb(1)-Os(5) bond length is 3.27 Å. There is one shorter (2.93 Å) and one longer (2.95 Å) Nb(1)-Os(2) bond length. There are two shorter (2.98 Å) and two longer (2.99 Å) Nb(1)-Os(4) bond lengths. In the second Nb site, Nb(2) is bonded in a 11-coordinate geometry to one Nb(2), two equivalent Nb(4), two equivalent Os(1), two equivalent Os(5), and four equivalent Os(3) atoms. The Nb(2)-Nb(2) bond length is 2.86 Å. Both Nb(2)-Nb(4) bond lengths are 2.75 Å. There is one shorter (2.84 Å) and one longer (3.00 Å) Nb(2)-Os(1) bond length. Both Nb(2)-Os(5) bond lengths are 3.19 Å. There are two shorter (2.95 Å) and two longer (3.02 Å) Nb(2)-Os(3) bond lengths. In the third Nb site, Nb(3) is bonded in a 7-coordinate geometry to one Nb(1), one Nb(3), one Os(5), two equivalent Os(3), and two equivalent Os(4) atoms. The Nb(3)-Nb(3) bond length is 2.66 Å. The Nb(3)-Os(5) bond length is 3.11 Å. There is one shorter (2.79 Å) and one longer (2.88 Å) Nb(3)-Os(3) bond length. There is one shorter (2.79 Å) and one longer (2.81 Å) Nb(3)-Os(4) bond length. In the fourth Nb site, Nb(4) is bonded in a 4-coordinate geometry to one Nb(2), two equivalent Os(3), and two equivalent Os(4) atoms. There is one shorter (2.79 Å) and one longer (2.82 Å) Nb(4)-Os(3) bond length. There is one shorter (2.79 Å) and one longer (2.86 Å) Nb(4)-Os(4) bond length. In the fifth Nb site, Nb(5) is bonded in a 7-coordinate geometry to two equivalent Nb(1), two equivalent Nb(7), one Os(2), two equivalent Os(3), and two equivalent Os(4) atoms. There is one shorter (2.54 Å) and one longer (2.55 Å) Nb(5)-Nb(7) bond length. The Nb(5)-Os(2) bond length is 2.85 Å. Both Nb(5)-Os(3) bond lengths are 2.89 Å. Both Nb(5)-Os(4) bond lengths are 2.91 Å. In the sixth Nb site, Nb(6) is bonded in a 7-coordinate geometry to one Nb(1), one Os(1), two equivalent Os(3), two equivalent Os(4), and two equivalent Os(5) atoms. The Nb(6)-Os(1) bond length is 2.89 Å. Both Nb(6)-Os(3) bond lengths are 2.85 Å. Both Nb(6)-Os(4) bond lengths are 2.84 Å. There is one shorter (2.53 Å) and one longer (2.56 Å) Nb(6)-Os(5) bond length. In the seventh Nb site, Nb(7) is bonded in a 7-coordinate geometry to two equivalent Nb(1), two equivalent Nb(5), one Os(2), two equivalent Os(3), and two equivalent Os(4) atoms. The Nb(7)-Os(2) bond length is 2.84 Å. Both Nb(7)-Os(3) bond lengths are 2.89 Å. Both Nb(7)-Os(4) bond lengths are 2.90 Å. There are five inequivalent Os sites. In the first Os site, Os(1) is bonded to two equivalent Nb(6), four equivalent Nb(2), two equivalent Os(5), and four equivalent Os(3) atoms to form distorted OsNb6Os6 cuboctahedra that share corners with eight equivalent Os(3)Nb9Os3 cuboctahedra, corners with eight equivalent Os(4)Nb9Os3 cuboctahedra, edges with two equivalent Os(1)Nb6Os6 cuboctahedra, and faces with four equivalent Os(3)Nb9Os3 cuboctahedra. Both Os(1)-Os(5) bond lengths are 2.77 Å. All Os(1)-Os(3) bond lengths are 2.62 Å. In the second Os site, Os(2) is bonded to two equivalent Nb(5), two equivalent Nb(7), four equivalent Nb(1), and four equivalent Os(4) atoms to form OsNb8Os4 cuboctahedra that share corners with eight equivalent Os(3)Nb9Os3 cuboctahedra, corners with eight equivalent Os(4)Nb9Os3 cuboctahedra, edges with two equivalent Os(2)Nb8Os4 cuboctahedra, and faces with four equivalent Os(4)Nb9Os3 cuboctahedra. All Os(2)-Os(4) bond lengths are 2.66 Å. In the third Os site, Os(3) is bonded to one Nb(5), one Nb(6), one Nb(7), two equivalent Nb(2), two equivalent Nb(3), two equivalent Nb(4), one Os(1), one Os(3), and one Os(5) atom to form distorted OsNb9Os3 cuboctahedra that share corners with two equivalent Os(1)Nb6Os6 cuboctahedra, corners with two equivalent Os(2)Nb8Os4 cuboctahedra, corners with three equivalent Os(3)Nb9Os3 cuboctahedra, corners with four equivalent Os(4)Nb9Os3 cuboctahedra, edges with three equivalent Os(3)Nb9Os3 cuboctahedra,  a faceface with one Os(1)Nb6Os6 cuboctahedra, faces with two equivalent Os(3)Nb9Os3 cuboctahedra, and faces with four equivalent Os(4)Nb9Os3 cuboctahedra. The Os(3)-Os(3) bond length is 2.67 Å. The Os(3)-Os(5) bond length is 2.85 Å. In the fourth Os site, Os(4) is bonded to one Nb(5), one Nb(6), one Nb(7), two equivalent Nb(1), two equivalent Nb(3), two equivalent Nb(4), one Os(2), one Os(4), and one Os(5) atom to form distorted OsNb9Os3 cuboctahedra that share corners with two equivalent Os(1)Nb6Os6 cuboctahedra, corners with two equivalent Os(2)Nb8Os4 cuboctahedra, corners with three equivalent Os(4)Nb9Os3 cuboctahedra, corners with four equivalent Os(3)Nb9Os3 cuboctahedra, edges with three equivalent Os(4)Nb9Os3 cuboctahedra,  a faceface with one Os(2)Nb8Os4 cuboctahedra, faces with two equivalent Os(4)Nb9Os3 cuboctahedra, and faces with four equivalent Os(3)Nb9Os3 cuboctahedra. The Os(4)-Os(4) bond length is 2.63 Å. The Os(4)-Os(5) bond length is 2.83 Å. In the fifth Os site, Os(5) is bonded in a distorted linear geometry to one Nb(1), two equivalent Nb(2), two equivalent Nb(3), two equivalent Nb(6), one Os(1), two equivalent Os(3), and two equivalent Os(4) atoms.